Figure 1.

A summary of our current understanding of factors that contribute to post-stroke impairment (I) and the assessment tools available for quantifying these changes (II). Loss of white matter projections is illustrated as a decreased number of CST projections (IA). Diaschisis, a remote functional depression, can impact intra- and interhemispheric areas (IB). A focal lesion can disrupt the mutual balanced inhibition between hemispheres. Damage from stroke disrupts the balance by decreasing the inhibition of the contralesional hemisphere, which results in increased inhibition of the injured hemisphere (IC). FreeSurfer-based volumetric analysis, using structural T1s, can be manually modified to correct for errors in the automated segmentation of injured brains (IIA). Identification of CST and CC in an individual with chronic stroke utilizing tractography of diffusion-weighted images (IIB). The axial brain image identifies the voxel placement in the hand knob of an individual with chronic stroke, the resulting spectra quantifies multiple neurotransmitters (IIC). BOLD signal during movements of the unaffected and affected hand in individuals with left-sided subcortical stroke; modified, with permission, from Grefkes et al. (16) (IID). EEG trace from an electrode located at Cz (over primary motor cortex) in an individual with chronic stroke and a healthy control as they take a step (time 0) (IIE). Transcallosal inhibition evoked from stimulation over ipsilesional and contralesional primary motor cortex (IIF). Ipsilesional stimulation failed to produce an observable iSP in the ipsilateral (to the TMS pulse) limb, whereas contralesional stimulation evoked a quantifiable iSP in the ipsilateral (to the TMS pulse) limb. iSP occurs in the time between the green (onset) and red (offset) lines. CST, cortical spinal tract; CC, corpus callosum; fMRI, functional MRI; BOLD, blood oxygen level dependent; iSP, ipsilateral silent period; TMS, transcranial magnetic stimulation.