Methods for automated delineation and assessment of EMG responses evoked by peripheral nerve stimulation in diagnostic and closed-loop therapeutic applications

Objective. Surface electromyography measurements of the Hoffmann (H-) reflex are essential in a wide range of neuroscientific and clinical applications. One promising emerging therapeutic application is H-reflex operant conditioning, whereby a person is trained to modulate the H-reflex, with generalized beneficial effects on sensorimotor function in chronic neuromuscular disorders. Both traditional diagnostic and novel realtime therapeutic applications rely on accurate definitions of the H-reflex and M-wave temporal bounds, which currently depend on expert case-by-case judgment. The current study automates such judgments. Approach. Our novel wavelet-based algorithm automatically determines temporal extent and amplitude of the human soleus H-reflex and M-wave. In each of 20 participants, the algorithm was trained on data from a preliminary 3 or 4 min recruitment-curve measurement. Output was evaluated on parametric fits to subsequent sessions' recruitment curves (92 curves across all participants) and on the conditioning protocol's subsequent baseline trials (& SIM;1200 per participant) performed near H (max). Results were compared against the original temporal bounds estimated at the time, and against retrospective estimates made by an expert 6 years later. Main results. Automatic bounds agreed well with manual estimates: 95% lay within & PLUSMN;2.5 ms. The resulting H-reflex magnitude estimates showed excellent agreement (97.5% average across participants) between automatic and retrospective bounds regarding which trials would be considered successful for operant conditioning. Recruitment-curve parameters also agreed well between automatic and manual methods: 95% of the automatic estimates of the current required to elicit H (max) fell within & PLUSMN;1.4%

Automated summary

A novel wavelet-based algorithm was developed to automatically determine the temporal parameters of the H-reflex in the human soleus muscle. The automatic results showed good agreement with manual estimates and provided valuable references for research and therapeutic applications. This algorithm is of great importance for surface electromyography measurements of the H-reflex in neuroscientific and clinical fields.