AMYGDALA

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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.

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Amygdala projections to lower brain structures
mediate auotonomic and behavioral responses to
significant stimuli
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Amygdala Projections to the Hypothalamus in turn
may activated a variety of homeostatic
Behaviors.
Circadian rhythms -sleep wake cycling And..
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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

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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
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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• may become withdrawn, lose all interest in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).

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Human Studies of Amygdala Stimulation

• - visceral sensation
• - deja vu experiences
• - memories
• - emotions

Human ESB Robert Heath , 1962
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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).

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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.

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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.

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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).

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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).

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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

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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.

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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).

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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

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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
  fearor 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.

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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 .

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TheAmygdala and The Frontal Lobes?