Lecture Notes on Biology in Psychology II

Introduction to Psychology: Biology in Psychology II

This session, PSYC BC 1001: INTRODUCTION TO PSYCHOLOGY, presented by Isabelle Portelinha, PhD, focuses on brain structures and the factors that shape the brain.

Previous Sessions Review

  • I

    ntroduction to Course


  • Introduction to Psychology

  • History of/Perspectives in Psychology

  • Research Methods

  • Biology in Psychology I

    • Nervous Systems

    • Neurons

Neurotransmitters in the Synapse

Neurotransmitters are chemical messengers that transmit signals across a chemical synapse.

  • Acetylcholine:

    • Motor control over muscles.

    • Involved in attention, memory, learning, and sleeping.

  • Epinephrine (i.e., adrenaline):

    • Primarily associated with energy.

  • Norepinephrine:

    • Plays a role in arousal and alertness.

  • Serotonin:

    • Influences emotional states, impulse control, and dreaming.

  • Dopamine:

    • Crucial for reward and motivation.

    • Involves motor control over voluntary movement.

  • GABA (gamma-aminobutyric acid):

    • Inhibits action potentials, reducing the likelihood of a neuron firing.

    • Known for anxiety reduction.

    • Its effects are enhanced by alcohol, leading to intoxication.

  • Glutamate:

    • Enhances action potentials, increasing the likelihood of a neuron firing.

    • Essential for learning and memory.

  • Endorphins:

    • Involved in pain reduction.

    • Contributes to reward pathways.

Drugs and Neurotransmitters

  • Agonists: Drugs that enhance the actions of neurotransmitters.

  • Antagonists: Drugs that inhibit the actions of neurotransmitters.

Neuronal Communication: Postsynaptic Signals

Postsynaptic neurons receive signals from presynaptic neurons, which can be of two types:

  • Excitatory: These signals increase the likelihood that the postsynaptic neuron will fire an action potential.

  • Inhibitory: These signals inhibit the neuron, decreasing the likelihood that it will fire an action potential.

Brain Structures

The brain is broadly divided into three main regions, with the spinal cord serving as the primary communication link between the brain and the body.

I. Hindbrain: Survival Programs

The hindbrain is located at the base of the skull, continuing from the spinal cord, and houses programs critical for survival.

  • Medulla:

    • Essential for basic survival functions, such as breathing and heart rate.

  • Pons:

    • Regulates sleep and arousal.

    • Coordinates movements of the left and right sides of the body.

  • Cerebellum:

    • Crucial for coordinated movement and balance.

II. Midbrain: Survival Programs

The midbrain is situated above the hindbrain and also plays a role in survival functions.

  • Reflexive movement:

    • Involved in reflexive movements of the eyes and body.

  • Substantia Nigra:

    • Critical for the initiation of voluntary motor activity.

    • Essential for dopamine production.

    • The death of substantia nigra cells is linked to Parkinson's disease.

III. Forebrain: Motivations, Emotions, and Complex Mental Activity

The forebrain is the largest and most complex part of the brain, responsible for higher-level cognitive functions.

A. Subcortical Structures: Motivations and Emotions

These structures are located beneath the cerebral cortex and are involved in regulating bodily functions, motivations, and emotions.

  • Thalamus:

    • Acts as a sensory gateway to the brain.

    • Almost all incoming sensory information (except smell) passes through the thalamus before reaching the cerebral cortex.

  • Hypothalamus:

    • Involved in regulating essential bodily functions (e.g., temperature, metabolism, blood pressure).

    • Influences basic motivated behaviors such as hunger, thirst, and sex drive.

  • Hippocampus:

    • Primarily associated with the formation of new memories.

  • Amygdala:

    • Plays a key role in learning to associate things with emotional responses.

    • Crucial for processing emotional information, particularly fear.

  • Basal Ganglia:

    • Involved in motor planning and movement.

    • Also contributes to the brain's reward system.

B. Cerebral Cortex: Complex Mental Activity

The cerebral cortex is the outer layer of the forebrain, responsible for complex thought, perception, and behavior.

  • Structure:

    • Divided into two halves: the left and right cerebral hemispheres.

    • Corpus Callosum: A large bridge composed of millions of axons that connects and allows communication between the two cerebral hemispheres.

  • Four Lobes (each hemisphere has these four lobes):

    • Occipital Lobe:

      • Located at the back of the brain.

