Fig. 4: Perception and memory have shared and distinct activation features in visual cortex.
From: Perception and memory have distinct spatial tuning properties in human visual cortex
a We created 1D polar angle response functions by restricting data to vertices with eccentricities near the stimulus and then binning the vertices according to polar angle distance from the stimulus. We computed the median evoked BOLD % signal change within these bins for each participant, ROI, task. We then performed a normed mean across participants. A difference of two von Mises distributions was fit to the group average response. The von Mises distributions over θ = [−180∘, 180∘] shared a location parameter (μ) but could differ in their concentration (κ1, κ2) and scale (β1, β2). An example participant's V1 data during the perception task is shown in the two left panels, and the group average V1 data during perception is shown at right with fit von Mises. b Group polar angle response functions are plotted separately for perception and memory. Dots represent group average BOLD % signal change at different polar angle distances from the stimulus. Responses in parts of cortex that have pRFs near the stimulus position are plotted at x = 0. Lines represent the fit of the difference of two von Mises distributions to the average data, and shading represents the 95% confidence interval around this fit. While the peak location of the response is shared across perception and memory, there are clear differences in the amplitude and width of the responses. c Location, amplitude and FWHM of the difference of von Mises fits to the group data (N = 9) are plotted to quantify the responses. Dots represent fit parameters and lines represent bootstrapped 68% confidence intervals (thick lines) and bootstrapped 95% confidence intervals (thin lines) generated from resampling participants with replacement. In all ROIs, the peak location of the response is equivalent during perception and memory (at 0∘, the stimulus location), while the amplitude of the response is reliably lower during memory than during perception. The FWHM of the response increases across ROIs during perception but not during memory, resulting in highly divergent FWHM for perception and memory in early visual areas.
