Magnetic Resonance Imaging of Plastic Changes in the Human Brain Following a Motor Task
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Brain plasticity forms the basis of many of our daily functions including memory and learning. Evidence of brain plasticity in humans mostly consists of morphological and functional changes following days, weeks, or years of specific usage. On a time scale of minutes, on the other hand, it is not yet clear whether such changes are detectable and what the nature of these changes is. If detected and understood, then these changes have the potential of becoming diagnostic or predictive parameters towards treatments or therapies. The experiments I performed showed that significant changes in brain’s organization can be detected within a single session using functional MRI technique. Here human volunteers were subject to a 23-minute button-press motor task and their resting-state brain activity before and after the task was assessed with functional connectivity MRI (fcMRI). It was found that, compared to the pre-task resting period, the post-task resting fcMRI revealed a significantly higher cross-correlation coefficient (CC) between left and right motor cortices. These changes were region-specific and required the motor task to take place as sham control study did not show CC changes. Furthermore, the amplitude of fcMRI signal fluctuation (AF) also demonstrated an increase in the post-task period compared to pre-task. These changes were observed using both right-hand-only task and two-hand task, and were demonstrated in two separate subject cohorts. The left-hand task group did not show significant changes in motor cortex CC. The recovery time-course of these changes was also investigated, and it was found that the CC change lasted for about 5 minutes while the AF change lasted for at least 15 minutes. Voxel-wise analysis revealed that pre/post-task differences were also observed in auditory cortex, visual areas, and thalamus. Finally, network analysis showed that simple motor tasks result in the strengthening of functional connectivity between these areas. My data suggest that elevated CC and AF in fcMRI may be potentially used as markers for brain plasticity. Further, these imaging parameters can be used to delineate network wide changes in the brain by the task.