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Beside-the-Ball Gaze Pattern
|I - Olfactory
II - Optic
III - Oculomotor
IV - Trochlear
V - Trigeminal
VI - Abducens
VII - Facial
VIII - Auditory
IX - Glossopharyngeal
X - Vagus
XI - Accessory
XII - Hypoglassal
Three of these cranial nerves (III, IV, and VI) emerge from the brain and attach to the various extraocular muscles, and signalling along these nerves controls the muscles that aim the eyeballs. The three controlling cranial nerves are the oculomotor nerve (Cranial Nerve III, Supplies four of the six extraocular muscles of the eye and the levator palpebrae superioris muscle of the upper eyelid),
the trochlear nerve (Cranial Nerve IV, innervates the superior oblique muscle of the contralateral orbit),
and the abducens nerve (Cranial Nerve VI, innervates the lateral rectus muscle of the ipsilateral orbit).
F. Checking Nerve Function.
A neurological examination of gaze tests the functioning of the nerves in different ways. Dr Hal Blumenfeld's Nueroexam.com illustrates with video clips the various gaze exams for Extraocular Movements. (Also see this ocular motility exam -- "follow the pencil").
G. Isolating action of muscles and nerves.
To see the independent functioning of the different extraocular muscles and the three cranial nerves, visit this Flash interactive Eye Simulation from UC Davis.
A. Vision for Action.
The brain tracks eyeball movements, head movements, and whole-body turns so that the visual information is "rooted" to the body position in space, and is not "free-floating" visual information about objects and locations in space exterior to the body. Basically, the brain is not interested in mere visual information: the brain wants visual information almost exclusively so that the brain can USE the visual information for the BODY to ACT with respect to the being or object or location being targeted. That means that visual information streaming in thru the eyeball is practically USELESS unless it is combined with body-head-eye orientation information. There is no THERE or WHERE without a HERE. The eyes never work alone, and ONLY work to SERVE THE BODY. (See Goodale & Milner, The Visual Brain in Action.)
As far as I can tell from the written record, so-called "vision experts" in academia and in optometry simply don't understand this basic point and their expertise remains flaccidly within the realm of "vision per se," a rather silly and unconnected-to-the-world approach to the subject. This seems to be the case in the written work of Joan Vickers, sports scientist and editor in chief of Sports Vision, whose articles about the "gaze" in putting do not recognize the definition of "gaze" used in neuroscience and whose work takes no account of body-head-eye relations, and the work of Craig Farnsworth, an optometrist who applies clinical tools of optometric practice to issues of human spatial targeting based on the uninformed notion that the mere operations of the aparatus of vision (such as the teaming vergence motions of the eyes) are the critical determinants for spatial perception and awareness rather than the more meaningful understanding that vision aids the body in relating the HERE of the body to the THERE of the target for purposes of action by the body.
What keeps account of the relationships of body-head-eyes? There are a number of systems that work in a coordinated, redundant, and layering fashion. The vestibular system keeps track of the body in gravity. The proprioceptive system tracks the relationship among joint angles and body parts, mostly by assessing muscle stretches. The neuromuscular system with the proprioceptive system track body parts in motion. The extraocular muscles themselves form part of the proprioceptive signalling of eyeball orientation. The muscles in the neck "read and report on" the relationship between the head and the upper trunk. The visual system itself reports on gaze, since each eye "looks out of" the face and eyeball socket while seeing the edges of the skull in a certain way, depending on the aim of the eyeballs. The memory system also helps, by tying together the state of the body and the external location at Time 1 with the states that exist at Time 2. All together, these systems build up a sense of HERE the body is in its position and posture, and THERE the object or location is in relation to the body, so that the body can ACT (move the body parts appropriately) in the selected manner with respect to the object or location.
B. Targeting Neurology.
i). Vestibular Neuroanatomy and the Cerebellum. Signals from the inner ear's positional and movement sensors feed to the brain stem into the two "vestibular nuclei". From there, vestibular projections extend to the cerebellum, extraocular nuclei, and spinal cord. The cerebellum combines vision, balance and proprioception to help coordinate timing and smoothing and targeting aspects of human movement in ACTION with respect to the target. This is one reason why the cerebellum plays a key role in LEARNING motor skills and PERFORMING motor skills. The cerebellum feeds signals back into the vestibular nuclei, modulating signalling into the spinal cord and to the eye muscles. Inner ear signalling to the cortex itself is not known clearly, but is suspected to feed into the temporal lobe near the auditory cortex and / or the insula. (See eMedicine.com.)
ii). Eye Movement Neuroanatomy -- Saccadic.
"For the most part different neural mechanisms control saccadic and smooth pursuit eye movements."(Schiller, The Neural Control of Visually Guided Eye Movements, Schiller Lab slide.) There is coordination of the two systems in reality, however, as saccades help guide smooth pursuit movements. (Blohm et al., Processing of retinal and extraretinal signals for memory-guided saccades during smooth pursuit, J Neurophysiol. 2005 Mar;93(3):1510-22. Epub 2004 Oct 13.)
a). Cortical areas. The Frontal Eye Field (both the dorsolateral Frontal Eye Field or FEF and the dorsomedial Eye Field or DMFC, also called the Medial Eye Field or MEF), the Supplementary Eye Field (SEF), and the Lateral Interparietal Cortex or Interparietal Sulcus (LIP / IPS), are the three mian cortical modules controlling eye movements. (Schiller & Chou, The effects of frontal eye field and dorsomedial frontal cortex lesions on visually guided eye movements, Nature Neuroscience 1, 248 - 253 (1998).)
The FEF plays a key role in the brain's execution of "gaze shifting" behaviors and / or "gaze holding" behaviors. Withholding or countermanding saccadic movement is a major function of targeting behaviors. (Hanes et al., Role of Frontal Eye Fields in Countermanding Saccades: Visual, Movement, and Fixation Activity, J. Neurophysiology, 79: 817.)
The different contributions of these three main cortical modules for eye movements is the subject of on-going research. For example, the Tony Ro Lab at Rice University reports: "These results demonstrate that the parietal and frontal lobes are involved with very different computations for the generation of saccadic eye movements. The parietal cortex may be more involved with specifying the metrics of saccadic eye movements, whereas the FEFs in the final generation." Also: "Although the DMFC and FEF are both active during the execution of saccadic and smooth pursuit eye movements, the FEF is more dedicated to these functions. Lesions of DMFC minimally affect the production of most types of saccadic eye movements and have no effect on the execution of smooth pursuit eye movements. In contrast, lesions of the FEF produce deficits in generating saccades to briefly presented targets, in the production of saccades to two or more sequentially presented targets, in the selection of simultaneously presented targets, and in the execution of smooth pursuit eye movements." (Tehovnik et al., Eye fields in the frontal lobes of primates, Brain Research Review, Apr 2000, 32(2-3):413-48.) Similarly, Coe and associates report: "Our results suggest that although all three cortical eye fields reflect attentional and intentional aspects of sensorimotor processing, SEF plays an earlier and perhaps more cognitive role in internally guided decision-making processes for saccades." (Coe et al., Visual and Anticipatory Bias in Three Cortical Eye Fields of the Monkey during an Adaptive Decision-Making Task, Journal of Neuroscience, June 15, 2002, 22(12):5081-5090.) The FEF neurons appear to relate more to saccadic movement itself as opposed to planning the movement. (Bizzi, Discharge of Frontal Eye Field Neurons during Eye Movements in Unanesthetized Monkeys, Science (29 September 1967): Vol. 157. no. 3796, pp. 1588 - 1590.)
b). Subcortical areas. The superior colliculus, a midbrain structure that is between the eyes and the occipital lobe along the optical pathway, also plays a role: "In humans, the superior colliculus (SC) is involved in the generation of saccadic eye movements and eye-head coordination." (Superior colliculus, Wikipedia.)
