Figure 4.

Structure in the responses of single units to movies revealed by principal components analysis. A, Heat map showing the mean responses of 69 different neurons to multiple presentations of all three 5 min movies. Each row corresponds to the modulation of a single neuron. The rows are sorted based on their decreasing PC1 eigenvalue. Horizontal lines indicate the boundaries between three groups of neurons (c1, c2, and c3) derived from the principal components analysis (see text and C). Vertical dashed lines indicate the points of concatenation of the three movies. B, Cumulative variance accounted for by all 69 principal components derived from the mean responses of 69 neurons analyzed in this study. C, Scatterplot of PC1 versus PC2 for all 69 neurons. Neurons showing similar response characteristics in A appear coarsely divided into clusters, designated as c1, c2, and c3. D, Correlation matrix of firing rate over time for 69 neurons, sorted first by membership in clusters shown in C and second by PC1 coefficient. Each element in the matrix represents the correlation coefficient in the mean firing rates of two neurons over the three movies concatenated together.