|
Edward L. Keller, Ph.D.
EECS Major Research Interest:
Oculomotor and visual system neurophysiology and modeling of same systems Phone: (415) 345-2102
Email:
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
Date Available: July 1, 2000 Project Type | | Funding | | | Rotation | Yes | NIH | Yes | | Summer | Yes | Private Foundation | No | | Thesis | No | Other | NSF | Project Title: Decoding of Information from Distributed Motor Maps Abstract: Several alternative methods for decoding the desired motor command vector from neural networks containing commanding distributed, place-coded information have been suggested. The two most widely accepted candidate mechanisms are vector summation (VS) and a center of mass computation (CM). The latter mechanism has also been called vector averaging. The present project is two pronged: In the first we compare the operation of these two methods in a model of an experimentally well-studied neural structure, the primate superior colliculus (SC). The SC is one structure that has been shown to be responsible for generating saccadic command vectors in the form of distributed neural activity that is topologically arranged across its surface. It has been suggested that the pattern of eye movement errors obtained following the placement of a collicular lesion can distinguish between these two mechanisms. Following this suggestion, the pattern of saccadic errors produced by lesions in the SC have been widely cited to support the CM hypothesis. The placement of a discrete lesion is simulated in a recurrent (dynamic) neural network model of the SC. Following the simulated lesions, the pattern of saccadic errors obtained in the model appears to support the CM hypothesis, even though in our simulations ensemble activity in the model colliculus is decoded by VS. This result demonstrates that, when ensemble activity on the SC motor map is dynamically modulated over space and time by intrinsic collicular circuitry, an explicit CM computation is not needed to reproduce the pattern of physiological results that follow focal SC lesions. In the second aim we record single- and multi-unit activity in the SC of the behaving monkey to provide data from which ensemble activity in the SC during saccades can be estimated.
|