"The oculomotor nerve arises from the anterior aspect of mesencephalon (midbrain), the oculomotor nucleus originates at the level of the superior colliculus. The muscles it controls are the ciliary muscle (affecting accommodation), and all extraocular muscles except for the superior oblique muscle and the lateral rectus muscle." (Oculomotor, Wikipedia.) In addition, the subthalamic nucleus (STN) has been shown active in controlling memory-driven saccades. (Rivaud-Péchoux et al., Improvement of memory guided saccades in parkinsonian patients by high frequency subthalamic nucleus stimulation, J Neurol Neurosurg Psychiatry 2000;68:381-384 (March).)
c). Cerebellar areas. The cerebellum also provides control for saccadic eye movements. The fastigial nuclei (channelling signals from the vermis) contribute to accuracy of saccades by regulating the timing of saccadic acceleration and deceleration, which appears to be a "bread-and-butter" function of the cerebellum for a wide variety of body movement patterns. This timing function sets the amplitude of the intended saccade. (e.g., Dean, Modelling the role of the cerebellar fastigial nuclei in producing accurate saccades: the importance of burst timing, Neuroscience, Volume 68, Number 4, October 1995, pp. 1059-1077(19).) "The posterior vermis regulates the amplitude of saccadic eye movements and is probably essential for the short-term adaptation [i.e., to muscle fatigue in saccadic movement]." (Barash et al., Saccadic Dysmetria and Adaptation after Lesions of the Cerebellar Cortex, Journal of Neuroscience, December 15, 1999, 19(24):10931-10939.)
An interesting model of saccadic planning and control proposes that the Superior colliculus and the cerebellum together operate to generate a "desired outcome" based on spatial awareness and "desired sensory outcome" of the anticipated successful (i.e., accurate) saccde. (Optican & Quaia, Distributed Model of Collicular and Cerebellar Function during Saccades, Annals of the New York Academy of Sciences 956:164-177 (2002).)
iii). Saccadic Accuracy. Saccades are generally spoken of as either visually-guided or memory-guided. This means that the saccade depends on the perceptions of the body's position in space and the perceptions of the target position in space. The body position in space is registered mostly in the parietal lobe in the somatosensory cortex, and is represented fancifully in the Sensory Homunculus drawn by showing the percentage and neighborly relations of brain matter given to the different body parts. The motor cortex in the frontal lobe has another, related Motor Homunculus with interconnections to the parietal homunculus. The cerebellum itself has at least two homunculi, the Anterior Homunculus and the Posterior Homunculus, and may have a third in the Pyramis Vermis. (Rijntjes et al., Multiple somatotopic representations in the human cerebellum, Neuroreport. 1999; 10(17):3653-8.) Similarly, the superior colliculus (SC) maintains a "visuotopic" representation of the visual signalling from the real world thru the retina and optic nerve and overlays this with a "somatotopic" representation of the body, joing the HERE of the body with the WHERE of the external world perceived visually, (Stein et al., Superior colliculus: visuotopic-somatotopic overlap, Science 18 July 1975: Vol. 189. no. 4198, pp. 224 - 226; Meredith et al., Somatotopic component of the multisensory map in the deep laminae of the cat superior colliculus, The Journal of Comparative Neurology, Volume 312, Issue 3 , Pages 353 - 370, online 9 Oct 2004.) These SC somatotopic representations appear to emanate from the parietal lobe's more all-purposebody- spatial processes. (Wu et al., Somatosensory areas S2 and PV project to the superior colliculus of a prosimian primate, Galago garnetti, Somatosensory & Motor Research, Volume 22, Number 3, Number 3/September 2005, pp. 221-231(11).)
Notwithstanding the somatotopic assistance in the saccadic system, saccades are generally either visually guided or memory guided. That is, the saccade is either generated in response to a recent visual stimuli in the periphery of vision, or is generated based unpon internal memory representations of target location. In golf, except when the stationary target is a hole appearing in the periphery of vision while gazing at the ball, there is no visual signal to generate the saccade, and saccades are therefore predominantly memory-driven. Various factors degrade saccadic accuracy, regardless of the generation, but probably degrade memory-driven saccades more than visually-driven saccades.
Generally, saccades to remembered targets have an initial end-point that is typically between 2% and 10% short of the target, followed by corrective saccades. (Laurutis & Robinson, The vestibulo-ocular reflex during human saccadic eye movements, J Physiol. 1986 April; 373: 209-233, at 213.)
Since saccades to remembered targets depend upon working spatial memory, factors that interfere with or degrade working spatial memory, such as delay and the presence of competing targets and distractors, also adversely affect saccadic accuracy. (See Nyffeler et al., Information processing in long delay memory-guided saccades: further insights from TMS, Biomedical and Life Sciences Volume 154, Number 1 (January, 2004).) Mnemonic deficits such as those in Parkinson's disease appear to underlie poor performance in saccades to remembered targets, and stimulation of the subthlamaic nucleaus (STN) has been shown to improve saccadic accuracy, presumably through activation of the dorsolateral prefrontal cortex (DLPFC), the brain area associated with working spatial memory. Saccadic accuracy degrades with the distance of the saccade. (Rivaud-Péchoux et al., Improvement of memory guided saccades in parkinsonian patients by high frequency subthalamic nucleus stimulation, J Neurol Neurosurg Psychiatry 2000;68:381-384 (March).)
"Saccades are less accurate the farther the endpoint is from fixation, regardless of the number of saccades made to reach it. This suggests that when planning a series of saccades, the total distance from fixation plays an important role in the calculation of saccade metrics." (Fine et al., Path length and number of saccades affect saccade accuracy [Abstract]. Journal of Vision, 6(6), 494a (2006).) Saccadic accuracy degrades in the presence of distractors that renders target identification problematic. (Aria et al., Properties of Saccadic Responses in Monkey When Multiple Competing Visual Stimuli Are Present, J Neurophysiol 91: 890-900, 2004.) Saccades typically land more or less in the center of a group of targets, rather than at a specific target, and this admits a heavy role for distraction and lack of focus in degrading saccadic accuracy. (Coeffe & O'Regan, Reducing the influence of non-target stimuli on saccade accuracy: predictability and latency effects, Vision Res. 1987;27(2):227-40.) Expanding the length of time between the appearance of the visual target and the onset of the saccade degrades accuracy. (Edelman & Goldberg, Dependence of Saccade-Related Activity in the Primate Superior Colliculus on Visual Target Presence, J. Neurophysiol. 86: 676-691, 2001.)
On the other hand, saccadic accuracy may well be related to the predictability of the target location and onset, which would certainly be the case with a stationary target like the hole in a green for a straight putt. (Wang & Stern, Saccade initiation and accuracy in gaze shifts are affected by visual stimulus significance, Psychophysiology (2001), 38: 64-75 ("Our results suggest that both timing and accuracy of gaze shift are affected by the observer's expectation of future events.") Tightening the definition (smallness of target, contrast of target with background) and providing local landmark references that define the localization of the target enhance accuracy of saccades. (Edelman & Goldberg, Saccade-Related Activity in the Primate Superior Colliculus Depends on the Presence of Local Landmarks at the Saccade Endpoint, J Neurophysiol 90: 1728-1736, 2003.) When the memory-driven target generates a saccadic plan during the delay between seeing the target and executing the saccade, the frontal eye field (FEF) level of activation correlates positively with greater saccadic accuracy. That is, when the impending saccadic target is known to be the same as the location of the target previously seen, the FEF activation enhances accuracy. (Curtis et al., Maintenance of Spatial and Motor Codes during Oculomotor Delayed Response Tasks, Journal of Neuroscience, April 21, 2004, 24(16):3944-3952.)
