Brain Structure, Neuroplasticity, and Function (Vocabulary)

Neuroplasticity, Learning, and Memory

• Neuroplasticity is the brain’s ability to change and build new neural pathways. The brain is sculpted by both genes and environment; the interaction of life experiences with genetic predispositions shapes the brain.
• Neuroplasticity is more efficient when you’re younger, but it continues to occur as you age, just not as dramatically.
• Learning a skill (e.g., riding a bicycle) creates neural pathways as neurotransmitters fire along specific routes; with repeated practice, those pathways become deeper and more ingrained (a “deep Play-Doh cut”).
  • The more you practice, the stronger the pathway; the more you stop practicing, the weaker the pathway becomes, illustrating the principle
  • "Use it or lose it": you either maintain a learned skill or the pathway dissipates over time.
• There is concern about AI analogies: if you don’t train your brain to perform certain tasks, you may lose ability; AI tools (e.g., chat-based models) can assist but should not replace practicing and understanding.
• The brain you’re born with is not the brain you’ll die with: every time you learn something, you’re creating new neural pathways; if you stop practicing, you may experience atrophy, a loss of previously learned pathways.
• Brain atrophy is associated with neurodegenerative conditions (e.g., Alzheimer's, dementia) where previously formed pathways degrade over time.
• Quick video takeaway: structure vs. function (anatomy vs. physiology) underpins how the brain processes information; learning strengthens neural networks and memory.

Brain Structure: Big Picture and Evolution

• Animals possess brains and nerves to process sensory information and move via muscles; nervous systems organize movement and perception.
• Basic body plans:
  • Radially symmetric: organized around a center (less relevant for directional movement in higher animals).
  • Bilaterally symmetric: left/right symmetry allows more complex, directional movement and centralized processing (e.g., a “front” and a “back”).
• Sensory information enters via neurons, is integrated in the brain, and motor commands exit via motor neurons.
• Primitive brains share a common plan: spinal cord, hindbrain, midbrain, forebrain. As brains evolved, the forebrain expanded, bringing more complex thoughts, memories, and emotions.
• The brain evolves from a more primitive core to a much larger, highly developed forebrain (humans have a very large frontal cortex).
• Two key concepts:
  • Sensation: data points gathered from senses (inputs).
  • Perception/Integration: the brain organizes data and generates an output based on learning and experience.
• Embryology note: early embryos have a brain that resembles the primitive layout (spinal cord, hindbrain, midbrain, forebrain); during development, the forebrain grows substantially to become the major, highly evolved brain in humans.
• Context for later sections: 17 distinct brain structures will be reviewed to understand the full plan of the brain.

The Four Major Brain Plans and the 17 Structures (Overview)

• The brain is organized into three major divisions along a rough axis: forebrain, midbrain, hindbrain.
• Major divisions and key structures include:
  • Brain stem (bottom): medulla oblongata, pons, midbrain.
  • Cerebellum (posterior to brain stem).
  • Diencephalon: thalamus, hypothalamus, posterior pituitary.
  • Cerebrum: the large, upper portion including the cerebral cortex and underlying structures.
• 17 structures to know (grouped by region):
  • Brain stem: ext{medulla oblongata}, ext{pons}, ext{midbrain}
  • Cerebellum
  • Thalamus
  • Hypothalamus
  • Posterior pituitary
  • Cerebrum
  • Corpus callosum (connects the two hemispheres)
  • Basal ganglia (a group of nuclei beneath the cortex)
  • Cerebral cortex (the highly folded outer layer of the cerebrum)
  • Frontal lobe (part of the cerebrum)
  • Parietal lobe
  • Occipital lobe
  • Temporal lobe
  • Somatosensory cortex (in the parietal lobe; sensory input mapping)
  • Motor cortex (in the frontal lobe; motor output)
  • Limbic system (emotional/memory network; includes amygdala, hippocampus, etc.)
• Functional theme: each structure has a distinct role in processing information, regulating the body, or controlling movement.
• Key idea: the closer a structure is to the brain stem, the more basic/survival-oriented its functions tend to be; structures higher up (e.g., cortex) support complex cognition, memory, and emotion.

