Biological Psychology Notes

Biological Psychology Week 7: Biological Psychology 2

  • This lecture builds upon concepts covered in Chapter 3 of Lilienfeld's Psychology: From Inquiry to Understanding, 3rd Edition.
  • Illustrates these concepts with case studies of abnormal behavior and cognition, exploring their neurobiological basis.
  • Focuses on the limbic system, autonomic nervous system, aggression, addiction, and the biological basis of alcoholism.
  • Thanks to Prof. Stephen Robinson for this lecture series

Learning Objectives

  • Explain with examples, how the ‘limbic system’ underpins aspects of emotionally-driven behaviours, especially aggression and addiction.
  • Describe the functional interrelationship of the limbic system and the autonomic nervous system.
  • Understand the biological basis of alcoholism and how alcohol affects brain function.

Case Studies: Tumors and Aggression

  • Ben Parry: Experienced mood swings due to a brain tumor; removal of the tumor restored his normal behavior.
  • 13-year-old boy: Aggressive and antisocial behavior due to a tumor in the medial temporal lobe; removal led to improved behavior and academic performance.
  • 5-year-old boy: Aggressive behavior due to a tumor in the inferior temporal lobe; removal resolved the aggression issues.

Charles Whitman: The Clock Tower Terrorist

  • Charles Whitman: Fired from the clock tower at the University of Texas in 1966, killing 14 and wounding 31.
  • Prior to the event, Whitman experienced rage, confusion, and violent impulses.
  • An autopsy revealed a glioblastoma (tumor) pressing on his thalamus, hypothalamus, and amygdala.

Limbic System and Autonomic Nervous System

  • The limbic system and autonomic nervous system are crucial in understanding the biological basis of behavior, especially in cases of uncontrolled anger and aggression.

The Limbic System

  • Term coined by Paul Broca, later confirmed by James Papez (1937), who discovered a circuit by injecting rabies virus into the hippocampus of cats
  • Papez's Loop: Hippocampus → Fornix → Mammillary body → Anterior nucleus of thalamus → Cingulate gyrus
  • Definition: A group of interconnected brain regions responsible for emotions, survival, reproduction, and memory.
  • Receives direct input from the olfactory system.
  • Strong modulatory influence on the autonomic nervous system.
  • Debate exists about the usefulness of the term. Hard to define the exact anatomy. Issues of specificity.

Autonomic Nervous System (ANS)

  • Responsible for:
    • Regulation of the body’s metabolism
    • Adjusting the body’s energy requirements.
  • Activity can be influenced by conscious awareness.
  • Components:
    • Sympathetic Nervous System: 'Fight, fright, and flight' (stress). Neurotransmitter: noradrenaline.
    • Parasympathetic Nervous System: 'Rest and digest' (calm). Neurotransmitter: acetylcholine.

Sympathetic vs. Parasympathetic Actions

  • Eye:
    • Sympathetic: Dilates pupil and elevates eyelid
    • Parasympathetic: Constricts pupil
  • Lacrimal Glands:
    • Sympathetic: Slight increase
    • Parasympathetic: Increases tear secretion
  • Salivary Glands:
    • Sympathetic: Secretion of thick saliva
    • Parasympathetic: Secretion of watery saliva
  • Heart:
    • Sympathetic: Increases rate and force of contraction
    • Parasympathetic: Decreases rate and force of contraction
  • Bronchi of Lungs:
    • Sympathetic: Bronchodilation
    • Parasympathetic: Bronchoconstriction and bronchosecretion
  • Liver & Pancreas:
    • Sympathetic: Glycogenolysis and glycolysis
    • Parasympathetic: Gluconeogenesis
  • Sweat Glands: Increases secretion (Sympathetic)
  • Piloerector Muscles: Contract (goose bumps) (Sympathetic)
  • Adrenal Medulla: Secretes adrenaline into bloodstream (Sympathetic)
  • Bladder:
    • Sympathetic: Constricts sphincter
    • Parasympathetic: Relaxes sphincter (micturition)
  • Reproductive Organs:
    • Sympathetic: Facilitates erection and ejaculation
    • Parasympathetic: Facilitates orgasm, cervical dilation
  • Gastrointestinal Tract:
    • Sympathetic: Decreases motility and secretion
    • Parasympathetic: Increases motility and secretion
  • Arteries:
    • Sympathetic: Vasoconstriction in most places, vasodilation in skeletal muscle
    • Parasympathetic: Vasodilation (but only in the intestine)

Key Points on Sympathetic and Parasympathetic Systems

  • The sympathetic nervous system is controlled largely at the thoracic level of the spinal cord.
  • The parasympathetic nervous system originates from the brainstem and the sacral levels of the spinal cord.
  • Both systems innervate all organs but largely have opposing effects.
  • Both systems are influenced by the limbic system via the hypothalamus.
  • Both systems are unconsciously controlled but play a key role in our body’s response to emotion.

