HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 96/2/765    most recent 01372.2005v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Nakahara, H. Articles by Optican, L. M. Search for Related Content PubMed PubMed Citation Articles by Nakahara, H. Articles by Optican, L. M.

Saccade-Related Spread of Activity Across Superior Colliculus May Arise From Asymmetry of Internal Connections

¹Laboratory for Mathematical Neuroscience and for Integrated Theoretical Neuroscience, RIKEN Brain Science Institute, Saitama; ²Institute of Industrial Science, University of Tokyo, Tokyo, Japan; and ³Laboratory of Sensorimotor Research, National Eye Institute, National Institutes of Health, Bethesda, Maryland

Submitted 27 December 2005; accepted in final form 24 April 2006

The superior colliculus (SC) receives a retinotopic projection of the contralateral visual field in which the representation of the central field is expanded with respect to the peripheral field. The visual projection forms a nonlinear, approximately logarithmic, map on the SC. Models of the SC commonly assume that the function defining the strength of neuronal connections within this map (the kernel) depends only on the distance between two neurons, and is thus isotropic and homogeneous. However, if the connection strength is based on the distance between two stimuli in sensory space, the kernel will be asymmetric because of the nonlinear projection onto the brain map. We show, using a model of the SC, that one consequence of these asymmetric intrinsic connections is that activity initiated at one point spreads across the map. We compare this simulated spread with the spread observed experimentally around the time of saccadic eye movements with respect to direction of spread, differing effects of local and global inhibition, and the consequences of localized inactivation on the SC map. Early studies suggested that the SC spread was caused by feedback of eye displacement during a saccade, but subsequent studies were inconsistent with this feedback hypothesis. In our new model, the spread is autonomous, resulting from intrinsic connections within the SC, and thus does not depend on eye movement feedback. Other sensory maps in the brain (e.g., visual cortex) are also nonlinear and our analysis suggests that the consequences of asymmetric connections in those areas should be considered.

This article has been cited by other articles:

				R. A. Marino, C. K. Rodgers, R. Levy, and D. P. Munoz Spatial Relationships of Visuomotor Transformations in the Superior Colliculus Map J Neurophysiol, November 1, 2008; 100(5): 2564 - 2576. [Abstract] [Full Text] [PDF]