iv.) Eye Movement Neuroanatomy -- Smooth Pursuit
Various spatial-awareness brain modules contribute to "smooth pursuit" eye movements, in a problem that is more anticipatory of the route of an object in motion than the saccadic problem of directing vision to a location.
a) Cortical area. The prinicpal neural circuits are in the posterior parietal lobe (see Ilg, Commentary: smooth pursuit eye movements: from low-level to high-level vision, Prog Brain Res. 2002;140:279-98), and the cerebellum, specifically the flocculus-paraflocculus and the posterior vermis (see Thier & Ilg, The neural basis of smooth-pursuit eye movements, Curr Opin Neurobiol. 2005 Dec;15(6):645-52. Epub 2005 Nov 3.) Naturally, the predictive process for target motion are closely allied with the brain processes for perceiving motion of objects, namely several known extraretinal motion processing areas including frontal (FEF) and supplemental eye fields (SEF), the middle temporal (MT) and medial superior temporal cortex (MST), and anterior cingulate. (See, e.g., Hong et al., Specific motion processing pathway deficit during eye tracking in schizophrenia: a performance-matched functional magnetic resonance imaging study, Biol Psychiatry. 2005 Apr 1;57(7):726-32; Goossens et al., Representation of Head-Centric Flow in the Human Motion Complex, Journal of Neuroscience, May 24, 2006, 26(21):5616-5627.) The FEF and MST have reciprocal connections and also code for motion in 3-D by incorporating the depth information of eye vergence signals. (Akao et el., Discharge characteristics of pursuit neurons in MST during vergence eye movements, J Neurophysiol. 2005 May;93(5):2415-34. Epub 2004 Dec 8; and Priebe & Lisberger, Estimating target speed from the population response in visual area MT, J Neurosci. 2004 Feb 25;24(8):1907-16 ("In the domain of visual motion, estimates of target speed are derived from the responses of motion-sensitive neurons in the middle temporal (MT) area of the extrastriate visual cortex and are used to drive smooth pursuit eye movements and perceptual judgments of speed.")
b) Pursuit Accuracy. Smooth pursuit is complicated when both the head and the eyes moves together. (Souman, Frame of reference transformations in motion perception during smooth pursuit eye movements, J Comput Neurosci. 2006 Feb;20(1):61-76. Epub 2006 Feb 20.) According to two Harvard researchers, gender differences appear to underlie male superior performance in hand-eye coordination tasks, and a superior precision on the part of male subjects in smooth pursuit plays a role in this. (Wilmer & Nakayama, A large gender difference in smooth pursuit precision, Journal of Vision, Volume 6, Number 6,Page 94a (2006).)
Evidence is conflicting on the point whether attention and focus enhance smooth pursuit accuracy or, to the contrary, divided attention with a conflicting task promotes smooth pursuit accuracy as an automatic, nonconscious process. (Compare Kathmann et al., Effects of dual task demands on the accuracy of smooth pursuit eye movements, Psychophysiology (1999), 36: 158-163 (automatic), with Hutton & Tegally, The effects of dividing attention on smooth pursuit eye tracking, Exp Brain Res. 2005 Jun;163(3):306-13. Epub 2005 Jan 15 (enhanced by attention).)
Hand movement (and presumably other proprioceptive-based body motions) works in tandem with smooth pursuit eye movements, so that each process has its accuracy enhanced. (van Donkelaar & Lee, Interactions between the eye and hand motor systems: disruptions due to cerebellar dysfunction, J Neurophysiol. 1994 Oct;72(4):1674-85.) "Coordination control results from the reciprocal transfer of sensory and motor information between two or more systems involved in the execution of single, goal-directed or conjugate actions. This control, originating in one or more highly specialized structures of the central nervous system, combines with the control processes normally operating in each system." (Gauthier et al., Oculo-manual tracking of visual targets: control learning, coordination control and coordination model, Exp Brain Res. 1988;73(1):127-37.)
Smooth pursuit eye movement can be used to enhance the accuracy of follow-on hand movement. According to Whitney and Goodale: "Movement of the body, head, or eyes with respect to the world creates one of the most common yet complex situations in which the visuomotor system must localize objects. In this situation, vestibular, proprioceptive, and extra-retinal information contribute to accurate visuomotor control. The utility of retinal motion information, on the other hand, is questionable, since a single pattern of retinal motion can be produced by any number of head or eye movements. Here we investigated whether retinal motion during a smooth pursuit eye movement contributes to visuomotor control. When subjects pursued a moving object with their eyes and reached to the remembered location of a separate stationary target, the presence of a moving background significantly altered the endpoints of their reaching movements. A background that moved with the pursuit, creating a retinally stationary image (no retinal slip), caused the endpoints of the reaching movements to deviate in the direction of pursuit, overshooting the target. A physically stationary background pattern, however, producing retinal image motion opposite to the direction of pursuit, caused reaching movements to become more accurate. The results indicate that background retinal motion is used by the visuomotor system in the control of visually guided action." (Whitney & Goodale, Visual motion due to eye movements helps guide the hand, Exp Brain Res. 2005 Apr;162(3):394-400. Epub 2005 Jan 15.)
v.) Multisensory Integration. Multisensory integration (MI) is the study of how overlapping sensory systems cooperate to sharpen up spatio-temporal perceptions of targets. (Holmes & Spence, Multisensory integration: Space, time, & superadditivity, Curr Biol. 2005 September 20; 15(18): R762-R764.)
a). MI in the Superior colliculus. "Multisensory integration in the superior colliculi has been understood for many years in terms of several simple rules: The neural responses to multisensory stimuli tend to be enhanced when the stimuli in different senses come from approximately the same location (the 'spatial rule'), when they occur at approximately the same time (the 'temporal rule'), and/or when at least one of the two stimuli is by itself only weakly effective in exciting a neuron (the 'inverse effectiveness rule')." The notions of "interest," "intentionality," "desire," "focus," "attention," and "will" come into all receive their due in this process of sharpening perceptions: "The spatial rule is a consequence of the fact that the superior colliculi align maps of space across different sensory modalities in approximately the same manner: Multisensory stimuli from a given location in space are represented in a given location in the colliculi. How this alignment across the modalities develops is an ongoing area of research,, but the importance of this alignment is obvious when one thinks about the function of the colliculi. The eyes can only be oriented in a single direction at any given time, so representing the same region of space across different senses in a small region of the colliculus should help individual neurons to integrate information about the currently most stimulated, and likely most important, region of space." Similar considerations apply to temporal integration of various sensory signals (e.g., the sight of a cat jumping onto a table and the sound breaking china shortly thereafter.)
b). Cortical Supervision of MI. Multisensory integration, then, does not necessarily occur, but must usually be nursed along with "cortical supervision." This mean, roughly, "looking for the combination" on purpose. Holmes and Spence write: "However, there are several collicular mysteries which are difficult to explain with a linear model alone. For example, the finding that multisensory integration in the superior colliculi is greatly reduced when inputs from the cerebral cortex are turned off: Without cortical supervision, collicular neurons respond to individual sensory stimuli, but they fail to shift from their unisensory baselines when both stimuli are presented simultaneously – in other words, the neurons act as if the sound of the breaking china was totally unrelated to the sight of your fleeing cat."
c). Binding Problem as MI. Mulitsensory integration beyond the SC in cortical processes generally is termed "the binding problem." The binding problem is how the independent and primal perceptions of certain edges and corners and colors and smells all get combined or integrated into a persisting awareness that the object under view is a plate of spinach for you to eat. (See Roskies, Review: The Binding Problem, Neuron, Vol. 24, 7-9, September, 1999.) Although the binding problem is most often referred to "object recognition," (e.g., Riesenhuber & Poggio, Neuron, Vol. 24, 87-93, September, 1999.) in principle the binding problem concerns more broadly the integration of multisensory perceptions far beyond the merely visual, comprehending sight, sound, smell, touch, and "action" perceptions as well in a unified "super-percept." (e.g., Billock & Tsou, A Role for Cortical Crosstalk in the Binding Problem: Stimulus-driven Correlations that Link Color, Form, and Motion, Journal of Cognitive Neuroscience. 2004;16:1036-1048.)
