Spatial overlap of ON and OFF subregions and its relation to response modulation ratio in macaque primary visual cortex

J Neurophysiol. 2005 Feb;93(2):919-28. doi: 10.1152/jn.00668.2004. Epub 2004 Sep 15.


We studied the spatial overlap of on and off subregions in macaque primary visual cortex and its relation to the response modulation ratio (the F1/F0 ratio). Spatial maps of on and off subregions were obtained by reverse correlation with a dynamic noise pattern of bright and dark spots. Two spatial maps, on and off, were produced by cross-correlating the spike train with the location of bright and dark spots in the stimulus respectively. Several measures were used to assess the degree of overlap between subregions. In a subset of neurons, we also computed the F1/F0 ratio in response to drifting sinusoidal gratings. Significant correlations were found among all the overlap measures and the F1/F0 ratio. Most overlap indices considered, and the F1/F0 measure, had bimodal distributions. In contrast, the distance between on and off subregions normalized by their size was unimodal. Surprisingly, a simple model that additively combines on and off subregions with spatial separations drawn from a unimodal distribution, can readily explain the data. These analyses clarify the relationship between subregion overlap and the F1/F0 ratio in macaque primary visual cortex, and a simple model provides a parsimonious explanation for the co-existence of bimodal distributions of overlap indices and a unimodal distribution of the normalized distance.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Action Potentials / physiology*
  • Animals
  • Brain Mapping / methods*
  • Macaca fascicularis
  • Photic Stimulation / methods
  • Space Perception / physiology*
  • Time Factors
  • Visual Cortex / physiology*