Learning Objectives

By the end of this session, the learner will be able to identify major cortical landmarks and layers, localize language functions in the dominant hemisphere, interpret homunculus organization, understand cerebral blood supply and vascular territories, and correlate lesions with clinical stroke syndromes and cortical deficits.

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1. General Features: Gross Anatomy

The cerebral cortex is highly folded into gyri (ridges) and sulci (grooves), increasing functional surface area.

Landmark	Anatomical Role	Clinical Importance
Lateral Fissure (Sylvian)	Separates the temporal from the frontal/parietal lobes	MCA runs here → stroke affects language
Central Sulcus	Separates frontal (motor) and parietal (sensory)	Key landmark for motor vs sensory deficits
Cingulate Sulcus	Separates the cortex from the limbic lobe	Important in emotion/behavior circuits
Parieto-occipital Sulcus	Separates parietal and occipital lobes	Visual vs sensory cortex boundary
Calcarine Sulcus	Primary visual cortex location	Lesion → homonymous hemianopia

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2. Cortical Histology & Layers

The cortex is functionally organized into layers that reflect input vs output roles.

Layer	Function	Clinical Relevance
I–III	Association & integration	Cortical processing
IV	Receives thalamic input	Primary sensory cortex prominent
V	Motor output (corticospinal)	Damage → paralysis (Betz cells)
VI	Projects back to the thalamus	Feedback regulation

Key Distinction:

• Neocortex: 6 layers (90%)
• Allocortex: 3 layers (hippocampus, olfactory)

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3. Language & Dominant Hemisphere

Dominance: Left hemisphere in most individuals

[Image of the brain showing Broca’s and Wernicke’s areas]

Condition	Location	Key Clinical Features
Broca Aphasia	Frontal (44,45)	Non-fluent speech, intact comprehension, frustrated
Wernicke Aphasia	Temporal (22)	Fluent but meaningless, poor comprehension, unaware
Conduction Aphasia	Arcuate fasciculus	Cannot repeat, fluent, aware
Gerstmann Syndrome	Angular gyrus	Agraphia, acalculia, finger agnosia, R-L confusion

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4. Frontal Lobe Functions

Functional Region	Physiological Role	Lesion Presentation
Primary Motor (Area 4)	Executes contralateral voluntary movement	Contralateral spastic weakness
Premotor (Area 6)	Planning/sequencing of complex movements	Apraxia
Frontal Eye Field (8)	Contralateral horizontal saccades	Eyes deviate toward the lesion
Prefrontal Cortex	Executive function, judgment, and social behavior	Apathy, disinhibition, poor judgment

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5. Parietal Lobe Functions

Functional Area	Normal Function	Lesion Presentation
Primary Sensory Cortex	Touch, pain, vibration, proprioception	Contralateral sensory loss
Association Cortex (5,7)	Sensory integration & spatial mapping	Astereognosis and Apraxia
Nondominant Parietal	Spatial awareness of the contralateral side	Hemispatial neglect syndrome

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6. Occipital & Temporal Lobes

Lobe	Functional Region	Clinical Deficit
Occipital	Primary Visual Cortex (Area 17)	Contralateral hemianopia with macular sparing
Temporal	Wernicke’s Area (Superior Gyrus)	Receptive aphasia (fluent nonsense)
Temporal	Meyer’s Loop (Optic Radiation)	Contralateral superior quadrantanopia (“pie in sky”)

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7. Homunculus Organization

Surface Aspect	Body Representation	Vascular Supply (Rule)
Lateral Convexity	Face and Upper Limb (Arm/Hand)	MCA → Face/arm deficits
Medial Surface	Lower Limb (Leg/Foot) and Perineum	ACA → Leg deficits

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8. Blood Supply: Circle of Willis

System	Key Components	High-Yield Clinical Connection
Internal Carotid	ACA, MCA, ACoA	Anterior circulation; supplies 80% of the brain
Vertebrobasilar	Vertebral, Basilar, PCA	Posterior circulation; supplies the brainstem/occipital
Communicating	Ant. & Post. Communicating Arteries	PCoA Aneurysm → CN III palsy

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9. Major Arterial Syndromes

Artery	Territory	Deficit
MCA	Lateral cortex	Face/arm paralysis, aphasia (L), neglect (R)
ACA	Medial cortex	Leg weakness, incontinence
PCA	Occipital	Hemianopia, macular sparing

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10. Hemorrhage Types

Type	Cause	Clue
Epidural	MMA rupture	Lucid interval
Subdural	Bridging veins	Slow bleed
Subarachnoid	Berry aneurysm	Worst headache
Intracerebral	Hypertension	Deep bleed

 

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