Method: The subjects were 10 healthy volunteers. The study was composed of 3 sessions: first session, baseline evaluation; second session, RES with a intensity for proprioceptive stimulation on tibial nerve at the right ankle for 3 different duration of 30 minutes, 1 hour, and 2 hours; third session, repeat of baseline evaluation after RES (post- RES evaluation). The baseline evaluation include somatosensory evoked potential study with stimulation of right tibial nerve and compound muscle action potential (CMAPs) of tibial nerve recorded at abductor hallucis and H reflex. The amplitude of each study were measured and compared between baseline evaluation and post-RES evaluation using Kruscal-Wallis test.

Results: There was no significant change in amplitudes of SSEP, CMAP and H reflex between baseline evaluation and post-RES evaluation of 30 minutes, 1 hour and 2 hours.

Conclusion: This study suggests that chronic repetitive proprioceptive afferent nerve stimulations could not modulate primary somatosensory cortex in healthy subjects. However, we could not rule out the limitations of sensitivity of somatosensory evoked potential study. (J Korean Acad Rehab Med 2003; 27: 224-227)

Objective: To investigate cortical reorganization of the brain during voluntary activities of the hand in patients with subcortical cerebral infarction.

Method: Twelve patients with first-ever subcortical brain lesion causing hemiparesis had been evaluated with functional MRI. Bilateral hand clenching was done to test voluntary hand activities. Recovery period ranged from 2 to 36 months.

Results: During the unaffected hand movement, activation of contralateral primary sensorimotor cortex (SMC) were recorded in all cases and supplmentary motor area (SMA) in 1 case. The affected hand movement showed activation of the cotralateral SMC in all cases, ipsilateral SMC in 4 cases, SMA in 4 cases and contralateral prefrontal area in 2 cases. As for the contralateral SMC, affected hand movement showed more increased activation than the unaffected. For the bilateral SMC activation during movement of the affected hand, contralateral SMC activation was greater than the ipsilateral.

Conclusion: Ipsilateral activation of the SMC, SMA, prefrontal area and increased activation of the contralateral SMC during affected hand movement suggest that these may play an important role in the reorganization of sensory and motor system in stroke patients with subcortical lesion. Functional MRI studies of patients who recovered from subcortical stroke provide evidence for several process that may be related to restoration of neurologic function.

The higher cognitive functions of human brain are hypothesized to be selectively distributed across large-scale neural networks interconnected cortical and subcortical areas. Recently, advances in functional imaging made it possible to visualize the brain areas activated by certain cognitive function in vivo. Out of several technologies currently available for brain activation study, functional magnetic resonance imaging (fMRI) is increasingly being used because of its superior time resolution and finer spatial resolution. The technique is non-invasive without radiation hazard, which allow to take repeated multiple scans within the same individual. The most common approach to fMRI of brain is the one using 'blood-oxygen level dependent (BOLD)' contrast, which based on the localized hemodynamic changes following neural activities in the certain areas of brain.

With functional imaging techniques including fMRI, neural networks subserving for higher cognitive functions such as language, memory, attention, and visuospatial functions could be visualized. Neural substrates of human emotion and motivation behaviors also begin to be unveiled. Brain mapping with functional imaging is a very useful method for detecting eloquent areas in a neurosurgical setting to prevent the residual disabilities. One of the issues recently having attention in the field of functional imaging is the reorganization of neural network following brain injuries. Much research results using fMRI identified intra- and/or interhemispheric reorganization of neural networks accompanied with functional recovery after brain injury. Effects of learning and rehabilitation on the extent and pattern of neural reorganization was also delineated. fMRI will be a very useful tool for developing of various rehabilitation treatments, which promote successful functional recovery by maximizing the plasticity of brain.