We found that the activity of individual PF neurons represented both the cues and the associated responses, perhaps providing a neural substrate for their association. Furthermore, during learning, neural activity conveyed the direction of the impending responses progressively earlier within each successive trial. The final level of activity just before the response, however, was unaffected by learning. These results suggest a role for the PF cortex in learning arbitrary cue-response associations, an ability critical for complex behavior. The figure shows the responses of four prefrontal neurons after learning of conditional associations between an object and a saccade direction.
Neural activity is shown to each of the four possible cue-saccade associations.
The shaded area represents the time of cue presentation. The colors used in the inset match those of the histograms, and are keyed by the legend. This suggests that the prefrontal cortex explicitly represented the object-saccade associations needed to perform the task. Change in latency of appearance of saccade direction related activity during learning of the object-saccade associations. The time at which half of the maximal selectivity was reached within each trial is plotted along with the fitting sigmoid function.