Figure 3.

Serotonin is known to promote adult cortical plasticity after injury. A. Studies have shown that pharmacotherapy after injury can increase BNDF-trkB signaling which increases the remodeling of chromatin structures ultimately lowering the threshold for cortical excitability, thus increasing the probability for sensory stimulation (in this case visual) to drive activity-dependent modification of synaptic transmission. Figure reproduced from Maya-Vetencourt et al. (2011), with permission. B. Similar results were observed after spinal cord injury. Top panel shows the responsiveness of the hindlimb sensory-motor cortex (HLSM, oval outlined in black) and forelimb motor cortex (quadrilateral located more rostrally) to tactile stimulation of the forepaw. Responsiveness is measured by the number of neurons that respond to the forepaw stimulation with increased firing rate. Middle panel shows expansion of the response into both the hindpaw sensory cortex and forepaw motor cortex after 8-weeks of a daily injection of a low dose (LD) of 5-HT agonists. Bottom panel shows greater expansion after 8-weeks of daily injection of a high dose (HD) of 5-HT agonists. Responses in the forepaw cortex (black outline more lateral from the hindpaw are not shown). Figure reproduced from Ganzer et al. (2013), with permission.