Abstract:
S troke impairs neuro-function in the brain system and causes functional disabilities. Functional recovery mostly occurs even after a severe stroke, however, changes in the brain connectivity that underlie such recovery are poorly studied. In current study, using rat MCAO models, we monitored changes in two ways. To confirmed structural changes using Diffusion Tensor Imaging (DTI) MR image at 7days after stroke surgery. Also brain functional changes monitored using functional Magnetic Resonance Imaging (fMRI) over a period of 30 days after transient cerebral ischemic damage. We used 7 Sprague-Dawley rats (~320g), which showed almost full recovery of both sensory and motor functions approximately 30 days at 90 min after ischemic/reperfusion in the right hemisphere. Six healthy age controlled rats were used for the control group. Functional MRI time courses during resting-state (10min, TR=1s, 9 slices) were collected. Both the voxel-wise analysis and the region of interested (ROI) based analysis were performed that voxel-wise analysis were selected in the left S1FL, and multiple ROIs were placed over the somatosensory regions. Diffusion Toolkit (http:// trackvis.org/dtk/) was used to calculate voxel-wise values for relative fractional anisotropy (rFA). All rFA values in each ROI are obtained individually to generate group differences. Significance testing between groups was performed with the two-tailed unpaired t-test. MCAO models showed the significantly increased rFA values only in penumbra (peri-infarct) region, especially in exercised group (Fig. 1). We also found that decreased brain functional connectivity in the ipsilateral (right) for both voxel-wise and ROI-based methods (Fig. 2). Interestingly, in contralateral (left), the voxel-wise analysis connectivity spatially expanded into the entire cortex area. The correlation coefficient values between ROI’s somewhat increased in the contralateral hemisphere compared to the control group. In conclusion, we showed that the renaturation of sensorimotor function is associated more with the increase and spatial expansion of functional connectivity within the contralateral than the ipsilateral hemisphere. Also, structural changes appear to occur more rapidly than functional changes in the brain recovery phase.