Recent studies indicate that a 40 Hertz oscillation serves to bind disparate percepts into a unified percept temporaly. (e.g., Joliot, Ribary & Llinas, Human Oscillatory Brain Activity Near 40 Hz Coexists with Cognitive Temporal Binding, Proceedings of the National Academy of Sciences, Vol 91, 11748-11751 (1994).) Gamma synchrony has been observed in working visual memory (e.g., Doesburg et al., Increased gamma-band synchrony precedes switching of conscious perceptual objects in binocular rivalry, Neuroreport. 2005 Aug 1;16(11):1139-42; and Tallon-Baudry et al., Induced -band activity during the delay of a visual short-term memory task in humans, J Neurosci 18: 4244-4254, 1998), and working audiospatial memory (Lutzenberger et al., Dynamics of Gamma-Band Activity during an Audiospatial Working Memory Task in Humans, J. Neurosci., July 1, 2002; 22(13): 5630 - 5638), and a wide variety of perceptual modalities (Howard et al., Gamma Oscillations Correlate with Working Memory Load in Humans Cereb Cortex, December 1, 2003; 13(12): 1369 - 1374) ("These findings support the hypothesis that gamma activity is used to organize and temporally segment the representations of different items in a multi-item working memory system.") Gamma synchronization is generally considered a correlative of "focused arousal" and "alert performance." (Keil et al., Human Gamma Band Activity and Perception of a Gestalt J. Neurosci., August 15, 1999; 19(16): 7152 - 7161.)
To clarify the issue of what sort of gaze pattern is best suited to putting, we first have to ask "What is the purpose of the gaze pattern in terms of its use by the brain and body?" This is so because of the characteristic organization of the brain's visual systems, multiple reference frames for spatial cognition, and the differing sorts of targeting processes.
"Evidence from both humans and monkeys has shown that this distinction between vision for perception and vision for action is reflected in the organization of the visual pathways in primate cerebral cortex. Two broad "streams" of projections from primary visual cortex have been identified: a ventral stream projecting to the inferotemporal cortex and a dorsal stream projecting to the posterior parietal cortex.
Both streams process information about the structure of objects and about their spatial locations -- and both are subject to the modulatory influences of attention. Each stream, however, uses this visual information in different ways. The ventral stream transforms the visual information into perceptual representations that embody the enduring characteristics of objects and their relations. Such representations enable us to identify objects, to attach meaning and significance to them, and to establish their causal relations -- operations that are essential for accumulating knowledge about the world. In contrast, the transformations carried out by the dorsal stream deal with moment-to-moment information about the location and disposition of objects with respect to the effector being used and thereby mediate the visual control of skilled actions directed at those objects. Both streams work together in the production of adaptive behavior. The selection of appropriate goal objects and the action to be performed depends on the perceptual machinery of the ventral stream, but the execution of a goal-directed action is carried out by dedicated on-line control systems in the dorsal stream." (Melvyn Goodale website.)
This traffic along this interrelated duplex of visual systems depends somewhat on whether the movement is initiated with respect to a visible goal or target object or whether the action is initiated without reference to a visible goal or target object. For example, in reaching and grasping a cup on a table, when the reaching is initiated with the cup in view, the dedicated, real-time visuomotor mechanisms of the dorsal stream are engaged. But when the target object is not visible when the movement is cued, then grasping is driven, not by the dedicated visuomotor systems in the dorsal stream, but by information provided by the ventral perception stream. (Melvyn Goodale website, citing Westwood, D.A., & Goodale, M.A. (2003). Perceptual illusion and the real-time control of action. Spatial Vision, 16, 243-254.) When reaching-grasping action is memory guided, the task performance is more susceptible to interference from a simultaneous task than is reaching-grasping under dedicated visuomotor control. (Singhal et al., Dual-Task Interference is Greater in Memory-Guided Grasping Than in Visually Guided Grasping, Poster (2005).)
The two basic frames of reference for spatial awareness of locations external to the body are "egocentric" and "allocentric." (Paillard J (1991). Motor and representational framing of space. In: Paillard J (ed) Brain and space. Oxford University Press, Oxford.) "Egocentric frames of reference use the organism as the centre of the organization of surrounding space, therefore memorized spatial representations maintain the perspective under which spatial information has been experienced and for this reason the access to spatial locations is not equally easy but depends on the relation between the required location and the organism. Allocentric frame of reference specify location and orientation independently of body's position; derived representations are centred on objects or environmental features." (Iachini & Ruggiero, Egocentric and allocentric spatial frames of reference: a direct measure, Cogn Process (2006) 7 (Suppl. 1):S126-S127.) Humans primarily interact with the environment via the egocentric frame. (Millar S (1994). Understanding and representing space. Theory and evidence from studies with blind and sighted children. Clarendon Press, Oxford.) This is a default from the fact that external space seldom has as useful set of cues to use for allocentric orientation as are present in the body-in-gravity symmetries useful for egocentric orientation. (Mou et al., Allocentric and Egocentric Updating of Spatial Memories, Journal of Experimental Psychology: Learning, Memory, and Cognition 2004, Vol. 30, No. 1, 142-157.)
While the different frames of reference typically overlap and work in tandem, the two visual systems appear to work in frame preferences differently, depending upon the USE of the visual information. "The vertical visual field asymmetries have been especially discussed within theoretical models describing how the brain represents the space. According to Previc, they are related to different neuro-behavioral systems that control the perceptual- motor operations that are mainly performed in different portions of the 3D space. Such systems include the dorsal and ventral visual pathways proposed by some authors. For example, the peripersonal (PrP) system, which mainly relies on the dorsolateral pathway of the visual system, is specialized for actions, such as reaching and manipulation, that are carried out in the near space, and is biased toward the lower visual hemifield. Differently, the focal extrapersonal (FcE) and the action extrapersonal (AcE) systems, respectively subserved by ventrolateral and ventromedial cortical pathways, are specialized for visual scene processing (e.g. visual search, recognition, scene memory, and target orientation), and are biased toward the upper visual hemifield. ... According to Previc, the PrP system is based on a body-centered coordinate system, needed to implement arm and hand actions, while the FcE and AcE systems are based on retinotopic and gaze-centered coordinate systems, respectively. ... Our results support this idea by showing a clear double dissociation between visual hemifield and task: an upper visual field advantage only arises when allocentric spatial judgments are required, whereas a lower visual field advantage arises when egocentric spatial judgments are required." (Sdoia, Couyoumdjian & Ferlazzo, Opposite visual field asymmetries for egocentric and allocentric spatial judgments, NeuroReport15:1303-1305 (2004).) "The superior hemiretina in primates and humans has a greater density of ganglion cells than the inferior hemiretina, suggesting a bias towards processing information in the lower visual field (loVF). In primates, this over-representation of the loVF is also evident at the level of striate and extrastriate cortex. This is particularly true in some of the visual areas constituting the dorsal “action” pathway, such as area V6A. Here we show that visually guided pointing movements with the hand are both faster and more accurate when performed in the loVF when compared to the same movements made in the upper visual field (upVF)." (Danckert & Goodale, Superior performance for visually guided pointing in the lower visual field, Experimental Brain Research, 137, 303-308 (2001) .) The use of motor movements as part of the targeting process (such as head rotation) tends to bias the preferences towards the allocentric frame. (Wexler, Voluntary head movement and allocentric perception of space, Psychological Science Volume 14 Issue 4 Page 340 (July 2003).)
