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Cortical stimulation mapping led to the development of a homunculus for the motor and sensory cortices, which is a diagram showing the brain's connections to different areas of the body. An example is the cortical homunculus of the primary motor cortex and the somatosensory cortex, which are separated by the central sulcus.
All the fibers from the corticopontine system terminate in the pontine nuclei.The fibers descend through the sublenticular and retrolenticular of internal capsule, then traverse the midbrain through the basis pedunculi (i.e. ventral part of cerebral peduncle) to reach the pontine nuclei and synapse with neurons that give rise to pontocerebellar fibers.
The loop involves connections between the cortex, the basal ganglia, the thalamus, and back to the cortex. It is of particular relevance to hyperkinetic and hypokinetic movement disorders , such as Parkinson's disease and Huntington's disease , [ 1 ] as well as to mental disorders of control, such as attention deficit hyperactivity disorder ...
The largest part of the cerebral cortex is the neocortex, which has six neuronal layers. The rest of the cortex is of allocortex, which has three or four layers. [7] The cortex is mapped by divisions into about fifty different functional areas known as Brodmann's areas. These areas are distinctly different when seen under a microscope. [22]
That is, the legs and trunk fold over the midline; the arms and hands are along the middle of the area shown here; and the face is near the bottom of the figure. Because Brodmann area 4 is in the same general location as primary motor cortex, the homunculus here is called the motor homunculus.
The corticospinal tract is a white matter motor pathway starting at the cerebral cortex that terminates on lower motor neurons and interneurons in the spinal cord, controlling movements of the limbs and trunk. [1] There are more than one million neurons in the corticospinal tract, and they become myelinated usually in the first two years of life.
The anterior corticospinal tract (also called the ventral corticospinal tract, medial corticospinal tract, direct pyramidal tract, or anterior cerebrospinal fasciculus) is a small bundle of descending fibers that connect the cerebral cortex to the spinal cord.
Estimates of the number of neurons in cortex or in neocortex are on the order of 2×10 10. [9] [10] Most [11] (perhaps 90% [citation needed]) of cortical neurons are neocortical neurons. Johansson and Lansner [4] use an estimate of 2×10 10 neurons in the neocortex and an estimate of 100 neurons per minicolumn, yielding an estimate of 2×10 8 ...