Biological Psychology Overview

Biological Psychology: A Bridge Between Psychology and Neuroscience

• Biological psychology explores how biological factors influence psychological phenomena like learning, memory, emotion, and perception.

History of Biological Psychology

• Phrenology (19th Century): Founded by Gall, phrenology proposed that personality and abilities could be determined by skull bumps.

Techniques in Biological Psychology

• Observations of behavior after head injuries: Studying how brain damage affects behavior.
• Animal brain dissection: Examining animal brains to understand brain structure and function.
• Post-mortem dissection of human brains: The examination of a dead person's brain after death.
• Microscopic examination of nerve cells: Investigating the structure and function of neurons at a cellular level.
• Neuroimaging techniques: Advanced methods for studying brain structure and function.

Neuroimaging Techniques

• Brain Structure:
  • CT scan (Computerized Tomography): Uses X-rays to create cross-sectional images of the brain.
  • MRI scan (Magnetic Resonance Imaging): Creates detailed images of brain structure using magnetic fields.
• Brain Function:
  • EEG (Electroencephalography): Measures electrical activity in the brain via electrodes on the scalp.
  • PET scan (Positron Emission Tomography): Measures brain activity by detecting radioactive substances injected into the bloodstream.
  • fMRI (Functional Magnetic Resonance Imaging): Measures brain activity by detecting changes in blood flow.
  • MEG (Magnetoencephalography): Measures magnetic fields produced by electrical activity in the brain.
  • TMS (Transcranial Magnetic Stimulation): Uses magnetic pulses to stimulate or inhibit brain activity.

Disorder of Consciousness

• Coma: No wakefulness or awareness, no response to commands.

• Vegetative State: Awake but unaware, can display sleep-wake cycles and reflexes but no response to commands.

• Locked-in Syndrome: Awake and aware, but unable to respond due to paralysis, only able to communicate via eye movements.

• EEG recording can investigate brain activity in vegetative patients. Healthy brains exhibit complex and interconnected networks which support awareness, some vegetative patients maintain well-preserved neural networks.

• Clinical assessments based on behavioral responses might not reveal residual awareness if motor skills are highly impaired.

• fMRI can detect signs of cognitive function and awareness consistent with locked-in syndrome in such patients. This offers these patients a means of communication with the outside world.

Basic Brain Anatomy

• Cerebral Cortex:

  • Frontal Lobe: Motor activity, speech, planning, impulse control.
  • Parietal Lobe: Integrating sensory information, spatial tasks.
  • Temporal Lobe: Auditory perception, memory, emotion.
  • Occipital Lobe: Visual perception.

• Lateralization of Function (Sperry, 1981):

  • Left Hemisphere: Language, computation, logic.
  • Right Hemisphere: Spatial reasoning, face recognition, music.
  • Corpus Callosum: Connects the two hemispheres.

• Contralateral Organization: Visual processing, muscle and limb control are organized on the opposite side of the brain.

• Effects of Brain Injuries (e.g., stroke): Injuries can affect various functions like face, arm, speech, and time perception.

• Split-Brain Patients: Patients with surgically severed corpus callosums. Information presented to one visual field is processed by the opposite hemisphere.

Nervous System

• Basal Ganglia: Includes caudate nucleus, putamen, and globus pallidus; involved in movement control, damaged in Parkinson's disease.

Emotion

• Emotional Responses: Measured via polygraph (lie detector), which measures galvanic skin response, heart rate, and blood pressure, although error rates are high (25-75%).
• Phineas Gage Case (Harlow, 1848): Accident caused damage to his frontal lobe (orbitofrontal cortex). His personality changed drastically, from well-balanced to impulsive.
• Biological Psychology of Emotion:
  • Cortex: Inhibits and directs emotions.
  • Sub-cortical Structures (Limbic System): Generates emotional responses.
• Amygdala: Crucial for fear conditioning and recognition of facial expressions of fear. Damage can cause a lack of fear. Criminal psychopaths show less activation in the amygdala.
• Psychopaths exhibit poor emotional development and reduced ability to feel, read, and learn from emotions.

Neuron

• Neuron (Nerve Cell): The fundamental unit of the nervous system.

  • Cell Body: Contains the nucleus.
  • Dendrites: Receive signals from other neurons.
  • Axon: Sends signals towards other neurons.
  • Axon Terminals: Synaptic sites, ends close to other neurons.

• Electrical Conduction: Positive sodium ions enter the neuron, causing depolarization (brief positive charge); then, potassium ions exit to restore negative charge.

• Myelination: Speeds up action potential propagation. Myelination continues into adolescence.

• Cell Firing: Excitatory influences lower firing threshold (more likely to fire); inhibitory influences raise threshold (less likely to fire).

Major Neurotransmitters

• GABA (gamma aminobutyric acid): Primarily inhibitory.
• Acetylcholine (ACh): Associated with memory, muscular movement, and Alzheimer's disease.
• Serotonin: Influences mood, sleep, and eating (implicated in depression and OCD).
• Dopamine (DA): Involved in voluntary movement, pleasure, and schizophrenia (implicated in Parkinson's disease).
• Endorphins: Neuromodulators playing a role in pain sensitivity.

Dopamine (DA) System

• DA neurons originate from two midbrain nuclei (substantia nigra and ventral tegmental area), projecting to various brain regions (nigrostriatal, mesocortical, mesolimbic pathways).

Drug Action

• Agonists: Facilitate neurotransmitter action.
• Antagonists: Reduce neurotransmitter action.

Psychoactive Drugs

• Depressants: Suppress bodily processes (alcohol, valium).
• Opiates: Pain relievers (morphine, heroin).
• Stimulants: Increase bodily processes (methamphetamine, cocaine).
• Hallucinogens: Produce sensory distortions (LSD, cannabis).

Substance Use Disorders (DSM-5 Criteria)

• Diagnosis based on criteria like hazardous use, social/interpersonal problems, neglect of roles, tolerance, withdrawal, misuse of substance, persistent efforts to quit, or give up social/occupational/recreational activities. Also including physical and psychological problems related to substance use and craving.

Physical Dependence: Tolerance

• Repeated drug use leads to decreased responsiveness at the site of action (fewer receptors, decreased binding efficiency, less responsive receptors).