Introduction to Brain Anatomy and Functionality

Brain Anatomy and Function — Surface-Level Notes

• Opening context
  • The brain is the most complex organ; this is a surface-level overview (not a full-depth neuroscience course).
  • Humans haven’t built a machine more complex than the human brain despite advanced tech (space travel, AI, etc.).
• Cerebrum and cerebral cortex
  • Cerebrum: the outside of the brain.
  • Cerebral cortex: the outer layer of the cerebrum; contains many regions and functions.
  • Homunculi (maps of brain regions): motor homunculus (left) and sensory homunculus (right).
  • These are stylized maps showing how much brain real estate is devoted to controlling or sensing various body parts, not literal body proportions.
  • Key idea: disproportionately large areas dedicated to motor control of the face and hands, and to sensory processing of the lips and hands.
  • Reason: many muscles and finely-tuned sensory receptors in these regions require more cortical real estate for precise control and processing.
  • Motor vs. sensory representations
  • Motor cortex controls movement; sensory cortex processes input from the body.
  • Facial expressions and speech-related movements require substantial motor control, hence large cortical representation.
  • Sensory cortex reflects high receptor density in lips and hands; large areas reflect high processing needs for those modalities.
  • The distinction between motor and sensory maps is about input/output processing, not about literal body part size.
• Lobes and their basic functions
  • Frontal lobe
  • Voluntary motor control (planning and execution of movements).
  • Personality traits (e.g., temperament) and higher intellect (thinking, reasoning).
  • Verbal communication: conceptual understanding and planning language, not just speaking.
  • Important note: verbal communication involves understanding concepts and forming meaningful sentences, not merely producing sounds.
  • Frontal damage can impair planning, reasoning, and complex language formulation.
  • Parietal lobe
  • Cutaneous (skin) and muscle sensations (somatosensory input).
  • Input-dense region; processes body position, muscle stretch, and proprioception.
  • Understanding speech and word formation rely on parietal processing in concert with other regions.
  • Temporal lobe
  • Auditory sensations and processing (sound input).
  • Auditory memory storage (and, more broadly, memory-related processing).
  • Occipital lobe
  • Visual processing (vision-related processing and interpretation).
  • Insula
  • Memory activity and integration of sensory and visceral information (interoception).

Brain organization concepts

Basal nuclei (basal ganglia)

• Gray-matter lumps within white matter; important for voluntary motor control.

Brain Layering Concept (Lizard brain / mammal brain / human brain)

• A rough layering concept: core, old structures (basic motor control) vs. newer, more complex regions (cognition, planning).

Hemispheric Lateralization and Corpus Callosum

• Hemispheres are structurally separate but functionally interconnected via the corpus callosum.
• Right hemisphere tends to receive sensory input and control the left side of the body; left hemisphere does the opposite.
• The eye wiring is more complex: each eyeball sends information to both hemispheres, but in a cross-wired pattern that preserves useful redundancy.
• Importantly, eyes are separately lateralized to different brain sides, providing a robust system for vision even with injury to one eye.

Language areas in the brain

• Language is primarily left-hemisphere-dominant, with contributions from other areas.
• Broca's area (located in the frontal lobe, near the motor cortex)
  • Responsible for forming words and coordinating speech production.
• Wernicke-like area (in the temporal lobe; the transcript refers to it colloquially as “Nikki's area”)
  • Involved in language comprehension and sentence construction.
• The motor cortex sends tongue/throat/airflow commands to produce sound once words and sentences are formed by other language areas.
• If word retrieval or sentence structure areas are damaged, people may say words in the wrong order or with incorrect grammar, even if they know the words.
• Limbic system: emotions and motivation
  • Key regions: hippocampus, amygdala, hypothalamus (among others).
  • Primary role: emotions and their regulation, memory, and drives (hunger, thirst, sex).
• Aggression
  • Localized in the amygdala and hypothalamus.
  • Aggression often coexists with fear; prudent interpretation of aggressive behavior considers underlying fear and past experiences.
• Fear
  • Also localized in the amygdala and hypothalamus.
• Feeding (hunger and satiety)
  • Involves hypothalamus and related circuits; emotional responses to food are a real, neurobiological phenomenon.
• Sex and reproduction
  • Localized in the hypothalamus but broadly distributed in the limbic system; linked to reward circuits and dopamine pathways.
• Memory and memory-associated emotions
  • Limbic regions interact with memory systems; memory formation is tied to emotional context.
• Moral and social behaviors
  • Emotions and rewards influence behaviors like generosity; the brain’s motivation for helping others can be emotionally driven.
• Practical implications discussed in class materials
  • Early trauma can establish lasting emotional associations that influence behavior and decision-making later in life.
• Memory systems in the brain
  • Long-term memory (LTM) has two major forms:
  • Nondeclarative (implicit) long-term memory
    • Examples: riding a bike, conditioning, procedural skills, habits.
    • Once learned, these skills are often retained even if conscious recall fades; modifications can be difficult due to ingrained pathways.
  • Declarative (explicit) long-term memory
    • Subtypes: semantic (fact-based) and episodic (event-based) memories.
    • Semantic: knowledge like civil war facts; episodic: personal experiences (you witnessed or participated in events).
  • Hippocampus
  • Critical for acquiring new memories; damage can impair new memory formation while older memories may remain.
  • Amygdala
  • Associates emotion (especially fear) with memories; emotional context can strength memory encoding.
  • Medial temporal lobe and memory consolidation
  • Involves hippocampus, amygdala, and surrounding cortex; consolidation largely occurs during sleep.
  • Short-term (working) memory
  • Conscious, temporary holding of information (e.g., a phone number during a call).
  • Converting short-term memory to long-term memory
  • Two key factors: repetition while awake and sleep for consolidation.
  • Memory distortions and reliability
  • Episodic memories are subject to retrievability errors and deliberate or inadvertent manipulation.
  • Eyewitness testimony can be unreliable; the judicial system historically relied on imperfect recollections.
  • Educational and practical notes
  • Safe and effective memory strategies: spaced repetition, sleep, and avoiding overreliance on confident but incorrect memories.
• Thalamus and epithalamus
  • Thalamus
  • Major relay center for sensory information (except smell—olfactory information takes a separate route).
  • Acts like a highway, transmitting signals to cortical areas without heavy processing itself.
  • Epithalamus
  • Regulates circadian rhythms (the brain’s internal clock) and is involved in sleep-wake cycles.
  • Circadian rhythms and jet lag
  • Jet lag results from misalignment between internal clock and external environment after time-zone travel.
  • The degree of jet lag depends on the magnitude and timing of travel; shorter trips may cause less jet lag due to quicker adjustment.

