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| Motor Cortex: Anatomy, Functions and Injury |
$45.00 |
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Authors: Volker Mall and Nikolai H. Jung
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Abstract:
Anatomy and Functions: The term motor cortex describes regions of the brain that are involved in planning, execution and control of voluntary movements. It mainly consists of the primary motor cortex (M1) with a somatotopical representation of body areas, premotor cortex, supplementary motor areas (SMA), posterior parietal cortex and primary somatosensory cortex. Histologically, the motor cortex shows a six-ply structure with all layers of younger neocortical origin. Motor cortex areas are connected with each other and with other brain areas. Current research with neuroimaging and non-invasive stimulation techniques (i.e., transcranial direct current stimulation (tDCS) and transcranial magnetic stimulation (TMS)) provided new insights into connectivity of motor areas, mechanisms of motor learning as well as into pathophysiology and rehabilitation mechanisms of congenital and acquired brain injuries affecting the motor cortex.
The motor cortex consists of excitatory and inhibitory networks with predominantly glutamate as excitatory and gamma-aminobutyric acid (GABA) and glycine as inhibitory neurotransmitters. GABAergic mechanisms seem to play a key role in learning motor skills and undergo maturational processes. The homeostatic properties to adapt for changing environmental circumstances are one of the central mechanisms of the motor cortex and in acquiring new movement patterns and coordination. Neuronal plasticity of the human motor cortex is a key mechanism in all kinds of learning procedures, as well as in recovery after brain injuries. Arising effects can be evaluated and induced by non-invasive tDCS or TMS and occur after plasticity inducing stimulation protocols or motor practice. They are referred to LTP-like and LTD-like plasticity in humans. In healthy individuals, those effects underlie the same properties as in animal models and are therefore suitable to investigate functions of motor cortex areas and motor learning in particular M1.
Injury: Congenital injuries (e.g., cerebral palsy) and acquired injuries (e.g., stroke in adulthood) of the motor cortex mostly result in different movement patterns and movement disorders. Cerebral palsy (CP) is the most frequent cause ofspastic movement disorders in young children. Due to different time points of the underlying lesion, in patients with unilateral CP two groups of cortico-spinal organisation exist (contralateral and ipsilateral). Clinical and neurophsiological evaluation of cortico-spinal organisation in these patients has direct implications for their therapy.
Developmental disorders (e.g., neurofibromatosis 1, Noonan syndrome) demonstrated an impaired synaptic plasticity of the motor cortex and impaired sensorimotor integration (autism spectrum disorders). Results from these patients provided new insights into pathophysiological mechanisms and may offer new insights into therapeutic options that are topics of current studies.
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