Beta bursts question the ruling power for brain–computer interfaces

Abstract

Current efforts to build reliable brain-computer interfaces (BCI) span multiple axes from hardware, to software, to more sophisticated experimental protocols, and personalized approaches. However, despite these abundant efforts, there is still room for significant improvement. We argue that a rather overlooked direction lies in linking BCI protocols with recent advances in fundamental neuroscience. In light of these advances, and particularly the characterization of the burst-like nature of beta frequency band activity and the diversity of beta bursts, we revisit the role of beta activity in “left vs. right hand” motor imagery tasks. Current decoding approaches for such tasks take advantage of the fact that motor imagery generates time-locked changes in induced power in the sensorimotor cortex, and rely on band-passed power changes in single or multiple channels. Although little is known about the dynamics of beta burst activity during motor imagery, we hypothesized that beta bursts should be modulated in a way analogous to their activity during performance of real upper limb movements. We show that classification features based on patterns of beta burst modulations yield decoding results that are equivalent to or better than typically used beta power across multiple open electroencephalography datasets, thus providing insights into the specificity of these biomarkers.

Surfing beta burst waveforms to improve motor imagery-based BCI

“…In order to select kernels for convolving the data from all channels we first detected bursts from channels C3 and C4 (or equivalently channels 43 and 44 for the MunichMI (Grosse-Wentrup 2009) dataset). To do so, we applied the pre-processing steps described above within a dataset-specific cluster of channels above the sensorimotor cortex (Papadopoulos et al, 2024). We applied a time-frequency (TF) decomposition in the 1 -43Hz range on each selected channel separately, using the superlets algorithm (Moca et al, 2021) (parameters: omin = 1, omax = 40, c = 4) with a frequency resolution of 0.5 Hz.…”

“…Based on observations from our previous study (Papadopoulos et al, 2024), we computed I m among components 2 to 9 in order to find three PCA axes that maximized this metric. We did not take into account the first component because it likely describes the temporal skew of the bursts (Papadopoulos et al, 2024;Szul et al, 2023).…”

“…Based on observations from our previous study (Papadopoulos et al, 2024), we computed I m among components 2 to 9 in order to find three PCA axes that maximized this metric. We did not take into account the first component because it likely describes the temporal skew of the bursts (Papadopoulos et al, 2024;Szul et al, 2023). Finally, we divided the score range of each of the three selected axes in seven equally spaced groups, each group corresponding to a set of "similarly shaped" bursts.…”

“…Beta burst rate has been shown to be more behaviorally relevant in motor processes (Enz et al, 2021;Hannah et al, 2020;Little et al, 2019;Rayson et al, 2023;Szul et al, 2023;Wessel, 2020) than averaged beta band power. Additionally, recent studies have shown that beta bursts are not a unitary phenomenon but rather constitute heterogeneous events (Szul et al, 2023) with different functions, alluded to by the differential modulation of their rate and shape depending on task conditions (Langford et al, 2023;Papadopoulos et al, 2024) or movement phase (Rayson et al, 2023;Szul et al, 2023). As such, beta bursts have the potential to be a more sensitive marker of brain processes during real or imagined movements on the single trial level.…”

“…To test this hypothesis, in a previous study we examined multiple open MI EEG datasets. We analyzed the activity of channels C3 and C4 during binary classification tasks of hand MI ("left" vs "right" hand) and demonstrated that the waveform-resolved beta burst rate is superior to beta band power changes in terms of classification (Papadopoulos et al, 2024). In this article we streamline our approach.…”