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Structure

Parietal lobe

Not medically reviewed · Content last updated · 2 min read ·

This is the date the draft was written, not a medical review date.

The parietal lobe integrates somatic sensation, spatial awareness and body schema. It contains the primary somatosensory cortex and association areas that combine sensory, visual and motor information for action and language.

Terminologia Anatomica (Latin): Lobus parietalis · Open in the 3D atlas

Location

It lies behind the central sulcus, above the lateral sulcus, and in front of the occipital lobe; on the medial surface the parieto-occipital sulcus marks its posterior limit. The lateral border with the temporal and occipital lobes is conventional, not marked by a sulcus.

Structure

The postcentral gyrus is the primary somatosensory cortex (Brodmann areas 3, 1 and 2). Behind it, the intraparietal sulcus separates the superior parietal lobule (areas 5 and 7) from the inferior parietal lobule, which contains the supramarginal gyrus (area 40) and the angular gyrus (area 39), important for language and calculation in the dominant hemisphere. The precuneus and paracentral lobule lie medially.

Blood supply

The middle cerebral artery supplies most of the lateral surface; the anterior cerebral artery supplies the medial paracentral lobule (leg sensation) and precuneus anteriorly; the posterior cerebral artery supplies the posterior medial portion. The watershed between territories is vulnerable to hypoperfusion.

Innervation

Afferents: sensory relay from the ventral posterolateral and ventral posteromedial thalamic nuclei to the postcentral gyrus, plus visual input from occipital cortex; efferents: to frontal motor and premotor cortex, to the striatum, thalamus and brainstem, and across the corpus callosum.

Function

It processes touch, proprioception and pain localisation, builds the body schema and spatial map, guides reaching and visuomotor action (dorsal visual stream), and in the dominant hemisphere supports reading, writing, calculation and praxis; the non-dominant hemisphere is more concerned with spatial attention.

Clinical correlations

Lesions cause contralateral cortical sensory loss (astereognosis, agraphaesthesia, impaired two-point discrimination) and inferior homonymous quadrantanopia. Non-dominant lesions cause hemispatial neglect, anosognosia and constructional apraxia; dominant angular gyrus lesions cause Gerstmann syndrome (agraphia, acalculia, finger agnosia, left-right disorientation).

Common exam points

  • Postcentral gyrus (areas 3, 1, 2) is the primary somatosensory cortex; the leg area is medial (ACA).
  • Cortical sensory signs: astereognosis, agraphaesthesia, loss of two-point discrimination, with intact primary modalities.
  • Non-dominant parietal lesion: hemispatial neglect and anosognosia; test with line bisection or clock drawing.
  • Dominant parietal lesion: Gerstmann syndrome; aphasia from supramarginal and angular gyrus lesions.
  • Optic radiation fibres passing through the parietal lobe give an inferior homonymous quadrantanopia.

References

  1. Drake RL, Vogl AW, Mitchell AWM. Gray's Anatomy for Students. Elsevier — Tier 3 (textbook)
  2. Kandel ER, Koester JD, Mack SH, Siegelbaum SA. Principles of Neural Science. McGraw-Hill, 6th edition (2021) — Tier 3 (textbook)
  3. Haines DE, Mihailoff GA. Fundamental Neuroscience for Basic and Clinical Applications. Elsevier, 5th edition (2018) — Tier 3 (textbook)

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