Research Description
Studies of the organization of central visual pathways
My neuroanatomical laboratory is interested in defining the circuitry over which sensory information is integrated into motor commands within the mammalian superior colliculus (SC). A major thrust of these studies involves defining the specific laminar/sublaminar distribution of many different "patchy" inputs to the large intermediate layer of the SC (stratum griseum intermediale; SGI). These studies have shown that different combinations of afferents target different horizontal "tiers" of the SGI. Moreover, these afferents terminate on different parts (dendrites versus somas) of specific tectofugal neurons and thus have different functional effects upon the outflow signals. We are continuing to explore the organization of these sensory-motor linkages within the modular organization of the SGI using neuoanatomical (light and ultrastructural) and, in the near future, electrophysiological methods in awake preparations.
Other studies in our lab are focused upon the broad influence of the SC upon thalamostriate circuitry and in particular on visual/oculomotor-striatal function(s). Our studies have emphasized that visually related thalamostriate projections must be considered in contemporary models of basal ganglia function. Thus, basal ganglia outflow reaching the SC via strio-nigrotectal circuitry not only influences SC projections that descend to eye movement centers in the brain stem but, just as important, regulate different ascending tectothalamic pathways. The robust and direct tecto-thalamostriate projections suggests that the constraints placed upon tectal processing by striatonigral control have important consequences for central perceptuomotor processing at the striatal and cortical levels.
Recent Publications
Harting, J. K., M. F. Huerta, T. Hashikawa, J. T. Weber, and D. P. Van Lieshout 1988 Neuroanatomical studies of the nigrotectal projection in the cat. J. Comp. Neurol., 278:615-631.
Harting, J. K., and D. P. Van Lieshout 1991 Spatial relationships of axons arising from the substantia nigra, spinal trigeminal nucleus, and pedunculopontine tegmental nucleus within the intermediate gray of the cat superior colliculus. J. Comp. Neurol., 305:543-558.
Huerta, M. F., D. P. Van Lieshout, and J. K. Harting 1991 Nigrotectal projections in the primate Galago crassicaudatus. Exp. Brain Res., 87:389-401.
Harting, J. K., B. V. Updyke, and D. P. Van Lieshout 1992 Corticotectal projections in the cat: anterograde transport studies of twenty-five cortical areas. J. Comp. Neurol., 324:379-414.
Harting, J.K., Feig, S., and David P. Van Lieshout (1997) Cortical somatosensory and trigeminal inputs to the cat superior colliculus: light and electron microscopic analyses. J. Comp. Neurol. 388: 313-326.
Harting, J.K. and D. P. Van Lieshout (2000) Projections from the rostral pole of the inferior colliculus to the cat superior colliculus. Brain Res. 881: 244-247.
Harting, J.K., Updyke, BV and D. P. Van Lieshout (2001) The visual-oculomotor striatum of the cat: functional relationship to the superior collicullus. Exp. Brain Res. 136:138-142.
Harting, J.K., Updyke, BV and D. P. Van Lieshout (2001) Striatal projections from the cat visual thalamus. Eur. J. Neurosci. 14:893-896.
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