[Somatotopy in the emotional expression by the amygdala]

Abstract

Sensory information of various modalities is integrated in the amygdala, where the emotional information is subsequently generated. The resultant emotional information is then sent to the widespread cortical and subcortical areas. This output to the cortex is directed to the prefrontal cortex and the medial temporal lobe, a memory system, and modulates the higher cortical functions as well as the learning and memory. The output to the subcortical structures is directed to the hypothalamus and brainstem, and the autonomic, hormonal and behavioral responses are elicited as the expression of the emotional response. Taking into account the above mentioned emotional system, the examination of somatotopic representation in the amygdala and related structures is very difficult. However, recent studies have elucidated the somatotopic representation of the amygdalar output system in the brain of rhesus monkey. The lateral basal nucleus of the monkey amygdala was proved to project to the cingulate motor cortex M3, and the target cortical neurons project somatotopically to the facial nucleus in the brain stem. Accordingly, the amygdala-cingulate cortex-facial nucleus system is involved in the emotional expression by the facial movement. This system might be involved in the pathophysiology of temporal lobe epilepsy and the facial expression of patients with Parkinson disease. Furthermore, the amygdala-cingulate cortex projection develops from adolescence to adulthood and reflects the emotional maturation and the development of social adaptation.