- It is composed of 2 large hemispheres (the left and the right cerebral hemispheres), which inhabit the anterior and middle cranial fossae and the supratentorial region of the posterior cranial fossa. The cerebrum is the largest part of the brain.
- A deep median longitudinal fissure named the longitudinal cerebral fissure partially divides the 2 hemispheres from every other. A huge commissure, the corpus callosum, whose fibres interconnect the corresponding cortical areas of the 2 cerebral hemispheres, is located in the floor of the fissure.
- Every cerebral hemisphere is made up of surface layer of grey matter named the cerebral cortex and a central core of white matter. In the basal part of the latter are situated large masses of grey matter, called basal nuclei/ganglia.
- The surface of cerebral cortex is convoluted, i.e., it’s a series of elevations, the gyri, divided by shallow depressions, the sulci, or deep grooves termed fissures.
There are individual differences in the look of the sulci and gyri, but some sulci are endless in their own position and look and function as significant landmarks.
The superolateral surface of every cerebral hemisphere is split into 4 lobes that are termed after the overlying skull bones:
- Frontal lobe-is anterior to the central sulcus and above the lateral sulcus.
- Parietal lobe-is posterior to the central sulcus and above the lateral sulcus.
- Occipital lobe-is behind a line stretching from the parieto-occipital sulcus to the preoccipital notch.
- Temporal lobe-is below the lateral sulcus and in front of preoccipital notch.
Frontal lobe: It’s essential for voluntary motor functions, motivation, aggression, emotions, affect, drive and comprehension of self.
Parietal lobe: It’s the major centre for reception and assessment of all sensory info with the exception of scent, hearing and eyesight.
Occipital lobe: It’s responsible for reception and integration of visual input signal.
Temporal lobe: It gets and assesses stimulation for smell and hearing and plays a significant part in recollection.
Deep inside the lateral sulcus is located a submerged portion of cerebral cortex, the insula that’s frequently called the 5th lobe or the central lobe of the cerebral hemisphere.
The so called limbic lobe is a complex bordering zone (limbus = border) between the cerebrum and diencephalon. It’s somewhat ring shaped. It’s related to basic survival instincts, viz. the acquisition of food and water and reproduction. It gives ability to shop and recover info and is especially essential for short-term memory.
The medial surface of the cerebral hemisphere isvisualized in the sagittal section of the brain and presents a number of features shown.
The inferior surface of the cerebral hemisphere is irregular and presents orbital and tentorial surfaces.
Basal Ganglia/Basal Nuclei
The basal ganglia are subcortical masses of grey matter that are situated in the white core of every cerebral hemisphere. The basal ganglia contain corpus striatum, claustrum and amygdaloid body.
During the development of links between the cerebral cortex and the brainstem, the bundles of fibres converging as internal capsule partially break up the corpus striatum into a medial caudate nucleus and a lateral lentiform nucleus. Between the internal capsule and the cerebral cortex, the nerve fibres diverge as the corona radiata.
Functionally, the basal ganglia also contain the subtha-lamic nucleus of diencephalon and the substantia nigra and red nucleus of midbrain.
The basal ganglia help determine the attribute of motor performance and are from time to time called extrapyramidal nuclei.