Brainstem, Cerebellum, Thalamus, Hypothalamus, and Pituitary

• Brain stem core functions:
  • Medulla oblongata, pons, and midbrain form the brain stem.
  • Basic life-sustaining functions: breathing, heart rate, digestion, swallowing, etc.
  • Routes and filters sensory information and coordinates that information with higher brain regions.
  • Damage to the brain stem can be catastrophic due to vital autonomic functions.
• Cerebellum:
  • Motor control and coordination; contributes to balance and motor memory (performing tasks like riding a bicycle).
• Thalamus:
  • Acts as a relay/router for sensory information entering the cerebrum; sorts data and directs it to appropriate cortical areas.
  • Sits atop the brain stem; acts as a sensory control center.
• Hypothalamus:
  • Maintains homeostasis: body temperature, osmolarity, circadian rhythms, hunger, thirst, sleep, and more.
  • Plays a key role in the endocrine system via links to the pituitary gland.
• Pituitary gland (posterior pituitary discussed here):
  • Hormone release controlled through neural input; poster pituitary releases hormones like antidiuretic hormone (ADH/vasopressin) and oxytocin.
  • Interaction with hypothalamus regulates water balance and social/connected behaviors via hormones.

Cerebrum and Cerebral Cortex: Higher-Order Processing

• Cerebrum overview:
  • The cerebrum is the largest part of the brain and is responsible for thinking, learning, memory, and complex decisions.
  • It contains billions of neurons and trillions of synapses that enable complex processing.
  • The outermost layer is the cerebral cortex (the top layer of folded brain tissue).
• Corpus callosum:
  • A thick bundle of nerve fibers connecting the right and left cerebral hemispheres, enabling interhemispheric communication.
• Lateralization and plasticity:
  • Some functions are more commonly associated with one hemisphere (e.g., left: mathematical reasoning and logic; right: facial recognition), but functions can shift with plasticity; significant reorganization can occur (e.g., hemispherectomy still allows many functions to persist).
• Basal ganglia:
  • A collection of nuclei below the cortex involved in motor control, inhibition, and excitation coordination.
  • Dysfunction in this area is linked to movement disorders such as Parkinson’s disease.
• Cerebral cortex and lobes (four lobes):
  • Frontal lobe: executive functions; emotional regulation; “boss” of the brain; impulse control and decision making; affected in mood changes when damaged.
  • Parietal lobe: processing sensory information and environmental interpretation; sensation and spatial awareness.
  • Occipital lobe: vision and visual processing; primary visual cortex and higher-order visual areas.
  • Temporal lobe: language, hearing, memory; important in processing auditory information and memory formation.
• Other cortical areas:
  • Somatosensory cortex (in the parietal lobe): maps sensory input from the body; disproportionately large representation for fingers, tongue, and lips (more cortical real estate for fine touch and proprioception).
  • Motor cortex (in the frontal lobe, just anterior to the central sulcus): sends motor commands to muscles; organized topographically (homunculus).
• Functional imaging demonstrations:
  • Functional MRI (fMRI) shows brain activity by detecting changes in blood flow; used to map brain functions during tasks or stimuli.
  • The example with brick wall, kitten, dirt, and puppies illustrates how different stimuli activate different brain regions.

The Limbic System, Emotion, and Memory

• Limbic system: emotional core of the brain; interacts with memory and autonomic regulation.
• Amygdala:
  • Central in processing emotions such as fear and anger; acts as the brain’s alarm system (smoke detector).
  • Hyper-reactivity is implicated in anxiety disorders and PTSD; contributes to rapid, automatic responses to perceived threats.
• Hypothalamus (in the limbic system context):
  • Regulates internal states (temperature, hunger, thirst, sleep) and links to the endocrine system via the pituitary.
  • Involved in emotion and reward circuits.
• Hippocampus:
  • Critical for conscious memory formation and the storage of conscious memory.
  • Distinguishes conscious memory (what you can recall) from unconscious memory (non-conscious processes).
• Prefrontal cortex (part of the frontal lobe, involved in higher-order thinking):
  • Regulates planning, judgment, decision-making, social behavior, and executive control; integrates information from emotion and memory systems to modulate behavior.
• Stress, memory, and decision-making (mechanisms):
  • Sympathetic nervous system triggers fight/flight; amygdala activates, increasing heart rate and respiration while eyes dilate.
  • The prefrontal cortex and hippocampus support thinking and memory, but under acute stress, the amygdala can dominate, reducing analytical thinking and memory coherence.
  • Chronic stress can sensitize the amygdala (lowering the threshold for activation) and may alter connections with the prefrontal cortex, affecting regulation and memory processing.
• Forensic/trauma implications:
  • Under stress, memories can be fragmented or flashbulb-like, with vivid recollection of certain details (e.g., a red lamp) and poor recall of others (e.g., sequence of events).
  • This explains why eyewitness memories after trauma can be unreliable or highly selective; the interaction of hippocampus and prefrontal cortex during encoding and retrieval is altered by stress and arousal.
• Practical example from practice:
  • In high-stress environments (e.g., detention settings), individuals may have heightened amygdala responses leading to impulsive actions; calm, measured thinking (prefrontal functioning) can reduce harm and improve memory integration.
• Imaging evidence and the PTSD note:
  • Imaging (e.g., fMRI, MRI, EEG, PET) shows structural and functional changes in PTSD: amygdala hyperactivity, altered connectivity with the prefrontal cortex, and changes in gray matter density in cognitive regions.
  • These findings help explain altered emotional processing, memory, and regulation in affected individuals.

