We found that, averaged over a wide frequency band, Granger causality during the learning process is actually stronger in the amygdala-to-OFC direction; causality in the OFC-to-amygdala direction

becomes predominant only after learning has taken place, consistent with the single unit findings. Moreover, this effect appears to be related to task engagement, as it emerges most prominently after CS onset. Finally, averaging across time during the trial, we found that this learning-related directional effect is robust 3-Methyladenine across frequencies ranging from the beta band (12–25 Hz) through the lower gamma band (25–40 Hz; Figure 9C). We compared the dynamics of simultaneously recorded neural signals in amygdala and OFC while monkeys performed a reversal learning task with both appetitive and aversive reinforcement contingencies. We found that neurons in amygdala and OFC exhibited different relative time courses when updating representations of impending reinforcement. Both amygdala and OFC neurons began to update their representations rapidly after a reversal of reinforcement contingencies,

but the rates of change in amygdala and OFC depended upon the preferred valence selleck products of neurons. Positive value-coding cells in OFC adapted to the reversed reinforcement contingencies significantly more quickly than positive value-coding cells in the amygdala; conversely, negative value-coding cells in OFC adapted more slowly than their

counterparts in the amygdala. These data suggest that distinct sequences of neural processing lead to the updating of activity in the appetitive and aversive neuronal 4-Aminobutyrate aminotransferase subpopulations. It has long been theorized that the amygdala is specialized, at least in part, for responding to aversive events and generating the associated responses of withdrawal, avoidance, or defense (Morrison and Salzman, 2010 and Phelps and LeDoux, 2005). Consistent with this idea, optical stimulation of pyramidal neurons in the lateral amygdala can act as a US to produce fear conditioning (Johansen et al., 2010). Thus, the fast adaptation of neural activity in the subcortical aspect of the aversive network—i.e., negative value-coding cells in the amygdala—might reflect the evolutionary preservation of a rapid-detection system for possible threats. Note, however, that negative value-coding cells do not exclusively encode aversive events, nor do positive value-coding cells respond only to rewarding events; rather, information about both rewarding and aversive cues and outcomes often converges in both positive and negative cells in the amygdala (Belova et al., 2008) and OFC (Morrison and Salzman, 2009). Despite this convergence, most neurophysiological studies in nonhuman primates have focused on reward processing.