3.3 The Brain–Behavior Network: Key Concepts and Structures
Central Nervous System (CNS) and Peripheral Nervous System (PNS)
CNS = brain + spinal cord; PNS = nerves outside CNS. CNS processes info; PNS carries it to/from body.
PNS has two main branches: somatic (voluntary movement) and autonomic (involuntary functions). Autonomic splits into divisions: sympathetic (arousal, fight/flight) and parasympathetic (rest and digest).
CNS Protection and Basic Organization
CNS is protected by three thin membranes (meninges) and cerebrospinal fluid (CSF) that cushions the brain/spinal cord.
The CNS contains neural networks that coordinate thoughts, emotions, and behavior.
The Central Nervous System: Six Distinct Systems (Table 3.2)
Cortex: outer layer responsible for higher-order processing; divided into lobes.
Basal ganglia: movement control, motor planning, emotion, habit learning.
Limbic system: emotion, motivation, learning, memory.
Cerebellum: balance, coordination, motor learning; contributes to some cognitive functions.
Brain stem: midbrain, pons, medulla; basic life support, arousal, and reflexes.
Spinal cord: conduit between brain and body; integrates sensory and motor information.
The Cerebral Cortex and Lateralization
The cortex is gray matter on the surface; white matter underneath (myelinated axons).
Two hemispheres (left and right) connected by the corpus callosum; they communicate continually.
Lateralization: functions can be more specialized in one hemisphere, but both sides work together. See Table 3.3 for typical specializations.
Split-brain findings show how separating hemispheres can disrupt integration; not all functions are strictly localized.
Phineas Gage example illustrates frontal lobe involvement in personality and executive function.
Lobes of the Cerebral Cortex and Key Areas
Frontal lobe: executive functions, motor planning, language; contains the motor cortex; prefrontal cortex oversees higher-order planning and decision making; Broca's area (language production) is in the left frontal lobe.
Parietal lobe: somatosensory cortex (touch); spatial processing, attention, numerical processing; involved in guiding actions.
Temporal lobe: auditory processing and language; Wernicke's area (language comprehension); memory formation; Fusiform Face Area (FFA) for face recognition (and object recognition with expertise).
Occipital lobe: visual processing; primary visual cortex and visual association areas.
Hemispheric specialization (left vs right) supports language (often left) and certain visuospatial skills (often right) but both hemispheres cooperate for most tasks.
Motor, Sensory, and Association Cortex
Motor cortex (frontal lobe) maps to body parts; more cortical area for parts requiring fine motor control (homunculus).
Somatosensory cortex (parietal lobe) maps body sensations; likewise organized somatotopically.
Association cortex (spread across lobes) integrates information to produce perception and thought; most of the cortex is association cortex.
Subcortical Structures and the Limbic System
Basal ganglia: action selection, movement control, reward learning; dopamine pathways implicated in PD and Tourette's.
Limbic system: interconnected structures below cortex; involved in emotion, motivation, learning, smell, memory.
Thalamus: sensory relay to cortex; integrates senses.
Hypothalamus: drives hunger, thirst, sexual motivation; regulates autonomic nervous system and hormones.
Amygdala: emotional learning, fear, arousal; helps interpret social cues.
Hippocampus: formation of new conscious memories; spatial navigation; contributes to memory consolidation.
Cerebellum: coordinates movement, balance; contributes to some cognitive functions and learning.
The Brain Stem and the Cerebellum; The Spinal Cord
Brain stem components: Midbrain (motor, reflexes, arousal), Pons ( connects cortex and cerebellum ), Medulla (vital reflexes like breathing).
Reticular Activating System (RAS): arousal and wakefulness; damage can cause coma.
Spinal cord: two-way information highway; contains interneurons enabling reflexes (e.g., stretch reflex) without brain input.
The Peripheral Nervous System (PNS) in Depth
Somatic nervous system: voluntary motor control via skeletal muscles.
Autonomic nervous system: controls internal organs; two divisions that oppose each other:
Sympathetic: prepares for crises (fight/flight); increases heart rate, respiration, etc.
Parasympathetic: promotes rest and digestion; conserves energy.
The Brain's Utilization Myth and Evidence
Myth: we use only a small portion of our brains (e.g., 10%).
Debunking evidence: neuroimaging and brain stimulation show widespread activity; all brain areas can be active; damage in small regions often causes deficits.
Lashley (1929) fought simplistic localization claims; modern data emphasize distributed processing and plasticity.
Emergent Concepts and Case Studies
Lateralization and the idea that the brain is a simple left-right split is overstated; interhemispheric communication is extensive.
Phineas Gage demonstrated the role of the frontal lobes in personality and social behavior, illustrating brain–behavior links.
Unilateral neglect (parietal damage) shows how damage can affect attention to one side of space, despite intact vision.
Quick Reference Points
CNS protection: meninges + CSF; ventricles distribute CSF.
Six CNS components: Cortex, Basal ganglia, Limbic system, Cerebellum, Brain stem, Spinal cord.
Cortex lobes: Frontal, Parietal, Temporal, Occipital; gray matter on surface, white matter inside.
Major subcortical structures: Basal ganglia; Thalamus, Hypothalamus, Amygdala, Hippocampus; Cerebellum.
Brain stem roles: Midbrain, Pons, Medulla; RAS for arousal.
PNS divisions: Somatic vs Autonomic; Sympathetic vs Parasympathetic.
Key themes: hierarchical processing, neural plasticity, integration across brain networks.
distinct CNS sections; hemispheres; meninges? (context-dependent as noted in materials).