Egocentric signal processing is further subdivided into body-centric, head-centric, and eye-centric frames of reference (e.g., Hillis et al., Stereo slant perception is more precise in an oculocentric task than in a headcentric task, Investigative Ophthalmology and Vision Science, 39(4) supplement (1998).) For example, head rotation generates an "optic flow" that is processed in a head-centric frame. This "visual motion" of the scene is processed in the middle temporal (MT) and medial superior temporal (MST) areas, where object motion relative to the body is typically processed, including smooth pursuit following of targets in motion with the gaze. In humans, the MT is probably mostly about motion elements, whereas the MST (or a part of the MT similar to that found in the MST in animals) is chiefly concerned with patterns of motion. (Goossens et al., Representation of Head-Centric Flow in the Human Motion Complex, Journal of Neuroscience, May 24, 2006, 26(21):5616-5627; PDF) (View experimental displays as Quicktime movies: consistent, fixation, opponent.) (See also Dukelow, Sean P., Joseph F. X. DeSouza, Jody C. Culham, Albert V. van den Berg, Ravi S. Menon, and Tutis Vilis. Distinguishing subregions of the human MT1 complex using visual fields and pursuit eye movements. J Neurophysiol 86: 1991-2000, 2001.)
When the eyeballs move in a pursuit pattern independently of head rotation, the brain is forced to estimate retinal image changes in comparison to extraretinal signals about eyeball movement relative to the head in order to sort out the real motion of the object being followed. (Freeman & Banks, Perceived head-centric speed is affected by both extra-retinal and retinal errors, Vision Res. 1998, vol. 38, no.7, pp. 941-945.)
When the head is tilted in gravity prior to rotation, the eye movements during head rotation are modulated by the cerebellum's balance system and the VOR. (Sheliga et al., Control of Spatial Orientation of the Angular Vestibulo-Ocular Reflex by the Nodulus and Uvula of the Vestibulocerebellum, Annals of the New York Academy of Sciences 871:94-122 (1999). ("Eye velocity produced by the angular vestibulo-ocular reflex (aVOR) tends to align with the summed vector of gravity and other linear accelerations [gravito-inertial acceleration (GIA)]. Defined as "spatial orientation of the aVOR," we propose that it is controlled by the nodulus and uvula of the vestibulocerebellum".)
In addition, there is evidence that somatotopic representations extend to include the shape and "business end" of handheld tools, as well, incorporating the end of the tool into body representations and somatosensory signals. (Yamamoto et al., Referral of Tactile Sensation to the Tips of L-Shaped Sticks, J Neurophysiol 93:2856-2863, 2005; see generally Paillard J. The hand and the tool: the functional architecture of human technical skills. In: The Use of Tools by Human and Non-Human Primates, edited by Berthelet A and Chavaillon J. New York: Oxford, 1993, p. 36–46.)
The integration of the different frames of reference occurs in the posterior parietal lobe, where sensory inputs in the different frames are combined with motor planning for action, and this process is regulated to some extent by attention and intentionality as well. (Andersen et al., Multimodal representation of space in the posterior parietal cortex and its use in planning movements, Annual Review of Neuroscience, March 1997, Vol. 20, Pages 303-330. ("Sensory signals from many modalities, as well as efference copy signals from motor structures, converge in the posterior parietal cortex in order to code the spatial locations of goals for movement. These signals are combined using a specific gain mechanism that enables the different coordinate frames of the various input signals to be combined into common, distributed spatial representations. These distributed representations can be used to convert the sensory locations of stimuli into the appropriate motor coordinates required for making directed movements.")
A third major characteristic of brain processes to take into consideration is the habit of the brain to treat all problems with the least effort. The Eli Brenner Lab puts the matter thusly:
"My group's research is concentrated on examining how visual information is used to guide our everyday actions. Beside this we study various basic aspects of vision (3D localisation, 3D shape perception, motion perception, colour vision), with a special emphasis on interactions between retinal and extra-retinal information. Our most recent psychophysical studies support the notion that different perceptual attributes are processed separately, and show that potentially useful combinations of sources of information are not made. The explanation for these missed opportunities is that the brain is more interested in getting a reliable estimate quickly, than in getting the best possible estimate. For perceptual judgements under laboratory conditions this may seem strange, but when we consider the conditions in which we have to make perceptual judgements in everyday life it is less strange. For our dynamic interactions with objects it is clearly not only important to make reliable judgements, but also to do so quickly. We found that subjects ignore potentially useful information if it takes too long to acquire. They also avoid combining different kinds of information whenever possible. Consequently they seem to plan different aspects of a movement, such as the speed and direction of a hitting movement, completely independently. This can result in quite complicated use of visual information to control actions, because errors in one aspect of motor control may compensate for unrelated errors in another." ( Eli Brenner Lab.)
To answer the primary question with respect to targeting from the address position, we first have to realize that "identification" of the target (a spot of grass or the hole in the green) or of the task (putt the ball into the hole) is not really part of the problem. So what is? The problem is to use a gaze pattern that effectively informs the body about the relationship of the body in its position and postures to the intended target for purposes of rolling a ball across the surface with the putter so that the ball successfully enters and stays inside the hole. There is the spatial awareness of HERE (body, putter, ball) and THERE (hole) and the IN-BETWEEN of the surface, plus the ACTION of the stroke with a start-line for direction and an impact velocity of putterhead thru ball for distance.
A. Check Aim of Putter Face. This is NOT to say that the purpose of the gaze pattern is to "locate" the target or to "find" the relationship between the body and the target. From beside the ball, the golfer should not attempt to adjust the aim of the putter face until he is satisfied that the putter face aims "straight at" the target. Instead, this aiming function is based upon perceptions of the connection between ball and target built up with targeting from behind the ball, followed by walking up to the ball and aiming the putter face thru the ball at the target, based upon these "behind the ball" perceptions. (The particulars of target selection and behind-the-ball perceiving of the line from ball to target and the aiming of the putter face through the ball down this line at the target are separate issues, unrelated to the beside-the-ball gaze pattern.) Once beside the ball, the putter face is already "aimed at" the target down the perceived line between ball and target. At this point, the purpose of the gaze pattern is to "ascertain where exactly the aiming of the putter face has ended up," or "to confirm or deny with this secondary targeting process whether in fact the putter face aims at the target as supposed."
B. Teach the Body about the Action. In addition to checking the aim of the putter face to insure that the face is actually aimed down the intended line, a second and complementary purpose of the gaze pattern from beside the ball is to "experience the space" between ball and target and to "preview and rehearse the action of the stroke." Building up a sense of the relationship of the body and the target across the surface for the forthcoming putt is served by "gazing" (directing the line of sight with a gaze and a head rotation) down the line of the intended putt. This gaze pattern has a well-defined extensiveness in space, and deliberately familiarizing oneself with this space with the forthcoming putt in mind in a manner that mimics the action of a successful putt facilitates the integration of sensory spatial mapping with motor planning. In fact, the motoric aspects of the gaze pattern sharpen up the awareness of the spatial relations between body, tool, ball, surface, and target.
What sort of gaze pattern best serves the purposes in this situation?
When the HERE is beside the ball, with the target down a line that extends sideways out of the setup, the controlling geometry of the head-eyes relationship determines the brain's information. Lack of understanding the geometery of the head-neck-eyes relationship has been a constant in golf instruction since the beginning.
The essential mistake of almost all golfers is making the attempt to build a perception of the relationship between the aim of the putter face and the target from beside the ball. The flaws in typical aiming movements beside the ball make this attempt extremely problematic, as is shown by the steady stream of studies to the effect that very few golfers aim the putter inside the 4.25-inch hole from as close as ten feet, and no golfer who is misaiming his putter habitually is aware of the flawed aiming. Fundamentally, the "usual" gaze patterns employed by golfers are ill-suited to building veridical target location perceptions or to building a linear relationship between the ball and the target with the putter face aim.
