Brain Structure and Function Overview

Overview

This lecture provides an overview of brain structure and function, focusing on how specific brain areas contribute to behavior, decision-making, and how new technologies allow us to study the living brain.

The Phineas Gage Case and Functional Specialization

• Phineas Gage survived a brain injury that changed his behavior, showing certain brain areas control specific functions.
• Damage to his orbital frontal cortex impaired his ability to use emotions to guide right and wrong behavior (conscience).
• This case launched the idea of functional specialization: different brain parts do different things.

Basic Brain Anatomy and Hierarchical Organization

• The brain has three main layers: the brain stem (basic life functions), the limbic system (emotions and core evaluations), and the cortex (higher cognition).
• The corpus callosum connects the two brain hemispheres, enabling communication.
• The brain’s convoluted surface increases surface area to accommodate more neural processing.

Brain Circuits and Emotional Regulation

• The limbic system detects important stimuli (threats or rewards) and signals the cortex.
• The amygdala triggers fear responses; the ventral striatum is linked to pleasure and craving.
• The orbital frontal cortex adds context and inhibits inappropriate impulses, as seen in Phineas Gage’s deficits.

Principles of Brain Localization

• Loss-of-function studies (e.g., strokes) show that damage to specific brain areas causes specific deficits.
• Broca’s area controls language production; Wernicke’s area controls language comprehension.
• The brain is organized via distributed processing—many tasks involve multiple specialized areas working together.

Advances in Brain Imaging

• Early X-ray and air-injection techniques offered crude images of the brain.
• The CT (CAT) scan and MRI brought high-resolution, 3D brain imaging.
• fMRI measures blood flow as an indirect marker of brain activity and has some limitations and lack of standardization.

Cellular Basis of Brain Function

• Brain circuits are made of neurons connected at synapses, communicating through electrical and chemical signals.
• Diffusion tensor imaging (DTI) maps brain wiring by tracking water movement along axons.

Decision-Making and Therapy Implications

• The brain integrates core drives and past experience to make decisions.
• Dysfunction in circuits, especially between limbic and cortical areas, impairs decision-making (e.g., addiction).
• Therapies (psychotherapy, CBT, medications, designer drugs) can target specific circuits to improve behavior and emotion regulation.

Key Terms & Definitions

• Functional Specialization — the concept that different brain regions perform distinct functions.
• Limbic System — brain structures involved in emotion and core evaluations.
• Cerebral Cortex — outer brain layer responsible for higher-level cognition and consciousness.
• Amygdala — limbic structure linked to fear detection.
• Ventral Striatum — limbic region involved in reward and pleasure.
• Orbital Frontal Cortex — brain area implicated in decision-making and inhibiting inappropriate impulses.
• Broca’s Area — cortex region for language production.
• Wernicke’s Area — cortex region for understanding spoken language.
• fMRI — imaging technique measuring blood flow as a marker for brain activity.
• Neuron — fundamental nerve cell in the brain.
• Synapse — junction where neurons communicate using neurotransmitters.

Action Items / Next Steps

• Review the brain anatomy diagrams provided in the briefing book.
• Read articles on functional specialization and recent advances in brain imaging.