情動，扁桃体と自律神経系

Emotion, Amygdala, and Autonomic Nervous System

はじめに

　情動（emotion）は，情と動の合成である。すなわち，心身の動揺を伴う感情の変化といえる。感情の変化や程度を客観的，あるいは定量的に評価することは現状では容易ではない（最近の脳科学では，後述するようにそれも可能になりつつある）。一方，身体活動は体性運動神経系と自律神経系が司る。体性運動神経系は骨格筋の運動であり，闘争や逃走のように目に見える動きを司る。これに対して，自律神経系は内臓の働きを司る。したがって，自律神経活性の変化から情動の程度を客観的かつ定量的に評価できる。また感情と身体活動の関係を解剖生理学的に解明する糸口になりうる。ここでは，自験例を中心に，情動，自律神経系を司る中枢神経回路，特に扁桃体を中心に解説する。

Abstract

　Emotion refers to the dynamic changes of feeling accompanied by the alteration of physical and visceral activities. Autonomic nervous system (sympathetic and parasympathetic) regulates the visceral activities. Therefore, monitoring and analyzing autonomic nervous activity help understand the emotional changes. To this end, the survey of the expression of immediate early genes (IEGs), such as c-Fos in the brain and target organs, and the viral transneuronal labeling method using the pseudorabies virus (PRV) have enabled the visualization of the neurocircuitry of emotion. By comparing c-Fos expression and data from PRV or other neuroanatomical labeling techniques, the central sites that regulate emotional stress-induced autonomic activation can be deduced. Such regions have been identified in the limbic system (e. g., the extended amygdaloid complex; lateral septum; and infralimbic, insular, and ventromedial temporal cortical regions), as well as in several hypothalamic and brainstem nuclei. The amygdala is structurally diverse and comprises several subnuclei, which play a role in emotional process via projections from the cortex and a variety of subcortical structures. All amygdaloid subnuclei receive psychological information from other limbic systems, while the lateral and central subnuclei receive peripheral and sensory information. Output to the hypothalamus and peripheral sympathetic system mainly originates from the medial amygdala. As estrogen receptor α, estrogen receptor β, and androgen receptor are expressed in the medial amygdala, sex steroids may modulate the autonomic nervous activities.