Brain and Body (2_24_25)

Brain and Body

• Date: 24 February 2025

Subcortical Structures

• Thalamus

  • Functions as the brain's sensory switchboard.

  • Directs messages to all sensory areas in the cortex (except olfactory signals).

• Hypothalamus

  • Regulates bodily functions and motivated behaviors such as hunger, thirst, aggression, and sex.

  • Located in the prefrontal lobe.

• Corpus Callosum

  • Directly connects the left and right hemispheres of the brain.

  • Aids in transmitting messages throughout the cerebral cortex.

Hippocampus

• Overview

  • C-shaped structure located at the center of the limbic system.

  • Essential for the formation of long-term memories.

  • Notably damaged in the case of Clive Wearing, affecting his memory abilities.

Amygdala

• Role

  • Involved in threat-related emotional processing.

  • Strongly linked to fear and anger responses.

  • Intensifies memory for threat-related events.

  • Works closely with the hippocampus in reactivating memories tied to strong emotional experiences.

  • Sensitive to fear-related stimuli.

• Cerebellum

  • Associated with timing and coordination, serves to enhance emotional memory through its proximity to the amygdala.

Brain Plasticity

• Definition

  • Plasticity refers to the brain's ability to change in response to experience.

  • Forms the foundation for learning, particularly strong during early development.

• Critical Periods

  • Specific times when input must occur for proper development.

  • Example: Cats and humans deprived of early visual experiences may never develop normal vision.

• Impact of Experience

  • Every experience can affect the strength of neural connections in the brain.

Cortical Plasticity

• Sensory Reorganization

  • Areas not receiving standard input may reorganize to process different types of sensory information.

  • Example: In blind individuals, the visual cortex is active when reading Braille.

• Function Recovery

  • Damaged areas of the brain can sometimes be compensated for by new neural pathways in undamaged regions.

  • Plasticity tends to decline with age.

  • Notable case: An individual without arms learned to write and paint using their feet, resulting in larger areas of the brain dedicated to foot control.

Nervous System Overview

• Definitions

  • The nervous system comprises all nerve cells in the body, functioning as a fast electrochemical communication system.

  • Central Nervous System (CNS)

    • Encompasses the brain and spinal cord.

    • Responsible for decision-making processes.

  • Peripheral Nervous System (PNS)

    • Sensory and motor neurons that connect the CNS to the rest of the body.

Peripheral Nervous System (PNS)

• Components

  • Autonomic Nervous System: Controls self-regulated actions of internal organs and glands.

    • Sympathetic Nervous System: Responsible for arousal and "fight or flight" responses.

    • Parasympathetic Nervous System: Regulates "rest and digest" functions.

  • Somatic Nervous System: Controls voluntary movements; sends sensory information from skin, muscles, and joints to the CNS.

Autonomic Nervous System Functions

• General Role

  • Regulates internal environment and actions of the body.

  • Controls organ functions and stimulates gland activity.

• Sympathetic vs. Parasympathetic

  • Sympathetic: Mobilizes the body for emergency action, increases heart rate, and energy arousal.

  • Parasympathetic: Maintains routine operations and aids recovery from stress, decreases heart rate and restores energy balance.

Genes and Environment

• Overview of Influence

  • Genetic factors lay the foundation for human traits.

  • Genotype: The unique genetic makeup of an individual.

  • Phenotype: Observable characteristics resulting from genotype and environmental interactions.

• Gene-Environment Interaction

  • Multiple factors influence the observable traits of an individual beyond genetic predispositions.

Heritability

• Definition

  • The estimate of variability in a trait within a population attributable to genetics.

  • Higher similarities in traits among genetically similar individuals suggest genetic influence on those traits.

Twin Studies and Genetics

• Purpose

  • Behavior geneticists aim to untangle the effects of genetics and environment.

  • If identical twins exhibit more similarities in psychological traits compared to fraternal twins, it indicates genetic influence.

• Findings

  • Studies have shown that identical twins tend to be more alike in traits such as intelligence and behavioral patterns than fraternal twins.

Studies of Separated Twins

• Minnesota Twin Study

  • Investigated identical and fraternal twins raised together and apart to assess similarities in traits.

  • Found that identical twins raised in different environments remain similar in personality, intelligence, and achievements.

• Critique

  • Some critics argue that similarities in twins may also reflect shared cultural or economic environments.

  • Identical twins may evoke similar responses from their surroundings due to their shared genetics.

Complications of Nature vs. Nurture

• Insights

  • Variability in responses to the same environment among different genotypes.

  • Example: Some boys with certain genetic markers (monoamine oxidase gene alleles) showed differing vulnerabilities to maltreatment.

Epigenetics

• Overview

  • Environmental influences can activate or deactivate genes.

  • Identical twins may have different epigenetic experiences due to factors such as stress, diet, or pollution.

  • Epigenetic changes can also be passed to offspring.