Fig. 1: Neural representation of orofacial movement and attempted speech.
a, Microelectrode array locations (cyan squares) are shown on top of MRI-derived brain anatomy (CS, central sulcus). b, Neural tuning to orofacial movements, phonemes and words was evaluated in an instructed delay task. c, Example responses of an electrode in area 6v that was tuned to a variety of speech articulator motions, phonemes and words. Each line shows the mean threshold crossing (TX) rate across all trials of a single condition (n = 20 trials for orofacial movements and words, n = 16 for phonemes). Shaded regions show 95% confidence intervals (CIs). Neural activity was denoised by convolving with a Gaussian smoothing kernel (80 ms s.d.). d, Bar heights denote the classification accuracy of a naive Bayes decoder applied to 1 s of neural population activity from area 6v (red bars) or area 44 (purple bars) across all movement conditions (33 orofacial movements, 39 phonemes, 50 words). Black lines denote 95% CIs. e, Red and blue lines represent classification accuracy across time for each of the four arrays and three types of movement. Classification was performed with a 100 ms window of neural population activity for each time point. Shaded regions show 95% CIs. Grey lines denote normalized speech volume for phonemes and words (indicating speech onset and offset). f, Tuning heatmaps for both arrays in area 6v, for each movement category. Circles are drawn if binned firing rates on that electrode were significantly different across the given set of conditions (P < 1 × 10–5 assessed with one-way analysis of variance; bin width, 800 ms). Shading indicates the fraction of variance accounted for (FVAF) by across-condition differences in mean firing rate.
