Functional Reorganization Of Motor Cortex Research Articles

Process of the Functional Reorganization of the Cortical Centers for Movement in GBM Patients: fMRI Study

PurposeThe aim of this study was to verify whether the functional reorganization of motor cortex is associated with the increase in the size of WHO type IV glioma lesion, that is, disease duration and development, and whether surgical treatment has an impact on cerebral plasticity.MethodsThe study included 16 patients with primary tumors of the brain located at the region of central sulcus. The clinical status of patients and tumor volume was determined. Functional magnetic resonance imaging examinations were performed before and 3 months after operation.ResultsThe activity of all cortical centers, both contralateral and ipsilateral, was observed in a group of small as well as large tumors. The intensity of activation and the number of activated clusters of small tumors were almost always higher as compared with the large tumors. The frequency of the activity of contralateral areas was similar during the first and the second examination. In the case of ipsilateral centers, the frequency of activation during the second examination was lower. Mean values of t-statistics during the first examination were higher than during the second examination. Supplementary motor area (SMAa) was the only center for which the mean values of activation intensity remained similar.ConclusionsSMAa seems to play the most important role in the processes of motor cortex plasticity in high-grade glioma patients. Surgery seems not having a significant influence on the pattern of functional reorganization of the cortical centers for movement. Identification of the individual patterns of the reorganization of motor centers plays an important role in clinical practice.

Dendritic spine remodeling induced by hindlimb unloading in adult rat sensorimotor cortex

A sensorimotor restriction, for instance in patients confined to bed, induces an impairment in motor function, which could be due to structural and functional reorganization of the sensorimotor cortex. Hindlimb unloading (HU) is a rodent model used to reproduce the chronic weightless bearing and reduction in hindlimb movement. In this study, we determined whether a 14-day period of HU in adult rats leads to dendritic spine plasticity. For this purpose, we visualized a large number of spines on pyramidal neurons located in superficial and deep layers of the cortex within the hindpaw representation area, by means of confocal microscopy. Spines were classified according to their shape, as stubby, thin, mushroom, or filopodium. Spine density was increased (+26%) after HU. The increase concerned mainly filopodium spines (+82%) and mushrooms (+33%), whereas no change was noticed for stubby and thin spines. Spine length was decreased, whatever their shape. Head diameter evolved differently depending on the layer: it was increased in superficial layers and decreased in deeper ones. These results indicate that morphological changes accompany functional reorganization of motor cortex in response to a decrease in sensorimotor function during adulthood.

Different functional reorganization of motor cortex after transfer of the contralateral C7 to different recipient nerves in young rats with total brachial plexus root avulsion

Clinically, contralateral C7 transfer is used for nerve reconstruction in brachial plexus injuries. Postoperatively, synchronous motions at the donor limb are noteworthy. This study studied if different recipient nerves influenced transhemispheric functional reorganization of motor cortex after this procedure. 90 young rats with total root avulsion of the brachial plexus were divided into groups 1–3 of contralateral C7 transfer to anterior division of the upper trunk, to both the musculocutaneous and median nerves, and to the median nerve, respectively. After reinnervation of target muscles, number of sites for forelimb representations in bilateral motor cortices was determined by intracortical microstimulation at 1.5, 3, 6, 9, and 12 months postoperatively. At nine months, transhemispheric reorganization of nerves neurotized by contralateral C7 was fulfilled in four of six rats in group 1, one of six in group 2 and none in group 3, respectively; at 12 months, that was fulfilled in five of six in group 1, four of six in groups 2 and 3, respectively. Logistic regression analysis showed that rate of fulfilled transhemispheric reorganization in group 1 was 12.19 times that in group 3 (95% CI 0.006–0.651, p=0.032). At 12 months, number of sites for hindlimb representations which had encroached upon original forelimb representations on the uninjured side was statistically more in group 3 than in group 2 (t=9.5, p<0.0001). It is concluded that contralateral C7 transfer to upper trunk or to both the musculocutaneous and median nerves induces faster transhemispheric functional reorganization of motor cortex than that to median nerve alone in rats.

An electrophysiological study on brain functional reorganization of different operative modes of contralateral C7 transference treating total brachiai plexus avuision in young rats

Objective To detected the motor cortex reorganization and compared the influence on reorganization process as regard to different transfer modes of contralateral seventh cervical nerve root (C7)in young rats model of total brachial plexus root avulsion. Methods The young Sprague-Dawley rats model of total brachial plexus root avulsion was established. The left radix dorsalis and radix ventralis from the fifth cervical nerve root (C5) to the first thoracic nerve root (T1)were exposed and the roots from C5 to T1 were avulsed from the spinal cord. Then, the contralateral C7 transfer operation was performed. Three different operative modes were applied randomly which included contralateral C7 transference to anterior division of the upper trunk (group A, n=30), to both musculocutaneous and median nerves (group B, n=30), or to median nerve (group C, n=30). The movement evocation of motor cortex was measured by intracortical microstimula-tion in both hemispheres, and functional reorganization was assessed dynamically in 1.5, 3, 6, 9 and 12 months after operation. Results After contralateral C7 transference, the ipsilateral motor cortex initially acti- vated the injured limb at 1.5 month, and subsequently the motor cortex of both hemispheres activated the in-jured limb at the 3rd and 6th month. The injured limb was activated mainly by the contralateral motor cortex in group A at the 9th month. The contralateral motor cortex exclusively controlled the injured limb in all three groups at the 12th month after the operation. Meanwhile, the extent of functional reorganization was better in group B than that of group C. Conclusion After contralateral C7 transfer operation, motor cortex in charging injured limb developed a transhemispheric functional reorganization in young rats with total brachial plexus root avulsion. Different operative modes contributed to the functional reorganization of motor cortex. Transferring contralateral C7 to anterior division of the upper trunk or to both musculocutaneous and median nerves provided better functional reorganization than to median nerve. Key words: Brachial plexus; Wounds and injuries; Motor cortex; Electrophysiology

Transhemispheric functional reorganization of the motor cortex induced by the peripheral contralateral nerve transfer to the injured arm

Peripheral nerve injury in a limb usually causes functional reorganization of the contralateral motor cortex. However, a dynamic process of the novel transhemispheric functional reorganization in the motor cortex was found in adult rats after transferring the seventh cervical nerve root from the contralateral healthy side to the injured limb. Initially the ipsilateral motor cortex activated the injured forepaw for 5 months after the operation. Then, both hemispheres of the cortex activated the injured forepaw, and finally the contralateral cortex exclusively controlled the injured forepaw. It is concluded an extensive functional shift occurred between two hemispheres based on neural plasticity in the CNS. The experimental results of the later lesions of the ipsilateral cortex suggest that maintaining transhemispheric functional reorganization does not depend on the corpus callosum, but depends on mechanisms involving central axonal sprouting. Possible mechanisms underlying the alternative changes in cortical functions were discussed in rats and in patients having similar operations.