Vibrotactile Stimulation Encoded by Beta and Gamma Bands Varies with Locations on the Upper Limbs

The perception of tactile locations is an important function of human's somatosensory system during body movements and its interactions with the surroundings. Our previous study on the perception of locations found that the gamma-frequency band provides better decoding accuracy than all the lower frequencies on the legs. In the present study, we recorded electroencephalography (EEG) responses evoked by four vibrotactile stimulators placed on the arms of 18 human subjects.

Human subjects were instructed to sit in a chair while somatosensory-evoked potentials were obtained using a 64-channel EEG. A linear classifier and an artificial neural network with 10 hidden-layer neurons were separately used to predict tactile locations based on EEG power obtained from various frequency bands.

We found that the beta (13-30 Hz) and high-gamma (50-100 Hz) bands can best predict the tactor locations on the arms. Interestingly, power information carried by the high-gamma band was uncorrelated to information contained in the lower frequency bands. Consequently, combining the beta and high-gamma bands significantly improved the prediction accuracy.

Our findings prove that tactile location information can be decoded from EEG signals, which agrees with previous studies regarding the importance of the gamma band during tactile perception.