Brain Imaging, Evidence, and Methods

• EEG (electroencephalography): measures electrical activity with scalp electrodes; good temporal resolution, limited spatial resolution.
• PET (positron emission tomography): tracks glucose metabolism to indicate brain activity during tasks; provides metabolic activity maps.
• MRI (magnetic resonance imaging): uses magnetic fields and radio waves to produce detailed structural images of the brain.
• fMRI (functional MRI): uses MRI to measure brain activity by detecting changes in blood flow (hemodynamic response) related to neural activity; maps functional areas and networks.
• Practical note on imaging in trauma and PTSD:
  • Imaging can reveal anatomical and functional differences, such as amygdala size and connectivity, that correlate with symptoms and risk factors.

Development, Concussion, and Real-World Relevance

• Sports injuries and concussions illustrate the practical importance of anatomy:
  • Occipital lobe injuries affect vision processing.
  • Temporal lobe injuries affect language, hearing, and memory.
  • Frontal lobe injuries can cause mood swings and impulsivity due to disrupted executive function.
• Forensics and memory reliability:
  • Under stress, encoding and recall can be impaired or altered; eyewitness testimony should be interpreted with an understanding of memory dynamics and brain physiology.
• The brain’s plasticity underlines the importance of practice and rehabilitation after injury; targeted cognitive and physical training can help recover or compensate for damaged networks.

Quick Review: Key Structures and Functions (Recall Practice)

• Brain stem: basic life support (breathing, heart rate, digestion); routing information (medulla oblongata, pons, midbrain).
• Cerebellum: motor coordination, balance, motor memory.
• Thalamus: sensory router for the cortex.
• Hypothalamus: homeostasis, circadian rhythms, endocrine regulation.
• Posterior pituitary: hormone release (e.g., ADH, oxytocin).
• Cerebrum: higher-order processing; contains the cerebral cortex.
• Corpus callosum: connects left and right hemispheres.
• Basal ganglia: motor control and inhibition/excitation balance; Parkinson’s disease relevance.
• Cerebral cortex: outer layer of the cerebrum; contains the four lobes.
• Frontal lobe: executive function, emotions, impulse control.
• Parietal lobe: processing sensory input and environmental interpretation; somatosensory cortex maps.
• Occipital lobe: vision.
• Temporal lobe: language, hearing, memory.
• Somatosensory cortex: sensory input mapping (fingers, tongue, lips prominent).
• Motor cortex: motor output.
• Limbic system: emotional processing and memory; key components include the amygdala and hippocampus; hypothalamus is closely linked in function.
• Amygdala: fear, anger, arousal; stress/trauma relevance.
• Hippocampus: conscious memory formation and storage; interaction with stress systems.
• Prefrontal cortex: planning, judgment, executive control; regulation of emotion and behavior.
• Plasticity concepts to remember:
  • Learning strengthens pathways; disuse weakens them.
  • The brain can reorganize functions across hemispheres (plasticity) and recover from certain injuries.

Practical Takeaways for Exam Preparation

• Be able to name the 17 brain structures discussed and summarize their primary functions.
• Explain the concepts of neuroplasticity, use it vs. lose it, and brain atrophy with concrete examples (e.g., learning a skill, aging, Alzheimer's).
• Describe the three major brain divisions (forebrain, midbrain, hindbrain) and their significance in evolution and function.
• Identify the lobes of the cerebrum and their main functions, plus the role of the somatosensory and motor cortices.
• Describe the limbic system's role in emotion and memory, especially amygdala and hippocampus, and how stress affects memory encoding and recall.
• Understand how imaging tools (EEG, PET, MRI/fMRI) contribute to our knowledge of brain function and pathology (e.g., PTSD).
• Recognize how injuries to different brain regions manifest in cognitive and emotional changes (e.g., frontal lobe damage and mood changes; occipital lobe damage and vision issues).
• Apply the forensic memory insights to discussions of eyewitness testimony and traumatic events.
• Remember metaphors used in teaching:
  • Play-Doh brain for pathway formation.
  • Guard dog (amygdala) and owl (prefrontal thinking) to illustrate stress and decision-making dynamics.
  • The importance of calming the amygdala to engage prefrontal functioning and memory processing.