Supplementary Figure 8: Learning-related information about trial outcome in oscillatory power in prefrontal cortex and hippocampus
From: Frequency-specific hippocampal-prefrontal interactions during associative learning
(a) Mean raw LFP signals (evoked potentials) in PFC (red; n = 250 electrodes) and HPC (blue; n = 166), following correct (top) and incorrect (bottom) trials. LFPs are time-locked to the onset of trial-outcome feedback (solid line; dashed line indicates behavioral response time). (b) Mean normalized LFP power spectrograms in PFC (left) and HPC (right), following correct (top) and incorrect (bottom) trials. To highlight components not time-locked to trial events (i.e., induced, rather than evoked, signals), mean raw LFPs were subtracted off each electrode prior to calculation of spectral power. To enhance visualization of band-specific signals relative to the well-known 1/frequency distribution of LFP power, power at each frequency was normalized by 1/frequency for display purposes only. (c) Mean z-scored difference in induced power between correct and incorrect trials across learning stages, for PFC (left) and HPC (right). While there is a strong alpha/beta-band signal for correct trials, the theta-band signal for incorrect trials observed in the cross-electrode synchrony results is not as robust in local power. (d) Summary of power learning effects—mean (± s.e.m.) induced power difference pooled within the alpha/beta-band (top) and theta-band (bottom) regions of interest, as a function of learning stage. Theta power exhibits a significant positive shift (from incorrect toward correct bias) with learning (P ≤ 10−4 for both areas), and alpha/beta power also shows a positive trend (significant only for HPC: P ≤ 10−4; PFC: P = 0.06, 2-sided permutation test on early vs. late learning). These results indicate a similar change with learning for both cross-area synchrony and within-area power.
