Accuracy of a P300 Speller for People with Motor Impairments: A Comparison

Abstract

A Brain-Computer Interface (BCI) provides a completely new output pathway that can provide an additional option for a person to express himself/herself if he/she suffers a disorder like amyotrophic lateral sclerosis (ALS), brainstem stroke, brain or spinal cord injury or other diseases which impair the function of the common output pathways which are responsible for the control of muscles. For a P300 based BCI a matrix of randomly flashing characters is presented to the participant. To spell a character the person has to attend to it and to count how many times the character flashes. Although most BCIs are designed to help people with disabilities, they are mainly tested on healthy, young subjects who may achieve better results than people with impairments. In this study we compare measurements, performed on people suffering motor impairments, such as stroke or ALS, to measurements performed on healthy people. The overall accuracy of the persons with motor impairments reached 70.1% in comparison to 91% obtained for the group of healthy subjects. When looking at single subjects, one interesting example shows that under certain circumstances, when it is difficult for a patient to concentrate on one character for a longer period of time, the accuracy is higher when fewer flashes (i.e., stimuli) are presented. Furthermore, the influence of several tuning parameters is discussed as it shows that for some participants adaptations for achieving valuable spelling results are required. Finally, exclusion criteria for people who are not able to use the device are defined.

P300 Brain Computer Interface Control after an Acquired Brain Injury

“…The findings indicated that end users with ABI can operate a BCI, which is promising for future research, however greater control is needed to ensure this technology could become an assistive technology (AT) solution for daily use for people with ABI. The difference between the healthy users and end user group"s accuracy score was to be expected and is also evident in previous studies [33] [34] [35]. The importance of the comparison groups is to provide baseline data of the BCI system when non-BCI experts undertake the set up for people with and without a cognitive impairment operate it.…”

“…A number of recommendations could be considered to increase the systems effectiveness in the future include the use of famous faces as an alternative stimuli to flashing lights on ; and for a simple way to adjust and change the parameters of the stimulus duration to make it easier for the end user to attend to their desired symbol [33]. Additionally, Mulvenna et al [24] suggests personalizing the BCI system for individual needs to increase the lower efficacy rates by users with ABI while Schreuder and his team [23] felt that a range of cognitive profiles need to be taken into account at the design stage of BCI development.…”

A P300-based brain–computer interface aimed at operating electronic devices at home for severely disabled people

“…Nevertheless, most BCI studies are performed with young healthy adults instead of severely impaired people who are the potential end-users [23]. Few studies verified the usefulness of P300-based BCIs for severely disabled people [3,10,24,28,29,37,40]. Furthermore, these studies use just one stimuli matrix with a reduced number of options and allowing limited interaction.…”

“…Most of them presented both motor and cognitive impairments. If we compare to previous works [3,10,24,28,29,37,40], in our study, a large population of potential BCI end-users interacted with the proposed assistive tool in their usual environment.…”

Interaction of BCI with the underlying neurological conditions in patients: pros and cons

“…This is one of the rare application for which a commercially available solution exists (intendix, g.tec medical engineering GmbH, g.USBamp P300 model, Guger Technologies OG, Austria). While accuracy of this type of BCI reaches 90% in able-bodied, only 70% can be achieved in patients (Ortner et al, 2011). Priftis (2014) therefore concluded that requirements of ALS patients haven't been met yet, and highlights a striking fact that a tiny portion of published papers on P300 BCI presents experimental studies on ALS patients.…”