Habit and neural fatigue: a study finalised to the development of a BCI for Locked-In subjects based on Single Trial EEG

The Locked-In Syndrome is a medical condition regarding awake subjects that are aware and conscious but are not able to communicate verbally and physically; they are subjected to complete paralysis of almost all voluntary skeletal muscles, except for those who regulate vertical eye movements and eye-blinking. This condition is also described as pseudocoma and is mainly due to ventral pontine injuries. The future aim of this research project is to develop a BCI for single trial EEG analysis, that would be able to recognize specific patterns in the electrical activity of the brain, called movement-related cortical potentials. Among these event-related potentials, those of great interest for this study are readiness potentials, that generate when volitional movements are performed. The research work was divided into two parts: the experimental data collection and subsequent data analysis. Habit and perceived tiredness can be listed among the factors that affect the readiness potential; in this preparatory study, the aim was to find evidence of that. Experimental data collection took several months and involved healthy subjects of age 20 to 60 and one injured subject, in minimally conscious state. The subjects underwent completely voluntary and semivoluntary tasks. The event-related potentials were extracted by simple averaging of the trials; the epochs ended with muscular activation. The algorithm successfully proved lateralization of the readiness potentials and identification of the main differences between the voluntary and semivoluntary task. In particular, by implementing a matched filter on semivoluntary task data, it was observed that the first epochs feature higher correlation, and that the latter decreases going towards the end of the trial. This suggests that habit and perceived mental tiredness affect the characteristics of the readiness potential, bringing brain electrical activity towards a quasi-involuntary pattern.