Neurofeedback Using Real-Time Near-Infrared Spectroscopy Enhances Motor Imagery Related Cortical Activation

Accumulating evidence indicates that motor imagery and motor execution share common neural networks. Accordingly, mental practices in the form of motor imagery have been implemented in rehabilitation regimes of stroke patients with favorable results. Because direct monitoring of motor imagery is difficult, feedback of cortical activities related to motor imagery (neurofeedback) could help to enhance efficacy of mental practice with motor imagery. To determine the feasibility and efficacy of a real-time neurofeedback system mediated by near-infrared spectroscopy (NIRS), two separate experiments were performed. Experiment 1 was used in five subjects to evaluate whether real-time cortical oxygenated hemoglobin signal feedback during a motor execution task correlated with reference hemoglobin signals computed off-line. Results demonstrated that the NIRS-mediated neurofeedback system reliably detected oxygenated hemoglobin signal changes in real-time. In Experiment 2, 21 subjects performed motor imagery of finger movements with feedback from relevant cortical signals and irrelevant sham signals. Real neurofeedback induced significantly greater activation of the contralateral premotor cortex and greater self-assessment scores for kinesthetic motor imagery compared with sham feedback. These findings suggested the feasibility and potential effectiveness of a NIRS-mediated real-time neurofeedback system on performance of kinesthetic motor imagery. However, these results warrant further clinical trials to determine whether this system could enhance the effects of mental practice in stroke patients

Scaling Parameters for Dynamic Diffusion-Reaction over Porous Catalysts

The effect of diffusion resistance in porous solid catalysts on reaction rate during periodic cycling of CO concentration is shown for CO oxidation over Pt/Al2O3 by numerical simulation. At some cycling frequencies, the average reaction rate during cycling is higher than the steady-state rate at the mean CO concentration, as expected for this nonlinear, reactant-inhibited reaction. In order to identify major aspects of dynamic diffusion-reaction behavior, a simple kinetic mechanism that shows the main features of CO oxidation and other reactions with significant inhibition by reactants is investigated. A single dimensionless parameter group, the dynamic diffusion coefficient, is added when going from steady-state to unsteady-state diffusion-reaction equations. In the dynamic diffusion coefficient, the rate at which the gas-phase reactant diffuses is reduced by the surface adsorption capacity of the catalyst. The frequency at which the peak average rate occurs is controlled by the dynamic diffusion coefficient