The superior colliculus is recognized as a key structure in the initiation of orientation responses of the eyes and head to visual, auditory and somatosensory cues. It is in the deep layers of the superior colliculus that these sensory inputs converge. Also present in the deep layers are efferent neurons which project to areas of brainstem and spinal cord, and thus influence orientation of the eyes and head. These deep collicular neurons are pivotal in sensorimotor transformations and have direct access to the motoneuron pool for orienting. Their response is directly dependent upon the number, type, distribution and location of synaptic inputs upon them. Deep collicular neurons are strongly influenced by the basal ganglia. It is well established that the basal ganglia are involved in the initiation of movement, and diseases which directly affect the basal ganglia also cause eye and head movement-related disorders. The basal ganglia, in particular the substantia nigra, appear to exert a tonic inhibitory influence upon cells in the deep superior colliculus. This project directly addresses the anatomical basis for the integrative properties of large efferent cells in the deep collicular layers which are involved in the control of head and eye movements. Using combined autoradiographic, horseradish peroxidase and immunocytochemical techniques for light and electron microscopy, it is hoped to show precisely how inputs from substantia nigra teminate upon deep collicular neurons, and to establish that their inhibitory effect is mediated by the neurotransmitter gamma aminobutyric acid (GABA). It is also proposed to identify other sources of inhibitory input on large efferent collicular neurons involved in orientation.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY004478-05
Application #
3258922
Study Section
Visual Sciences B Study Section (VISB)
Project Start
1982-05-01
Project End
1988-11-30
Budget Start
1986-12-01
Budget End
1987-11-30
Support Year
5
Fiscal Year
1987
Total Cost
Indirect Cost
Name
University of Wisconsin Madison
Department
Type
Schools of Veterinary Medicine
DUNS #
161202122
City
Madison
State
WI
Country
United States
Zip Code
53715
Behan, M; Kime, N M (1996) Spatial distribution of tectotectal connections in the cat. Prog Brain Res 112:131-42
Behan, M; Kime, N M (1996) Intrinsic circuitry in the deep layers of the cat superior colliculus. Vis Neurosci 13:1031-42
Plummer, K L; Behan, M (1993) Development of corticotectal synaptic terminals in the cat: a quantitative electron microscopic analysis. J Comp Neurol 338:458-74
Behan, M; Appell, P P; Kime, N (1993) Postnatal development of substance-P immunoreactivity in the rat superior colliculus. Vis Neurosci 10:1121-7
Plummer, K L; Behan, M (1992) Postnatal development of the corticotectal projection in cats. J Comp Neurol 315:178-99
Behan, M; Jourdain, A; Bray, G M (1992) Calcium binding protein (calbindin D28k) immunoreactivity in the hamster superior colliculus: ultrastructure and lack of co-localization with GABA. Exp Brain Res 89:115-24
Appell, P P; Behan, M (1990) Sources of subcortical GABAergic projections to the superior colliculus in the cat. J Comp Neurol 302:143-58
Weber, A J; Kalil, R E; Behan, M (1989) Synaptic connections between corticogeniculate axons and interneurons in the dorsal lateral geniculate nucleus of the cat. J Comp Neurol 289:156-64
Behan, M; Appell, P P; Graper, M J (1988) Ultrastructural study of large efferent neurons in the superior colliculus of the cat after retrograde labeling with horseradish peroxidase. J Comp Neurol 270:171-84
Behan, M; Lin, C S; Hall, W C (1987) The nigrotectal projection in the cat: an electron microscope autoradiographic study. Neuroscience 21:529-39

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