Fig. 1: Hand position specific tuning in the dorsal premotor cortex.

A Recording sites mainly covered the hand area of the dorsal premotor cortex in each monkey. Black squares denote the position of inserted Utah arrays (96 electrodes for Monkey X, 48 electrodes for Monkey A, B, and Z). Black lines denote brain sulci used to locate the implantation site. PS, principal sulcus; AS, accurate sulcus. B Diagram of the naturalistic reach-and-grasp task. C Upper row: trajectories (black lines) of monkeys’ hand from four example sessions (one for each monkey). Spikes from four exemplary cells in each corresponding session are plotted as circular markers. The color and size of the circles are set according to the spike counts. The brown triangle indicates the position of the monkey’s nose (facing right). Peak firing rate for each cell is labeled on the top of panels. The vertical scale bars represent 5 cm along the x axis and the horizontal scale bars represent 5 cm along the y axis in each panel. Bottom row: corresponding 2D spatial firing rate maps, denoted with SI. Dark blue indicates the minimal firing rate within the map, and dark red indicates the maximal firing rate within the map. D The distribution of SI of hand position-tuned cells (n = 132). E Fitting the hand position firing fields using a 2D Gaussian function. Left, color-coded firing activity of the first cell in (C), shown as a function of hand position. The area outside the field is masked with gray. Right, fitted Gaussian function of the field, coefficient of determination, r² = 0.83, one-sided F-test, F-statistic = 170.75, P = 0.0000. F Comparison between the r² of Gaussian fitting and that of linear fitting, P = 2.46 × 10⁻²⁶, n = 132 cells, one-sided paired t-test. *** P < 0.001. Source data is provided as a Source Data file.