Figure 5. Changes in neural coding over time could be decomposed into changes in differential firing magnitude vs. consistency.
(A) Three examples of firing differentiation of a neuron between trials with the auditory conditioned stimulus (CS, magenta) and those with the visual CS (blue). A neuron is more ‘selective’ for the physical feature, if it has a greater difference in the mean firing rate (vertical lines) between two conditions (Magnitude) and a smaller variance in trial-by-trial firing rates in each condition (arrows; Consistency). (B) Mean ranks of the differential index between CS-alone trials and CS-US paired trials (Relational, left) increased during weeks after learning, whereas that between the auditory and visual CS trials (Physical, right) did not. (C) The proportion of neurons (±95% confidence intervals) with high differentiation index for relational or physical feature did not change across the stages. (D) Across five stages, mean ranks of mutual information for the relational feature did not change. In contrast, mean ranks of mutual information for the physical feature decreased over the stages. (E) The proportion of neurons (±95% confidence intervals) with significantly high mutual information for the physical feature showed a trend toward decreasing across stages. (Symbols: #, **, and *** indicate p<0.01, 0.01, and 0.001, respectively).