RNEL Studies Effects of Stimulus Pulse Rate on Somatosensory Adaptation in the Human Cortex
April 27, 2023
Robert Gaunt, PhD, associate professor, University of Pittsburgh Department of Physical Medicine and Rehabilitation collaborated with colleagues from the Rehab Neural Engineering Labs to publish “Effects of stimulus pulse rate on somatosensory adaptation in the human cortex” in Brain Stimulation.
Intracortical microstimulation (ICMS) of the somatosensory cortex can restore sensation to people with neurological diseases. However, many aspects of ICMS are poorly understood, including the effect of stimulation on percept intensity over time.
In this study, the team evaluates how tactile percepts evoked by ICMS in the somatosensory cortex of a human participant adapt over time.
They delivered continuous and intermittent ICMS to the somatosensory cortex and assessed the reported intensity of tactile percepts over time in a human participant. Experiments were conducted over approximately one year, and linear mixed effects models were used to assess significance.
Continuous stimulation at high frequencies led to rapid decreases in intensity, while low frequency stimulation maintained percept intensity for longer periods. Burst-modulated stimulation extended the time before the intensity began to decrease, but all protocols ultimately resulted in complete sensation loss within one min.
Intermittent stimulation paradigms with several seconds between stimulus trains evoked intermittent percepts and also led to decreases in intensity on many electrodes, but never resulted in extinction of the sensation after over three min. of stimulation. Longer breaks between each pulse train resulted in some recovery in the intensity of the stimulus-evoked percepts. For several electrodes, intermittent stimulation had almost no effect on the perceived intensity.
Overall, intermittent ICMS paradigms were more effective at maintaining percepts. Given that transient neural activity dominates the response in somatosensory cortex during mechanical contact onsets and offsets, providing brief stimulation trains at these times may more closely represent natural cortical activity and have the additional benefit of prolonging the ability to evoke sensations over longer time periods.
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