Fig. 6: MT activity co-varies with perceptual segmentation judgments on a trial-by-trial basis.
From: A neural correlate of perceptual segmentation in macaque middle temporal cortical area
a Distribution of choice probabilities for plaids with no texture cue for the sample recorded from monkey N. Each cell could contribute up to two data points (one for each direction of plaid motion). A mean CP greater than chance (white arrow) indicates that, overall, there was a significant relationship between MT activity and perception. b To examine the influence of any potential choice biases we calculated CP separately for any stimulus for which the monkey made at least a single error. Choice probability is plotted against choice ratio (pref/null) for all stimuli (left) and versus the absolute value of the contrast of the texture cue (right – data from 120 single units). Solid line and the shaded region in the left panel is the mean ± s.e.m. for a 20-point moving average. Choice probabilities calculated for stimuli with unbalanced choice ratios, e.g., those plaids with high cue contrast, were more variable and clustered around chance. Gray shaded region in the right panel highlights the cue contrasts included in the grand choice probability calculation. c Grand choice probability (ordinate) is plotted versus neuronal threshold (abscissa). There was a significant negative correlation between choice probability and threshold. d–f Convention as in a–c but, unless otherwise noted, are for data from 157 single units from monkey S. g Grand choice probability (ordinate) is plotted against normalized preferred direction (abscissa) separately for both monkeys. Each MT unit contributed two data points (one for each plaid pattern direction). h Box plots of grand choice probability for each inter-grating angle. Solid lines mark the median, the bottom and top edges of the box indicate the 25th and 75th percentiles respectively, whiskers extend to 1.5x the inter-quartile range, outliers are marked beyond this limit. Data in the left (right) panel is from 120 (157) single units from monkey N (S). i Grand choice probability (ordinate) is plotted against time from stimulus onset (abscissa). Grand CP was calculated in a sliding bin (100 ms width, 10 ms steps) throughout a trial and then averaged across units.
