psychology lec 2- 2025-02-01T17:35:09

Evolution and Structure of the Brain

• Advances in technology provide clearer insights into brain structure and function.

• The brain stem contains older structures common to many animals, including humans.

• Basic physiological functions such as breathing and heart rate are controlled by the brain stem.

• Modern structures, such as the cerebrum, are built upon the brain stem and are involved in higher-order processes, including thinking and reasoning.

Hierarchical Structure of the Brain

Major Components

• The brain consists of three primary parts:

  • Hindbrain: Involved in essential survival functions.

  • Midbrain: Controls movement patterns, sleep, and arousal.

  • Forebrain: Comprises the limbic system, thalamus, and cerebral cortex.

Hindbrain Functions

• Brain Stem: The most primitive part, vital for life support systems; loss of function can be fatal.

  • Components:

    • Medulla: Controls heartbeat and breathing; well-developed at birth.

      • Mediates contralateral control (e.g., right side of the body controlled by the left side of the brain).

    • Pons: Connects various parts of the nervous system; facilitates autonomic functions, sleep, and arousal.

    • Cerebellum: Coordinates muscle movement and balance; affected significantly by alcohol consumption.

Midbrain Contributions

• Houses centers for vision, eye movement, hearing, and body movement.

• Reticular Formation: Filtering information, regulating arousal, important for multitasking.

• Damage can lead to coma, while stimuli such as smelling salts can arouse patients.

The Limbic System

• Involved in emotion, motivation, and memory, often called the visceral brain.

• Components:

  • Hypothalamus: Regulates autonomic functions, body temperature, hunger, and thirst; includes reward centers.

  • Amygdala: Regulates fear responses and aggression; damage can impair emotional reactions.

  • Hippocampus: Critical for memory formation and spatial orientation; involved in processing new information.

Forebrain Functionality

Thalamus

• Acts as the brain's switchboard, relaying information between various parts.

• Processes neural rhythms related to sleep and waking.

Cerebral Cortex

• The outer layer of the cerebrum, about 2.5mm thick; responsible for higher cognitive functions like thinking and learning.

• Comprises about 80% of the human brain's volume.

• Contains sensory and motor areas as well as association areas that integrate information.

Lobes of the Cerebral Cortex

Occipital Lobe

• Processes visual information from the eyes via the optic nerve.

• Contains the primary and secondary visual cortex.

Temporal Lobe

• Involved in processing auditory input and memory recognition.

• Engages in functions like speech recognition.

Parietal Lobe

• Responsible for processing sensory input and spatial awareness.

• Integrates information from touch, vision, and audition.

Frontal Lobe

• Houses the motor cortex, responsible for motor functions and speech production (e.g., Broca's area).

• Involved in planning, judgment, and higher-order cognitive functions.

Association Areas

• Highly integrative, supporting complex mental activities.

• Not easily mapped; activation observed in neuroimaging studies.

• Prefrontal cortex: Responsible for executive functions like decision-making and impulse control.

Brain Hemisphere Lateralization

• Each hemisphere specializes in different functions:

  • Left Hemisphere: Language, logic, mathematics, and positive emotions.

  • Right Hemisphere: Spatial awareness, pattern recognition, melodies, and negative emotions.

• Contralateral Control: Sensory and motor functions are cross-related between the hemispheres.

Corpus Callosum

• A major neural pathway connecting the two hemispheres.

• Allows for efficient communication between them.

Split-Brain Research

• Severing the corpus callosum treats extreme epilepsy but disrupts inter-hemispheric communication.

• Findings from Split-Brain Patients:

  • Tasks involving stimuli presented to one hemisphere highlight independence.

  • Example: Patients may not name an object in the left visual field but can draw it with the left hand, controlled by the right hemisphere.

Conclusion

• The brain operates through complex interactions between its parts, illustrating how specific areas relate to cognitive functions and emotional responses.