Induced and Evoked Properties of Vibrotactile Adaptation in the Primary Somatosensory Cortex.

Nicolaas A J Puts,Krish D Singh,Suresh Muthukumaraswamy,Richard A E Edden,David J Mcgonigle

doi:10.1155/2019/5464096

Nicolaas A J Puts, Krish D Singh + Show 3 more

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https://doi.org/10.1155/2019/5464096

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Abstract

Prolonged exposure to afferent stimulation (“adaptation”) can cause profound short-term changes in the responsiveness of cortical sensory neurons. While several models have been proposed that link adaptation to single-neuron dynamics, including GABAergic inhibition, the process is currently imperfectly understood at the whole-brain level in humans. Here, we used magnetoencephalography (MEG) to examine the neurophysiological correlates of adaptation within SI in humans. In one condition, a 25 Hz adapting stimulus (5 s) was followed by a 1 s 25 Hz probe (“same”), and in a second condition, the adapting stimulus was followed by a 1 s 180 Hz probe (“different”). We hypothesized that changes in the mu-beta activity band (reflecting GABAergic processing) would be modulated differently between the “same” and “different” probe stimuli. We show that the primary somatosensory (SI) mu-beta response to the “same” probe is significantly reduced (p = 0.014) compared to the adapting stimulus, whereas the mu-beta response to the “different” probe is not (p = n.s.). This reduction may reflect sharpening of the spatiotemporal pattern of activity after adaptation. The stimulus onset mu-beta response did not differ between a 25 Hz adapting stimulus and a 180 Hz probe, suggesting that the mu-beta response is independent of stimulus frequency. Furthermore, we show a sustained evoked and induced desynchronization for the duration of the adapting stimulus, consistent with invasive studies. Our findings are important in understanding the neurophysiology underlying short-term and stimulus-induced plasticity in the human brain and shows that the brain response to tactile stimulation is altered after only brief stimulation.

Highlights

Prolonged exposure to afferent stimulation can cause profound changes in the responsiveness of cortical sensory neurons
The 25 Hz and 180 Hz probe stimuli both produced clear peaks within SI in the group Synthetic aperture Magnetometry ERF (SAM) analysis (XYZ; 25 Hz; 48.228.1-44; 180 Hz; 44.2-28.1-44), but t-weighted comparison analysis between the two group SAM images did not show significant differences between the two locations (independent locations shown in Figure 2(a) at p < 0 05 using nonparametric permutation testing for statistical significance of the group peak SI activity thresholded using the omnibus test statistic at p < 0 05)
We have measured the neurophysiological response to tactile adaptation, a form of short-term plasticity, for the first time with MEG

Summary

Introduction

Prolonged exposure to afferent stimulation can cause profound changes in the responsiveness of cortical sensory neurons. This process is commonly referred to as “adaptation” and occurs over a number of timescales ranging from milliseconds to minutes (reviewed in [1], see [2]). While the effects of adaptation at the single-cell level typically lead to a time-dependent decrement of neuronal responsiveness, a number of studies have shown improvements in behavioral performance following exposure to an “adaptor”: for example, a long (10–20 s) vibrotactile stimulus improves subsequent vibrotactile frequency discrimination at the same skin site [3]. The duration of the stimulus is significant, with longer stimuli producing larger adaptation effects.

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