Fig. 1: Tracking phonetic representations by prefrontal neurons during the production of natural speech.
From: Single-neuronal elements of speech production in humans
a, Left, single-neuronal recordings were confirmed to localize to the posterior middle frontal gyrus of language-dominant prefrontal cortex in a region known to be involved in word planning and production (Extended Data Fig. 1a,b); right, acute single-neuronal recordings were made using Neuropixels arrays (Extended Data Fig. 1c,d); bottom, speech production task and controls (Extended Data Fig. 2a). b, Example of phonetic groupings based on the planned places of articulation (Extended Data Table 1). c, A ten-dimensional feature space was constructed to provide a compositional representation of all phonemes per word. d, Peri-event time histograms were constructed by aligning the APs of each neuron to word onset at millisecond resolution. Data are presented as mean (line) values ± s.e.m. (shade). Inset, spike waveform morphology and scale bar (0.5 ms). e, Left, proportions of modulated neurons that selectively changed their activities to specific planned phonemes; right, tuning curve for a cell that was preferentially tuned to velar consonants. f, Average z-scored firing rates as a function of the Hamming distance between the preferred phonetic composition of the neuron (that producing largest change in activity) and all other phonetic combinations. Here, a Hamming distance of 0 indicates that the words had the same phonetic compositions, whereas a Hamming distance of 1 indicates that they differed by a single phoneme. Data are presented as mean (line) values ± s.e.m. (shade). g, Decoding performance for planned phonemes. The orange points provide the sampled distribution for the classifier’s ROC-AUC; n = 50 random test/train splits; P = 7.1 × 10−18, two-sided Mann–Whitney U-test. Data are presented as mean ± s.d.
