The pattern of afferent and efferent connections of the superior colliculus suggests that this area of the brain is involved in sensory-motor integration. In particular, the colliculus is involved in the integration of visual, auditory and somatosensory information, and the subsequent generation of eye and head movements. Despite the accumulated evidence for this role, surprisingly little is known about the intrinsic organization of the superior colliculus. Thus there is a special need for anatomical studies to identify the precise morphology of local circuits in the colliculus. Without this knowledge it is almost impossible to begin to construct a model of how the colliculus is involved in the control of orienting movements. Up to this time it has been almost impossible to analyze the intrinsic organization of the colliculus due to the technical limitations of the techniques available. Recently, a new anterograde anatomical tracer has been discovered: Phaseolus vulgaris-leucoagglutinin (PHA-L). This plant lectin is non-cytotoxic, does not appear to be taken up by axons of passage, and is compatible with light and electron microscopy. Thus, for the first time it is possible to examine the intrinsic connections of neurons in the superior colliculus. Our preliminary studies with PHA-L show axonal arborizations throughout the colliculus following very restricted injections in specific collicular laminae. We have also seen extensive connections between the superficial and deep layers of the colliculus, a finding that has been disputed for several decades. In the proposed experiments specific models of intrinsic circuitry will be tested to establish how functional units in the deep layers of the colliculus are organized. We will determine whether there is direct visual input to the deep layers from the overlying superficial layers, and how this visual input is organized. Finally, we will establish whether efferent neurons in the deep layers also receive direct visual input from the lateral suprasylvian visual cortex. These studies will enable us to outline a model of how sensory information is disseminated throughout the colliculus, how visual and motor maps in the colliculus are woven into functional units, and how they contribute to the generation of eye and head movements.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
2R01EY004478-07
Application #
3258919
Study Section
Visual Sciences B Study Section (VISB)
Project Start
1982-05-01
Project End
1993-11-30
Budget Start
1988-12-01
Budget End
1989-11-30
Support Year
7
Fiscal Year
1989
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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