Development of a quantitative technique to assay changes in markers of neural plasticity in response to intermittent theta burst stimulation

Delivery of intermittent theta burst stimulation (iTBS) can modulate cortical excitability, and if delivered prior to motor training, it can facilitate performance. These effects suggest that iTBS can induce long term potentiation (LTP) like changes within the associated brain areas. However, currently there is a lack of physiological evidence for such processes. Evidence for molecular changes obtained using animal models of iTBS is inconclusive, and methodologically varied. In addition, the use of human sized coil in laboratory rodents further compromises translational merits of obtained findings. Present study is conducted as part of a larger project that uses translational approach to study neurophysiological mechanisms of iTBS in rodents with species specific stimulation coil. Using immunohistochemical analysis of mouse brain sections, changes in presynaptic LTP marker Synaptophysin were investigated in eight animals that demonstrated increased forelimb reaching accuracy over 10 days in a skilled-motor-task after receiving iTBS. Changes in expression of Synaptophysin were compared between three groups (iTBS, sham, handling control), within three brain regions (primary motor cortex, dorsal striatum, piriform cortex). In all three regions, there were no significant differences found between the three groups, suggesting that after 10 days of training, homeostatic process of synaptic scaling may have taken place.