Amphibian brain

AFFERENT CUE

Neuro term. 1. A nonverbal sign received, as opposed to one sent (see EFFERENT CUE). 2. An incoming sign received by receptors in our eyes, ears, nose, mouth, skin, hair follicles, muscles, tendons, joints, vestibular apparatus, or viscera, relayed to centers in the spinal cord and brain for processing. 3. Our bones and teeth conduct incoming signs of vibration and temperature; otolith organs and semicircular canals process signs of motion, balance, and gravitational force. 4. Additionally, pleasure areas of the brain respond to the afferent cues of sex, drugs, and rock-and-roll.

Usage: As concepts, afferent and efferent reflect the two sides of every nonverbal cue: (1) ingress (as an in-bound sign to be processed) and (2) egress (as an out-bound sign to be produced).

See also ENTERIC BRAIN, NICOTINE.

AGNOSIA

Neuro term. 1. The inability to recognize a coin, key, or other object merely by its feel, e.g., when held in the hand. 2. The inability to recognize a door by the sound of its slamming or from its photograph alone. 3. In agnosia, while perception itself (i.e., feeling a coin's shape or hearing a door slam) is normal, recognition of objects is not.

Usage: Studies of agnosia reveal how the brain processes nonverbal gestures, objects, and sensations apart from speech or words. (Though very vocal, human beings still spend a great deal of their lives in Nonverbal World.)

Stereognosis: The tactile ability to recognize objects placed in the hand. (Graphesthesia is the tactile ability to recognize figures drawn on the skin.)

Neuro-notes. 1. Inability to recognize a coin by the sound of its dropping suggests problems with the auditory association areas of the temporal lobe. 2. Inability to recognize a coin held in the hand suggests problems with the tactile association areas of the parietal lobe. 3. Inability to recognize a coin by its photograph suggests problems with the visual association areas of the occipital lobe. These nonverbal brain modules exist independently of the cortical modules used to recognize and produce speech sounds.

See also APRAXIA.

AKINESIA

Neuro term. 1. Difficulty beginning or maintaining a body motion. 2. Symptoms include: a. slowed voluntary movements; b. difficulty in reaching for objects; c. inability to perform repetitive, simultaneous, or sequential body movements; d. immobile, expressionless, or masked face; e. loss of normal "restless" body movements while sitting; f. loss of arm swinging while walking; g. shuffling gait; and h. diminished finger dexterity.

Usage: Akinesia points to a variety of neurological problems (including, e.g., Parkinson's disease and brain damage associated with strokes). Akinesic behaviors affect an individual's normal nonverbal response, and may be (especially in older people) misconstrued as mood signs expressing emotions and feelings.

See also APRAXIA.

AMPHIBIAN BRAIN

Evolution. 1. Collectively, those older parts of the human brain which developed during the amphibian transition from water to land in the Devonian period of the Paleozoic Era. 2. Specifically, those modules of the amphibian midbrain and forebrain which evolved to further life above the waterlines of ancient seas. 3. Those amphibian-inspired paleocircuits a. for hearing and seeing in a higher, drier world, and b. for postural stance in terra firma's gravitational pull.

Usage: Several common gestures and postures (derived, e.g., from the auditory startle and the high-stand display) originated ca. 380 m.y.a. in modules of the amphibian brain. (The latter itself evolved from modules and paleocircuits of the aquatic brain.) Today these play key roles in the expression of dominance and submission.

Media. Sudden movements, looming objects, and bright lights trigger midbrain vision centers which reflexively orient our face and eyes to novel or dangerous stimuli. Meanwhile, midbrain hearing centers stay tuned to abrupt changes in sound. Thus, with its fluctuating cuts in scenery, camera angle, and volume, TV addresses the amphibian brain.

Neuro-notes I: midbrain. As amphibian ancestors emerged from primeval lakes and seas to live part of their lives on land, seeing and hearing sharpened. Two paired centers of the amphibian midbrain--the inferior and superior colliculi --evolved as processing stations for audiovisual cues. The former's hearing centers (the auditory lobes) unconsciously prompt us to crouch from loud noises. The latter's vision centers (the optic lobes) reflexively focus our attention on body motions, gestures, and objects that move.

Neuro-notes II: forebrain. Unlike water's buoyancy, land presents an incredibly heavy environment in which antigravity signs (e.g., the reptilian press-up to a high stand) evolved. The forebrain module in charge of the earliest aggressive "pushup" was a motor area presently called the striatal complex. What remain of its paleocircuits (see BASAL GANGLIA) inspire us to extend our limbs to show dominance as John Wayne did in the 1960 movie, The Alamo, by similarly "standing tall."

See also PALM-DOWN, REPTILIAN BRAIN.

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. 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.

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.)

Дата добавления: 2015-10-28