The brain
The human brain [53] (prosencephalon [8, 64] , the most prominent part of the encephalon) consists of two nearly symmetrical right and left cerebral hemispheres [224] forming the telencephalon [58] , in addition to the diencephalon [41, 51] - an unpaired, median part covered by the telencephalon - that includes the thalamus and hypothalamus [8, 59].
Internal Configuration :
The cerebral hemispheres constitute the uppermost and largest part of the central nervous system [60]; both are linked by nerve commissures, primarily the corpus callosum [37, 61, 62].
Each cerebral hemisphere comprises two distinct regions: a peripheral one, the cortex (gray matter) [36, 49], containing the cell bodies of the nerve cells; and a central one made of white matter, containing essentially the axonal extensions of the neurons as well as their myelin sheaths [39].
Inside each hemisphere are islands of gray matter called the basal ganglia [4]. These essentially include the caudate nucleus [32, 66] , the putamen [32, 51] , the globus pallidus [32] , and the claustrum [50].
External Configuration :
Each hemisphere is marked by deep sulci [91] that delineate lobes [224]. The first is the lateral sulcus (or Sylvian fissure [91] ), through which the Sylvian artery [38] passes; this separates the frontal lobe from the temporal lobe.
The second fissure is the central sulcus (or Rolandic fissure [63, 72]), which separates the frontal lobe from the parietal lobe.
The third is the parieto-occipital sulcus [64] , which separates the occipital lobe from the temporal and parietal lobes.
There is also a fifth lobe not visible on the surface: the insula [65], which is found by retracting the Sylvian fissure.
Within each lobe, there are shallower sulci that delineate gyri (convolutions) [66].