File:Rebalance inter-hemispheric inhibition model.jpg

English: A schematic depicting that presumed to be the consequence of applying non-invasive brain stimulation (NIBS) with the intent of decreasing the excitability of circuits in the contralesional motor cortex. Panel A represents the notional asymmetry of inter-hemispheric inhibition that is believed to arise as a consequence of a unilateral infarct caused by stroke. Panel B depicts non-invasive brain stimulation (NIBS) applied with the intent of decreasing the excitability of circuits in the contralesional motor cortex. The forms of NIBS applied most frequently in this context are repetitive transcranial magnetic stimulation (rTMS) and cathodal transcranial direct current stimulation (tDCS). Panel C represents the assumption that these forms of stimulation have the potential to decrease inhibition of the lesioned hemisphere by the non-lesioned hemisphere, and as a consequence reduce the net inhibition of motor centres that give rise to efferent projections to the paretic limb. It is emphasised that Panels B and C represent physiological states that are not necessarily separable in time. The key (enclosed by the rectangle) shows the symbols used to represent the presumed characteristics of the cortical motor output associated with each state. In an abstract sense, these might be conceived of in terms of spatial and/or temporal “noise”. Plausible corresponding effects on general motor function are given in the lower portion of each panel. It should be noted that the potential impact of such interventions upon the bilateral character of deficits in motor control (shown here) that are observed frequently following unilateral brain injury (e.g. Desrosiers et al., 1996) is not usually considered.