Perceptual Correlates of Neuronal Synchronization in a Network of Realistic Cortical Cells with Long-Range Horizontal Connections
Shih-Cheng Yen1 , Elliot D. Menschik2 , John Nafziger2 and Leif H. Finkel1,2
1Department of
Bioengineering
2Institute of
Neurological Sciences
3320 Smith Walk, 301 Hayden
Hall
University of Pennsylvania
Philadelphia, PA 19104, U.
S. A.
Abstract
We show results of a model in which long-range horizontal connections mediate the perceptual salience of contours (Gilbert, 1992, Neuron 9:1-20) based on temporal synchronization of cell activity. The model consists of oriented simple cells, with co-axial and trans-axial facilitatory connections. Inhibitory connections modulate facilitatory effects based on the density of stimuli in the surround. Strongly facilitated cells enter a "bursting" mode in which cells can synchronize with other bursting cells. The sum of synchronized activity represents the perceptual salience of a contour. Realistic multi-compartment pyramidal cells and interneurons were used to model bursting cells. Cells in each orientation column were represented by a group of eight pyramidal cells and eight interneurons (adapted from Traub et al., 1996, Nature 383:621-4). Horizontal connections were represented by connections between neighboring groups. The peak conductance of the inter-group connections was modulated to reflect the strength of the horizontal connections.
Interneuron-based synchronization leads to global synchronization with only local connections. In addition, at the same connection strength, synchrony on a closed chain is much more robust than synchronization on an open chain. The dramatic change in perceptual salience that accompanies closure (Kov?cs and Julesz, 1993, PNAS 90:7495-7) can thus be understood as a transition to synchrony of an initially desynchronized neuronal population. The model also accounts for a number of other physiological and psychophysical results on contour salience (Kapadia et al., 1995, Neuron 15:843-56; Polat and Sagi, 1994,Vis Res 34:73-8; Field et al., 1995, Vis Res 33:173-93; Kov?cs et al., 1996, ARVO 37:3078; Pettet et al., 1996, ARVO 37:4368).
Supported by ONR N00014-93-1-0242,
NSF, and The Whitaker Foundation