amygdala

Brain. 1. An almond-shaped neuro structure involved in producing and responding to nonverbal signs of anger, avoidance, defensiveness, and fear. 2. A small mass of gray matter that inspires aversive cues, such as the freeze reaction, sweaty palms, and the tense-mouth display. 3. A primeval arousal center, originating in early fishes, which is central to the expression of negative emotions in man.

Usage: Many gestures reflect the amygdala's turmoil. In an anxious meeting, e.g., we may unconsciously flex our arms, lean away, or angle away from colleagues who upset us. Lip, neck, and shoulder muscles may tense as the amygdala activates brain-stem circuits designed to produce protective facial expressions (see, e.g., TENSE-MOUTH) and protective postures (see, e.g., BOW and CROUCH). The amygdala also prompts releases of adrenaline and other hormones into the blood stream, thus stepping-up an avoider's response and disrupting the control of rational thought.

RESEARCH REPORTS: 1. "The amygdala coordinates the actions of the autonomic and endocrine systems and is involved in emotions" (Kelly and Dodd 1991:277). 2. The amygdala may be part of a "general-purpose defense response control network" (LeDoux 1996:158). 3. "Unpleasant odours . . . activate the amygdala and the cortex in the temporal lobe (insula)" (Carter 1998:114; see BIG MAC).

Neuro notes I. In addition to its other duties, the amygdala's gray matter evolved to mediate the evolutionary ancient chemical nervous system, represented today by our bloodstream. Working through the hypothalamus, the amygdala releases excitatory hormones into circulating blood. After surgical removal of the amygdala, growls, screams, angry voices, and other negative signs may lose their meaning and become incomprehensible as afferent cues.

Neuro-notes II. In 2020, brain researchers found a role for sexual behavior in the amygdala. Previously, sexual roles were thought to be regulated principally by the hypothalamus (see HYPOTHALAMUS). For the first time the researchers found intercellular communication related to sexuality between the amygdala and hypothalamus.

See also AQUATIC BRAIN & SPINAL CORD, CINGULATE GYRUS.

YouTube Video: Watch a one minute tutorial on the amygdala. (Note the professor's palm-up and palm-down hand gestures.)