Week 1 – Brains (PSY224 Behavioural & Cognitive Neuroscience)

General Brain Facts

  • Contains approximately 86\,\text{billion} neurons

  • Average weight ≈ 1.4\,\text{kg} (soft, tofu-like texture)

  • Consumes >20\% of body energy while being 2\% of body mass

  • Generates about 12–25\,\text{W} of electrical power

Protective Structures & Fluids

  • Meninges (outer ➜ inner): dura mater, arachnoid, pia mater

  • Cerebrospinal fluid (CSF)

    • Produced in choroid plexus within ventricles

    • Circulates ventricles & sub-arachnoid space: cushioning, nutrient delivery, waste removal

  • Blood–brain barrier (BBB): tightly-packed capillary cells selectively allow nutrients, block toxins

Surface Anatomy

  • Gyri (ridges) & sulci (grooves) increase cortical surface area; named & functionally relevant

  • Grey matter: neuronal cell bodies; white matter: myelinated axons

  • Key fissures: longitudinal (hemispheres), central (motor/sensory division), lateral (temporal separation)

Anatomical Directions & Planes

  • Directions: dorsal/ventral, anterior/posterior (rostral/caudal), medial/lateral, superior/inferior, proximal/distal

  • Planes: frontal (coronal), horizontal, sagittal

Nervous System Organisation

  • Central nervous system (CNS): brain & spinal cord; protected by BBB & CSF

  • Peripheral nervous system (PNS): nerves & ganglia outside CNS

    • Somatic: afferent sensory + efferent voluntary motor (includes most cranial nerves)

    • Autonomic: involuntary; sympathetic (fight/flight) vs parasympathetic (rest/digest)

Major Brain Divisions

  • Forebrain

    • Telencephalon: cerebral cortex, basal ganglia, limbic structures

    • Diencephalon: thalamus, hypothalamus

  • Midbrain (mesencephalon): tectum (superior & inferior colliculi), tegmentum (red nucleus, substantia nigra)

  • Hindbrain

    • Metencephalon: cerebellum, pons

    • Myelencephalon: medulla oblongata

Cerebral Cortex

  • Outer grey layer; ≈16\,\text{billion} neurons; surface area ≈1.5\,\text{m}^2

  • Lobes & general functions (coarse):

    • Frontal: cognition, decision, voluntary movement

    • Parietal: somatosensation, spatial attention

    • Temporal: audition, language, memory

    • Occipital: vision

    • Cerebellum (posterior/inferior): balance & coordination (not a lobe but functionally distinct)

  • Primary areas: motor (precentral gyrus), somatosensory (postcentral gyrus), visual (occipital), auditory (temporal)

  • Association areas: premotor, prefrontal, language (Broca’s/Wernicke’s), multimodal integration

Cortical Architecture

  • Six laminae (I–VI) from pia ➜ white matter

    • Layer IV: thalamic sensory input (prominent in primary sensory cortex)

    • Layer V: large pyramidal (Betz) cells, output to brainstem/spinal cord (motor cortex)

  • Columnar organisation: vertical information processing units

Subcortical Structures

  • Basal ganglia: caudate, putamen, globus pallidus; movement gating, reward; implicated in Parkinson’s & Huntington’s

  • Limbic components

    • Hippocampus: formation of new declarative memories; adult neurogenesis

    • Amygdala: emotion (fear/anxiety), emotional memory, social processing

    • Cingulate gyrus (historically included)

Diencephalon

  • Thalamus: major sensory relay to cortex; roles in sleep & consciousness

  • Hypothalamus: homeostasis (temperature, hunger, thirst, circadian), stress (HPA axis), controls pituitary (endocrine link)

Brainstem & Cerebellum

  • Midbrain tectum: superior colliculus (visual-motor orienting), inferior colliculus (auditory)

  • Midbrain tegmentum: red nucleus & substantia nigra (motor modulation, dopamine)

  • Pons: sleep, arousal, cranial nerve nuclei, movement coordination

  • Medulla oblongata: autonomous vital functions (cardio-respiratory)

  • Cerebellum: coordination, posture, fine motor control, motor learning; receives corticospinal efferents & spinocerebellar afferents

Quick Reference Summary

  • 86 billion neurons, 1.4 kg, >20\% energy use

  • Protective: meninges, CSF, BBB

  • CNS vs PNS; somatic vs autonomic

  • Key cortical lobes & primary areas

  • Six cortical layers; layer IV (input), V (output)

  • Basal ganglia = movement gating; limbic (hippocampus, amygdala) = memory & emotion

  • Thalamus = relay; hypothalamus = homeostasis & endocrine

  • Midbrain (colliculi), pons, medulla = brainstem functions

  • Cerebellum = coordination & motor learning