Comparison of the Efficacy of a Real-Time and Offline Associative Brain-Computer-Interface

Abstract

An associative brain-computer-interface (BCI) that correlates in time a peripherally generated afferent volley with the peak negativity (PN) of the movement related cortical potential (MRCP) induces plastic changes in the human motor cortex. However, in this associative BCI the movement timed to a cue is not detected in real time. Thus, possible changes in reaction time caused by factors such as attention shifts or fatigue will lead to a decreased accuracy, less pairings, and likely reduced plasticity. The aim of the current study was to compare the effectiveness of this associative BCI intervention on plasticity induction when the MRCP PN time is pre-determined from a training data set (BCIoffline), or detected online (BCIonline). Ten healthy participants completed both interventions in randomized order. The average detection accuracy for the BCIonline intervention was 71 ± 3% with 2.8 ± 0.7 min-1 false detections. For the BCIonline intervention the PN did not differ significantly between the training set and the actual intervention (t9 = 0.87, p = 0.41). The peak-to-peak motor evoked potentials (MEPs) were quantified prior to, immediately following, and 30 min after the cessation of each intervention. MEP results revealed a significant main effect of time, F(2,18) = 4.46, p = 0.027. The mean TA MEP amplitudes were significantly larger 30 min after (277 ± 72 μV) the BCI interventions compared to pre-intervention MEPs (233 ± 64 μV) regardless of intervention type and stimulation intensity (p = 0.029). These results provide further strong support for the associative nature of the associative BCI but also suggest that they likely differ to the associative long-term potentiation protocol they were modeled on in the exact sites of plasticity.

Self-Paced Online vs. Cue-Based Offline Brain–Computer Interfaces for Inducing Neural Plasticity

“…This study validates previous findings that cue-based and self-paced EEG-triggered electrical stimulation can increase the motor cortical excitability [4,14,15,17,18], and in a very recent study, the two systems were compared with similar results [36]. It was not tested if imagination alone and stimulation alone would change the motor cortical excitability, but it has been shown previously that a similar number of imaginary movements and stimuli do not change the motor cortical excitability [4,14].…”

Induction of Neural Plasticity Using a Low-Cost Open Source Brain-Computer Interface and a 3D-Printed Wrist Exoskeleton

“…The BCI system that was used in this study performed well in terms of the true positive rate and number of false positive detections per minute. The performance is comparable with other asynchronous BCI studies that have been used for inducing plasticity, which have reported true positive rates in the range of 67–85% and a number of false positive detections per minute in the range of 0.5–2.8 [ 5 , 7 , 8 , 9 , 10 , 11 , 31 ]. The approaches to movement intention detection in those studies have primarily relied on movement-related cortical potentials, but the results of the current study show that a BCI based on sensorimotor rhythms is just as effective in terms of movement intention detection, and it has also been used successfully for BCI training in stroke patients [ 4 , 5 , 52 , 53 ].…”

“…In addition, the changes in excitability are in a similar range of what has been reported previously for BCI-triggered electrical stimulation of the common peroneal nerve and exoskeleton movement of the ankle joint. The BCI intervention in these studies has consistently reported increases in corticospinal excitability in the range of 40–100% [ 7 , 8 , 9 , 10 , 11 , 31 ]. In this study, the increase from pre- to post-intervention measurement was not significant, however, it could be attributed to the large standard deviation of approximately 60%, or to the fact that the effect of the intervention takes some time to consolidate.…”

Investigating the Intervention Parameters of Endogenous Paired Associative Stimulation (ePAS)

“…Like PAS, there is some suggestion that the neuromodulatory effects of ePAS are dependent on the ISI, because CME is increased when the peripheral afferent stimulus is hypothesised to arrive in the M1 during the PN of the MRCP [ 22 ]. A single session of ePAS has been shown to increase CME for up to 60 min post-intervention in healthy participants performing imagined movement [ 22 , 23 , 24 , 25 , 26 , 27 ] and up to 30 min post-intervention in people with subacute [ 28 ] and chronic stroke [ 29 ] attempting voluntary movement. Improvements in motor function [ 28 , 30 ] and locomotor abilities have also been noted following ePAS interventions in people with chronic stroke [ 29 ].…”

“…Therefore, it seems reasonable to investigate whether ePAS is more effective when delivered using suprathreshold PES compared to motor threshold PES. With regards to movement type, ePAS research in healthy participants has largely utilised an MRCP derived from imagined movement as the endogenous signal [ 22 , 23 , 24 , 25 , 26 , 31 ]. Whilst there are similarities in cortical activation between voluntary and imagined movement [ 38 ], voluntary movement calls upon more complex cortical networks [ 39 ], whereas imagined movement engages inhibitory networks to prevent the occurrence of voluntary movement [ 40 , 41 ].…”