Event-related desynchronization/synchronization (ERD/S) is an electroencephalogram (EEG) feature widely used as control signals for Brain-Computer Interfaces (BCIs). Nevertheless, the underlying neural mechanisms and functions of ERD/S are largely unknown, thus investigating them is crucial to improve the reliability of ERD/S-based BCIs. This study aimed to identify Motor Imagery (MI) conditions that enhance ERD/S. We investigated following three questions: 1) whether target-directed MI affects ERD/S, 2) whether MI with sound imagery affects ERD/S, and 3) whether ERD/S has a body part dependency of MI. Nine participants took part in the experiments of four MI conditions; they were asked to imagine right foot dorsiflexion (F), right foot dorsiflexion and the sound of a bass drum when the sole touched the floor (FS), right leg extension (L), and right leg extension directed toward a soccer ball (LT). Statistical comparison revealed that there were significant differences between conditions L and LT in beta-band ERD and conditions F and L in beta-band ERS. These results suggest that mental rehearsal of target-directed lower limb movement without real sensory stimuli can enhance beta-band ERD; furthermore, MI of foot dorsiflexion induces significantly larger beta-band ERS than that of leg extension. These findings could be exploited for the training of BCIs such as powered prosthetics for disabled person and neurorehabilitation system for stroke patients.

In the field of neurorehabilitation with brain-computer interfaces (BCIs) technology, an EEG feature, event-related desynchronization/synchronization (ERD/S) caused by motor imagery (MI) is widely used for estimating human motor intention. However, sufficient neurofeedback training is required for the use of the MI-based BCI system, because the ability to generate ERD/S is highly dependent on individuals. To find an effective MI condition for the BCI system, we hypothesize that having a conscious target during MI would enhance the extent of ERD/S. In the experiments, we investigated the individual effect of two types of MIs: leg extension (L) and leg extension with a conscious target (i.e., kicking a ball (KB)) on the resultant ERD/S. We evaluated time-frequency maps of ERD/S and statistically compared these two conditions (i.e., L and KB). As a result, a significant difference was found in beta-ERD (paired t-test, p <; 0.01), while there were no significant differences in mu-ERD and beta-ERS. These results suggest that having a conscious target during lower extremity MI would strengthen the ERD in beta frequency band compared to the case without target.

For the sake of brain-computer interfaces (BCIs) neurorehabilitation, an EEG feature, event-related (de)synchronization (ERD/S) caused by motor imagery (MI) is widely used. However, its availability and reliability are limited. Thus, a neurofeedback training is required for the use of the BCI system. To find an effective training condition of the MI-based BCI neurorehabilitation system for lower extremity, in this study, we investigated two types of MIs: foot dorsiflexion and leg extension. As the result, a clear trend toward significant difference (p = 0.057) was found between foot and leg motor imageries. It suggests that foot-MI might cause larger beta ERD than leg-MI.

No abstract