Midbrain and hindbrain structures

Midbrain (mesencephalon)

• Corpora quadrigemina: visual reflexes (superior colliculi) and auditory relays (inferior colliculi).
• Cerebral peduncles: ascending and descending fiber tracts (bundle-like nerve pathways).
• Red nucleus: motor coordination.
• Dopaminergic neurons: coordinate movement with reward and motivation (links between movement and reward circuits).

Pons

• Pons: contains motor and sensory tracts; houses respiratory control centers.
• Respiratory centers can be influenced by autonomic control and higher brain input; breathing can be voluntarily modified but largely operates on autopilot.

Medulla Oblongata

• Vital involuntary functions: controls heart rate, breathing, blood pressure, and reflexes like vomiting, coughing, and sneezing.
• Acts as a relay station for sensory and motor signals between the brain and spinal cord.
• Plays a crucial role in maintaining basic life support.

Cerebellum

• Motor coordination and motor learning (often referred to as “muscle memory”).
• Inhibition of the motor cortex during sleep helps prevent movement while dreaming; sleep-related inhibition varies by person.
• Not just for smooth movement, but for timing, precision, and learning complex motor tasks.
  • Spinal cord (brief mention)
  • The slides include more content on the spinal cord, but these notes focus on the brain structures discussed in class.
  • Functional and practical implications
  • Language and cognition rely on distributed networks; damage to specific areas can affect word formation, sentence construction, or comprehension.
  • Emotional and motivational systems are deeply intertwined with memory and decision-making; trauma can have lasting neurobiological effects.
  • Memory is not a flawless recorder of reality; memory traces can be altered over time, especially episodic memories.
  • Sleep and repetition are crucial for consolidating learning; adequate rest enhances the transition from short-term to long-term memory.
  • Memory reliability has real-world consequences for forensic contexts and how we understand past events.
  • Classroom and study-related notes
  • Do not confuse the function of nearby regions; many functions are distributed and interconnected.
  • Use the sensory-motor and language differentiation to study how damage in different areas may present with distinct clinical signs.
  • When studying memory, differentiate between types (declarative vs nondeclarative) and subtypes (semantic vs episodic) to organize information clearly.
  • Remember the general hierarchical flow: cortex (higher processing) over limbic and hypothalamic systems (emotion, drives) with brainstem and cerebellar modulation of motor output.
  • Quick recap of key terms
  • Cerebrum, Cerebral cortex, Basal nuclei, Lateralization, Corpus callosum, Broca’s area, Wernicke’s area, Limbic system, Hippocampus, Amygdala, Hypothalamus, Thalamus, Epithalamus, Corpora quadrigemina, Superior colliculi, Inferior colliculi, Cerebral peduncles, Red nucleus, Dopaminergic neurons, Pons, Medulla oblongata, Cerebellum, Medial temporal lobe, Semantic memory, Episodic memory, Nondeclarative (implicit) memory, Declarative (explicit) memory, Working memory, Circadian rhythms, Jet lag
  • Notable caveats mentioned in lecture
  • Visual perception is not a direct copy of the world; it is a constructed interpretation based on multiple inputs and processing.
  • Eyewitness memory can be unreliable; memory is reconstructed and can be biased by later information or storytelling.
  • Some examples in the lecture were used to illustrate broader concepts (e.g., “My Cousin Benny” courtroom scene) to highlight memory issues in real-world contexts.
  • Philosophical and ethical notes touched upon
  • The brain’s role in producing emotion and moral behavior invites reflection on responsibility and bias.
  • Understanding that memory is fallible can influence how we evaluate testimony and historical narratives.
  • The interplay between biology and behavior underscores that many behaviors have neurobiological underpinnings, which can inform empathy and justice decisions.
  • Final reminders from the lecturer
  • Themes of the brain’s layered evolution (older lizard brain core, newer mammalian, newest human expansions).
  • Emphasis on practical study habits: sleep and repetition are crucial for learning.
  • Acknowledgement of lecture dynamics and the importance of accurate note-taking and class procedures for effective learning.