Prediction of Single Trial Somatosensory Evoked Potentials From Mechanical Stimulation Intensity

Somatosensory evoked potentials (SSEPs) are important for both scientific research and the evaluation of treatment efficacy in neurorehabilitation. SSEPs measure the response in the sensorimotor cortex to a peripheral stimulation. Individual responses are often noisy, so SSEPs have typically required hundreds of stimulation-response trials to produce a single measurement. This work presents a method to estimate single trial SSEPs from tendon hammer accelerations. While predictions from the input side can not completely replace actual measurements of SSEPs, the results produced may help to provide clinicians insight where full scale SSEP measurement is not practical.

Statistical Inter-stimulus Interval Window Estimation for Transient Neuromodulation via Paired Mechanical and Brain Stimulation

For achieving motor recovery in individuals with sensorimotor deficits, augmented activation of the appropriate sensorimotor system, and facilitated induction of neural plasticity are essential. An emerging procedure that combines peripheral nerve stimulation and its associative stimulation with central brain stimulation is known to enhance the excitability of the motor cortex. In order to effectively apply this paired stimulation technique, timing between central and peripheral stimuli must be individually adjusted. There is a small range of effective timings between two stimuli, or the inter-stimulus interval window (ISI-W). Properties of ISI-W from neuromodulation in response to mechanical stimulation (Mstim) of muscles have been understudied because of the absence of a versatile and reliable mechanical stimulator. This paper adopted a combination of transcranial magnetic stimulation (TMS) and Mstim by using a high-precision robotic mechanical stimulator. A pneumatically operated robotic tendon tapping device was applied. A low-friction linear cylinder achieved high stimulation precision in time and low electromagnetic artifacts in physiological measurements. This paper describes a procedure to effectively estimate an individual ISI-W from the transiently enhanced motor evoked potential (MEP) with a reduced number of paired Mstim and sub-threshold TMS trials by applying statistical sampling and regression technique. This paper applied a total of four parametric and non-parametric statistical regression methods for ISI-W estimation. The developed procedure helps to reduce time for individually adjusting effective ISI, reducing physical burden on the subject.

Automated Variable Stimulus Tendon Tapping Modulates Somatosensory Evoked Potentials

Somatosensory Evoked Potentials (SSEPs) are an important tool for both basic neuroscience research and evaluation of therapeutic techniques. While a large body of work exists in the study of electrically induced SSEPs both as a metric for therapeutic performance and tool for physiological research, comparatively little work has explored stretch response SSEPs evoked via tendon tapping. The measurement of SSEPs necessitates both timing and stimulation intensity consistency. This work presents an evaluation of a simple tapping device for automating this procedure and a comparison to manual tendon tapping demonstrating significantly reduced variability in both timing and intensity. The variable intensity nature of automated tapping is then used to measure SSEPs in a single subject, with apparent modulation of peak-peak amplitude by stimulation intensity.

Optimal inter-stimulus interval for paired associative stimulation with mechanical stimulation

In this paper, inter-stimulus interval (ISI) of paired associative stimulation (PAS) with mechanical stimulation was analyzed. PAS is a prominent therapeutic intervention for individuals after stroke and helps to improve limb function by strengthening excitatory synapses and inducing neural plasticity. This intervention involves repeated application of transcranial magnetic stimulation (TMS) followed by peripheral stimulation. When responses to both stimulations are overlapped in the brain at the same time, this successful PAS is expected to induce long term potentiation (LTP) which leads to a neural plasticity phenomenon. Therefore ISI between these two stimulations is very crucial in this treatment. Instead of electrical stimulation in general PAS, mechanical stimulation was used in this study due to some promising aspects of mechanical stimulation. Long latency stretch response (LLSR) was observed in electromyography (EMG) during the PAS with mechanical stimulation, since LLSR reflects successful overlapping of two stimulations. Each subject had specific range of ISIs, or a time window, that leads to successful overlapping of paired stimulations. These time window lengths varied between 5ms and 105 ms, and within this range it can be guaranteed to obtain LLSR in EMG at least 40% among the all PAS trials. In addition, normally distributed responses within time window suggests that the optimal ISI which results in the highest number of LLSRs is the average of the time window. This result suggests that PAS with mechanical stimulation could lead to a rehabilitation effect by regaining motor functionality when the two stimulations are paired with the optimal ISI and it could provide a significant advancement in neuromodulation.