Cerebrum
Cerebrum (telencephalon)
Also known as: cerebral hemispheres, telencephalon, endbrain
The largest part of the brain: two cerebral hemispheres, each with a folded cortex, underlying white matter, basal nuclei and limbic structures, responsible for perception, voluntary movement and all higher mental functions.
Overview
The two cerebral hemispheres (≈83% of brain mass) are separated by the longitudinal cerebral fissure, which contains the falx cerebri, and are connected across the midline mainly by the corpus callosum. The transverse cerebral fissure separates them from the cerebellum, with the tentorium cerebelli between. The surface is folded into gyri separated by sulci, which roughly triples the cortical area. The central sulcus and the lateral (Sylvian) sulcus divide each hemisphere into the frontal, parietal, temporal and occipital lobes. The insula lies hidden in the depth of the lateral sulcus, and the limbic lobe encircles the corpus callosum on the medial surface.
Each hemisphere has three layers of tissue. Outermost is the grey cerebral cortex. Beneath it is the white matter, made of three kinds of fibre:
• association fibres link areas within one hemisphere, e.g. the arcuate fasciculus (Wernicke to Broca), the superior longitudinal fasciculus, the uncinate fasciculus and the cingulum;
• commissural fibres cross between the hemispheres in the corpus callosum and the anterior, posterior and hippocampal commissures;
• projection fibres connect the cortex with the thalamus, brainstem and cord, fanning out as the corona radiata and converging into the internal capsule.
Deepest are the basal nuclei, and the lateral ventricle forms the cavity of each hemisphere.
Each hemisphere receives sensation from, and controls movement of, the opposite side of the body and visual field. The hemispheres are also functionally lateralised:
• the left hemisphere is dominant for language in ≈95% of right-handers and ≈70% of left-handers;
• the right (non-dominant) hemisphere is specialised for spatial attention, face recognition and prosody.
- Location
Anterior and middle cranial fossae, above the tentorium cerebelli; fills most of the cranial vault.
Parts & subdivisions
- Anterior to the central sulcus: motor, premotor, Broca and prefrontal cortex.
- Between the central and parieto-occipital sulci: somatosensation, spatial attention.
- Below the lateral sulcus: hearing, language comprehension, memory.
- Posterior pole: vision.
- Hidden in the lateral sulcus: interoception, taste, viscerosensation.
- Cingulate and parahippocampal gyri around the corpus callosum.
- Largest commissure (≈200 million axons).
- Caudate, putamen and globus pallidus.
- Projection-fibre bottleneck between the thalamus/caudate and the lentiform nucleus.
Anatomy
- Arterial supply
Anterior cerebral artery (medial surface, superior border, anterior four-fifths of the corpus callosum), middle cerebral artery (most of the lateral surface, insula, and via lenticulostriate branches the basal nuclei and internal capsule) and posterior cerebral artery (occipital lobe, inferomedial temporal lobe, splenium).
- Development
From the paired telencephalic vesicles. Hemispheric growth sweeps backwards and then forwards in a C-shape, which is why the lateral ventricle, caudate nucleus, fornix, hippocampus and stria terminalis are all C-shaped. Gyri appear from mid-gestation; the central and lateral sulci are visible by ≈24–26 weeks.
Function
- Conscious perception of somatic, visual, auditory, olfactory and gustatory sensation
- Voluntary motor control
- Language, praxis and attention
- Learning, memory and emotion (with limbic structures)
- Executive function, reasoning, social behaviour and personality
Clinical significance
Dominant vs non-dominant hemisphere lesions
• Left (dominant) hemisphere lesions cause aphasia, ideomotor apraxia, alexia and agraphia, and Gerstmann syndrome (angular gyrus).
• Right (non-dominant) hemisphere lesions cause left hemispatial neglect, anosognosia (unawareness of the deficit), dressing and constructional apraxia, and aprosodia.
Either side produces contralateral hemiparesis, hemisensory loss and homonymous hemianopia.
Compiled from standard anatomy and physiology references — see the Nervous System sources. For education only; not medical advice.