Figure 3. PFC retains memory of object values in the absence of reward for several months.

(A) Examples of single neurons tested in the same session with good and bad objects that were trained with reward days and months before (one example from in each monkey). Top row shows average firing to good and bad objects in a set. Bottom row shows raster plot of firing to each object in the set with dots indicating spike times. Actual fractals used are shown to the left and grouped into good and bad fractals. (B). Population average firing (left y-axis) to preferred vs non-preferred values and differential firing (right y-axis) to preferred vs non-preferred value hours, days, weeks and months after reward association. The differential firing was significant in all memory periods (p<1e-2). The dots show significant time points in difference (corrected for multiple comparison, Family-wise error <0.05, see STAR Methods) (C) Differential firing shown in B overlaid for 4 memory periods. The differential firing was not significantly different across memory periods (P=0.83, 1-way permutation test, see STAR Methods). Horizontal bar: object-on duration in A-C and subsequent similar plots in passive viewing task. See also Figure S4