Increasing Robustness of Intracortical Brain-Computer Interfaces for Recording Condition Changes via Data Augmentation.

BACKGROUND AND OBJECTIVE: Intracortical brain-computer interfaces (iBCIs) aim to help paralyzed individuals restore their motor functions by decoding neural activity into intended movement. However, changes in neural recording conditions hinder the decoding performance of iBCIs, mainly because the neural-to-kinematic mappings shift. Conventional approaches involve either training the neural decoders using large datasets before deploying the iBCI or conducting frequent calibrations during its operation. However, collecting data for extended periods can cause user fatigue, negatively impacting the quality and consistency of neural signals. Furthermore, frequent calibration imposes a substantial computational load. METHODS: This study proposes a novel approach to increase iBCIs' robustness against changing recording conditions. The approach uses three neural augmentation operators to generate augmented neural activity that mimics common recording conditions. Then, contrastive learning is used to learn latent factors by maximizing the similarity between the augmented neural activities. The learned factors are expected to remain stable despite varying recording conditions and maintain a consistent correlation with the intended movement. RESULTS: Experimental results demonstrate that the proposed iBCI outperformed the state-of-the-art iBCIs and was robust to changing recording conditions across days for long-term use on one publicly available nonhuman primate dataset. It achieved satisfactory offline decoding performance, even when a large training dataset was unavailable. CONCLUSIONS: This study paves the way for reducing the need for frequent calibration of iBCIs and collecting a large amount of annotated training data. Potential future works aim to improve offline decoding performance with an ultra-small training dataset and improve the iBCIs' robustness to severely disabled electrodes.

Speaker identification in courtroom contexts - Part II: Investigation of bias in individual listeners' responses.

In "Speaker identification in courtroom contexts - Part I" individual listeners made speaker-identification judgements on pairs of recordings which reflected the conditions of the questioned-speaker and known-speaker recordings in a real case. The recording conditions were poor, and there was a mismatch between the questioned-speaker condition and the known-speaker condition. No contextual information that could potentially bias listeners' responses was included in the experiment condition - it was decontextualized with respect to case circumstances and with respect to other evidence that could be presented in the context of a case. Listeners' responses exhibited a bias in favour of the different-speaker hypothesis. It was hypothesized that the bias was due to the poor and mismatched recording conditions. The present research compares speaker-identification performance between: (1) listeners under the original Part I experiment condition, (2) listeners who were informed ahead of time that the recording conditions would make the recordings sound more different from one another than had they both been high-quality recordings, and (3) listeners who were presented with high-quality versions of the recordings. Under all experiment conditions, there was a substantial bias in favour of the different-speaker hypothesis. The bias in favour of the different-speaker hypothesis therefore appears not to be due to the poor and mismatched recording conditions.