Advanced Primary Somatosensory Cortex Quiz

Q1. Why can a focal lesion of the lateral postcentral gyrus preferentially impair sensation in the contralateral face or upper limb?

• The lower limb occupies the entire lateral cortex
• The lateral cortex receives only ipsilateral sensation
• All body regions have identical cortical locations
• Face and upper limb representations occupy lateral somatosensory cortex

Q2. Why can an anterior cerebral artery infarct cause prominent cortical sensory loss in the contralateral lower limb?

• The lower limb representation lies in medial cortex supplied by the anterior cerebral artery
• The face representation lies in the occipital lobe
• The anterior cerebral artery supplies only the brainstem
• Lower limb sensation bypasses the thalamus

Q3. What distinguishes primary somatosensory cortex from posterior parietal association cortex?

• Both regions are anatomically identical
• Primary cortex performs initial cortical sensory processing while association cortex performs higher-order integration
• Association cortex receives no sensory information
• Primary cortex generates all voluntary motor output

Q4. Why can a primary somatosensory cortical lesion impair two-point discrimination even when crude sensation is partly preserved?

• Fine discriminative sensation depends heavily on cortical processing
• The cortex contains no spatial sensory maps
• Crude sensation requires the visual cortex
• Two-point discrimination occurs only in the spinal cord

Q5. What is the functional significance of the columnar organization of primary somatosensory cortex?

• Columns replace the thalamus
• Columns are bundles of peripheral nerves
• Columns organize related sensory inputs within local cortical circuits
• Columns carry cerebrospinal fluid

Q6. How do areas 3, 1, and 2 differ within the primary somatosensory complex?

• They are three cranial nerve nuclei
• Only area 2 receives any sensory input
• They form interconnected subdivisions with differing sensory processing roles
• They are separate lobes of the brain

Q7. Why can damage to somatosensory cortex impair stereognosis when basic peripheral sensation is adequate?

• Stereognosis is performed entirely by the retina
• It depends only on lower motor neurons
• It requires no cortical processing
• Object recognition by touch requires cortical integration of multiple somatic features

Q8. How does the medial-to-lateral somatotopic sequence generally progress in primary somatosensory cortex?

• Face to lower limb to occipital cortex only
• Trunk to retina to lower limb
• Lower limb to trunk and upper limb to face
• Upper limb to cerebellum to face

Q9. Why does a lesion of the posterior limb of the internal capsule potentially affect somatosensation from a broad body region?

• The internal capsule contains only visual fibers
• Sensory fibers avoid the internal capsule
• Many sensory projection fibers are concentrated within a compact white matter region
• Each body region uses a separate cerebral hemisphere

Q10. Which statement best integrates the anatomy of the primary somatosensory cortex?

• It is a somatotopically organized postcentral cortical region receiving contralateral thalamic sensory input
• It is a temporal auditory region receiving cochlear input
• It is a frontal motor region supplied only by the posterior cerebral artery
• It is an occipital visual region receiving retinal input