Typically, the golfer moves BOTH the head and the eyeballs to direct his gaze to the target, in the quick and dirty "good enough for government work" habit. This pattern is simply: starting from gazing down at the ball below the face with the gaze aimed not straight out of the plane of the face but somewhat down the nose, the golfer gets the face sort of aimed towards the target generally with any old head motion and then once the target comes into the broad view, he directs the eyeballs to the target with a saccadic shift. Tracking the body parts separately (right-handed golfer putting to his left on a 10-foot straight putt with the hole as the target): 1. the neck swings the top of the head to the inside, left, as 2. the head and face rotate to aim the nose targetward, and this neck swing and head rotation plus the gaze angled down the face curl the end-points of the line of vision successively along a curve to the inside of the intended line of the putt, with the gaze aimed approximately 4-5 feet down the line at a spot on the surface inside the line perhaps 8 inches or so, and 3. after the face has rotated about halfway along to the target so that the image of the target is now available in the periphery of the visual field, the eyeballs complete the complex movement with a saccadic gaze shift from the spot just inside the line up and over and farther along to the target guided by the peripheral image of the hole.
Over time, with experience of the frustrations of poor targeting information generated by this pattern, many golfer adapt to use a straight head-eye movement from ball at feet to target. This is especially evident when the hole-as-target is within the peripheral field of view when gazing down at the ball before any movement to look at the target. This situation encourages a saccadic look from ball straight at target without independent head motion. Another adaptation involves cocking the line of the neck backwards away from the target, once the sight is noticed (subconsciously) not to be headed towards the target, to force the off-curving line of sight back onto a trajectory towards the target.
These "quick and dirty" combinations have a number of deleterious effects on the accuracy of the build-up of the body's sense of target location. Typically, without attempting to be too precise, the axis of head rotation up through the neck out the top of the head swings about 10 degrees left, the face rolls to redirect the aim of the face about 30 degrees targetward, and then the eyes shift another 10-20 degrees or so targetward to "sight" the hole. If the gaze begins "straight out of the face" when looking down at the ball so the principal visual direction is aligned in the sagittal plane, even if angled up or down in this sagittal plane, the final gaze looking at the hole has shifted to aim left out of the sagittal plane and into the lower quadrant. This gaze shift from ball-as-target to hole-as-target alters the retinal location of the "target" from centered on the back of the eyeball to some retinal location on the back of the eyeball to the right of center.
The brain is being asked to track precisely the angle and orientation of extraocular muscles as they aim the eyeball, to learn this specific combination of neck move, head rotation, and eyeball shift, to learn the "look" out of the skull of the final positioning of the retinal image in relation to the shape of the skull and face as seen separately by each eye, and to disentagle and prioritize different systems of aiming the body and its forthcoming action (allocentric targeting, head-centric targeting, ego-centric targeting, and tool-centric targeting). And none of this happens in the same way for an 11-foot putt, as the amplitudes of the three movements vary with the length of the putt, and the ratios of the movements to one another are not especially stable and repeating either. This is probably the main reason for golfers to abandon this sort of targeting in favor of the so-called "million dollar look" made famous by Ben Crenshaw's excellent putting.
When the purpose of the gaze pattern besidce the ball is to assess the accuracy of the putter face as aimed based upon behind-the-ball perceptions of the line from ball to target, a simple, straight-forward head turn with a fixed, straight-out gaze runs the line of sight in a straight line along the ground perpendicular to the axis of rotation of the neck line. By setting the line of the throat to match the orientation of the putter face (as shown by its top edge), this simple gaze pattern then 1) drives the line of sight down a straight line on the ground, and 2) this line is the same line as the aim of the putter face. Whether this aim of the putter face is the same as the actual line between the ball and the target is what the golfer is assessing with the gaze pattern.
This much simpler targeting behavior consists in rotating the head about a fixed axis of rotation (no swinging of the neck) while keeping the gaze aimed perpendicularly out of the face along the sagittal plane of the head. This gaze pattern eliminates two out of the three variables (eyeball movement and trunk/neck movement), eliminates the complex pathway that visual attention is forced to follow across the surface, and simplifies the brain's tracking of information from disparate sources immensely. With this pattern, the head rotation, starting with a gaze straight out of the face vertically down at a horizontal and flat surface, will deliver successive end-points of the line of vision in a perfectly straight line along this flat surface. The orientation of the line along the surface will be perpendicular to the axis of rotation of the head (in the neck line). The axis of rotation does not have to be oriented parallel to the surface, but may be tilted up out of parallel, and the head rotation will still deliver the end-point of the line of sight along a straight line perpendicular to the neck line / axis of rotation, albeit offset further out on the surface from the eyes and head. If the orientation of the gaze is "normal" to the surface, as in a gaze directed vertically down into a horizontal surface, then the line of end-points of vision generated by the head turn will lie directly beneath the eyes and proceed perpendicularly to the axis of head rotation (the neck).
This sort of gaze requires no variation in the targeting movements based on the length of the target distance except for the amplitude of the head rotation. This in turn makes for a one-to-one association of head-turn angle (as sensed in the neck proprioceptors) with distance along the line on the ground to the end-point of vision, that depends solely upon the height of the eyes at address (itself a fixed variable unique to each golfer).
What separates the "quick and dirty" gaze patterns from the straight-forward and uncomplicated gaze pattern is 1. the gaze being directed perpendicularly out of the face, and 2. the rotation of the head around an axis that itself does not swing about. With these two characteristics in the movement, the usefulness of saccadic eye movements is eliminated, as is the variability of the curling pathways of the line of vision on the surface.
The "amateur" gaze pattern in its variants generates targeting information that is unreliable, variable, and ill-suited to building up a verdicial spatial awareness of target location. In contrast, the "master" gaze pattern avoids complicating the information and builds up a simple, reliable, veridical awareness of target location with attendant features of the process that further enhance spatial awareness and motor planning.
A. What's Ineffective about the "Amateur" Gaze Pattern. In the typical "amateur" gaze pattern, the eye sight about halfway to the target on a 10-foot putt is aimed off the line to the inside and the neck line is cocked to the inside perhaps 10 degrees. The eyeball motion has proceeded from alignment centered sagittally to shifting into the lower-left quadrant of the visual field. From this stage of the targeting process, the body-centered frame of reference is re-aligned by the neck swing to the left of the real target, and the vision is not correcting the misinformation. Thereafter, when the eyeballs shift saccadically from inside the line to the target on the line, the fixation gaze swings from the lower left quadrant to the upper left quadrant. This saccadic shift does little to override the body misalignment. The typical, unadapted gaze pattern generates a biasing of target localization to the inside (left), as this is where the face and head aims and where the neck swing aims the alignment of the shoulders and upper torso. Everything important except the gaze direction signals a target location left of the veridical location.
Over time, aiming left and missing left (poor aiming but straight stroking based upon body alignment) teaches the golfer to adapt with a "push stroke." The aims stays flawed and the stroke becomes flawed to compensate.
In the "saccades only" adaptation, with a combined head and eye movement proceeding from ball directly to target, the targeting process works differently depending on whether the target is visible in the periphery at the start of the movement. When the target is visible, the dorsal system takes the predominant control and generates the movement fairly accurately by direct visuomotor processes. However, there is another problem when the target is within the peripheral visual field: the target is visually too large and complex. Given human visual accuity and a standard putting setup, the hole is within peripheral vision when located within 8-10 feet sideways from the golfer's eyes. At this distance, the 4.25-inch hole presents a complex array of possible fixation points that is on the order of 50-100 targets from seide to side, and the overall shape is "oval" with a curved front and a curved back with a dark core in between. The visually-guided saccade, in this situation, typically tends to direct the gaze into the "center of gravity" of this complex array, which is the dark center, also the largest feature. Saccade movements to a dark region or to a complex array of possible targets are not particularly accurate and consistent. And in putting, for a 6-foot putt with the usual modest break, targeting the center of the front of the cup or hole is probably not good enough.
