Identical Auditory Stimuli Render Distinct Cortical Responses Across Subjects—An Issue for Auditory Oddball-Based BMIs

A brain-machine interface (BMI) can be defined as a system that translates the brain activity patterns of a user into messages or commands for an interactive application. For patients with neurodegenerative diseases, who lost the ability to communicate during the progression of the disease, a BMI could be the only remaining possibility to interact with the environment. Event-related potentials (ERPs), especially the P300 component, are commonly used as control signal for these systems. The P300 component is elicited by rare stimuli amid a stream of frequent standard stimuli, such as in oddball tasks and can be influenced by several parameters related the stimulation, biological and psychological factors. The literature shows inconclusive results for the influence of frequency and channel of stimulation in the P300 component and the effect of these parameters on BMI. The goal of this study was to evaluate the impact of the stimulation frequency to find out if the same pattern of stimuli can be used for different subjects to promote similar ERPs. The experimental procedure consisted of the presentation of five mono target frequencies at the two channels of the headphone. The amplitude and latency of P300 was analyzed. The results indicate distinct individual responses and, therefore, the responses of different subjects should be properly evaluated before considering the use of auditory oddball paradigms for BMI interaction so that better performances and Information Transfer Rates can be achieved.