The Cerebrum Notes

NEU10002 Neuroscience: Intro to the Cerebrum - Dr. Nicolene Lottering

Learning Objectives

  • Describe and identify major sulci and gyri of the brain and summarize their functions.
  • Describe and locate the major divisions of each of the lobes of the cerebral cortex.
  • Compare and contrast the functional components of the right and left hemispheres.
  • Localize the functional areas of the cortex.
  • Name the Brodmann area that major structures of the cerebral cortex correspond to.

Neuralation: The Basics

  • Forms from the ectoderm, the outermost germ layer.
  • Neuroectoderm thickens into the neural plate (flat sheet of cells) approximately 17 days post-conception.
  • Neural groove forms rostral to caudal.
    • Walls of groove form the neural folds.
    • Neural folds move together and fuse dorsally to form the neural tube.
    • The entire CNS develops from walls; occurs around 22 days post-conception.
    • Failure to fuse posteriorly results in spina bifida.
  • As the tube closes, the lateral area becomes the neural crest.
    • The entire PNS develops from the crest.

Differentiation: Primary

  • Primary Brain Vesicles
    • The neural tube differentiates into three brain vesicles (-cephalon). The earliest subdivisions of the brain have developed by the end of 4 weeks:
      • Prosencephalon:
        • Most rostral
        • "pro" = "before", "encephalon" = brain
        • Forebrain
      • Mesencephalon:
        • "mes" = "middle" (Greek)
        • Midbrain
        • Remains the same as the secondary vesicle.
      • Rhombencephalon:
        • Most caudal
        • Hindbrain

Differentiation: Secondary

  • Secondary Brain Vesicles
    • By 5 weeks post-conception, the three primary vesicles have become five secondary vesicles.
    • Each is associated with a distinct division of the brain:
      • Telencephalon
      • Diencephalon
      • Mesencephalon
      • Metencephalon
      • Myelencephalon
  • Prosencephalon, Mesencephalon, Rhombencephalon

Telencephalon: Forebrain Differentiation

  • Secondary vesicles that form off of the forebrain (prosencephalon):
    • Two telencephalic vesicles = cerebral hemispheres and subcortical structures.
    • Two optic vesicles = Invaginate to form optic stalks and cups (retina & optic nerves).
    • Diencephalon = Forms thalamus and hypothalamus.
    • Associated ventricles = lateral ventricles (telencephalon) and third ventricle (diencephalon).
      • Cerebral cortex
      • Basal Ganglia
      • Hippocampus and Amygdala (Limbic System)

Cerebral Hemispheres

  • Hemispheric Overview (Right-handed individuals):
    • Left: Speech and Language
    • Right: Interpreting visual information and spatial processing
  • Contra-lateral functions in movements and sensation
  • Site of conscious thought, sensation, intellect, memory, and complex movements.

Gyrus versus Sulcus

  • Gyri Importance:
    • Increase the surface area of the brain up to 2000cm22000cm^2
    • Better cognition without having to increase the size of the brain.
    • Gray matter of the cortex.
  • Gyrus: ridge-like elevation found on the surface of the cerebral cortex.
  • Sulcus: a depression (groove) that surrounds a gyrus.
  • Fissure: narrow elongated cleft or groove that separates structures.

Major Sulci

  • Important Sulci:
    • Longitudinal fissure: separates the two cerebral hemispheres
    • Central sulcus: runs between the longitudinal and lateral fissures; separates frontal and parietal lobes.
    • Parieto-occipital sulcus: between parietal and occipital lobes.
    • Lateral fissure: separates temporal lobe from the frontal and parietal lobes.

Cerebral Lobes

  • Frontal Lobe:
    • Organization of movement (primary motor area; supplementary motor areas) and executive function (prefrontal area); Abstract thinking.
  • Temporal Lobe:
    • Auditory processing
    • In dominant area, comprehension of language.
  • Occipital Lobe:
    • Vision and processing (interpretation of visual stimuli).
  • Parietal Lobe:
    • Complex language network; reading and writing; somatosensory complex (touch, pressure, temperature, and pain); spatial processing.

Major Gyri

  • Primary Motor Cortex (Pre-central Gyrus):
    • Precentral gyrus - lateral surface of the frontal lobe and acts as the primary motor area of the brain.
  • Primary Somatosensory Cortex (Post-central Gyrus):
    • Postcentral gyrus - lateral surface of the parietal lobe, and acts as the primary somesthetic area of the brain.
  • Superior Temporal Gyrus:
    • lateral surface of the temporal lobe, contains Wernicke’s area: compute language.

Brodmann’s Areas

  • Areas 3, 1, 2: Primary Sensory Cortex (Post-central gyrus), conscious awareness of sensation for discrimination of touch, vibration, position of body, pain, on the contralateral side of the body.
  • Area 4: Primary motor cortex (pre-central gyrus). Voluntary control of skeletal muscle on the contralateral side.
  • Area 6: Premotor cortex, motor planning area.
  • Area 9, 10: Prefrontal cortex, organizes and plans intellectual and emotional aspects of behaviour.
  • Areas 44, 45: ‘Broca’s Area’ – Speech.
  • Areas 41, 42: Primary Auditory Cortex. Reception and recognition of auditory stimuli.
  • Areas 22, 39, 40: ‘Wernicke’s Area’. Language comprehension center.
  • Areas 17, 18: Primary Visual Cortex. Reception and recognition of visual stimuli.

Functional Cortical Areas

  • Primary Motor Cortex (Pre-central Gyrus)
  • Primary Somatosensory Cortex (Post-central Gyrus)
  • Areas 44,45: ‘Broca’s Area’ – Speech
  • Prefrontal Cortex: Executive Function (e.g., problem-solving, attention)
  • Supplementary/Association Motor Area
  • Areas 41, 42: Primary Auditory Cortex
  • Wernicke’s Area: Language comprehension
  • Supplementary Somatosensory Area: Interpretation of the SIGNIFICANCE of sensory info
  • Visual Association Area: Meaning and interpretation of visual stimuli
  • WHAT IF PATIENT HAS…
    • Sudden numbness/weakness of face/arm/leg
    • Sudden trouble speaking/understanding others

Limbic System

  • FUNCTION: Associated with motivation, emotion, drives, and aggression.
    • Hippocampus: memory
    • Amygdala: emotion
    • Olfactory bulbs: smell
  • The limbic system consists of a number of other interlinked structures that form a border around the brainstem.

Basal Nuclei

  • Basal ganglia: Gray matter structures - comprised of the caudate nucleus, the putamen, the globus pallidus, subthalamic nucleus, and the substantia nigra.
  • FUNCTIONS
    • Planning of motor movement, and aspects of memory and emotional expression.
    • Attention, language planning, and cognition.
    • Dysfunctional in diseases like Parkinson’s and Huntington’s.

Revision Questions

  • For each patient, determine the:
    • (a) Side and lobe/area that the tumor is located in
    • (b) What function may be impaired (presentation)?