Does training or deprivation modulate amygdala activation?

Amygdala involvement in visual emotional processing has been unequivocally established, but the amygdala's participation in auditory emotional processing is less clear. In a previous functional magnetic resonance imaging study (Klinge et al., 2010) we investigated the amygdala's role in auditory emotional processing in blind and sighted humans. We observed stronger amygdala responses to auditory emotional stimuli in the blind who were also better at discriminating emotional stimuli. Importantly, inter-individual differences in this skill correlated with amygdala activation. While these data suggested that the amygdala serves the dominant sensory modality for emotional perception, we could not rule out possible influences of use-dependent training effects. To disambiguate between plastic changes due to deprivation or training we now studied professional actors who have undergone extensive perceptual and expressive auditory emotional trainings but no sensory deprivation. Actors showed emotion discrimination skills comparable to those of blind individuals. However, in contrast to blind volunteers they lacked increased amygdala activations. Surprisingly, actors selectively rated angry stimuli as less intense than control participants, paralleled by a down-regulation of amygdala responses via the anterior cingulate cortex. Taken together, the data from our two studies suggest that enhanced amygdala responses in the blind are mainly due to deprivation-induced plasticity, as highly trained actors who possess the same excellent emotion discrimination skills as the blind did not show these responses. It is also conceivable that the actors' training requires a more professional and controlled dealing with the emotional stimuli, resulting in a down-regulation of affective experience and accompanying amygdala responses.