Cerebral Cortex Quiz

Learning Outcomes

• Identify major sulci, gyri, and lobes.
• Identify and describe major cortical areas in terms of their pathway and function.
• Explain signs and symptoms following a lesion to major cortical areas.
• Identify and describe white matter (commissural, association, and projection fibers) of the cerebral hemisphere.
• Describe major layers (layer 3, 4, and 5) of the cerebral cortex and their significance.
• Identify and describe the major blood supply of the brain.
• Describe the formation and significance of the circle of Willis.

Cerebral Cortex

• Cortex is composed of gray matter.
• It forms a complete covering of the cerebral hemisphere.
• Sulci = grooves/depressions.
• Gyri = folds/convolutions.

Sulcus vs Fissure

• Fissure = deeper groove compared to a sulcus.
• Longitudinal fissure = separates the left and right cerebral hemispheres.

Lobes

• Central sulcus = starts at the superior medial border of each hemisphere and separates the frontal lobe from the parietal lobe.
• Lateral sulcus (aka sylvian fissure) = separates the frontal lobe from the temporal lobe.
• Parieto-occipital sulcus = separates the parietal lobe from the occipital lobe.

Calcarine Sulcus

• Runs within the occipital lobe.

Corpus Collosum

• Composed of nerve fibers that connect the cerebral hemispheres.

Above the Corpus Collosum

• Cingulate gyrus is involved in the limbic system (memory and emotion).
• Paracentral lobule is divided into anterior and posterior parts by the central sulcus.
• The paracentral lobule surrounds the central sulcus.
• Anterior = precentral gyrus.
• Posterior = postcentral gyrus.

Primary Motor Area

• Occupies the precentral gyrus and anterior part of the paracentral lobule.

Primary Somesthetic Area

• Occupies the postcentral gyrus and posterior part of the paracentral lobule.

Insula

• Cannot be seen unless the surrounding brain matter is removed.
• Lies deep within the lateral sulcus.
• Function of left frontal lobe is involved in personality and behavior.

Cortical Areas

• Precentral gyrus = primary motor area.
• Postcentral gyrus = primary somesthetic (somatosensory) area.
• Below the lateral sulcus = superior temporal gyrus.
• Primary auditory area = receives auditory impulses.
• Primary visual area = receives visual impulses.

Primary Visual Cortex

• Surrounded by the calcarine sulcus.

Overview of Cortical Areas

• Premotor area = programming of and preparing for movement and is involved in posture control.
• Prefrontal area (cortex) = personality, thinking, judgment, and decision-making.
• Taste area = at the lower end of the postcentral gyrus and insula.
• Insula = part of the cortex hidden deeper than the lateral sulcus.

Somesthetic Association Area

• Occupies the superior parietal lobule.
• Allows recognition of general sensations with other sensory stuff along with past sensory experience.
• Ability to recognize form, size, and texture of an object by touch—known as stereognosis.
• Lesion = astereognosis.

Auditory Association Area

• Ability to recognize what causes the sound.

Visual Association Area

• Ability to recognize and appreciate what is seen.

Language Areas

• Broca's area: found in the inferior frontal gyrus of the frontal lobe (dominant hemisphere).
  • Responsible for expressive aspects of language, allowing the formation of words.
  • Lesion results in expressive aphasia (difficulty forming words or expressing speech, but understanding meaning).
• Wernicke's area: mainly located in the superior temporal gyrus and extends around the posterior end of the lateral sulcus into the parietal region (dominant hemisphere).
  • Responsible for comprehension of spoken words.
  • Allows understanding of written and spoken language, reading sentences and expressing them out loud
  • Lesion results in receptive aphasia (speaking but unable to understand spoken and written words resulting in incorrect words and nonexistent words)

Everything Labelled

• Diagram showing various labelled areas of the brain (frontal, parietal, temporal, occipital).

Motor and Sensory Homunculi

• Diagram showing specific body parts mapped onto the motor and sensory cortex.

