3. BCI-HMI

Objectives:

Gaze-independent P300-based BCIs suitable for people with ocular impairment, in particular patients in (complete) locked-in state (LIS);
Self-paced control of P300-based BCIs;
Single-time calibration for P300-based BCIs;
Validation of the above topics in applications for communication and wheelchair steering;
Research of new BCI approaches based on visual motion imagery;

Hybrid Visual-Auditory P300-Based BCI

Achievements:

A hybrid visual-auditory (HVA) P300-based BCI combining simultaneously visual and auditory stimulation was proposed. Auditory stimuli are based on natural meaningful spoken words. The paradigm was designed to match the skills of LIS patients, minimizing memory and cognitive demand, and maximizing stimuli discrimination and perception. The comparison of HVA with purely auditory (AU) and purely visual covert (VC) stimulation, showed that HVA evidences a neurophysiologic sum of the two independent processes (see left figure). This effect leads to an increase of 32% in online classification accuracy in comparison to AU and VC approaches.

Self-paced control and one-time calibration

Achievements:

A P300 self-paced approach was implemented in the domain of classification projections and was tested to steer an intelligent wheelchair in realistic scenarios. Two approaches were successfully validated: static window (constant number of repetitions within a trial) and dynamic window (adaptive number of repetitions within a trial). A collaborative system supports human, performing navigation manoeuvres, and dealing with eventual wrong user commands. Experiments were performed with participants with motor impairments recruited from cerebral palsy association APCC (see tasks 7 and 10).
In the context of a communication speller (LSC), self-paced control and one-time calibration were combined in the same framework. Methods developed in "Task4-Biosignals processing" (DTA and SSST) allowed classification accuracies similiar to those obtained if calibration and use were made in the same session .

BCIs based on visual motion imagery

Achievements:

Visual motion imagery was proposed as a new mental strategy for BCI control. EEG experiments consisting of visual imagery of a static point, motion in opposing directions and motion in 4 alternating directions showed the possibility of a parametric discrimination in the visual cortex. These findings suggest the feasibility of visual motion imagery for multiclass BCI control.

Fig. Time-frequency of EEG during imagery of 4 alternating motions

Publications

S. Barbosa, G. Pires, U. Nunes, "Toward a reliable gaze independent hybrid BCI combining visual and natural auditory stimuli", Journal of Neuroscience Methods, Elsevier (in press), 2015, doi:10.1016/j.jneumeth.2015.11.026;
A. Lopes, J. Perdigão, J. Rodrigues, G. Pires, U. Nunes, Robchair: An Intelligent Brain-actuated Wheelchair for Mobility Assistance of Motor Impaired People (submitted to int. journal).
J. Figueiredo, G. Pires, U. Nunes, “Self-paced control of a P300-based BCI-speller using one-time calibration: performance analysis”, (to be submitted to int. journal).
T. Sousa, C. Amaral, J. Andrade, M. Castelo-Branco, "Visual motion imagery as tool for parametric BCI", Annual Conference Joint Meeting of ECNS, ISNIP and ISBET, September 09 - 13, 2015.

Invited talks

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