title: Spatial overlap of ON and OFF subregions and its relation to response modulation ratio in macaque primary visual cortex.
abstract: 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.
authors.affiliation: Department of Neurobiology, David Geffen School of Medicine, Los Angeles, CA 90095-1563, USA.
authors.forename: Mario L
authors.initials: ML
authors.lastname: Mata
authors.forename: Dario L
authors.initials: DL
authors.lastname: Ringach
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D001931:Brain Mapping / Q000379:methods*; D008252:Macaca fascicularis; D010775:Photic Stimulation / Q000379:methods; D013028:Space Perception / Q000502:physiology*; D013997:Time Factors; D014793:Visual Cortex / Q000502:physiology*