Two example MTL neurons that encoded a region containing visually similar faces in the VTC neural feature space. The left panel shows the neuronal responses to 500 faces (50 identities). Trials are aligned to stimulus onset (gray line) and are grouped by individual identity. On each box, the central mark is the median, the edges of the box are the 25th and 75th percentiles, the whiskers extend to the most extreme data points the algorithm considers to be not outliers, and the circles denote the outliers. The middle panel shows the projection of the firing rate onto the feature space. Each color represents a different identity. The size of the dot indicates the firing rate. The right panel shows the estimate of the spike density in the feature space. By comparing observed (upper) vs. permuted (lower) responses, we could identify a region where the observed neuronal response was significantly higher in the feature space. This region was defined as the tuning region of a neuron (delineated by the red/cyan outlines; also shown in A).
