Figure 11.

Schematic depictions of two ways in which identification-based feedforward inhibition from area V4 might be physically realized. Saccades in one of three directions (arrows in top row) result from activation in one of three columns of neurons in FEF (second row) that are innervated by neurons in V4 (third row) with receptive fields representing the three possible saccade endpoints. A simplified rendering of the circuitry of FEF is illustrated with the upper and lower layers populated by pyramidal neurons (triangles) sandwiching the middle layer populated by stellate neurons (stars). Inputs from V4 terminate in the middle layer. The three columns in FEF producing saccades in each direction receive topographically organized input from columns in V4. Neural inhibition is mediated by the vertically elongated red neurons. The left panel illustrates feedforward inhibition mediated through the pattern of extrinsic inputs from V4 to FEF, which converge in the middle layers of FEF such that V4 neurons with non-overlapping receptive fields send inhibitory signals to layer 4 of FEF. The right panel illustrates feedforward inhibition mediated through the intrinsic circuitry in FEF wherein the inhibition occurs between the middle and upper layers of FEF.