Toward a P300 Based Brain-Computer Interface for Aphasia Rehabilitation after Stroke: Presentation of Theoretical Considerations and a Pilot Feasibility Study

You'll have to have someone else analyze this for you. Whatever the hell a P300 is.
http://journal.frontiersin.org/article/10.3389/fnhum.2016.00547/full?

Sonja C. Kleih^1*, Lea Gottschalt¹, Eva Teichlein² and Franz X. Weilbach²

• ¹Institute of Psychology, University of Würzburg, Würzburg, Germany
• ²Department of Neurology, Klinik Bavaria Bad Kissingen, Bad Kissingen, Germany

People with post-stroke motor aphasia know what they would like to say but cannot express it through motor pathways due to disruption of cortical circuits. We present a theoretical background for our hypothesized connection between attention and aphasia rehabilitation and suggest why in this context, Brain-Computer Interface (BCI) use might be beneficial for patients diagnosed with aphasia. Not only could BCI technology provide a communication tool, it might support neuronal plasticity by activating language circuits and thereby boost aphasia recovery. However, stroke may lead to heterogeneous symptoms that might hinder BCI use, which is why the feasibility of this approach needs to be investigated first. In this pilot study, we included five participants diagnosed with post-stroke aphasia. Four participants were initially unable to use the visual P300 speller paradigm. By adjusting the paradigm to their needs, participants could successfully learn to use the speller for communication with accuracies up to 100%. We describe necessary adjustments to the paradigm and present future steps to investigate further this approach.

Introduction

Brain-computer interfacing (BCI) does not require motor control, but instead either willful brain activation or attention allocation to certain stimuli (Wolpaw and Wolpaw, 2012). Successful BCI use was reported in severely motor-impaired but cognitively intact patients (Hoffmann et al., 2008; Silvoni et al., 2009; Nijboer et al., 2010). One possible BCI input signal is the P300 which represents a positive deflection in the EEG occurring 300 ms after the onset of a relevant stimulus, or target, presented within a stream of irrelevant stimuli, or non-targets (oddball paradigm, Sutton et al., 1965). In a classic visual P300 spelling paradigm (Farwell and Donchin, 1988), letters of the alphabet are arranged in a matrix of rows and columns. The target stimulus is the letter to be selected which is highlighted (flashed) once in the row and once in the column accordingly. The non-target stimuli are to be ignored by the BCI user. The BCI detects the P300 response to the target stimulus cell, displays the target letter on a computer screen and thereby allows for communication (Farwell and Donchin, 1988).

Even though establishing communication in paralyzed patients has been one of the major goals of BCI research for decades, BCIs were most recently also used in rehabilitation contexts (Daly and Huggins, 2015) including rehabilitation after stroke. Morone et al. (2015) reported on the use of BCI technology for rehabilitation of the upper limb by having patients undergo a BCI based training schedule. Patients had to imagine movements with their paralyzed arms and hands and these imagined movements were translated into movements of a virtual hand. The authors hypothesized this training to boost neuronal plasticity after stroke and thereby support motor rehabilitation. And indeed, patients improved their ability to move hands and arms (as measured by the Fugl-Meyr scale) to a clinically relevant extent.

Besides possible motor impairments, manifold cognitive impairments might occur after stroke (Jokinen et al., 2015). Up to 50% of all stroke survivors are affected by attention impairments (Leśniak et al., 2008) and up to 30% suffer from language production or language comprehension deficits (= aphasia, Flowers et al., 2013). In the pilot study presented here, we aimed at focusing on aphasia caused by lesions in the opercular and triangular part of the inferior frontal gyrus, the Broca area, the temporoparietal region and related circuits of the brain (motor aphasia e.g., Berndt and Caramazza, 1999). Usually, afferent fibers receive information from the primary and secondary auditory cortices and several association fields. Efferent fibers to the precentral gyrus are activated directly via the basal ganglia and indirectly via the thalamus and cerebellum (Trepel, 2011). Corticonuclear fibers activate nuclei in the brainstem, which initiate muscle activation in the larynx and the pharynx. Mimics and language are produced. With motor aphasia, language can still be perceived and understood, but language production is limited or impossible. In case language is not completely lost, sentences are short, word production is flawed and self-expression is very demanding (Kelly et al., 2010).

Language therapy as provided by the healthcare system was shown to have positive effects mainly in early rehabilitation phases (Robey, 1994) and for patients who suffered from language comprehension disorders (Kelly et al., 2010). Therefore, traditional language therapy is highly valuable, but unfortunately might not be sufficient. Half of the aphasic patients do not recover fully (Hartje and Poeck, 2000). In the long term, not only might the psychological burden become manifest as a consequence of chronic aphasia (Gainotti, 1997), but also the economic situation might deteriorate (Hinckley, 1998) as in many workplaces employees must be able to communicate elaborately. Therefore, aphasia rehabilitation after stroke is a challenge deserving more attention by research and rehabilitation care.

BCI use for communication was tested and reported successful in eight participants diagnosed with aphasia (Shih et al., 2014). The authors used a visual P300 based checkerboard paradigm and reported achieved accuracies of between 60% and 65%. Another approach was presented most recently by Musso et al. (2016) who presented an auditory BCI system being used by a patient with chronic aphasia. Their goal was to identify neuronal markers of auditory attention. However, in both mentioned studies, the theoretical background for BCI use and therefore, attention allocation which might be useful in aphasia rehabilitation, were missing. To our knowledge, the presented relation between attention, aphasia and BCI use and its potential implications for aphasia rehabilitation are the first theory-based considerations on this research topic.

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