Functional organization of the human amygdala in appetitive learning

The amygdala is a small subcortical structure located bilaterally in medial temporal lobes. It is a key region for emotional processes and some forms of associative learning. In particular, the role of the amygdala in processing of negative emotions and aversive learning has been shown in numerous studies. However, involvement of this structure in processing of positive affect and appetitive learning is not fully understood. Previous experiments in animals are not consistent. While some authors implicate only the centromedial part of the amygdala in appetitive learning, the others suggest contribution of both centromedial and basolateral subregions. Although from the evolutionary perspective appetitive learning is equally important as aversive learning, research on the role of the human amygdala and its subregions in appetitive learning is undertaken relatively rarely and the results are not conclusive. Therefore, the aim of this review is twofold: to summarize the current knowledge in this field and to indicate and discuss the factors, which might affect the observed level of the amygdala activity during appetitive learning in humans.