CorpusHuman Anatomy

Brain — Lateral View

Left cerebral hemisphere, cerebellum and brainstem

The left (usually language-dominant) cerebral hemisphere seen from the left side: anterior is to the left. The four lobes visible on the superolateral surface are tinted in different colours and are separated by two constant landmarks — the central sulcus (frontal | parietal) and the lateral sulcus (temporal below | frontal and parietal above) — and by an imaginary line from the parieto-occipital notch to the preoccipital notch (parietal and temporal | occipital). The insula lies hidden in the depth of the lateral sulcus (dashed outline).

Brighter overlays mark the classic functional areas with their Brodmann numbers: primary motor and premotor cortex, prefrontal cortex, Broca and Wernicke areas, primary somatosensory, auditory and visual cortex. The animated pulse runs along the arcuate fasciculus, the association bundle that links Wernicke area (comprehension) with Broca area (speech production). Below the hemisphere are the cerebellum and the pons, medulla oblongata and upper spinal cord.

Step-by-step

  1. The cerebral hemisphere

    Each hemisphere is divided into lobes named after the overlying skull bones. On the lateral surface you see four: frontal (blue), parietal (green), temporal (orange) and occipital (pink). The cerebral cortex is a 2–4 mm sheet of grey matter, folded into gyri and sulci so that about two-thirds of its area is hidden in the sulci.

  2. Landmark sulci

    The central sulcus separates frontal from parietal lobe. The lateral sulcus separates the temporal lobe from the frontal and parietal lobes above it. The occipital lobe is marked off by an imaginary line from the parieto-occipital notch to the preoccipital notch.

  3. Frontal lobe — planning and movement

    From front to back, the prefrontal cortex handles executive function and personality, the premotor cortex (area 6) plans and sequences movement, and the primary motor cortex (area 4, precentral gyrus) sends the corticospinal and corticobulbar fibres that execute it, mapped as a motor homunculus.

  4. Broca area — speech production

    Areas 44 and 45 of the inferior frontal gyrus in the dominant (usually left) hemisphere. A lesion causes expressive, non-fluent aphasia: comprehension is relatively spared but speech is effortful and telegraphic.

  5. Parietal lobe — body sensation

    The postcentral gyrus (areas 3, 1, 2) is the primary somatosensory cortex, receiving touch, pressure, vibration, proprioception, pain and temperature from the opposite half of the body via the thalamus. The parietal association cortex behind it builds the spatial body map; a non-dominant parietal lesion causes contralateral hemineglect.

  6. Temporal lobe — hearing and comprehension

    The primary auditory cortex (areas 41 and 42, Heschl gyri) lies largely inside the lateral sulcus. Behind it, Wernicke area (posterior area 22) decodes spoken language; a lesion causes fluent, receptive aphasia. The medial temporal lobe (hippocampus, amygdala) handles memory and emotion.

  7. The language loop

    The arcuate fasciculus carries information from Wernicke area around the end of the lateral sulcus to Broca area, which is why we can repeat what we hear. If it is damaged, the result is conduction aphasia: comprehension and fluency are preserved but repetition fails.

  8. Occipital lobe — vision

    The primary visual cortex (area 17) lines the calcarine sulcus on the medial surface; only the occipital pole, which represents the macula, shows laterally. Visual association areas (18, 19) surround it. A lesion here causes a contralateral homonymous hemianopia, often with macular sparing.

  9. Hidden cortex and the hindbrain

    The insula (dashed) lies buried in the lateral sulcus; it handles taste, visceral sensation and interoception. Below the hemisphere, the cerebellum coordinates movement and balance on the same side of the body, and the pons and medulla oblongata carry the long tracts and the nuclei of cranial nerves V–XII before continuing as the spinal cord at the foramen magnum.

Labelled parts