Crosstalk disrupts the production of motor imagery brain signals in brain-computer interfaces.

Brain-computer interfaces (BCIs) target specific brain activity for neuropsychological rehabilitation, and also allow patients with motor disabilities to control mobility and communication devices. Motor imagery of single-handed actions is used in BCIs but many users cannot control the BCIs effectively, limiting applications in the health systems. Crosstalk is unintended brain activations that interfere with bimanual actions and could also occur during motor imagery. To test if crosstalk impaired BCI user performance, we recorded EEG in 46 participants while they imagined movements in four experimental conditions using motor imagery: left hand (L), right hand (R), tongue (T) and feet (F). Pairwise classification accuracies of the tasks were compared (LR, LF, LT, RF, RT, FT), using common spatio-spectral filters and linear discriminant analysis. We hypothesized that LR classification accuracy would be lower than every other combination that included a hand imagery due to crosstalk. As predicted, classification accuracy for LR (58%) was reliably the lowest. Interestingly, participants who showed poor LR classification also demonstrated at least one good TR, TL, FR or FL classification; and good LR classification was detected in 16% of the participants. For the first time, we showed that crosstalk occurred in motor imagery, and affected BCI performance negatively. Such effects are effector-sensitive regardless of the BCI methods used; and likely not apparent to the user or the BCI developer. This means that tasks choice is crucial when designing BCI. Critically, the effects of crosstalk appear mitigatable. We conclude that understanding crosstalk mitigation is important for improving BCI applicability. SUPPLEMENTARY INFORMATION: The online version of this article contains supplementary material available (10.1007/s13755-021-00142-y).

Improved Visualization of Gastrointestinal Slow Wave Propagation Using a Novel Wavefront-Orientation Interpolation Technique.

OBJECTIVE: High-resolution mapping of gastrointestinal (GI) slow waves is a valuable technique for research and clinical applications. Interpretation of high-resolution GI mapping data relies on animations of slow wave propagation, but current methods remain as rudimentary, pixelated electrode activation animations. This study aimed to develop improved methods of visualizing high-resolution slow wave recordings that increases ease of interpretation. METHODS: The novel method of "wavefront-orientation" interpolation was created to account for the planar movement of the slow wave wavefront, negate any need for distance calculations, remain robust in atypical wavefronts (i.e., dysrhythmias), and produce an appropriate interpolation boundary. The wavefront-orientation method determines the orthogonal wavefront direction and calculates interpolated values as the mean slow wave activation-time (AT) of the pair of linearly adjacent electrodes along that direction. Stairstep upsampling increased smoothness and clarity. RESULTS: Animation accuracy of 17 human high-resolution slow wave recordings (64-256 electrodes) was verified by visual comparison to the prior method showing a clear improvement in wave smoothness that enabled more accurate interpretation of propagation, as confirmed by an assessment of clinical applicability performed by eight GI clinicians. Quantitatively, the new method produced accurate interpolation values compared to experimental data (mean difference 0.02 ± 0.05 s) and was accurate when applied solely to dysrhythmic data (0.02 ± 0.06 s), both within the error in manual AT marking (mean 0.2 s). Mean interpolation processing time was 6.0 s per wave. CONCLUSION AND SIGNIFICANCE: These novel methods provide a validated visualization platform that will improve analysis of high-resolution GI mapping in research and clinical translation.

Patterns of Abnormal Gastric Pacemaking After Sleeve Gastrectomy Defined by Laparoscopic High-Resolution Electrical Mapping.

BACKGROUND: Laparoscopic sleeve gastrectomy (LSG) is increasingly being applied to treat obesity. LSG includes excision of the normal gastric pacemaker, which could induce electrical dysrhythmias impacting on post-operative symptoms and recovery, but these implications have not been adequately investigated. This study aimed to define the effects of LSG on gastric slow-wave pacemaking using laparoscopic high-resolution (HR) electrical mapping. METHODS: Laparoscopic HR mapping was performed before and after LSG using flexible printed circuit arrays (64-96 electrodes; 8-12 cm2; n = 8 patients) deployed through a 12 mm trocar and positioned on the gastric serosa. An additional patient with chronic reflux, nausea, and dysmotility 6 months after LSG also underwent gastric mapping while undergoing conversion to gastric bypass. Slow-wave activity was quantified by propagation pattern, frequency, velocity, and amplitude. RESULTS: Baseline activity showed exclusively normal propagation. Acutely after LSG, all patients developed either a distal unifocal ectopic pacemaker with retrograde propagation (50%) or bioelectrical quiescence (50%). Propagation velocity was abnormally rapid after LSG (12.5 ± 0.8 vs baseline 3.8 ± 0.8 mm s-1; p = 0.01), whereas frequency and amplitude were unchanged (2.7 ± 0.3 vs 2.8 ± 0.3 cpm, p = 0.7; 1.7 ± 0.2 vs 1.6 ± 0.6 mV, p = 0.7). In the patient with chronic dysmotility after LSG, mapping also revealed a stable antral ectopic pacemaker with retrograde rapid propagation (12.6 ± 4.8 mm s-1). CONCLUSION: Resection of the gastric pacemaker during LSG acutely resulted in aberrant distal ectopic pacemaking or bioelectrical quiescence. Ectopic pacemaking can persist long after LSG, inducing chronic dysmotility. The clinical and therapeutic significance of these findings now require further investigation.

Fooling the brain by mirroring the hand: Brain correlates of the perceptual capture of limb ownership.

BACKGROUND: Mirror therapy (MT) is an increasingly employed method aimed at reducing phantom pain and other negative sensations following loss of a limb or damage to sensorimotor systems. However, the brain processes associated with the perception of limb ownership, a key correlate of MT, are unknown. OBJECTIVE: To examine whether transient perceptions of limb ownership together with associated neural activity can be elucidated using a purpose-developed mirror reflection task combined with electrophysiological (EEG) measures and cutting-edge analyses. METHODS: Brain activity was measured online using EEG in 20 healthy controls while they produced opening-closing movements of one hand in control conditions or while viewing the mirror reflection of the movements. The key experimental condition required participants to make a foot pedal response whenever a change in perception of ownership (of a mirror-reflected limb) occurred (Mirror condition). Control conditions and a strict epoching regime were employed using standard subtractive logic to isolate the perception of limb ownership (which was further verified by self-reports). RESULTS: Data from 15 participants were suitable for complete analysis; the remaining reported no experience of ownership. Significant spectral power increases were found in central-parietal regions in association with perceptions of ownership, with the most prominent effect specific to the alpha frequency band (8-13 Hz) measured at the right parietal area. Source localization analyses further identified brain networks associated with the mirror reflection condition in the alpha frequency (parietal lobe) and the beta frequency (middle temporal areas). These were distinct from localized networks associated with the foot pedal response. CONCLUSION: Transient perceptions of ownership can be captured experimentally, and are associated with localized sites of neural activation. This is an initial step toward eventual development of therapeutic targets for interventions including brain computer interfaces (BCIs) aimed at ameliorating the negative effects associated with impaired or missing limbs.