Superolateral surface of brain

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Here is a complete, structured account of the superolateral (lateral) surface of the brain:

Superolateral Surface of the Brain

The superolateral surface is the large, convex outer surface of each cerebral hemisphere facing the calvarium. It is the most extensive of the three surfaces (the others being the medial and inferior surfaces). The surface is thrown into folds called gyri, separated by grooves called sulci (deeper ones are called fissures).

Lateral view of cerebral hemispheres showing lobes, gyri, and sulci - Neuroanatomy through Clinical Cases

Detailed labeled diagram of lateral surface gyri and sulci - Localization in Clinical Neurology

Key Fissures/Sulci Dividing the Surface

Fissure / Sulcus	Separates
Central sulcus (of Rolando)	Frontal lobe (anterior) from parietal lobe (posterior)
Lateral sulcus (Sylvian fissure)	Frontal & parietal lobes (above) from temporal lobe (below)
Imaginary parieto-occipital line	Parietal & temporal lobes from occipital lobe laterally

The insula lies buried in the depths of the Sylvian fissure, covered by the frontal operculum anteriorly and parietal operculum posteriorly.

Lobes on the Superolateral Surface

1. Frontal Lobe

Bounded posteriorly by the central sulcus and inferolaterally by the lateral sulcus
Precentral gyrus - lies immediately anterior to the central sulcus; contains the primary motor cortex (Brodmann area 4)
The remaining lateral frontal surface is divided by the superior frontal sulcus and inferior frontal sulcus into three horizontal gyri:
- Superior frontal gyrus
- Middle frontal gyrus
- Inferior frontal gyrus - divided by the anterior ascending and horizontal limbs of the Sylvian fissure into three parts:
  - Orbital part (pars orbitalis)
  - Triangular part (pars triangularis)
  - Opercular part (pars opercularis)
- The triangular + opercular parts of the left inferior frontal gyrus form Broca's area (Brodmann areas 44 & 45) - expressive speech

2. Parietal Lobe

Bounded anteriorly by the central sulcus and antero-inferiorly by the Sylvian fissure
Postcentral gyrus - immediately posterior to the central sulcus; contains the primary somatosensory cortex (areas 3, 1, 2)
The intraparietal sulcus divides the lobe into:
- Superior parietal lobule (above intraparietal sulcus)
- Inferior parietal lobule (below), which consists of:
  - Supramarginal gyrus - caps the upturned end of the Sylvian fissure
  - Angular gyrus - caps the upturned end of the superior temporal sulcus
- The angular gyrus forms part of Wernicke's area (language comprehension)

3. Temporal Lobe

Lies inferior to the Sylvian fissure
Divided by the superior temporal sulcus and inferior temporal sulcus into:
- Superior temporal gyrus - its upper bank (planum temporale) contains Heschl's gyrus (primary auditory cortex, Brodmann area 41/42); the posterior portion of the superior temporal gyrus is part of Wernicke's area
- Middle temporal gyrus
- Inferior temporal gyrus

4. Occipital Lobe

Forms the posterior pole of the hemisphere on the lateral surface
Contains lateral occipital gyri; the primary visual cortex (calcarine cortex) is mostly on the medial surface but extends onto the lateral surface near the occipital pole
No sharp lateral boundary separates it from parietal and temporal lobes; an imaginary line from the parieto-occipital sulcus to the preoccipital notch is used

Functional Areas (Lateral Surface)

Area	Location	Function
Primary motor cortex	Precentral gyrus	Voluntary movement (contralateral body)
Primary somatosensory cortex	Postcentral gyrus	Contralateral sensation (touch, pain, proprioception)
Broca's area	Left inferior frontal gyrus (pars triangularis + opercularis)	Expressive/motor speech
Wernicke's area	Left posterior superior temporal gyrus + angular gyrus	Receptive/comprehension of speech
Primary auditory cortex	Heschl's gyrus (superior temporal gyrus, buried in Sylvian fissure)	Hearing
Premotor cortex	Anterior to precentral gyrus	Motor planning
Prefrontal cortex	Anterior frontal lobe	Executive function, working memory
Association cortex	Parietal, temporal, occipital junction	Multimodal sensory integration

Clinical Relevance

Lesion of precentral gyrus - contralateral spastic paresis (UMN pattern)
Lesion of postcentral gyrus - contralateral cortical sensory loss (loss of discriminative touch, 2-point discrimination, graphesthesia)
Broca's aphasia - non-fluent aphasia with intact comprehension; lesion in left inferior frontal gyrus
Wernicke's aphasia - fluent aphasia with poor comprehension; lesion in left posterior superior temporal gyrus
Supramarginal gyrus lesion - ideomotor apraxia, conduction aphasia
Angular gyrus lesion - alexia, agraphia, acalculia, finger agnosia, left-right disorientation (Gerstmann's syndrome with involvement of left angular gyrus)
Middle cerebral artery (MCA) supplies most of the superolateral surface; infarction causes contralateral hemiplegia, hemisensory loss, and aphasia (dominant hemisphere)

Sources: Neuroanatomy through Clinical Cases, 3rd Ed. | Localization in Clinical Neurology, 8th Ed.

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