Main Components of the Emotion Processing and Regulation System (Limbic System)

  • Cingulate gyrus
  • Amygdala
  • Cerebral cortex (frontal, olfactory)
  • Hippocampal formation
  • Septal area
  • Hypothalamus (mainly mammillary nuclei)
  • Thalamus (anterior & dorsomedial nucleus)

Septal Area

  • Stimulation results in pleasure, lust, euphoria, and orgasm.
  • Connected with the ventral tegmental area, involved in addictive behaviors.
  • Rats will perform up to 6000 bar-presses an hour to obtain self-stimulation of this region.

Amygdala

  • Strongly connected with the olfactory system, hippocampus, and hypothalamus.
  • Plays a key role in evaluating threats and changing behavior accordingly.
  • Evaluation is done subconsciously, drawing on previous experience.
  • Bilateral amygdalectomies were once used to 'tame' violently aggressive individuals.
  • Implicated in anxiety disorders, phobias, PTSD, social phobia, obsessive-compulsive disorder, and schizophrenia.

Alcohol and Brain Function

Background

  • Humans possess very active versions of enzymes that metabolize alcohol
  • Breakdown of ethanol produces acetate, a rich source of energy.
  • Historically, alcoholic beverages were preferred over water to avoid gastrointestinal infections.

How Alcohol Affects Brain Function

  • Ethanol is a small, lipid-soluble molecule that readily enters the brain.
  • Binds to many neurotransmitter receptor types, altering their activity.
  • Primary effects are on GABA signal pathways.

GABA and Alcohol

  • GABA is an inhibitory neurotransmitter that reduces neuronal activation.
  • Ethanol binds to GABAA receptors, increasing their sensitivity and making cells more likely to become hyperpolarized and less responsive to stimulation.
  • 70% of all neurons have GABAA receptors, so the inhibitory effect of ethanol is widespread.

Effects of Ethanol

  • Mild depression of neural activity in limbic circuits leads to an anxiolytic effect.
  • Higher doses depress activity in the motor cortex and cerebellum, impairing coordination.
  • Severe intoxication can lead to flaccid paralysis and cessation of breathing.
  • Reduced neuronal activity in the sensory cortex impairs balance, hearing, and pain awareness.
  • Inhibition of the prefrontal cortex leads to disinhibition and risk-taking.
  • Ethanol also acts on dopaminergic cells in the septal area, increasing dopamine release.
  • This underpins the sensation of pleasure and the addictive quality of alcohol.

Genetics of Alcoholism

  • Alcohol decreases stress to a greater extent in sons of alcoholics.
  • Sons of alcoholics show less-than-average intoxication after alcohol consumption.
  • Genes linked to alcoholism:
    • Dopamine type 4 receptor: Alcoholics may have a less sensitive form, seeking greater intoxication for pleasure.
    • COMT enzyme: Alcoholics may have a more active form, clearing dopamine more rapidly and blunting the pleasurable effect.

Alcohol and Memory Loss

  • Memory loss is more pronounced for transfer from short to long-term memory (blackouts).
  • Alcohol acts to suppress NMDA receptors (a glutamate receptor) in the hippocampus.
  • Hippocampus volume reduction correlates with alcohol consumption.

Wernicke-Korsakoff Syndrome

  • Alcohol causes thiamine (vitamin B1) deficiency.
  • Thiamine is necessary for metabolizing glucose to produce energy for the brain.
  • Wernicke Encephalopathy:
    • Confusion and loss of mental activity
    • Loss of motor coordination (ataxia)
    • Back and forth movements of the eyes (nystagmus)
    • Brain volume shrinkage
  • Korsakoff’s Psychosis:
    • Inability to form new memories
    • Loss of recent memories
    • Making up stories (confabulation)
    • Hallucinations

Brain Shrinkage in Alcoholism

  • Mammillary nuclei in the hypothalamus are prone to damage in Korsakoff’s psychosis.
  • Patients have anterograde amnesia, which they conceal by confabulation.
  • Mammillary nuclei may be involved in tagging memories with an emotional label for easier retrieval.

Summary

  • Growing appreciation of the interplay between the brain, our organs, our genome and our environment.
  • Our growing awareness of the biological basis of behaviour raises many thorny ethical issues.