White Matter of the Cerebral Hemisphere

• Commissural fibres = connect regions of the two hemispheres.
• Association fibres = connect cortical regions within the same hemisphere.
• Projection fibres = afferent and efferent fibres.
• Corpus callosum = largest commissural fibre connecting the two cerebral hemispheres.

Corpus Collosum Structures

• Made up of four parts: splenium, body, genu, and rostrum.
• Forceps minor = fibres of genu curve forward into the frontal lobe.
• Forceps major = fibres of splenium curve backward into the occipital lobe.

Commissural Fibres

• Anterior commissure fibres = connect the two hemispheres via the temporal lobe.

• Association fibres = connect cortical regions within the same hemisphere.

• Short association fibres = lie beneath the cortex, connecting adjacent gyri.

• Long association fibres = connect lobes within the same hemisphere.

  • Superior longitudinal fasciculus = largest association fibre, connecting frontal, parietal, occipital, and temporal lobes.
  • Inferior longitudinal fasciculus = connects occipital and temporal lobes.

• Uncinate fasciculus = connects motor/speech areas and gyri of the frontal lobe with the temporal lobe.

• Cingulum = found in the cingulate gyrus connecting the frontal lobe, parietal lobe, parahippocampal gyrus and temporal lobe

Naming an Object

• Different cortical regions work together to decipher an object (like a chair).
• Angular gyrus & supramarginal gyrus = important in naming, reading, writing and calculation, serve as an interface between auditory and visual association areas.
• Pathway = visual cortex → higher-order visual association area → angular gyrus → Wernicke's area → arcuate fasciculus → Broca's area → primary motor area

Projection Fibres

• Afferent fibres.
• Efferent fibres.

Internal Capsule

• Superior to the brainstem.
• Composed of the anterior limb, genu, and posterior limb.
• Caudate nucleus = medial to the internal capsule.
• Thalamus = medial to the internal capsule.
• Lentiform nucleus = lateral to the internal capsule..
• Consists of the putamen and globus pallidus
• Corona radiata = superior to the nuclear masses of gray matter.

Layers of the Cerebral Cortex

• Consists of six layers.
• Layer 1 = more superficial layer.
• Layer 3 = neurons give rise to association/commissural fibres.
• Layer 4 = termination site for thalamocortical afferents.
• Layer 5 = efferent fibres (e.g., pyramidal cells forming the pyramidal tract in the primary motor area)

Variation in Cortical Layers

• Different cortical areas have different layer thicknesses depending on their function.
• Layer 5 is thicker in the primary motor cortex due to the abundance of Betz cells.
• Layer 4 is thicker in the primary sensory cortex due to more termination of thalamocortical afferents.

Arterial Supply - Circle of Willis

• Ventral arteries (paired, left and right) travel across the neck and enter the skull.
• They join to form the basilar artery (on the basilar part of the pons).
• Anterior spinal arteries branch off to supply the spinal cord.
• Posterior inferior cerebellar artery supplies the cerebellum.
• Basilar artery branches into pontine arteries—supplying the pons.
• Basilar artery also supplies the cerebellum via the anterior inferior cerebellar artery and superior cerebellar artery.
• Posterior arteries (paired, left and right).
• Internal carotid arteries (left and right) enter the skull and branch into:
  • Anterior cerebral artery
  • Middle cerebral artery
  • Posterior cerebral artery
• Anterior communicating artery provides lateral circulation.
• Anterior cerebral artery + middle cerebral artery + posterior cerebral artery = supply the cortex.

Medial and Inferior Surfaces

• Medial surface is associated with lower limbs and supply the leg area.
• ACA/Anterior cerebral artery
• MCA/Middle cerebral artery
• PCA/Posterior cerebral artery.

Loss of Function – Cerebral Artery

• Stroke occurs due to haemorrhagic or ischaemic conditions.
• Results in various functional losses depending on the affected cerebral artery and region of brain damage.

Test your knowledge on the anatomy and functions of the cerebral cortex, including major sulci, gyri, lobes, and cortical areas. This quiz also covers the significance of white matter and the brain's blood supply. Perfect for students studying neuroanatomy!