The motor cortex Sample Clauses

The motor cortex. The motor cortex is immediately anterior to the central sulcus in the posterior frontal lobe. The primary motor cortex is located on the precentral gyrus (Figure 4). Muscles are somatotopically organised in an inverted form with the feet at the upper medial region. The amount of tissue devoted to an area is proportional to the complexity of the function and required accuracy of motor control. This is reflected in the homunculus, see Figure 3, therefore, for practical reasons TMS of the primary motor cortex is by far the most well documented as even relatively weak pulses can produce observable responses. Figure 3 Homunculus xxxx://xxxxxxxxxxxxxxxxxx.xxx Figure 4 Primary motor cortex in lateral and medial orientatations xxx.xxxxxxxxx.xxx The primary motor cortex is not only distinguishable from adjacent “premotor” areas cytoarchitectonically, but also by the low intensity of current necessary to elicit movements by electrical stimulation in this region. A TMS pulse over this region initiates a chain of events that begins with the stimulation of multiple axons distributed across the different cortical layers from which a wide variety of parameters can be investigated (described below). Neuronal axons have the highest density of ion channels which become preferentially activated by TMS, (described in greater detail below). A TMS pulse always activates a mixture of excitatory and inhibitory neurons..