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Neural Structures, CNS/PNS, and Memory – Vocabulary Flashcards

Language and Brain Plasticity

  • Limited vocabulary and language processing in early life: Twenties, thirties, and forties—language neurons had been dormant and are hard to activate if not used, leading to severely restricted language capabilities.
  • Second language learning across the lifespan:
    • Most people grow up using a primary language with family and community.
    • Without exposure to a second language, learning later in life is markedly harder, with lower fluency rates.
    • Early exposure to second/third languages (even if not continued into elementary school) increases later learning potential.
    • Exposure to secondary language recruits brain regions not used for the primary language, helping maintain activity and facilitate later activation, though activation remains challenging.
    • Prolonged dormancy of a function (e.g., a language) makes reactivation harder over time; "use it or lose it" applies to languages as well as other skills.
  • Practical implications:
    • Short-term, even minor language exposure (e.g., preschool experiences) can improve future language acquisition.
    • If you want to become fluent in a foreign language, start early or maintain some practice (e.g., apps like Duolingo) to keep brain regions involved.
    • Reading regularly maintains language-processing abilities in aging brains.
    • As people age, brain plasticity decreases, and prolonged dormancy reduces the likelihood of easy reactivation.
  • Real-world framing and motivation:
    • Acknowledges potential frustration with foreign language requirements but emphasizes long-term cognitive preparedness.
    • Encourages ongoing engagement with reading and multilingual exposure to preserve neural flexibility.

Peripheral Nervous System and Information Flow

  • PNS definition and purpose:
    • Peripheral nervous system consists of nerves throughout the body extending from the central nervous system (brain and spinal cord).
    • Central nervous system (CNS) communicates with the body via the PNS.
  • Afferent vs efferent channels:
    • Afferent neurons (sensory): carry information from the body to the CNS (mostly to the spinal cord). Also called sensory neurons.
    • Efferent neurons (motor): carry information from the CNS to skeletal muscles to produce movement.
    • Note: In the lecture, there’s a common confusion where afferent neurons are sometimes mis-stated as motor neurons; the mnemonic used is:
    • A comes before E in the alphabet, and sensing precedes responding: Afferent → Sensing; Efferent → Responding.
    • Interneurons in the spinal cord can mediate fast reflexes (via a reflex arc) that bypass the brain when the signal is extremely strong or urgent (e.g., pain from touching something hot).
  • Important concept:
    • Nerves traditionally carry information in one direction; however, the CNS relies on both afferent (sensory input) and efferent (motor output) pathways to interact with the body.

Brainstem (Old Brain / Hindbrain)

  • Overview:
    • The brainstem (also called hindbrain or old brain) is the oldest part of the vertebrate brain and oversees basic life-sustaining functions.
    • As you move upward in the brain, functions become more complex.
  • Medulla:
    • At the bottom of the brainstem; essential for basic life support: regulates heart rate and breathing.
  • Reticular formation:
    • Runs through the brainstem; consists of ascending (sensory) and descending (motor) pathways.
    • Ascending reticular formation carries sensory information upward toward the brain.
    • Descending reticular formation carries motor information downward to the body.
    • Plays a key role in arousal and wakefulness.
  • Pons:
    • Partly an extension of the reticular formation; involved in sleep regulation and general arousal.
    • Interacts with neurotransmitter systems (e.g., norepinephrine, epinephrine, GABA) to modulate arousal states and transitions between wakefulness and sleep.
  • Core idea:
    • The brainstem ensures basic survival (heartbeat, respiration) and regulates states of arousal necessary for processing information.

Cerebellum

  • Location and role:
    • Located behind the brainstem; closely associated with the reticular formation.
    • Does not initiate movement; it coordinates and smooths movements initiated by other brain regions (e.g., primary motor cortex).
  • How it works:
    • Coordinates multiple muscle groups across the body for smooth, coordinated action.
    • Integrates sensory feedback to adapt motor output in real time as conditions change (e.g., walking on changing surfaces).
    • Helps adjust motor responses in response to changing sensory information to maintain balance and precision.
  • Metaphor:
    • Like a coordinator that ensures actions are smooth rather than starting movements; it handles timing, accuracy, and coordination rather than initiation.

