Time-Masked Transformers with Lightweight Test-Time Adaptation for Neural Speech Decoding

Abstract: Speech neuroprostheses aim to restore communication for people with severe paralysis by decoding speech directly from neural activity. To accelerate algorithmic progress, a recent benchmark released intracranial recordings from a paralyzed participant attempting to speak, along with a baseline decoding algorithm. Prior work on the benchmark showed impressive accuracy gains. However, these gains increased computational costs and were not demonstrated in a real-time decoding setting. Here, we make three contributions that pave the way towards accurate, efficient, and real-time neural speech decoding. First, we incorporate large amounts of time masking during training. On average, over $50\%$ of each trial is masked. Second, we replace the gated recurrent unit (GRU) architecture used in the baseline algorithm with a compact Transformer. The Transformer architecture uses $77\%$ fewer parameters, cuts peak GPU memory usage by $36\%$ relative, and is significantly faster to calibrate relative to the GRU. Third, we design a lightweight variant of an existing test-time adaptation method developed for decoding handwriting from neural activity. Our variant adapts the model using multiple time masked augmentations of a single trial and requires only one gradient step per trial. Together, these contributions reduce word error rate by $19.5\%$ and effectively mitigate performance degradations across held-out days in a real-time decoding setting while substantially lowering computational costs.