Figure 3: V4, but not V1, population activity is reformatted to enable the flexible mapping of curvature to different actions.

A. To enable a flexible mapping between curvature judgments and eye movement responses, the curvature representation of a shape could be transformed to align with a fixed readout axis that communicates with eye movement planning areas. In other words, the same curvature judgment should be mapped to different parts of the saccade direction axis depending on the location and length of the arc.

B. In simulations, we randomly assigned the arc-dependent gain modulations to neurons by drawing from a distribution of response gains that is consistent with single neuron results (see Methods). Only some draws of the same distribution enabled the mapping of curvature representations to the appropriate portions of the readout axis such that the saccade could be decoded from the population (light and dark green). Most other draws did not (gray).

C. Schematic depicting analyses that would reveal whether neural population responses reflect only the curvature judgment and not the upcoming eye movement used to communicate that judgment (left) or whether they also reflect the upcoming eye movement (right). Colors represent predictions for the different arc locations (top) or lengths (bottom).

D. V4, but not V1, responses reflect the direction of the upcoming eye movement in example sessions. The impending saccade direction was decoded from V1 (left) and V4 (right) responses during the period when the monkeys have not yet moved their eyes but after the onset of the arc that allows them to plan the eye movement. Shading indicates SEM and the correlation between actual and predicted saccade direction is labeled on the bottom-right of each panel.