      • Primarily responsible for vision, housing the primary visual cortex.

    • Parietal Lobe:

      • Located above the temporal lobe and behind the frontal lobe.

      • Processes touch information (primary somatosensory cortex).

      • Involved in spatial relations and picturing the layout of spaces in an environment.

    • Temporal Lobe:

      • Located below the parietal and frontal lobes.

      • Processes auditory information (primary auditory cortex).

      • Important for perceiving objects and faces (e.g., Fusiform Face Area for face recognition).

      • Involved in memory.

    • Frontal Lobe:

      • Located at the front of the brain.

      • Involved in movement (primary motor cortex).

      • Prefrontal Cortex: The foremost part of the frontal lobe, crucial for rational thought, attention, self-control, and social processes. Damage here can lead to significant personality changes and impaired social behavior.

Brain Research Techniques

Various techniques allow scientists to study brain activity and structure.

  • Electroencephalograph (EEG):

    • Measures electrical activity in the brain.

    • Different behavioral states (e.g., sleep, wakefulness) produce distinct and predictable EEG patterns.

  • Functional Magnetic Resonance Imaging (fMRI):

    • Detects changes in the blood's oxygen level, which correlate with neural activity.

    • Provides spatial information about active brain regions.

  • Transcranial Magnetic Stimulation (TMS):

    • Uses a fast and powerful magnetic field to momentarily disrupt or stimulate activity in a specific brain region.

    • Allows researchers to infer causality between brain activity and behavior.

Shaping the Brains: Roles of Nature & Nurture

The brain, and consequently our thoughts and behaviors, are continually shaped by the interaction between our genetic makeup and environmental experiences.

Behavioral Genetics

  • The study of how genes and environment interact to influence psychological factors.

  • Genes: Units of heredity that partially determine an organism’s characteristics and impact thoughts and behaviors.

  • Genotype: An individual's complete genetic makeup.

  • Phenotype: The observable physical and psychological characteristics of an organism, resulting from the interaction of genotype and environment.

  • Studies involving Monozygotic (identical) and Dizygotic (fraternal) twins are commonly used to assess the relative contributions of genes and environment.

Plasticity

  • The property of the brain that allows it to change and reorganize itself through experience, drug use, or injury. This enables learning and adaptation.

  • Reflects the interactive nature of biological and environmental influences.

  • Strengthening existing connections:

    • The principle "neurons that fire together, wire together" describes how synchronous activity between neurons strengthens their synaptic connections.

  • Brain reorganization:

    • Involves the development of entirely new connections between neurons.

    • New growth and reorganization are major factors in recovery from brain injury.

    • Brain reorganization is generally more common and robust in children compared to adults.

Classic Case Studies and Clinical Implications
Phineas Gage (1848)

  • Case: A railroad worker who survived a yard-long metal rod piercing his brain.

  • Symptoms: Experienced significant changes in personality, including agitation, disrespect, use of gross profanity, poor self-control, giving in to "animal" desires, and decreased social abilities.

  • Brain Area Injured: Most likely the prefrontal cortex in his frontal lobe.

  • Implications: This case demonstrated that the prefrontal cortex is responsible for understanding social norms, exhibiting self-control, and avoiding socially inappropriate behaviors. Damage results in a decreased ability to get along with others.

Parkinson's Disease

  • Symptoms: Difficulty starting movements, changes in thought and emotions, an odd shuffling walk, rigid muscles, and tremors at rest.

  • Brain Cause: Damage to the substantia nigra, a part of the midbrain.

  • Pathology: Neurons that produce dopamine in the substantia nigra die off.

  • Treatment: Patients are sometimes given L-DOPA, a chemical precursor (building block) of dopamine, which can lead to temporary recovery of motor functions.

Conclusion

  • The hindbrain and midbrain house programs essential for our survival, regulating basic life-sustaining functions and reflexive movements.

  • The forebrain's subcortical structures control our motivations and emotions, playing roles in memory, sensory processing, and homeostatic regulation.

  • The forebrain's cerebral cortex is responsible for complex mental activity, including thought, planning, perception, and voluntary movement.

  • Our brain, and consequently our thoughts and behavior, are profoundly affected by the dynamic interaction between our genes and the environment.

  • Learning is enabled by the remarkable plasticity (both chemical and structural) of our brains, which allows for adaptation and reorganization.