The role of ipsilateral primary motor cortex in movement control and recovery from brain damage.

The role of ipsilateral motor areas for movement control is not yet fully understood. The relevance of these areas to the recovery of motor function following a brain lesion is a matter of dispute. It has recently been stated that increased ipsilateral activation following brain damage is maladaptive and hindering the process of recovery. Others have presented evidence that ipsilateral motor areas subserve motor recovery. A recent study published in Experimental Neurology [Lotze, M., Sauseng, P., Staudt, M., 2009. Functional relevance of ipsilateral motor activation in congenital hemiparesis as tested by fMRI-navigated TMS. Exp. Neurol., 217, 440-443.] on patients with congenital hemiparesis presents evidence for the importance of ipsilateral primary motor cortex and dorsal premotor cortex to movement control even in the absence of direct ipsilateral descending output in this special set of patients. This comment briefly summarizes the relevant findings supporting both views and discusses potential causes for the prima facie contradictory findings.

Left and right superior parietal lobule in tactile object discrimination.

Tactile object discrimination is one of the major manual skills of humans. While the exploring finger movements are not perceived explicitly, attention to the movement-evoked kinaesthetic information gates the tactile perception of object form. Using event-related functional magnetic resonance imaging in seven healthy subjects we found one area in the right superior parietal cortex, which was specifically activated by kinaesthetic attention during tactile object discrimination. Another area with similar location in the left hemisphere was related to the maintenance of tactile information for subsequent object discrimination. We conclude that kinaesthetic information is processed in the anterior portion of the superior parietal cortex (aSPL) with a right hemispheric predominance for discrimination and a left hemispheric predominance for information maintenance.

Use-dependent cortical plasticity in thalidomide-induced upper extremity dysplasia: evidence from somaesthesia and neuroimaging.

In this study cerebral reorganization was investigated in thalidomide-damaged subjects who use their feet to compensate for their malformed upper extremities. Tactile localization across toes was combined with fMRI to study use-dependent plasticity of the human somatosensory cortex. The manner of compensatory foot use was assessed by a questionnaire. In the behavioural experiment toes were stimulated with above threshold monofilaments and subjects had to report which toe was stimulated. When feet were employed for all everyday actions subjects made significantly fewer errors in the localization task. In subjects who use their feet only for specific actions such as grasping objects there were as many localization errors as in the control group of thalidomide-affected subjects with normal extremities. However, the patterns of mislocalizations were different with less errors occurring for the toe of the dominant foot involved in these actions. Functional MRI showed stronger haemodynamic responses to electrical stimulation of the toes in subjects using their feet for everyday actions as compared to controls. Our data show that long-term use of the feet for fine sensorimotor skills leads to better performance in tactile localization and changes in cerebral SI representation supporting the notion of use-dependent plasticity in the somatosensory cortex.

Reorganization of motor representation in a patient with epilepsia partialis continua as shown by [O15]-labeled butanol positron emission tomography and functional magnetic resonance imaging.

The authors investigated a 38-year-old patient with focal cortical dysplasia in the right precentral cortex using positron emission tomography and functional magnetic resonance imaging to localize the hand and finger motor representations. The patient presented clinically with epilepsia partialis continua, supposed to originate from the perirolandic area harboring the cortical malformation. Both methods revealed an abnormal bilateral activation of motor cortex during left-hand finger movements. The results suggest that the so-called eloquent but nevertheless pathological dysplastic cortex accommodates motor representations.