An auditory brain-computer interface (BCI)

Abstract

Brain-computer interfaces (BCIs) translate brain activity into signals controlling external devices. BCIs based on visual stimuli can maintain communication in severely paralyzed patients, but only if intact vision is available. Debilitating neurological disorders however, may lead to loss of intact vision. The current study explores the feasibility of an auditory BCI. Sixteen healthy volunteers participated in three training sessions consisting of 30 2-3 min runs in which they learned to increase or decrease the amplitude of sensorimotor rhythms (SMR) of the EEG. Half of the participants were presented with visual and half with auditory feedback. Mood and motivation were assessed prior to each session. Although BCI performance in the visual feedback group was superior to the auditory feedback group there was no difference in performance at the end of the third session. Participants in the auditory feedback group learned slower, but four out of eight reached an accuracy of over 70% correct in the last session comparable to the visual feedback group. Decreasing performance of some participants in the visual feedback group is related to mood and motivation. We conclude that with sufficient training time an auditory BCI may be as efficient as a visual BCI. Mood and motivation play a role in learning to use a BCI.

Figure 1:

Schematic of one of sixteen possible angles (a) in which the mouse was supposed to be moved. When, for example, the mouse was moved in a 30 degrees angle to the upper right, harp sounds were produced. When the mouse was moved in a 210 degrees angle to the lower left, bongo sounds were produced. Participants had to figure out the correct angle by trial and error with the aids of auditory feedback.

Figure 2:

Timing of the trial design in both the auditory and the visual feedback group.

Figure 3:

Average accuracy per block for the visual feedback group (solid line) and the auditory feedback group (dashed line).

Figure 4:

From top to bottom performance is plotted against mood, mastery confidence, fear of incompetence, interest and challenge. Left column: data from the visual feedback group, right column: auditory feedback group. Diamonds represent the ratings prior to session one, triangles prior to session two and squares prior to session three.