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AMYGDALA. The amygdala is preeminent in the mediation of most higher order emotional and motivational processing. massive interconnections with lower brain structures and the cerebral cortex the amygdala is able to scrutinize sensory information for emotional significance.
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AMYGDALA The amygdala is preeminent in the mediation of most higher order emotional and motivational processing. • massive interconnections with lower brain structures and the cerebral cortex • the amygdala is able to scrutinize sensory information for emotional significance. • This includes the ability to discern and express even subtle social-emotional nuances such as friendliness, fear, love, anger, or threat, and at a more basic level, determine if something might be good to eat.
Amygdala projections to lower brain structures mediate auotonomic and behavioral responses to significant stimuli
Amygdala Projections to the Hypothalamus in turn may activated a variety of “homeostatic” Behaviors. Circadian rhythms -sleep wake cycling And..
hypothalamus -Deeply ingrained species-specific behaviors • simulation of the hypothalamus produces many of the behaviors • rage and aggression • cowering or docile behavior. • Eating/satiety • Drinking • Thermo-regulation • Nesting • Reproduction etc
Passivity and emotionally unresponsiveness (like “Psychic blindness”). For example, in research with monkeys and cats, those with damage to their amygdalas would attempt to eat burning matches, their own feces, and other objects that normally would elicit fear or disgust. Monkeys who had responded to snakes with terror before the lesioning of their amygdalas would, after the lesioning, show no fear of the same snakes. Some monkeys even placed the snakes inside their mouths!can lead to furious attacks on others ( may depend on what parts of the amygdala are destroyed/left intact)Changes in sexual behavior Amygdala Lesions/Animals
AMYGDALA DAMAGE/Humans • Dramatic alterations in personality are not uncommon (Lilly et al., 1983; Marlowe et al., 1975; Shenk & Bear, 1981; Terzian & Ore, 1955). • may become withdrawn, lose all interest in social activities, - inability to depict/imagine fear - impaired recognition of emotional facial expressions -impaired recognition of emotional tone of voice (esp. anger, fear) • may become aggressive and violent, (like TLE IED) • May experience significant alterations in sexual drive ( like TLE and Kluver-bucy).
Human Studies of Amygdala Stimulation Human ESB Robert Heath , 1962 - visceral sensation - deja vu experiences - memories - emotions
Amygdala Stimulation and Sex • Penile erections, ovulation, uterine contraction and lactogenetic responses, and vaginal-vulva secretions in conjunction with orgasm and sexual feelings in the genital areas are all associated with heightened activity in the amygdala. (Halgren, 1992; Jacome, et al. 1980; Gloor, 1986; Remillard, et al. 1983; Robinson & Mishkin, 1968; Shealy & Peele, 1957).
Stimulation of the Amygdala-fear • Extreme fear is the most common emotional reaction elicited with direct electrode stimulation of the human or non-human amygdala (Chapman, 1960; Davis et al., 1997; Gloor, 1997; Halgren, 1992; Rosen & Schulkin, 1998; Strauss, Risser, & Jones, 1982; Williams 1956). • the subject will cringe, withdraw, and cower. • Experience extreme panic and attempt to take flight. • Alternatively, the experimental animal may “freeze.” a Catanonic-like state of imobility.
Amygdala Stimulation- Fear and autonomic reactions • Likewise, abnormal activity originating in the amygdala can evoke overwhelming, terrifying feelings of "nightmarish" fear (Herman & Chambria, 1980; Strauss et al., 1982; Weil, 1956). • Physiological arousal • the EEG becomes desynchronized (indicating arousal), heart rate becomes depressed, respiration patterns change, the galvanic skin response significantly alters, the face contorts, the pupils will dilate, and the subject will look anxious and afraid (Bagshaw & Benzies, 1968; Davis, 1992; Kapp, Supple, & Whalen, 1994; Ursin & Kaada, 1960). • These effects may persist for long periods of time following stimulation.
Amygdala Stimulation- Conditioning • In consequence, the subject may continue to feel extreme terror long after the threat has been removed. • Fear Conditioning- amygdala-induced fear may be re-evoked even by neutral cues or stimuli associated with the original threat or trauma (Davis, 1992; LeDoux, 1996).
Amygdala/fear induced immobility • - paralyzed and numb with fear • they may appear catatonic, and may fail to make any effort to resist or to save their lives (Courtois, 1995; Galliano et al., 1993; Miller, 1951; Nijenhuis et al., 1998). • -stiff and rigid, as if rigor mortis has set in. • psychological and emotional numbness • (Courtios, 1995; Foa, Riggs, & Gershuny, 1995; Krystal, 1988) • blocking of cognition and memory -they may resist and fail to respond even to attempts at assistance (Krystal, 1988).
Amygdala fear- • -25% of rape victims report body stiffening (Galliano et al., 1993), • in air and sea disasters 10-25% of the victims may become frozen, stunned, and immobile (Krystal, 1988). • will also fail to take any action to save their lives, • Fear-driven catatonic-paralytic states are prevalent in the animal kingdom (Kalin, 1993; Nijenhuis et al., 1998) and constitute an adaptive, life preserving reaction that appears to be largely mediated by the amygdala, supplementary motor area, and striatum
Amygdala fear- animal immobility • May be adaptive • unless exceedingly hungry, some predators avoid food that appears to be already dead, though just as commonly the hapless victim is ripped to pieces and readily consumed.
Amygdala fear-Immobility and opiates • massive secretion of opiates activated by the amygdala – • high enkephalins content • High in numbers of opiate receptors (Atweh & Kuhar, 1977; Uhl, Kuhar, & Snyder, 1978). May explain fear or stress induced emotional and physical numbing ..hence • The wounded warrior to keeps fighting, • The wounded beast calmly allows itself to be eaten alive. • Similarly, may account for the psychological numbing reported by victims of catastrophe, or sexual or physical trauma (Courtios, 1995; Foa et al., 1995).
Amyg-and basal ganglia • In response to amygdala activation, the striatum (including the subthalamic nucleus) may trigger a variety of stereotyped (automatic) and ballistic motor actions such as • running, kicking, and punching, or conversely "freezing" • emotional postures and expressions
Amyg/fear/basal ganglia/loss of refined movements Amygdala activation of the secondary motor association cortex take precedence over Motor Cortex • Thus fine motor responses may be most affected by fear…or anxiety…. Shooting free throws under pressure!! • extreme stress amygdala activation of the frontal lobe areas are indicated when the individual becomes rigid, stiff, and unmoving, and will cease to speak or react to questions, threats, or external stimulation (Goto et al., 1990; Hassler, 1980; Joseph, 1999a; Kish et al., 1988; Laplane et al., 1977; Luria, 1980; Spiegel & Szekely, 1961). After the stimulation is removed, patients have reported that their mind essentially had become a blank, a void, and that thoughts no longer entered their head.
Frontal motor areas • Immobility effects are also associated with tumors, strokes, or lesions of the frontal lobes and adjoining tissues (Feeman & Watts, 1942; Gasper et al., 1991; Hornykieciz, 1982; Playford et al., 1992). • For example, if a physician attempts to move the patient's arm, it will become stiff and rigid .
