Changes in visuocortical engagement and oscillatory brain activity during associative learning.

Aversive conditioning produces selectively heightened visuocortical responses to conditioned stimuli (CS) that predict aversive unconditioned events (US). However, it is unclear whether these responses are unique to aversive conditioning or if similar neural signatures emerge when a CS predicts a neutral event. To address this question, we paired a soft tone with one of two oriented circular gratings (CS+; counterbalanced), while two intermediate orientations were never paired with the neutral tone, serving as generalization stimuli (GS). Twenty-two participants viewed gratings for 3000 ms, with the tone presented during the last 1000 ms of the CS+. Gratings were flickered at a rate of 15 Hz to evoke steady-state Visual Evoked Potentials (ssVEPs), a metric of visuocortical engagement. Time-frequency decomposition quantified changes in alpha-band (8–13 Hz) spectral amplitude — another electrophysiological index of aversive conditioning. Contrary to findings observed during aversive conditioning, alpha amplitude increased, rather than decreased, during CS+ trials relative to GSs. ssVEP amplitude was higher for GSs than for the CS+ — opposite to findings in aversive conditioning. Thus, a CS paired with non-aversive outcomes engaged mechanisms consistent with working memory, anticipation, or imagery processes, reflected in heightened alpha amplitude and attenuated ssVEP, rather than the defensive potentiation observed during aversive conditioning.