Figure 2
Changes in neuronal firing rate account for information coding in the PFC. (a) Histograms summarizing the across-trial firing rate distributions for all (black), GO-only (blue) and NoGO-only (red) trials from a neuron that increased its firing rate during the GO tone and decreased it during the NoGO tone. A 1 s duration window was used to compute the histograms before tone presentation (Basal) and during the tone (Tone). White dashed lines indicate the mean firing rate for all trials. Note that the firing rate distributions for GO and NoGO trials are similar during the basal period (i.e., no information regarding stimulus identity can be extracted). However, the opposite/differential response during tone presentation for both GO and NoGO trials leads to an increased decoding power, as reflected by the ROC curve analysis (AUC = 0.93). The information conveyed by the neuronal response is also evidenced by the marked increase in mutual information (MI) value computed from the binary model (the probability P1 of being in a high state is shown for each condition). (b) Summary of the across-trial firing rate histograms from a neuron with opposite firing behaviour to that shown in a. Here, the neuron codes stimuli by decreasing its firing rate during GO tone and increasing it during the NoGO tone, leading to an increased decoding power during tone presentation as revealed by the ROC curve analysis (AUC = 0.84). (c) Dot plot showing PFC neuronal responses (ΔFR relative to baseline) exhibiting increased (blue) or decreased (red) firing rate during GO and NoGO trials. (d) Average mutual information (MI) for all PFC neurons computed from the binary model during tone presentation. Average MI decreases when mean firing rate values are subtracted within GO and NoGO conditions (MIZM), becoming indistinguishable from basal values. This suggests that PFC neurons are coding stimuli by means of increments or decrements in their average firing rates.
