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Comparative Study
, 126 (11), 2170-80

The Influence of Central Neuropathic Pain in Paraplegic Patients on Performance of a Motor Imagery Based Brain Computer Interface

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Comparative Study

The Influence of Central Neuropathic Pain in Paraplegic Patients on Performance of a Motor Imagery Based Brain Computer Interface

A Vuckovic et al. Clin Neurophysiol.

Abstract

Objective: The aim of this study was to test how the presence of central neuropathic pain (CNP) influences the performance of a motor imagery based Brain Computer Interface (BCI).

Methods: In this electroencephalography (EEG) based study, we tested BCI classification accuracy and analysed event related desynchronisation (ERD) in 3 groups of volunteers during imagined movements of their arms and legs. The groups comprised of nine able-bodied people, ten paraplegic patients with CNP (lower abdomen and legs) and nine paraplegic patients without CNP. We tested two types of classifiers: a 3 channel bipolar montage and classifiers based on common spatial patterns (CSPs), with varying number of channels and CSPs.

Results: Paraplegic patients with CNP achieved higher classification accuracy and had stronger ERD than paraplegic patients with no pain for all classifier configurations. Highest 2-class classification accuracy was achieved for CSP classifier covering wider cortical area: 82±7% for patients with CNP, 82±4% for able-bodied and 78±5% for patients with no pain.

Conclusion: Presence of CNP improves BCI classification accuracy due to stronger and more distinct ERD.

Significance: Results of the study show that CNP is an important confounding factor influencing the performance of motor imagery based BCI based on ERD.

Keywords: BCI; Central neuropathic pain; EEG; Event related synchronisation/desynchronisation; Motor imagery; Paraplegia.

Figures

Fig. 1
Fig. 1
Body maps showing perceived location pain in patients in PWP group.
Fig. 2
Fig. 2
The experimental paradigm for a motor imagination task.
Fig. 3
Fig. 3
Location of a smaller set of electrodes used to build a CSP1 classifier (black dots only) and a larger set used to build a CSP2 classifier (black and grey dots). All 61 electrodes (including the ones with white circles) were included when creating ERS/ERD scalp maps.
Fig. 4
Fig. 4
Classification accuracy (mean ± STD) between two different limbs for all three groups of volunteers using bipolar montage (Fig. 3a), CSP1A (Fig. 3b), CSP1B (Fig. 3c) and CSP2 (Fig. 3d). The numbers above bars show mean values for a single group. Abbreviations: RH: right hand; LH: left hand; F: feet; AB: able bodied; PNP: patients with no pain; PWP: patients with central neuropathic pain.
Fig. 5
Fig. 5
Averaged classification accuracy for all combinations of limbs (mean ± SE) for CSP1A (23 electrodes) with the variable number of CSP. Abbreviations: AB: able bodied; PNP: patients with no pain; PWP: patients with central neuropathic pain.
Fig. 6
Fig. 6
ERS/ERD maps over the central cortical area during MI (a) ERS/ERD maps for motor imagery of different limbs over the electrode locations C3 for the right hand, Cz for feet and C4 for the left hand. Dashed lines at t = −1 s show a moment when a readiness cue appeared at the screen while a vertical solid line at t = 0 s shows a moment when the initiation cue appeared on the screen. Positive numbers are for ERS and negative for ERD. A column to the right shows areas of statistically significant differences among the groups. (b) Ares of statistically significant differences between ERS/ERD maps between different groups, shown in Fig. 5a.
Fig. 7
Fig. 7
Scalp maps of ERS/ERD during MI of feet for three groups of participants. (a) Averaged scalp maps over a period t = 0.4 s to 0.8 s post cue. Upper raw is for the theta band, middle raw is for the alpha band and the lower raw is for the beta band. (b) Marked electrode locations shows areas of statistically significant differences between groups for three different frequency bands. Abbreviations: AB: able bodied; PNP: patients with no pain; PWP: patients with central neuropathic pain.

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