Event-Related Desynchronization induced by Tactile Imagery: an EEG Study

Abstract

It is well known that both the movement of the hand itself and the mental representation of it lead to event-related desynchronization (ERD) of EEG recorded over the corresponding motor areas of the cerebral cortex. Similarly, in somatosensory cortical areas, ERD occurs upon tactile stimulation of the hand, but whether this effect is caused by mental representation of sensations from tactile stimulation remains poorly understood. In the present study, the effects on the EEG of imaginary vibrotactile sensations on the right hand were compared with the effects of real vibrotactile stimulation. Both actual vibrotactile stimulation and mental representation of it have been found to elicit contralateral ERD patterns, particularly prominent in the μ-band and most pronounced in the C3 region. The paper discusses tactile imagery as a part of the complex sensorimotor mental image and its prospects for using EEG patterns of imagery-induced tactile sensations as control signals in BCI circuits independently and when combined with ERD based on movement imagination to improve the efficiency of neurointerface technologies in rehabilitation medicine, in particular, to restore movements after a stroke and neurotrauma.

Tactile versus Motor Imagery: Differences in Corticospinal Excitability Assessed with single-pulse TMS

“…In this study, we complemented the previous findings, where changes in EEG rhythms were found during TI (12,16,17), with the demonstration that TI effects on the TMS-evoked responses in the forearm and hand muscles were different from those of kMI and TS.…”

“…During the TI task, participants were asked to mentally reproduce the sensations experienced during the vibrotactile stimulation (12,17). Before the TI trials, participants were also acquainted with the tactile sensations produced by stimulation with a brush of the proximal parts of index, middle, ring and little fingers and distal part of the palm.…”

“…Additionally, we evoked tactile sensations with a brush of these fingers and the distal part of the palm. During the TI run, the participants were asked to mentally reproduce the tactile sensations as emerging from these skin locations (12,16). The participants were instructed not to look at the hand and instead direct their gaze to the fixation cross.…”

“…Unsurprisingly, TI specifically activates the primary somatosensory cortex (10,11,13,14), as well as the areas subserving the act of mentally imagery, namely the prefrontal cortex (11) and parietal cortex (15). TI-induced cortical activities can be revealed using electroencephalographic (EEG) recordings, where event related desynchronization (ERD) of the mu rhythm is the most prominent effect (12,16,17).…”

Improving Performance of Motor Imagery-Based Brain–Computer Interface in Poorly Performing Subjects Using a Hybrid-Imagery Method Utilizing Combined Motor and Somatosensory Activity

“…Previous studies reported that somatosensory stimuli, which differs in its pattern or type, induces other patterns of cortical activity [63], [64], [65], [66]. In addition, imagery and execution of somatosensory stimulation can facilitate cortical excitability [67], [68]. In this study, our results for HC II also indicated that the EEG activities (deactivation) at somatosensory area (CPz) appeared strong not only in poor performers, but also good performers.…”