The Brian (2_19_25)

The Brain Overview

• Cerebrum: Major part of the brain responsible for higher brain functions.

• Cerebral Cortex: Outer layer of the cerebrum involved in complex functions.

• Thalamus: Sensory relay station.

• Corpus Callosum: Connects left and right hemispheres, facilitating communication.

• Hypothalamus: Regulates bodily functions (thirst, hunger, emotions).

• Pituitary Gland: Endocrine gland controlled by the hypothalamus, involved in hormone regulation.

• Pons: Key structure in sleep and arousal.

• Cerebellum: Coordinates voluntary movements and motor learning.

• Reticular Activating System: Regulates wakefulness and sleep-wake transitions.

• Medulla: Controls basic life functions (heart rate, breathing).

Historical Context of Brain Studies

Phrenology (1800)

• Proposed by Franz Gall: bumps on the skull correlated with mental abilities.

• While the theory was incorrect, it introduced the idea of brain localization, suggesting specific brain areas are linked to psychological traits.

Techniques to Study the Brain

Lesion Studies

• Definition: Areas of brain tissue that have been destroyed.

• Experimental Use: Lesions applied in animals to understand specific brain functions.

• Human Studies: Observing behaviors after brain injuries (e.g., TBI, stroke, surgeries).

• Notable Areas:

  • Lesion to Wernicke’s Area: Affects language comprehension.

  • Lesion in rats modeled Tourette Syndrome.

  • Lesion to Broca’s Area: Alters speech production.

Non-Invasive Techniques

EEG (Electroencephalogram)

• Measures electrical activity in the brain via scalp electrodes.

• Pros: Excellent for timing brain activity.

• Cons: Poor at pinpointing the location of activity; primarily measures surface activity.

• Useful for examining neural processes related to evolving stimuli like language.

PET (Positron Emission Tomography)

• Measures brain activity by injecting a radioactive tracer.

• Functionality: Directly measures metabolic processes in the brain.

MRI (Magnetic Resonance Imaging)

• Utilizes powerful magnets to align hydrogen protons in body tissues.

• Advantages: Produces high-quality structural images with excellent spatial resolution.

fMRI (Functional MRI)

• Measures blood flow to active brain regions.

• Strengths: High spatial resolution for identifying active regions during tasks.

• Limitations: Poor temporal resolution; data are correlational, thus not definitive about causation.

Transcranial Magnetic Stimulation (TMS)

• Uses electromagnetic fields to temporarily disrupt or enhance brain regions.

• Overall Use: To study brain function and modulation of specific areas.

Brain Anatomy and Function

Cerebral Cortex

• Description: Outer layer of the brain with approximately 14-16 billion neurons; consists of gray and white matter.

• Functionality of Wrinkling: Increases surface area, allowing for a greater number of connections without enlarging the skull.

Cortical Structures

• Four major lobes:

• Occipital Lobe: Vision.

• Parietal Lobe: Touch, sensory integration, spatial processing.

• Temporal Lobe: Sound, language comprehension, smell.

• Frontal Lobe: Motor control, executive functions.

Frontal Cortex

• Role: Responsible for complex cognitive functions and behaviors.

• Comprised of the Prefrontal Cortex (30% of the cortex) for decision-making, attention regulation, and planning.

• Stress can impair its function.

Motor Cortex

• Located at the back of the frontal lobes, controls voluntary movements.

• Body parts needing precision occupy larger cortical space (mapped through Wilder Penfield’s electrical stimulation in surgeries).

Somatosensory Cortex

• Found at the front of the parietal lobe; processes tactile sensations and body movements.

• Greater sensitivity corresponds to more cortical space dedicated to that body part's control.

Insular Cortex

• Involved in taste perception, disgust, and bodily sensations linked to emotions.

Subcortical Structures

Basal Ganglia

• A network that coordinates motor signals, influencing actions, motivation, habits, and reward processing.

Key Structures:

• Thalamus: Sensory switchboard directing input to respective cortical areas (excluding smell).

• Hypothalamus: Regulates bodily functions (hunger, thirst, aggression, sex).

• Hippocampus: Important for long-term memory formation; associated with damage in conditions like Clive Wearing.

• Amygdala: Critical for emotional processing, especially related to fear and threat, enhancing memory formation for significant events.

Brainstem and Midbrain

Functions

• Medulla: Controls vital functions such as heart rate and respiration.

• Pons: Regulates sleep and arousal levels.

• Cerebellum: Coordinates motor control, timing, and learning.

• Substantia Nigra: Involved in voluntary movement and serves as a sensorimotor relay station.