Humans and nonhumans alike interact with the environment by orienting to objects of interest. Such responses are typically generated by integrating movements across multiple effectors. The long- term objective of the research program is to understand the coordinated eye-head movements that produce a change in the line of sight (gaze).
The specific aims are designed to delineate feedforward, feedback and interactive mechanisms that result in the coordinated control of two different groups of muscles. A gaze shift is thought to be triggered by a command encoding the desired change in gaze, and structures in the brain stem determine the eye and head components required to generate the gaze shift.
Specific Aim 1 seeks to identify where in the pontine reticular formation are the separate commands of eye and head movement control formulated. Head-restrained saccadic eye movements are controlled by an error-sensing feedback circuit that preserves its accuracy.
Specific Aim 2 will investigate how the feedback principle extrapolates to head-unrestrained gaze shifts. Does it preserve accuracy of the gaze signal or just its saccadic eye component? Specific Aim 3 will test whether head movement commands can influence the dynamics of the eye component of gaze shift.
Specific Aim 4 will revisit the gain of the vestibulo-ocular reflex during gaze shifts by evaluating the saccadic input into the extraocular motoneurons during gaze shifts. Overall, the results of these experiments will provide insights into the neural control of gaze shifts and offer diagnostic value for deficits resulting from oculomotor, vestibular and cervical disorders.

Public Health Relevance

We interact with our environment by orienting to objects of interest. A coordinated eye-head movement is a basic orienting response that shifts the line of sight, but many questions remain about the mechanisms that cooperatively control the two groups of muscles. Delineating the neural circuits that produce such integrated movements will provide diagnostic value for understanding spatial orientation deficits (vertigo) and motor control disorders (torticollis, Parkinsonism, strabismus).

National Institute of Health (NIH)
National Eye Institute (NEI)
Research Project (R01)
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Central Visual Processing Study Section (CVP)
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Araj, Houmam H
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University of Pittsburgh
Schools of Medicine
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Katnani, Husam A; Gandhi, Neeraj J (2013) Time course of motor preparation during visual search with flexible stimulus-response association. J Neurosci 33:10057-65
Katnani, Husam A; Van Opstal, A J; Gandhi, Neeraj J (2012) A test of spatial temporal decoding mechanisms in the superior colliculus. J Neurophysiol 107:2442-52
Gandhi, Neeraj J (2012) Interactions between gaze-evoked blinks and gaze shifts in monkeys. Exp Brain Res 216:321-39
Katnani, Husam A; Van Opstal, A J; Gandhi, Neeraj J (2012) Blink perturbation effects on saccades evoked by microstimulation of the superior colliculus. PLoS One 7:e51843
Katnani, Husam A; Gandhi, Neeraj J (2012) The relative impact of microstimulation parameters on movement generation. J Neurophysiol 108:528-38
Destefino, V J; Reighard, D A; Sugiyama, Y et al. (2011) Responses of neurons in the rostral ventrolateral medulla to whole body rotations: comparisons in decerebrate and conscious cats. J Appl Physiol (1985) 110:1699-707
Gandhi, Neeraj J; Katnani, Husam A (2011) Motor functions of the superior colliculus. Annu Rev Neurosci 34:205-31
Katnani, Husam A; Gandhi, Neeraj J (2011) Order of operations for decoding superior colliculus activity for saccade generation. J Neurophysiol 106:1250-9
Bechara, Bernard P; Gandhi, Neeraj J (2010) Matching the oculomotor drive during head-restrained and head-unrestrained gaze shifts in monkey. J Neurophysiol 104:811-28
Anderson, Sean R; Porrill, John; Sklavos, Sokratis et al. (2009) Dynamics of primate oculomotor plant revealed by effects of abducens microstimulation. J Neurophysiol 101:2907-23

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