James F. Baker
James F. Baker
We study the vestibular and visual sensory systems and the reflex motor outputs to the eyes, neck, and limbs. Our basic question is "How does the brain process sensory signals to produce appropriate coordinated motor behavior?" and our animal models range from mice and rats to primates.
Much of our research explores the vestibulo-ocular reflex, which responds to head rotations by rotating the eyes in an equal and opposite way so that the line of sight remains constant during head movement, maintaining fixation on an object. We have documented the pattern of vestibular sensory nerve fiber convergence that controls the direction of vestibulo-ocular responses, and we have studied the role of the cerebellum in processing visual signals that correct or adjust this pattern.
Our recent work examines the contribution of gravity sense to vestibular reflexes. Gravity sense both supplements and controls the vestibular reflexes elicited when the vestibular canals are stimulated by head rotation.
Another important and more complex reflex we study is the vestibular-neck reflex or vestibulocollic reflex, which serves to stabilize the head against forces that would move it. We have recorded the patterns of neck muscle electromyographic activity as this reflex coordinates the contraction of many neck muscles to produce an accurate muscular reaction that counters the forces against the head.
Brettler SC, Rude SA, Quinn KJ, Killian JE, Schweitzer EC, Baker JF. (2000) The effect of gravity on the horizontal and vertical vestibulo-ocular reflex in the rat. Exp. Brain Res.132:434-444
Baker J.F. (1999) Supraspinal descending control, the medial postural system. In: Fundamental Neuroscience. Edited by Zigmond, M.J., Bloom, F.E., Landis, S.C., Roberts, J.L., and Squire, L.R. Academic Press, New York, NY. 32: 913-930.
Perlmutter, S.I., Iwamoto, Y., Baker, J.F. and Peterson, B.W. (1999) Spatial alignment of rotational and static tilt responses of vestibulospinal neurons in the cat. J. Neurophysiol.82: 855-862.
Quinn, K.J., Rude, S.A., Brettler, S.C., and Baker J.F. (1998) Alterations in rat horizontal vestibulo-ocular reflex phase as a function of orientation in gravity. J. Gravitational Physiol. 5: 41-49.
Quinn, K.J. and Baker, J.F. (1998) Processing of spatial information by floccular and non-floccular target neurons in the alert cat. Brain Research780: 143-149.
Mason, C., Miller, L., Baker, J. and Houk, J. (1998) Organization of reaching and grasping movements in the primate cerebellar nuclei as revealed by focal muscimol inactivations. J. Neurophysiol.79: 537-554.
Quinn, K.J., Didier, A.J., Baker, J.F. and Peterson, B.W. (1998) Modeling learning in brainstem and cerebellar sites responsible for VOR plasticity. Brain Res. Bull.46: 333-346.
Quinn, K.J., Rude, S.A., Brettler, S.C., and Baker J.F. (1998) Chronic recording of the vestibulo-ocular reflex in the restrained rat using a permanently implanted scleral search coil. J. Neurosci. Methods80: 201-208.