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Because the left arm is controlled by the right hemisphere and vice versa, the corpus callosum has also been found to be larger in left-handers. This is theoretically so that language comprehension and production can more efficiently move from the primary language areas into the motor areas which control the contralateral arm.
Consequently, the left side of the forebrain mostly represents the right side of the body, and the right side of the brain primarily represents the left side of the body. The contralateral organization involves both executive and sensory functions (e.g., a left-sided brain lesion may cause a right-sided hemiplegia).
As speech is a very complex motor control task, the specialised fine motor areas controlling speech are most efficiently used to also control fine motor movement in the dominant hand. As the right hand is controlled by the left hemisphere (and the left hand is controlled by the right hemisphere) most people are, therefore right-handed.
Control of more central axial and girdle muscles comes from the anterior corticospinal tract. [3] Damage to different parts of the body will cause deficits, depending on whether the damage is above (rostral) or below (caudal) the pyramidal decussation. Damage to the body above the pyramidal decussation will cause contralateral motor deficits.
In Tan's autopsy, Broca determined he had a syphilitic lesion in the left cerebral hemisphere. This left frontal lobe brain area (Broca's area) is an important speech production region. The motor aspects of speech production deficits caused by damage to Broca's area are known as expressive aphasia. In clinical assessment of this type of aphasia ...
The left and right hemispheres operate the contralateral sides of the body. Each hemisphere contains sections of all 4 lobes: the frontal lobe, parietal lobe, temporal lobe, and occipital lobe. The two hemispheres are separated along the mediated longitudinal fissure and are connected by the corpus callosum which allows for communication and ...
The arm and hand motor area is the largest, and occupies the part of precentral gyrus between the leg and face area. These areas are not proportional to their size in the body with the lips, face parts, and hands represented by particularly large areas due to the comparative enrichment and density of motor receptor in these regions.
Thus, hand preference (which hand someone prefers to use) is also related to hemisphere lateralization. [citation needed] In some aspects, the hemispheres are asymmetrical; the right side is slightly bigger. There are higher levels of the neurotransmitter norepinephrine on the right and higher levels of dopamine on the left. The right ...