| Summary: | 碩士 === 國立成功大學 === 生物醫學工程學系 === 106 === According to the theory of neural plasticity, brain can compensate the impaired function by rebuilding the neural circuit. As the result, many researchers tried to use external stimulation methods to modulate the neural activities to enhance or improve the brain recovery after stroke. Repetitive transcranial magnetic stimulation (rTMS), theta burst stimulation (TBS), and transcranial direct current stimulation (tDCS) are the common techniques that used to modulate the neural activities in clinical studies. The aim of this study is to apply patterned stimuli and to monitor hymodynamic changes in the brain. The EEG-liked electrode is replaced of the conventional sponge electrode for cortical electrical stimulation, which not only provides a more flexible stimulation arrangement at focused area but also fits in the headset of monitoring of hymodynamic changes.
Functional near infrared spectroscopy (fNIRS) is adopted in this study which uses the optical method to measure the concentration changes of hemoglobin representing the brain activities similar to the BOLD effect of fMRI. Stroke subjects were recruited for investigating the effect of cortical intermittent TBS (iTBS) electrical stimulation. Stroke subjects were asked to perform the cycling tasks to induce the cortical activation. During cycling, brain hemodynamic activity and kinematic information were measured before and after the stimulation. A concurrent stimulation with iTBS1200 and direct current was delivered during the stimulation session for a session of about 7 minutes. fNIRS signal was analyzed as the hemodynamic response function as concentration changes in hemoglobin in time domain and frequency domain. For kinematic information, the surface EMG on quadriceps muscles were for analyzing the symmetry between affected and unaffected leg using the shape symmetry index (SSI) and area symmetry index (ASI), and torque and speed information of ergometer to obtain the smoothness.
Our NIRS data show the decreasing value in power spectrum density band I(0.01Hz~0.02Hz), and increasing in band II(0.02Hz~0.05Hz) and band III(0.05Hz~0.15Hz) during the stimulation which suggest the brain might respond to the stimulation. Moreover, similar changes in frequency bands changes were observed in the active cycling session after stimulation. The enhanced regional brain activation value also found in primary motor cortex (PMC), sensorimotor cortex (SMC), and secondary sensory cortex (S2). The symmetry indices of SSI and ASI are significant different between healthy and stroke subjects. However, SSI and ASI did not show the significant difference before and after the stimulation. The advantage of the stimulation technique used in this study is the highly flexibility and compatibility with the functional brain activity monitor techniques like fNIRS. Although the stimulation effects to blood flow oscillation bands still need to be clarified, it is a potential stimulation technique for neural degeneration diseaseses.
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