startle

STARTLE REFLEX

I'm an eccentricity specialist. --Michael Richards (Kramer on Seinfeld)

Neuro term. 1. A sudden, involuntary movement made in response to a touch, an unexpected motion, or a loud noise. 2. A set of automatic protective movements designed to withdraw the body and its parts from harm.

Usage: Many defensive postures and submissive gestures (e.g., diverse movements of the shoulder-shrug display) derive from paleocircuits of the mammalian startle. Its status as a reflex explains why human beings (in all cultures) a. blink and grimace; b. flex the neck, elbows, trunk, and knees; and c. elevate the shoulders when feeling physically, emotionally, or socially threatened (Andermann and Andermann 1992:498).

Media. Eccentric twisting, plunging, blinking, and flexing spasms made from 1989-98 by Seinfeld TV character, Cosmo Kramer are typical of people with an exaggerated startle response. Increasing with anxiety and fatigue, the startle underlies such culturally recognized "startle syndromes" as Indonesian latah, Japanese imu, and Lapland's Lapp panic (Joseph and Saint-Hilaire 1992:487-88).

RESEARCH REPORTS: The startle reflex is related to the Moro or "clamping" reflex of young primates, which includes a. arm, leg, and spinal-column extension movements; b. head bowing (over the chest); and c. crying (McGraw 1943:19). Present in the human fetus after 30 weeks, the startle is predominantly a flexor reflex, possibly rooted in the primitive orienting response (Joseph and Saint-Hilaire 1992:487).

Neuro-notes. Sudden movements, looming objects, or bright lights trigger midbrain optic centers which automatically turn our faces and eyes toward what could be dangerous--before the forebrain knows, on a conscious level, danger even exists. The midbrain's auditory lobes, meanwhile, are reflexively attuned to changes in sound. Located just below the optic-center lobes, these pea-sized areas control our auditory startle. Picked up by the cochlear nucleus, a scream received by the auditory lobes triggers the amygdala and circuits of the reticulospinal tract to activate the startle. Thus, recoiling from a karate yell, e.g., is a primal response prompted by paleocircuits of the amphibian brain.

See also CHATTERING TEETH, FLEXION WITHDRAWAL.