Abstract
Brain-Computer interface technologies mean to create new communication channels between our mind and our environment, independent of the motor system, by detecting and classifying self regulation of local brain activity. BCIs can provide patients with severe paralysis a means to communicate and to live more independent lives. There has been a growing interest in using invasive recordings for BCI to improve the signal quality. This also potentially gives access to new control strategies previously inaccessible by non-invasive methods. However, before surgery, the best implantation site needs to be determined. The blood-oxygen-level dependent signal changes measured with fMRI have been shown to agree well spatially with those found with invasive electrodes, and are the best option for pre-surgical localization. We show, using real-time fMRI at 7T, that eye movement-independent visuospatial attention can be used as a reliable control strategy for BCIs. At this field strength even subtle signal changes can be detected in single trials thanks to the high contrast-to-noise ratio. A group of healthy subjects were instructed to move their attention between three (two peripheral and one central) spatial target regions while keeping their gaze fixated at the center. The activated regions were first located and thereafter the subjects were given real-time feedback based on the activity in these regions. All subjects managed to regulate local brain areas without training, which suggests that visuospatial attention is a promising new target for intracranial BCI. ECoG data recorded from one epilepsy patient showed that local changes in gamma-power can be used to separate the three classes.
Highlights
In any interactions with our environment, including speech, we fully depend on the motor system
In this study we show that brain signals associated with covert visuospatial attention can be used for BCI control
Unique to this approach is that the user can process information in the central visual field while simultaneously exerting control over a device merely by directing attention to the peripheral field
Summary
In any interactions with our environment, including speech, we fully depend on the motor system. Because the dominating modality in BCI research has been EEG, the control strategies investigated, for invasive measurements, have mainly been based on systems located in cortical areas accessible by scalp electrodes. Patients might have clinical issues making these strategies inapplicable It is for example uncertain whether paralysed people are capable of engaging their motor cortex after a long period of non-use [26]. This indicates that in the light of intracranial solutions, alternative avenues, using other brain systems, are worth exploring to further the BCI field and to be able to create an individually optimized setup for each patient. While the term ‘‘BCI illiteracy’’ is sometimes used for subjects not able to control a BCI it is more likely that the particular control task is not suitable and that by choosing the right task these subjects can learn to gain control
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