Figure 1. Speech sounds evoke responses in the human motor cortex.

(a) Magnetic resonance image surface reconstruction of one representative subject’s cerebrum (subject 1: S1). Individual electrodes are plotted as dots, and the average cortical response magnitude (z-scored high gamma activity) when listening to CV syllables is signified by the color opacity. CS denotes the central sulcus; SF denotes the Sylvian fissure. (b) Acoustic waveform, spectrogram, single-trial cortical activity (raster), and mean cortical activity (high gamma z-score, with standard error) from two vSMC sites and one STG site when a subject is listening to /da/. Time points significantly above a pre-stimulus silence period (p<0.01, bootstrap resampled, FDR corrected, alpha < 0.005) are marked along the horizontal axis. The vertical dashed line indicates the onset of the syllable acoustics (t=0). (c) Same subject as in (a); distributed vSMC cortical activity when speaking CV syllables (mean high gamma z-score). (d) Total number of significantly active sites in all subjects during listening, speaking, and both conditions (p<0.01, t-test, responses compared to silence and speech). Electrode sites are broken down by their anatomical locations. S denotes superior vSMC sites; I denotes inferior vSMC sites.

DOI: http://dx.doi.org/10.7554/eLife.12577.003

Figure 1—figure supplement 1. Average cortical responses to speaking and listening in all subjects (S2-S5).

(a) Average Z-scored responses in active electrodes when listening to (left) or speaking (right) CV syllables in all subjects, as shown in Figure 1a and c. (b) Results from spatial clustering of significantly active electrodes in each subject. S1, S4, and S5 showed spatially segregated clusters (see Materials and methods) and were included in k-means clustering analysis. The silhouette index shows that the best number of clusters for S1 (from Figure 1) and S4 was k=2, whereas the best number of clusters for S5 was k=5.

DOI: http://dx.doi.org/10.7554/eLife.12577.004

Figure 1—figure supplement 2. Neural responses while listening to CV syllables in 4 additional subjects not included in MDS analyses (S6 - S9).

Responses are plotted on each subject’s brain surface and are shown for each electrode as the average Z-scored high gamma activity across all syllables, aligned to the acoustic onset of the stimulus (indicated by dashed line at t = 0). As in Figure 1 and Figure 1—figure supplement 1, strong responses are seen during listening in inferior and superior regions of the vSMC (primarily precentral gyrus) in addition to the superior temporal gyrus (STG). For each subject, SF indicates the location of the Sylvian fissure, and CS indicates the central sulcus.

DOI: http://dx.doi.org/10.7554/eLife.12577.005