# Attentional markers during auditory BCI: healthy subjects and patients with locked-in syndrome

Perrine Rose Seguin, Emmanuel Maby, Anatole Otman, Mélodie Fouillen, Dominique Morlet, Jacques Luauté, Pascal Giraux, Jérémie Mattout

► To cite this version:

Perrine Rose Seguin, Emmanuel Maby, Anatole Otman, Mélodie Fouillen, Dominique Morlet, et al. Attentional markers during auditory BCI: healthy subjects and patients with locked-in syndrome. Cortico days 2022, Mar 2022, Autrans, France. . hal-04095581

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Submitted on 11 May 2023

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# Attentional markers during auditory BCI: healthy subjects and patients with locked-in syndrome

P. SÉGUINª, b, E. MABYª, A. OTMANª, M. FOUILLENª, D. MORLETª, J. LUAUTÉª, c, P. GIRAUXª, b, J. MATTOUTª

## Introduction

<table><tr><td><strong>Syndrome</strong></td><td colspan="3">(Complete) Locked-in Syndrome</td></tr><tr><td><strong>Pathologies</strong></td><td>Brainstem lesion</td><td>Severe cerebrolesion</td><td>Amyotrophic Lateral Sclerosis</td></tr><tr><td><strong>Impairments</strong></td><td colspan="3">Motor +/- Sensory +/- Cognitive</td></tr><tr><td><strong>Activity limitations</strong></td><td colspan="3">Communication</td></tr></table>

**Aims:** Detect consciousness and restore communication

**How?** With an auditory Brain-Computer Interface (BCI)

## Protocol

**Instructions:** To answer « Yes »: Please, pay attention to the right audio stream and try to count the deviant sound « Yes », without paying attention to the left.

<figure><img src="image_2.png" /></figure>

**Analysis:**

- Online (real-time) : BCI accuracy**

- Offline (a posteriori) :

- evoked responses,

- design optimization

**Datasets:**

- 18 healthy subjects

- 7 patients

## Methods : online data processing

<figure><img src="image_3.png" /></figure>

<table><tr><td><strong>Feature extraction</strong></td><td><ul><li>Bandpass filter (0.5-20 Hz)</li><li>Spatial filter (xDAWN)</li><li>Averaged evoked responses</li></ul></td><td><strong>Classification</strong></td><td><ul><li>Probabilistic binary classification (target/non-target) for each trial type (Standard/deviant x Yes/No)</li></ul></td><td><strong>Decision</strong></td><td><ul><li>Based on the combined posterior probabilities in each trial</li><li>Auditory feedback to the subject</li></ul></td></tr></table>

**Data sets:**

calibration (14 trials)

+

test (50 trials)

## Offline results

<table><caption>Offline reduction of the number of electrodes</caption><thead><tr><th></th><th>32 electrodes</th><th>15 electrodes</th></tr></thead><tbody><tr><th>Accuracy</th><td>~ 86%</td><td>~81%</td></tr></tbody></table>

<figure><img src="image_4.png" /><figcaption>Offline reduction of trial duration</figcaption></figure>

<figure><img src="image_5.png" /><figcaption>Effect of ICA pre-processing</figcaption></figure>

<figure><img src="image_6.png" /><figcaption>Patients (n=7)</figcaption></figure>

<figure><img src="image_7.png" /><figcaption>Stimulations</figcaption></figure>

## Individual evoked potentials

<figure><img src="image_8.png" /><figcaption>Patient with online BCI control</figcaption></figure>

Accuracy: 100%
Amyotrophic lateral sclerosis

<figure><img src="image_9.png" /><figcaption>Patient without BCI control</figcaption></figure>

Brainstem injury

<figure><img src="image_10.png" /></figure>

Significant attentional modulation for each electrode
Method: Threshold-free cluster enhancement
(Smith and Nichols, 2009)

Attended

1sec [ 5 µV ]

Ignored

| Stimuli onset

<table><thead><tr><th></th><th>Healthy subjects</th><th>Patients</th></tr></thead><tbody><tr><td>Response to deviance</td><td>94 % (17/18)</td><td>29 % (2/7)</td></tr><tr><td>Attentional modulation on STD</td><td>83 % (15/18)</td><td>29 % (2/7)</td></tr><tr><td>Attentional modulation on DEV</td><td>72 % (13/18)</td><td>42 % (3/7)</td></tr></tbody></table>

## Discussion

### Attentional markers

- **Standards:** a steady-state potential arises at the frequency of the attended stimulus, its shape varies across subjects

- **Deviants:** they elicit a P3b component

### Clinical results

- Even when they control the BCI, patients show abnormal attentional modulation patterns

- The impact of oculomotor impairment onto covert attention has to be further explored

## Conclusion

### Auditory BCI

- Show a drop of performance in conscious but severely paralyzed patients

- Patients tend to show a very frontal activity that has to be explored

- Attention abilities may be affected in case of severe (oculo-)motor impairment

<footnote>caCentre de Recherche en Neurosciences de Lyon, INSERM U1028-CNRS, UMR5292, 69000 Lyon, France; Université Lyon 1, France</footnote>

<footnote>b Médecine Physique et de Réadaptation, Hôpital Bellevue, CHU de Saint-Etienne, France</footnote>

<footnote>c Médecine Physique et de Réadaptation, Hospices civils de Lyon, Hôpital Henry Gabrielle, Mouvement et Handicap, Saint-Genis Laval 69230, France</footnote>