The Biopsychology of Emotion

 

Anatomy of Emotion

u   Limbic System Structures – experience & expression of emotion

    Hypothalamus critical for expression

    Amygdala critical for experiencing fear, rage

u   Cortex, especially frontal lobe – moderates & controls expression

    “Decorticate” animals highly emotional

u   ANS  & endocrine system– routes for triggering body signs of emotion

 

The Limbic System

u   Frontal lobe & limbic system

 

The Case of Phineas Gage

MRI Reconstructions of Prefrontal Damage

u   Lack of tact, restraint, empathy; decreased “conscience”, immature, irresponsible, coarse, lack of social graces.

u   More common after orbitofrontal damage(bottom part of prefrontal cortex)

u   Patients don’t experience stress either

 

Physiological Responses to Stress

u   Stress activates the sympathetic portion of the autonomic nervous system (the “fight-or-flight” system), including  release of adrenaline from the middle of our adrenal glands (“adrenal medulla”).

 

Autonomic nervous system

Sympathetic Responses

u    Release of adrenaline

u    Increase HR & BP

u    Increase respiration

u    Increase blood flow to heart & muscles

u    Dilate pupils

 

u    Release stored energy

u    Sweat to cool body

u    GI tract slows down; mouth dry

u    Decrease blood to skin

 

Parasympathetic Responses

u    Decreases HR & BP

u    Slows breathing

u    Lubricates mouth

u    Stimulates digestion and storing of energy

u    Constricts pupil

u    Responsible for elimination

u    Increased blood flow to skin

Psychosomatic Symptoms/Illnesses

u   These are real physical symptoms (increased blood pressure, ulcers, asthma, headaches, etc) that have a psychological cause or contributing factor.

u   Depend in part on your genetic predisposition, lifestyle, stresses, and coping strategies.

 

Ulcers

u   Painful lesions in the stomach/duodenal lining are more common in humans or rats experiencing stress

u   More recently ulcers have been linked to bacterial infection in almost all cases except those taking NSAIDS like aspirin or ibuprofen.

Ulcers continued

u   BUT: 75% of us without ulcers still have this bacterial infection

u   Stress and infection seem to interact to induce ulcers, perhaps through lowered resistance

 

Harm From Parasympathetic Rebound

u   During sympathetic arousal gastric secretions are decreased, but in the aftermath of stress they rebound.

u   Likewise cases of “voodoo death” or death due to expectancy or giving up appears to be due to excess parasympathetic slowing of heart!

 

Physiological  Responses to Stress – Part 2

u   Sympathetic activation is usually rapid and temporary.

u   More prolonged stress activates the 2nd component of our stress response: the “Hypothalamus-pituitary-adrenal cortex axis” (HPA).

 

Hypothalamus-Pituitary

u   Hypothalamus controls anterior pituitary via hormones secreted into portal blood supply

Chain of command – hypothalmus-pituitary-adrenals

u   Hypothalamus tells pituitary to release ACTH.

u   ACTH tells adrenal cortex to release cortisol, an adrenal steroid.

 

Location of adrenals

 

Adrenal cortex vs adrenal medulla

 

Immune System

u   System which produces a variety of cells and a variety of responses to protect the body against intruders (infection)

u   2 categories of immune reactions:

    Quick (1-2 hrs) Nonspecific Reactions to destroy invaders or decrease their reproduction

    Slower (4-5 days or more) Specific Reactions to specific strains & lasting immunity

 

Leukocytes (white blood cells)

Trigger 2 Types of Specific Reactions:

u   Cell-mediated defenses: T-cells with surface antibodies attack invaders & stimulate the production of more immune system cells

u   Chemically-mediated or “humoral” defenses:          B-cells which produce circulating antibodies. When the antibodies attach to the intruder, they mark those sells for destruction                                                                  

 

Psychoneuroimmunology

u   Interdisciplinary field studying the connections between psychological processes, the nervous system and the immune system function

 

Stress Effects on Immune System

u   Cortisol initially helps supply energy & reduce inflammation to sustain your ability to function under stress, but, in the long-run, suppresses immune function.

u   Stress hormones decrease production of both T and B cells lowering resistance to infection.

u   Immune cells also have receptors for neurotransmitters

u   Stress hormones also affect lower resistance of areas of CNS

 

Stress & Immune Function

u   Research shows that not only do major stresses decrease immune function (re-entry of space shuttle; caring for family member with serious cancer or Alzheimer’s), so do:

u   the end of a relationship

u   exam periods

u   frustrating tasks, stressful jobs

Immune System to Brain Signals

u    Cytokines activate vagus nerve which in turn signals hypothalamus & hippocampus to produce brain cytokines.

u    Cytokines produce changes in feeling (pain, fatigue, lack of energy) and behavior (decreased activity, eating, sexual behavior, increase shivering, desire to curl up under the covers) to combat infection and promote healing

 

Amygdala Within Limbic System

 

fMRI to seeing a fearful face

 

Amygdala Reactivity Partly Determined by Genes

u   Those who inherit gene causing less effective 5HT transport show stronger responses

 

Urbach-Wiethe Disease

u   Rare, hereditary metabolic disorder causing calcification of amygdala, disrupting its normal functions.

u   Do not seem to experience or recognize negative emotions (fear, anger, upset, dislike) in faces or body language. Do not develop classically conditioned fear responses.

 

Neurochemistry of Anxiety

u   Excitatory transmitter in amygdala: CCK (cholecystokinin)

u   Inhibitory transmitter: GABA

Increased CCK or decreased GABA à increased fear/anxiety

Increased GABA action à decreased anxiety

(benzodiazepines, barbiturates, alcohol do this)

 

GABA Receptor

Research on The Biological Basis of Aggression & Violence

u   Genetic

u   Hormonal

u   Brain research

u   Pharmacological/neurochemical

Genetics

u   Identical twins: ~.60 concordance for aggressive/antisocial/criminal behaviors

u   Fraternal twins: ~ .30 concordance

u   In adoption studies, criminality/aggression of biological dad is better predictor of child’s adult behavior than that of adopted parent.

u   BUT: Highest probability of aggression in those with both “bad” biological & adoptive parent.

 

Neuroanatomy

u   Electrical stimulation of amygdala or ventromedial hypothalamus can trigger aggressive behaviors

u   Seizures in the temporal lobe are one of the few types of epilepsy associated with violent behavior.

u   Removal of the amygdala results in tameness and placid behavior.

 

Brain Chemistry

u    Aggression associated with reduced 5HT turnover in mice, rats, monkeys.

u    Reduced 5HT turnover also observed in humans, from aggressive adolescents to those convicted of violent crimes.

u    Also seen in those who attempt suicide by violent means.

u    Low turnover was also a good predictor of future aggressive acts & future violent suicide attempts.