Identity and expression processing during classical conditioning with faces.

In classical conditioning, conditioned responses (CRs) to aversively paired (CS+) relative to unpaired (CS-) face images are often interpreted in terms of the specific individual displayed in the CS + face image having adopted an aversive emotional connotation. This interpretation requires conditioning to rely on an association between CS + face identity and the occurrence of the aversive event (UCS). Here, we tested this requirement assuming that if an association between CS + face identity and UCS occurrence is established, CRs to originally conditioned face images should transfer to novel images of same-identity faces. Forty-eight participants underwent MultiCS conditioning with eight neutral faces as CSs and electric shock as UCS. Central, peripheral, evaluative, and behavioral CRs signaled successful emotional learning (as reported in Pastor et al., 2015). Behavioral and EEG responses of consecutive passive viewing showed enhanced reactions to novel angry and happy expressions of previously shocked CS + versus nonshocked CS- identities, indicating successful CR transfer within the dimension of face identity. Investigating the nature of CR transfer, EEG revealed an interaction of identity and expression information during face processing that followed emotional congruency (i.e., stronger reactions to congruent angry CS + and happy CS- vs. incongruent angry CS- and happy CS + compounds). While correlates of transfer appeared in late and midlatency time intervals, the congruency interaction became significant within the first 100 ms of face processing. Our results suggest conditioning to rely on an association of UCS occurrence with CS + identity and point to fast dynamic interrelations between identity and expression processing.

Rapid plasticity in the prefrontal cortex during affective associative learning.

MultiCS conditioning is an affective associative learning paradigm, in which affective categories consist of many similar and complex stimuli. Comparing visual processing before and after learning, recent MultiCS conditioning studies using time-sensitive magnetoencephalography (MEG) revealed enhanced activation of prefrontal cortex (PFC) regions towards emotionally paired versus neutral stimuli already during short-latency processing stages (i.e., 50 to 80 ms after stimulus onset). The present study aimed at showing that this rapid differential activation develops as a function of the acquisition and not the extinction of the emotional meaning associated with affectively paired stimuli. MEG data of a MultiCS conditioning study were analyzed with respect to rapid changes in PFC activation towards aversively (electric shock) paired and unpaired faces that occurred during the learning of stimulus-reinforcer contingencies. Analyses revealed an increased PFC activation towards paired stimuli during 50 to 80 ms already during the acquisition of contingencies, which emerged after a single pairing with the electric shock. Corresponding changes in stimulus valence could be observed in ratings of hedonic valence, although participants did not seem to be aware of contingencies. These results suggest rapid formation and access of emotional stimulus meaning in the PFC as well as a great capacity for adaptive and highly resolving learning in the brain under challenging circumstances.