When the target is not visible at the start of the targeting movement from ball to target, the saccadic movement is memory driven and span a considerable distance -- two factors not calculated to encourage accuracy in the build-up of a sense of target location. And only golfers who use a consistent manner of turning the head are likely to adapt to the inherent peculiarities of this gaze pattern.
In the case of the neck line cocking rearwards to redirect the line of sight back up and out to the target line, the targeting movement ensemble results in the body cues being mis-aligned to the outside of the veridical target location. The neck misaims the shoulder frame to the outside (right) of the target. Because the gaze was directed down the face to begin with (instead of perpendicularly straight out of the face), and the head-neck motion swinging rearwards was taken to correct for this flawed geometry, the gaze at the end of the targeting movement is directed either in the same downward-left direction or is directed more upward and left but not sufficiently so that the gaze is centered vertically out of the orbit. The retinal imagining of the target starts in the lower half of the field of vision instead of centered vertically, and ends up still in the lower half even if closer to the vertical midline.
Over time, aiming right and missing right (poor aiming with a straight stroke based upon body alignment) teaches the golfer to adapt a "pull stroke." The aim stays flawed and now the stroke becomes flawed to compensate for poor aim.
Because the "push" or "pull" action requires different putter paths across the real line of the putt depending upon the distance of the target, golfers implicitly learn that either the path has to change with different length putts or the face angle has to change at impact or a combination of the two. For right-aiming golfers, this engenders a "pull-cut" stroke. For the left-aiming golfers, this engenders experimentation with ball position and back-and-thru strokes on an inside-to-out "push" path.
In sum, poor gaze patterns engender poor stroke patterns, whereas the simple geometry of an "orthogonal" gaze pattern leaves a straight-stroke dynamic undisturbed and effective in rolling the ball where the golfer expects it to go. probably as many as 90 percent of all golfers, pro and amateur alike, have adapted to poor aiming skills with a flawed stroke.
B. What's Effective about the "Master" Gaze Pattern.
i). Build-up of Spatial Awareness. A saccadic-dependent gaze pattern that is memory-driven "spends targeting capital" in comparison to a gaze pattern that "compiles targeting capital." A straight-out gaze with a fixed-axis head rotation is a pattern that sends the end-point of vision in a straight line along the surface, and not one that "seeks" a target based upon sensory mapping of the external world. In this "assessment of aim" process, the gaze pattern adds to the store of brain awareness of putter aim, line along ground, target location, and distance to target.
ii). Motoric Previewing of Action. In addition, the motoric targeting process of "rolling the head" a definite angle corresponding to a distance, and "running the sight" linearly along the full length of the surface between ball and target, and "feeling" the plane of the head turn in the relationship between the turning head and the stationary shoulder frame and upper trunk as mediated at the base of the neck in neck proprioceptors, perhaps combined with visually imagining the realtime roll of a perfectly putted ball along the line, and imaging the stroke movement in plane that will roll the ball with appropriate line and speed, are all positive contributions to the egocentric and allocentric mapping of the relationship of the body to the target for purposes of the stroke. The head turn in time registers in the proprioceptors of the neck as a movement from facing straight vertically down to facing off to the left a very specific angle, as an orientation in space of the base of the neck as a plane mediating the rotating head and the stationary shoulder frame, and as a pacing of the head turn. The pacing of the head turn can be chosen to mimmick the pacing that the head turn would exhibit if the golfer were in fact watching a perfectly putted ball roll along the line of the putt in its realtime velocity pattern (starting fast, smoothly slowing along the course of travel, and then coming to a full stop at the end of the line). This technique adds a temporal-motoric component to the gaze pattern that combines with the same brain processes engaged by visuo-kinetic "mental practice." The result is both sharper perceptions of the spatial relations and a more astute motor planning for the appropriate stroke that accomplishes the intent. The planned stroke path will parallel the shoulder alignment (at least through impact) as revealed by the head turn on the "plate" of the neck having the same orientation in space and the motion of the shoulder frame in the forthcoming stroke will have a strong association with the neck turn's amplitude and pacing.
iii). Orthogonal Optic Flow. Another aspect to this gaze pattern is the "optic flow" pattern of the background surface as the head rotation carries the vision linearly across the surface. The gaze pattern is similar to a smooth pursuit movement of the head with gaze direction unchanging, and is thus similar to what would eventuate if the golfer actually watched a perfectly putted ball roll straight along the target line with realtime velocity changes by turning his head as the ball rolled further along, but there is a significant difference. The intent is not to vividly "see in the mind's eye" a movie of a ball rolling straight along the line, but to "glide" vision in an unengaged manner, without intermittent fixations of focus and attention and saccadic jumps from fixation to fixation at a new location. The quarry is to experience the right sort of "optic flow" in a smooth manner. If one compares the "optic flow" of the background during an "amateur" gaze pattern from ball to target with that of the straight-out gaze and fixed-axis head turn, the differences become readily apparent.
In an "amateur" gaze pattern, the backsground "optic flow" shifts mostly diagonally across the retinal fields, as the gaze traces an inside-curving trajectory. If the background were conceived of as a set of evenly spaced dots in a rectilinear grid pattern matching the up-down and left-right orientation of vision at the beginning, this grid would start with the visual field of the left eye and the visual field of the right eye both aligned laterally with one row of dots, with the "ball" dot being centered with the fixation point and the "target" dot being left along this same row of dots. Imagining the head and gaze held still while this background scene is shifted sideways beneath the face, to indicate the swinging left of the neck line and the down-the-face gaze that the head rotation sends curling off to the inside of the line by a succession of fixation points on the grid, the whole grid appears to "skew" up and to the right while shifting to the right laterally. The end result is a fixation that arrives inside and off the line about halfway along laterally to the target several dot rows low, and the "optic flow" that was experienced in this gaze pattern thus far is neither headed towards the target nor reliably indicating a pathway to the target. It is only the chance appearance of the target on the line up and to the left of fixation that rescues the badly-developing targeting with a (now possible) visually-guided saccade that corrects the problem. The "optic flow" that corresponds to this corrective saccadic jump is largely "masked" by the saccadic process that conceals abrupt visual shifts and discontinuities from conscious awareness.
In contrast, the "master" gaze pattern generates an "optic flow" that shifts the grid ONLY linearly across the anatomically aligned eye sockets in the skull. The left eye's field of vision shifts laterally along the same row of dots as the initial alignment, and the right eye's field of vision does likewise. Because the brain is constantly comparing the views of the left and right eyes, the brain "instinctively" knows when the "optic flow" is shifting linearly as opposed to a "skewing" action. In fact, it is this "skewing" of the "optic flow" that most typically gives the golfer disease about the accuracy of his appreciation of target location when "gazing" targetward from beside the ball. Uniformly, golfers instinctively feel a need to eliminate this "skewing" of the "optic flow," or at least to ignore it. And when the golfer becomes sensible to whether the "optic flow" is skewing or proceeding in a rectilinear shifting only laterally with the skull alignment, then the golfer is able to use this sense of "skewing" or "non-skewing" to check and monitor the on-going straightness of his gaze pattern from ball to target.
iv). Target Occupies the Aim Spot of the Gaze the Same as Did the Ball. With the "master" gaze pattern, the ball at the beginning of the head turn occupies one and only one spot in the visual field -- the spot transected by the line of sight of a straight-out aiming eyeball. There is only one such spot, called here for convenience the "aim spot" of the visual field.
