Fig. 2. LIP recordings during discrimination and categorization tasks.

A Mean firing rates of six single LIP cells recorded during each task. Colors correspond to the stimulus direction and category. Firing rates aligned to the sample stimulus onset are averaged by sample direction (left), and the test stimulus aligned rates are averaged over test direction (right). Although motion categories were not part of the discrimination task, the directions are labeled blue or red for consistency. (Inset polar plots) The mean firing rate for each sample direction during the sample stimulus presentation (circles and solid lines; 0–650 ms after motion onset) and delay period (triangles and dotted lines; 800–1450 ms after motion onset). The solid black line denotes 20 sp s⁻¹. B Mean category and direction tuning measured in single cells during the sample (open symbols) and delay periods (filled symbols) in each population (number of cells per population: B n = 31, J n = 29, D-disc. n = 81, D-early n = 63, D-late n = 137, H-disc. n = 89, H-early n = 106, H-late n = 114). The receiver operating characteristic (ROC) based category tuning index (rCTI⁴⁵) measures category-specific responses in a range of –0.5 to 0.5, where positive values indicate category-selective neurons while negative values indicate more selectivity for within-category directions. Similarly, positive values of the ROC-based direction selectivity index (rDSI¹³) indicate direction selectivity. Error bars denote a 95% interval over bootstraps. Individual cell results are shown in Supplementary Fig. 1.