Increased Firing Irregularity as an Emergent Property of Neural-State Transition in Monkey Prefrontal Cortex
Figure 2
lPFC neurons showing representational transitions.
(A) Temporal sequence of events in the path-planning task (maze task). The behavioral sequence is depicted from left to right. Each panel represents a maze displayed on a monitor, with green squares denoting current cursor positions, and red squares representing the position of the final goal. Yellow squares represent movement initiation (go) signals, and black arrows delineate cursor movements. Start display, final goal display, and delay periods constitute the preparatory period. (B) Discharge properties of an lPFC neuron that represents the final goal followed by the immediate goal during the preparatory period. Raster plots and spike-density histograms of neuronal activity under task conditions for each combination of final and immediate goals are shown. A red square indicates the location of the final goal remembered during the preparatory period, and a blue square indicates the planned immediate goal. In the early phase of the preparatory period, this neuron was selectively active when the final goal was located at the top right of the maze. In the late phase, selectivity was most prominent when the immediate goal was above the starting position. (C) The time course of modulation of the final- (red line) and immediate-goal (blue line) selectivity of the neuron shown in B. The goal selectivity, or regression coefficient, is normalized by the t value at the significant level, P = 0.05. (D) The mean ± SEM of selectivity for the final (red line) and immediate (blue line) goals of the population of neurons (n = 148) with F-I (final-immediate) shifts. Arrows, F-I transition times.