At the end of a fixed-axis head turn with a straight-out gaze, when the head turn has driven the line of sight the approriate distance along the surface to the target, WHATEVER location in the real world occupies this "aim spot" is in fact where the putter face is aimed. Of course, the golfer hopes that he has aimed the putter face correctly at the target, but this "checking" procedure will reveal whether in fact he has done as hoped, or has aimed his putter face slightly to the left or right of the intended target. If the target appears at the end of the head turn in the "aim spot," the golfer has a check that verifies his aiming of the putter face and he is ready to putt straight. If some other location on the ground left or right of the target at the target distance occupies the "aim spot", then the golfer has good reason to revisit the aiming of the putter face, as there is now a strong indication of inaccuracy. Knowing the "aim spot" with this degree of certainty and knowing its importance is what allows good instinctive targeting to take place.
Moreover, the fact that the target and the ball are BOTH relying upon the same eyeball-in-head arrangement that corresponds to this "aim spot", and this arrangement is by far the most used and common and familiar arrangement in contrast to the shifting head-eye arrangement in the "amateur" gaze pattern, the chances of using this pattern repetitively in a consistent manner are much greater than the other patterns and the resonant signalling about what location the putter face actually aims at is clearer and stronger and more potent than otherwise. And finally, there is an after-image effect on the retina from looking steadily at a white ball on a green background that is independently useful when turning to the target, as the real location aimed at by the putter shows up in this after-image so long as the gaze direction does not shift during the head turn.
v). Part-for-Whole Representation of Line to Target. A not-insignificant benefit of the "master" gaze pattern is that the putter face itself becomes incorporated into the somatosensory appreciation of body aligned in space at target for the action of the putt. And the putter face as the business end of the handheld tool in its aiming is joined not only with the line at the target, but also with the actual surface in between ball and target. The flatly-soled putter head macthes the plane of the surface; the directional aim of the putter face indicates the very grass blades that the ball in a straight putt will in fact traverse; the target is "known" to be located where the putter face is pointing; the stroke will move the putter face squarely down this line above these very grass blades in the direction of the target. All this allows the conscious mind to regard the putter face itself as the primary focus of the action of the putt. When the targeting process includes distance awareness, as it does, the putter face itself "stands for" the entire forthcoming action of making a straight stroke that rolls the ball the correct pace and distance. The usual "visual wondering" about where the target is located and whether the putter is in fact aimed at the target and whether in fact the planned stroke will be the stroke that rolls the ball at the target is diminished nearly to extinction, allowing the golfer simply to make a beautiful stroke instinctively. In other words, the "master" gaze pattern more naturally and extensively facilitates "binding" disparate perceptions into a functioning whole for action than the "quick and dirty" patterns.
A straight gaze is an aim of the eyeballs straight or perpendicularly out of the plane of the face SO THAT:
i). The rotation of the head about the axis of middle of neck through top of head does not curl the line of sight out of a straight line to the inside.
ii). Only because the gaze is straight out of the plane of the face will a fixed-axis head rotation run the line of sight in a straight line along the ground, this line being perpendicular to the axis of head rotation.
iii). The line of sight of each eye "pierces" that eye's "field of vision" (the egg-shape scene seen by one eye only) in only one exact spot that is about 1" in sideways from the bridge of the nose, and every straight-out gaze always looks "through" this precise point in the visual field (the "aim spot").
iv). A straight-out gaze aligns the pupils with the line across the skull formed by connecting the tops of the ears, the temples, the outside corners of the eye sockets, the inside corners of the eye sockets, and the bridge of the nose in usual anatomical features of the skull.
v). A straight-out gaze aims the face at the ball, and the eyeballs simply look where the face is aimed.
vi). A straight-out gaze aims the eyeballs along the same line that the side pieces on a pair of glasses aim out of the face.
vii). The nose partially blocks the rear eye's field of view of the target side, always in the same extent and visual manner based upon the shape and size and orientation of the golfer's nose with respect to the ball and the line.
viii). A straight-out gaze combines with the sense of balance and uprightness in gravity when standing erect to align the left-right line across the pupils and features of the skull with the flat horizon of an ocean or level desert, with the distant horizon line apparently at the same vertical height as the line across the pupils.
ix). A straight-out gaze need NOT meet the surface of the ground perpendicularly, as this depends upon whether the head is tilted up out of parallel to the surface and upon whether the surface beneath the feet has the same tilt in gravity as the location of the ball where the gaze fixates on the surface.
x). When a straight-out gaze on a flat and uniformly tilted surface that is the same beneath the feet and the ball meets the surface perpendicularly, the head's axis of rotation and the coronal plane of the face are both parallel to the plane of the surface.
xi). Merely positioning the eyeballs above the ball vertically in gravity or even perpendicularly to the surface does not by itself vouchsafe that the gaze will thereby be "straight-out", as this will require that the axis of rotation of the head also parallel the surface.
(Golfer's face does not aim at ball, even though eyeballs are vertically above ball, with result that "gaze" is necessarily directed below the straight-out direction, resulting in targeting perceptual problems.)
xii). When the head's axis of rotation does not parallel the surface, but is instead tilted forehead up out of parallel, combined with the eyeballs being positioned directly above the ball, the gaze cannot possibly be straight-out.
xiii). When the head's axis of rotation does not parallel the surface, but is instead tilted forehead up out of parallel, the gaze MAY still be straight-out but the angle of inclination of the head will compel that the ball be further out from the stance than directly beneath the eyeballs.
When the face aims perpendicularly into the surface at the ball, the
straight-out gaze meets the left-right line through the ball in a
manner similar to standing before a vertical wall with a level left-right
line painted on the wall at the same height as the pupils.
xv). When the head's axis of rotation does not parallel the surface, but is instead tilted forehead up out of parallel, the face aims into the surface at the ball on a tilt out of perpendicular, meets the left-right line through the ball in a manner similar to standing before a wall with a level left-right line painted on the wall at the same height as the pupils but with the wall tilted top-away from the face to match the angle of the head tilt.
A straight-out gaze is simple physical geometry in the relationship between the eyeballs, the skull and face, and the neck or axis of rotation of the head in relation to the surface and the ball. But this simple geometry, when disregarded, generates problematic targeting movements that degrade targeting perceptions and ultimately stroke movements. Habitual or so-called "natural" targeting movements are "quick and dirty" and not efficacious. A gaze pattern that works with innate, instinctive perceptual processes to generate veridical awareness of target location starts with setting the gaze straight out of the plane of the face an head.
A fixed-axis head rotation combined with a straight-out gaze is required to send the line of sight in a straight line sideways along the surface. A fixed-axis head rotation is contrasted to a rotation about a moving or shifting axis. A fixed-axis head rotation:
i). Begins and finishes with both ends of the axis in the same position in space, without shifting either the near end (center of base of neck) or the far end (top or crown of skull) at any time during the rotation.
A fixed-axis head rotation with a straight-out gaze will run the line of sight in a straight line along the surface, but the setting up of the head and neck to the putter face as aimed is what makes this line on the ground the SAME as the aim of the putter face. Only when the setup aligns the head and gaze correctly to the putter face is it possible to use a gaze pattern that reliably checks the aim of the putter face. A setup to match the line of sight along the ground to the aim of the putter face:
i). Matches the axis of rotation of the head to the leading edge of the putter face by aligning the axis parallel to if not also in the plane of the vertical plane of the face of the putter.
ii). Does not necesarily position the axis of rotation directly in plane with the vertical face of the putter, so long as the axis parallels the plane of the putter face.
iii). Does not necessarily position the throat line directly above the leading edge of the putter face.
As a bonus, so long as the line of the throat and neck extends perpendicularly out of the shoulder frame, the setting of the throat line to the putter face will necessarily set the alignment of the shoulders parallel to the aim of the putter face as well.
For Illustrative Examples of the Good, the Bad, and the Ugly for Putting Setups, see Page 2.