Limbic System and Associated Structures

  • General placement:
    • A set of midline structures embedded in the brain, involved in motivation, emotion, memory, and arousal.
  • Thalamus:
    • Located at the top of the brainstem; a central relay station for sensory information.
    • Routes most sensory signals to cortical areas for conscious processing (e.g., touch to somatosensory cortex, gustation, audition, vision processing related to movement detection).
    • Smell bypasses the thalamus and goes directly to the olfactory bulb; vision information is processed after routing through the thalamus.
    • Acts as a central post office: receives sensory input and directs it to the appropriate cortical destinations.
  • Hippocampus:
    • Plays a crucial role in memory formation, particularly encoding information for storage.
    • Memory is a multistep process: encoding → storage → retrieval.
    • Damage to the hippocampus can disrupt encoding, producing amnesia.
    • Amnesia types:
    • Retrograde amnesia: loss of memories from before the injury (storage/retrieval deficits).
    • Anterograde amnesia: inability to form new memories after the injury (encoding impairment);
      • Often linked to hippocampal damage; individuals can stay aware in the moment but fail to store new information.
    • Example in pop culture: Dory from Finding Nemo/Discoveries shows anterograde amnesia (briefly remembering people she meets, then forgetting). Retrograde amnesia can also be present in other contexts.
  • Amygdala:
    • Two almond-shaped structures involved in basic emotional processes (e.g., fear and anger) and survival-related responses.
    • Emotion and memory connection: emotionally charged events (especially fear/anger) tend to be more memorable, possibly due to amygdala-hippocampus interactions and adjacent anatomical proximity.
    • The amygdala has widespread influences on the brain through its connections; it tends to drive activity toward other regions more than it receives feedback from them (described humorously as a “poor relationship partner”).
    • The amygdala’s role in emotion has nuance; recent studies suggest the amygdala responds to environmental changes and threatening contexts, with ongoing debate about its exact role in basic emotions.
  • Hypothalamus and Pituitary gland:
    • Hypothalamus sits at the center of motivators and homeostasis; regulates activity of the pituitary gland.
    • Pituitary gland is the master endocrine gland; hormones circulate through the bloodstream to influence various organs.
    • The hypothalamus monitors internal bodily signals (hormone levels, hunger, thirst, temperature) and responds by adjusting endocrine output via the pituitary.
    • Motivational states and homeostatic processes:
    • Hunger, thirst, and related hormones (e.g., ghrelin and leptin) are examples discussed.
    • Hormones regulate reproductive functions and associated drives, such as testosterone and related androgen influences on dominance and sex drive.
  • Summary insight:
    • The limbic system connects basic survival functions with higher cognitive processes, facilitating motivation, emotion, memory, and homeostatic regulation.

White Matter, Gray Matter, and Brain Organization

  • White matter:
    • The majority of the brain’s volume consists of white matter, which is composed of myelinated axons that connect different brain regions.
    • White matter pathways enable communication between distant brain regions (e.g., limbic system to cortex) to support integrated processing.
    • The corpus callosum is a key white matter structure; it is a dense bundle of axons that connects the left and right hemispheres, allowing interhemispheric communication.
  • Gray matter:
    • The outer crust of the brain; the cerebral cortex houses densely packed neuronal cell bodies involved in processing, perception, language, thinking, and conscious experience.
    • Gray matter is where much of the brain’s “high-level” processing happens (conscious perception, speech, numbers, self-awareness).
  • Ventricles:
    • The brain contains ventricles (holes) filled with cerebrospinal fluid that nourishes the brain and may cushion it from injury.
  • Surface area and cortical folding:
    • The cortex has large surface area to accommodate extensive processing without requiring an impractically large skull.
    • Instead of a huge smooth brain, humans have a wrinkled cortex (gyri and sulci), which increases surface area within the confines of the skull.
    • Wrinkled brain design enhances processing capacity and network connectivity while remaining biologically feasible for birth and development.
  • Brain organization principle:
    • No single brain region handles a complex function in isolation; almost all processes involve distributed networks across multiple regions communicating through white matter tracts.

Hemispheres, Lobes, and Future Topics

  • Two hemispheres:
    • The brain is divided into left and right hemispheres; they process different types of information but are extensively connected.
    • The lecture anticipates discussion of the lobes within each hemisphere and their specialized functions (e.g., frontal, parietal, temporal, occipital lobes) in future sessions.
  • Practical takeaway:
    • Understanding brain function requires considering distributed networks and inter-regional communication rather than attributing capabilities to isolated regions.

Quick Reference: Key Concepts and Mnemonics

  • Afferent vs Efferent mnemonic:
    • Afferent (sensory) input goes to the CNS; Efferent (motor) output goes from the CNS to muscles.
    • Remember: A before E, Sensing before Responding.
  • Major brain areas and roles (high-level):
    • Medulla: basic life support (heart rate, breathing).
    • Reticular Formation: arousal and wakefulness; ascending and descending information.
    • Pons: sleep regulation and arousal.
    • Cerebellum: coordination and timing of movements, motor learning, adapting to sensory input.
    • Thalamus: relay station for conscious processing of sensory information.
    • Hippocampus: encoding memory; role in encoding and memory formation.
    • Amygdala: basic emotions; links emotion with memory formation.
    • Hypothalamus: homeostasis, motivation; regulates pituitary and endocrine system.
    • Pituitary: master endocrine gland; secretes hormones into bloodstream.
    • White matter: axonal connections between regions.
    • Gray matter: cortical processing and conscious experience.
  • Basic developmental and functional principles:
    • Brain plasticity is higher earlier in life and decreases with age, especially as dormant circuits remain unused.
    • Surface area is expanded via cortical folding rather than simply enlarging the brain; birth constraints prevent large head sizes, and folding increases processing capacity while enabling feasible birth.

Connections to Earlier and Later Topics

  • The brain’s plasticity sets the stage for discussing how neural networks adapt to learning, injury, and sensory experiences in later lectures.
  • The current and future exploration of the central nervous system (CNS) builds on understanding peripheral pathways (afferent/efferent) and how the brain integrates signals to produce behavior.

End of Note on Transcript Theme

  • The takeaway is that language, perception, memory, emotion, and action emerge from coordinated activity across many brain regions and networks, with structure-function relationships adding nuance to how we learn, remember, feel, and move.