Contra-lateral desynchronized alpha oscillations linearly correlate with discrimination performance of tactile acuity

Abstract

Objective. We used EEG to investigate cortical oscillatory activities during the tactile discrimination task and characterize the correlation between the EEG features and subjects’ discrimination performance. Approach. Transcutaneous electrical nerve stimulation (TENS) was applied on two finger areas (thumb and index for healthy hands, thumb and index-projected areas for disabled hands) to evoke two kinds of tactile sensations (vibration and pressure) with three levels of intensities (low, medium and high). Four forearm amputees and thirteen able-bodied subjects were recruited to discriminate the specific intensity and area of the applied stimulation. We assessed the discrimination performance [discrimination accuracy rate (AR) and response time (RT)] to quantify the tactile acuity. During the stimulation, EEG signals were recorded and the evoked cortical oscillatory activities were analyzed. Linear regression analyses were performed between EEG features and tactile discrimination performance. Main results. Spectral analysis revealed that alpha ERD over somatosensory regions persisted the whole task period and was related to the sensory information processing. Alpha ERD over prefrontal regions was only found during the stimulation judgement period and might reflect advanced cognitive process. There was no linear correlation between prefrontal alpha ERD and tactile discrimination performance. While contralateral somatosensory alpha ERDs exhibited significantly negative correlations with ARs () and positive correlations with RTs (). Specifically, the fitting results of higher alpha band (10–13 Hz) were superior to lower alpha band (8–10 Hz). Significance. Alpha ERD over contralateral somatosensory cortex could be used as an objective index for the evaluation of tactile acuity and might have the potential to be applied in sensory rehabilitation for amputees.

Directionality of the injected current targeting the P20/N20 source determines the efficacy of 140 Hz transcranial alternating current stimulation (tACS)-induced aftereffects in the somatosensory cortex

“…Decreases in alpha (8-12 Hz) and beta (17-25 Hz) oscillatory power indicated activation of the somatosensory system during the tactile stimulus presentation and confirmed the inhibition hypothesis. Previous studies mentioned that suppression of alpha power (ERD) reflects activation processes, while increases in alpha power (ERS) indicate inhibitory control processes [87,88]. However, we also did not observe the modulatory effects of oscillatory activity induced by tACS as no changes in the power of alpha and beta bands occurred after stimulation.…”

Neurophysiological correlates of tactile width discrimination in humans

“…These studies have, mostly, explored EEG correlates of tactile processing using stimulation current, textures, or vibratory stimuli; due to their ability to generate EEG evoked responses. For example, previous studies have found that changes in the alpha frequency band in the C3 electrode are correlated to tactile performance [24]. However, based on our previous study [13], analysis of passive tactile width discrimination in humans may bene t from analysis of longer periods (e.g., larger than 1.0 second) due to the relatively large period of contact occurring between the bars and the nger.…”

“…Power changes in theta, alpha, and beta frequency bands for the C3 electrode during discrimination and response periods, as well as the changes in ratios of frequencies, are in line with previous studies of tactile function. Tactile discrimination is often associated with changes in EEG activity recorded from the electrode C3/4, namely with the appearance of event related potentials or power changes in alpha and beta frequency bands [17][18][19][20][21][22][23][24][28][29]. For example, a relevant contribution of mu (8-15 Hz) and beta (16-30 Hz) frequency bands has been demonstrated for texture discrimination using a support vector machine classi er in electrodes recording from primary and secondary somatosensory cortex [23].…”

“…Previous studies of EEG activity in other tactile discrimination paradigms indicate the engagement of a complex network of regions involving the somatosensory cortex, prefrontal cortex, and the parietal cortex, typically in alpha, mu, and beta frequency bands [17][18][19][20][21][22][23][24]. These studies have, mostly, explored EEG correlates of tactile processing using stimulation current, textures, or vibratory stimuli; due to their ability to generate EEG evoked responses.…”

Neural evidence for functional roles of tactile and visual feedback in the application of myoelectric prosthesis

“…The value of measured pinch distance was used to modulate the stimulation frequency, meanwhile pulse width and current amplitude were fixed as 200 µs and 3 mA, respectively. These two parameters have been used in our previous work [31,32]. Eight subjects in the previous study were recruited again in this study.…”