Fig. 1: Angular velocity cell in the parahippocampal cortex.

a Whole rat brain, with partially removed left hemisphere to enable a midsagittal view of the right hemisphere and outlines of hippocampal formation (yellow), presubiculum (blue), parasubiculum (pink) and MEC (green). Adapted from³⁶ (b) Schematic representation of three type of angular head velocity (AHV) movement, from left to right: counterclockwise (CCW, dark pink), clockwise (CW, light pink) and bidirectional (BiDir, purple). c Schematics ring attractor depicting theoretical updating of head direction code from position at time _t (left) to position at a later time _t+1 (right) following angular movement (middle). The outer layer of head direction (HD) cells is connected to a ‘hidden’ inner layer of conjunctive HD-by-AHV cells. The colour represents neural activation from maximum (red) to minimum (blue). d Proportions of AHV cells within MEC (top), PaS (middle) and PrS (bottom). From left to right: all AHV cells (fuchsia, MEC:17%, n = 67; PaS:17%, n = 75; PrS:17%, n = 104), CCW-AHV cells (dark pink, MEC:5%; PaS: 5%; PrS:4%), CW-AHV cells (light pink, MEC:5%; PaS: 6%; PrS: 5%), and BiDir-AHV cells (purple, MEC:10%; PaS:9%; PrS:11%). The shaded areas represent the intersection between AHV-CCW & AHV-BiDir (darker shade) or between AHV-CW & AHV-BiDir (lighter shade). Upper right corner boxes: representative Nissl-stained sagittal section showing example recorded track for each area. e Example AHV cells in MEC (top), PaS (middle) and PrS (bottom) showing firing rate as a distribution of angular velocity (in rad/s), score in upper right corner. From left to right: CW-AHV (dark pink), CCW-AHV (light pink) and BiDir-AHV (purple). f Distribution of unidirectional (left) and bidirectional (right) AHV scores across MEC (top), PaS (middle) and PrS (bottom) cell population comparing observed (coloured curve) and shuffled data (grey bars). Dashed lines represent 99 percentile thresholds for CCW- and CW-AHV (left) and Bidir-AHV (right). g Snapshot comparison between z-scored firing rate of an example AHV cell (pink curve) and instantaneous angular head velocity (black curve). h Scatter plots showing the correlation between the AHV scores calculated in the first and second half of each recording sessions (Left: unidirectional, CW- and CCW-AHV cells in pink; Right: bidirectional, BiDir-AHV cells in purple; rho stability = 0.52). Credits to Silvia Girardi for schematics and drawings.