EEG Features of Evoked Tactile Sensation: Two Cases Study

Abstract

Purpose: Sensory feedback for prosthetics is an important issue. The area of forearm stump skin that has evoked tactile sensation (ETS) of fingers is defined as the projected finger map (PFM), and the area close to the PFM region that does not have ETS is defined as the non-projected finger map (NPFM). Previous studies have confirmed that ETS can restore the tactile pathway of the lost finger, which was induced by stimulation of transcutaneous electrical nerve stimulation (TENS) on the end of stump skin. This study aims to reveal EEG features between the PFM and the NPFM regions of the stumps under the same TENS stimulation condition.Methods: The PFM and NPFM regions of the two subjects were stimulated with the same intensity of TENS, respectively. TENS as target stimuli are modulated according to the Oddball paradigm to evoke the P300 components.Result: The PFM regions of both subjects were able to elicit P300 components, while their NPFM regions were not able to elicit P300 components. However, this P300 appears early (249 ms for subject 1,230 ms for subject 2) and has continuous positive peaks (peak 1,139 ± 3 ms, peak 2,194 ± 0.5 ms) in front of it.Discussion: N30 and P300 can prove that the two subjects with PFM can perceive and recognize ETS. The heteromorphisms of the P300 waveform may be related to the difficulty in subjects’ cognition of ETS or caused by the fusion of P150, P200, and P300.

Study of Tactile Sensation Somatotopy and Homology Between Projected Fingers in Residual Limb and Natural Fingers in Intact Limb

“…However, in normal conditions, for the skin surfaces of the wrist of the intact limb of the able-bodied and the distal stump of an amputee who does not have the projected fingers, obviously, there is a common consensus that the mechanical press and slide on these skin surfaces are not able to evoke the tactile sensation of the finger. This consensus also exists in our previous research, where external stimuli on the skin surface of NPFM (non-PFM) for amputees who have projected fingers are unable to evoke the tactile sensation of the finger [29].…”

“…2, a Matlab-installed computer is used to control and program the Master-9 stimulator. According to previous research [21], [22], [27], [29], multi-pulse of biphasic, rectangular, and charged-balanced current pulses are produced to evoke tactile sensation (see Fig. 3(a)).…”

“…In the procedure of finding the threshold, the amputee is asked to self-report the sensation feeling of stimulation in the projected finger. In order to stimulate with the same level of tactile sensation, the authors adopt the approach that the amplitude of stimulation current is set as 1.5 times the infimum threshold for each projected finger and natural finger [29]. The current amplitude of stimulation for each projected finger in PFM is listed in Fig.…”

“…The PFM is located in the skin of the distal of the forearm stump, and can evoke the tactile sensation of the missing fingers while different parts of the PFM are stimulated by mechanical or electrical stimuli. The evoked tactile sensation (ETS) is as if the missing finger is being touched, where, by adopting magnetoencephalography (MEG) and electroencephalogram (EEG), researchers have shown that the location and characteristic of the cortex activity of the projected finger are similar to that of the natural finger [21], [29]. Based on previous research, the restoration approach based on PFM accords with the characteristics of somatotopy and homology to some extent.…”

The Activity of the Dorsal Anterior Cingulate Cortex Promotes the Top–down Regulation of Sensorimotor Synchronization

“…We could identify risk-hedge manners form N200. We also focused on the P150, considered to arise from the salience network including the anterior cingulate cortex and anterior insula [62], is sensitive to absence of repeated stimuli, and associated with recognition of the part-whole configuration [63,64]. Hence, we used the P150 for distinguishing whether the risk-taking was driven by mistake or promoted by the part-whole configuration [65].…”