Self-modulation of primary motor cortex activity with motor and motor imagery tasks using real-time fMRI-based neurofeedback

Advances in fMRI data acquisition and processing have made it possible to analyze brain activity as rapidly as the images are acquired allowing this information to be fed back to subjects in the scanner. The ability of subjects to learn to volitionally control localized brain activity within motor cortex using such real-time fMRI-based neurofeedback (NF) is actively being investigated as it may have clinical implications for motor rehabilitation after central nervous system injury and brain-computer interfaces. We investigated the ability of fifteen healthy volunteers to use NF to modulate brain activity within the primary motor cortex (M1) during a finger tapping and tapping imagery task. The M1 hand area ROI (ROI_m) was functionally localized during finger tapping and a visual representation of BOLD signal changes within the ROI_m fed back to the subject in the scanner. Surface EMG was used to assess motor output during tapping and ensure no motor activity was present during motor imagery task. Subjects quickly learned to modulate brain activity within their ROI_m during the finger-tapping task, which could be dissociated from the magnitude of the tapping, but did not show a significant increase within the ROI_m during the hand motor imagery task at the group level despite strongly activating a network consistent with the performance of motor imagery. The inability of subjects to modulate M1 proper with motor imagery may reflect an inherent difficulty in activating synapses in this area, with or without NF, since such activation may lead to M1 neuronal output and obligatory muscle activity. Future real-time fMRI-based NF investigations involving motor cortex may benefit from focusing attention on cortical regions other than M1 for feedback training or alternative feedback strategies such as measures of functional connectivity within the motor system.