Thigpen, N. | Search bioRxiv

bioRxiv2021

Oscillatory brain activity links experience to expectancy during associative learning

Associating a novel situation with a specific outcome involves a cascade of cognitive processes, including selecting relevant stimuli, forming predictions regarding expected outcomes, and updating memorized predictions based on experience. The present manuscript uses computational modeling and machine learning to test the hypothesis that alpha-band (8-12 Hz) neural oscillations are involved in the updating of expectations based on experience. Participants learned that a visual cue predicted an aversive loud noise with a probability of 50 percent. The Rescorla-Wagner model of associative learning explained trial-wise changes in self-reported noise expectancy as well as alpha power changes. Both experience in the past trial and self-reported expectancy for the subsequent trial were accurately decoded based on the topographical distribution of alpha power. Decodable information during initial association formation and contingency report recurred when viewing the conditioned cue. Findings support the idea that alpha oscillations have multiple, simultaneous, and unique roles in association formation.

neuroscience↗

bioRxiv2020

Fear conditioning prompts sparser representations of conditioned threat in primary visual cortex

Repeated exposure to threatening stimuli alters sensory responses. We investigated the underlying neural mechanism by recording simultaneous EEG-fMRI from human participants viewing oriented gratings during Pavlovian fear conditioning. In acquisition, one grating (the CS+) was paired with a noxious noise, the unconditioned stimulus (US). The other grating (CS-) was never paired with US. In habituation, which preceded acquisition, and in final extinction, the same two gratings were presented without the US. Using fMRI-BOLD multivoxel patterns in primary visual cortex during habituation as reference, we found that during acquisition, aversive learning selectively prompted systematic changes in multivoxel patterns evoked by the CS+. Specifically, CS+ evoked voxel patterns in V1 became sparser as aversive learning progressed, and the sparse pattern was preserved in extinction. Concomitant with the voxel pattern changes, occipital alpha oscillations were increasingly more desynchronized during CS+ (but not CS-) trials. Across acquisition trials, the rate of change in CS+-related alpha desynchronization was correlated with the rate of change in multivoxel pattern representations of the CS+. Furthermore, alpha oscillations co-varied with BOLD in the right temporal-parietal junction, but not with BOLD in the amygdala. Thus, fear conditioning prompts persistent sparsification of threat cue representations, likely mediated by attention-related mechanisms.

neuroscience↗