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There is increasing interest in exploring the use of functional MRI neurofeedback (fMRI-NF) as a therapeutic technique for a range of neurological conditions such as stroke and Parkinson's disease (PD). One main therapeutic potential of fMRI-NF is to enhance volitional control of damaged or dysfunctional neural nodes and networks via a closed-loop feedback model using mental imagery as the catalyst of self-regulation. The choice of target node/network and direction of regulation (increase or decrease activity) are central design considerations in fMRI-NF studies. Whilst it remains unclear whether the primary motor cortex (M1) can be activated during motor imagery, the supplementary motor area (SMA) has been robustly activated during motor imagery. Such differences in the regulation potential between primary and supplementary motor cortex are important because these areas can be differentially affected by a stroke or PD, and the choice of fMRI-NF target and grade of self-regulation of activity likely have substantial influence on the clinical effects and cost effectiveness of NF-based interventions. In this study we therefore investigated firstly whether healthy subjects would be able to achieve self-regulation of the hand-representation areas of M1 and the SMA using fMRI-NF training. There was a significant decrease in M1 neural activity during fMRI-NF, whereas SMA neural activity was increased, albeit not with the predicated graded effect. This study has important implications for fMRI-NF protocols that employ motor imagery to modulate activity in specific target regions of the brain and to determine how they may be tailored for neurorehabilitation.

Movements of the paretic hand in patients with chronic subcortical stroke are associated with high interhemispheric inhibition (IHI) targeting the motor cortex in the lesioned hemisphere relative to healthy controls. The purpose of this investigation was to determine whether this abnormality also involves IHI operating during movements of the non-paretic hand. Here, we studied IHI in the process of generation of voluntary index finger movements by the paretic and non-paretic hands in a simple reaction time paradigm in a group of patients with chronic subcortical stroke. With movements of the non-paretic index finger, IHI targeting the contralateral primary motor cortex ((c)M1) decreased progressively to turn into facilitation at around movement onset, similar to healthy controls. In contrast, movements of the paretic index finger resulted in significantly deeper inhibition at all premovement timings relative to the non-paretic hand. In conclusion, these results document a deeper premovement IHI with paretic than non-paretic hand movements of patients with chronic subcortical stroke, a possible mechanism underlying deficits in motor control.

Five patients with left striatocapsular infarction were studied twice with PET during auditory-cued right thumb-index tapping, around 2 months after stroke and again around 8 months after stroke. At PET1 and PET2, the ipsilesional primary sensorimotor (SM1) activation peak Talairach coordinates were compared to those from seven aged-matched healthy controls. At PET1, there was a significant posterior displacement of SM1 activation peak, which confirms a previous report and may represent unmasking/disinhibition of motor representations. Over time, there was no significant change in the coordinates, and no significant correlation between coordinate changes from PET1 to PET2 and concomitant motor recovery. The implications of posterior displacement of SM1 activation peak for recovery therefore remain elusive.