Extended Data Fig. 4: Example closed-loop speech synthesis trial.

Spike-band power and threshold crossing spikes from each electrode are shown for one example sentence. These neural features are binned and causally normalized and smoothed on a rolling basis before being decoded to synthesize speech. The mean spike-band power and threshold crossing activity for each individual array are also shown. Speech-related modulation was observed on all arrays, with the highest modulation recorded in v6v and 55b. The synthesized speech is shown in the bottom-most row. The gray trace above it shows the participant’s attempted (unintelligible) speech as recorded with a microphone.