SUPPLEMENTARY MATERIALS FOR Neurons in Cat V1 show significant clustering by degree of tuning (Published in Journal of Neurophysiology)

Abstract

Contents: S1. Supplementary Methods: Description of spike-merging software S2. Supplementary Results: S2.1 Analysis with spontaneous activity included S2.2 Clustering of Spontaneous Activity and Measures of Response at the Null Orientation S2.3 Outliers for differences of orientation with multiunits S2.4 Relationship between Orientation Selectivity and Direction Selectivity S2.5 F1/DC ratios S2.6 Clustering of properties according to simple/complex cell classification S2.7 Subpopulations of the between-site distributions S2.8 Using the between-site, within-animal distributions as a control S3. Supplementary Discussion: Comparison to Previous Studies of Clustering of Preferred Stimuli Abstract (from Journal of Neurophysiology paper): Neighboring neurons in cat primary visual cortex (V1) have similar preferred orientation, direction, and spatial frequency. How diverse is their degree of tuning for these properties? To address this, we used single-tetrode recordings to simultaneously isolate multiple cells at single recording sites and record their responses to flashed and drifting gratings of multiple orientations, spatial frequencies and, for drifting gratings, directions. Orientation tuning width, spatial frequency tuning width and direction selectivity index (DSI) all showed significant clustering: pairs of neuron recorded at a single site were significantly more similar in each of these properties than pairs of neurons from different recording sites. The strength of the clustering was generally modest. The percentage decrease in the median difference between pairs from the same site, relative to pairs from different sites, was: for different measures of orientation tuning width, 29-35% (drifting gratings) or 15-25% (flashed gratings); for DSI, 24%; and for spatial frequency tuning width measured in octaves, 8% (drifting gratings). The clusterings of all of these measures were much weaker than for preferred orientation (68% decrease), but comparable to that seen for preferred spatial frequency in response to drifting gratings (26%). For the above properties, little difference in clustering was seen between simple and complex cells. In studies of spatial frequency tuning to flashed gratings, strong clustering was seen among simple-cell pairs for tuning width (70% decrease) and preferred frequency (71% decrease), whereas no clustering was seen for simple/complex or complex/complex cell pairs