Many types of experiments indicate that the superior colliculus plays a key role in initiating orienting movements of the head, eyes and ears toward objects of interest. At least three classes of models of the relationship between its structure and function can be distinguished: those proposing that pathways between the layers of the superior colliculus integrate the sensory and motor systems involved in initiating orienting movements; those arguing that the layers are independent and serve mainly to distribute information to different destinations; and those proposing that connections between compartments within individual layers provide the substrate for interactions between the sensory and motor systems.
The specific aims of this application are to test these models. Because of technical limitations, past anatomical studies have provided few clues to intracollicular circuitry. Consequently, current models have been based primarily on physiological properties of collicular neurons, such as the latencies of their responses and properties of their receptive and movement fields. These models postulate specific patterns of connections, but the postulates are difficult to test with physiological methods. The proposed research will test the current models directly by intracellularly injecting cells of each layer and tracing their intracollicular connections, using living brain slices from the tree shrew, Tupaia belangeri. Relative to other commonly studied species, this primate-like mammal has an especially large and well differentiated superior colliculus, which greatly facilitates the task of analyzing the connections between the layers. In some cases, cells will be prelabeled by retrograde axonal transport so that the injected cells can be identified by the extracollicular destinations of their axons, in addition to their location, morphology and intracollicular connections. In other experiments, sensory or motor pathways to the superior colliculus will be prelabeled to determine whether they converge on collicular neurons of different types. These experiments are designed to provide a framework for new models based on knowledge of intracollicular circuitry and, in this way, will contribute to our understanding of the neural mechanisms underlying sensorimotor integration in the vertebrate brain.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY008233-12
Application #
6489792
Study Section
Visual Sciences B Study Section (VISB)
Program Officer
Oberdorfer, Michael
Project Start
1989-08-01
Project End
2002-12-31
Budget Start
2002-01-01
Budget End
2002-12-31
Support Year
12
Fiscal Year
2002
Total Cost
$366,623
Indirect Cost
Name
Duke University
Department
Biology
Type
Schools of Medicine
DUNS #
071723621
City
Durham
State
NC
Country
United States
Zip Code
27705
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Prochnow, N; Lee, P; Hall, W C et al. (2007) In vitro properties of neurons in the rat pretectal nucleus of the optic tract. J Neurophysiol 97:3574-84
Lee, Psyche; Hall, William C (2006) An in vitro study of horizontal connections in the intermediate layer of the superior colliculus. J Neurosci 26:4763-8
Helms, Matthew C; Ozen, Gulden; Hall, William C (2004) Organization of the intermediate gray layer of the superior colliculus. I. Intrinsic vertical connections. J Neurophysiol 91:1706-15
Lee, P H; Schmidt, M; Hall, W C (2001) Excitatory and inhibitory circuitry in the superficial gray layer of the superior colliculus. J Neurosci 21:8145-53
Schmidt, M; Boller, M; Ozen, G et al. (2001) Disinhibition in rat superior colliculus mediated by GABAc receptors. J Neurosci 21:691-9
Ozen, G; Augustine, G J; Hall, W C (2000) Contribution of superficial layer neurons to premotor bursts in the superior colliculus. J Neurophysiol 84:460-71
Pettit, D L; Helms, M C; Lee, P et al. (1999) Local excitatory circuits in the intermediate gray layer of the superior colliculus. J Neurophysiol 81:1424-7

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