Article Figures & Data
Figures
- Figure 1.
Intersubject phase-locking approach. A, Left and right auditory cortices (ACs) served as seed regions for the phase-locking analysis. For each trial, mean signal time courses were extracted from the seed region (outline shown in gray) for all but one subject. Signals were z-normalized, and averaged across subjects (black lines show individual data; the intersubject average is depicted in bold red). Phase locking was computed between the intersubject seed time course and 15,000 source time courses of the left-out subject in four frequency bands, covering the delta to beta range. For each frequency band, the resulting intersubject PLV maps were averaged across all trials and downsampled to 500 similarly sized surface parcels. This procedure was iterated for all individuals. B, Relative to single-subject (SS) auditory cortex time courses, intersubject (IS) averages showed increased phase locking to the envelope of the speech input, suggesting that the approach can be used to extract stimulus-driven auditory cortex activity during continuous listening. C, Intersubject phase locking was analyzed as a function of individual musical training. The figure depicts individual training duration and the main type of training.
- Figure 2.
Phase synchronization to stimulus-driven auditory cortex (AC) activity during continuous naturalistic listening. A, Relative to resting state, we observed enhanced stimulus-driven phase synchronization in the delta (1–4 Hz), theta (4–8 Hz), and alpha (8–12 Hz) range while listening to the speech input (at p < 0.05, FDR corrected for multiple comparisons). For all of these frequency bands and both seed regions (top row: left auditory cortex; bottom row: right auditory cortex; seed outline shown in gray), phase locking was maximal in ipsilateral and contralateral auditory sensory areas. Phase-locking magnitude decreased with increasing frequency; the color bar is adjusted to the maximum (max) phase-locking value in each frequency band. B, To investigate the spectral profile of the observed intersubject phase locking in more detail, PLV was computed for 30 consecutive frequency bands (0.1–30 Hz) between the auditory cortex seed time courses and single surface parcels localized to temporal, frontal, and inferior parietal cortices. For all tested brain regions, a consistent PLV profile was observed, which suggests that intersubject phase locking effectively shows two distinct peaks in the delta- and theta-band range. Exemplarily, the figure depicts the PLV pattern during listening (solid lines) and resting state (dashed lines) for left AC, right AC, left inferior frontal gyrus (IFG), and right precentral gyrus (PrCG).
- Figure 3.
Simulation of phase locking expected as a result of signal leakage from a bilateral auditory source (outline shown in black). A, Simulated stimulus-driven phase locking was maximal over auditory cortices, spreading toward adjacent brain regions. Phase-locking magnitude decreased from the delta to the beta band; the color bar is adjusted to the maximum (max) phase-locking value in each frequency band. B, Compared with the original data, simulated phase locking was significantly reduced over frontal and anterior temporal regions, whereas phase locking to parietal cortex was relatively enhanced (two-tailed paired t test at p < 0.05, FDR corrected).
- Figure 4.
Relationship between stimulus-driven phase synchronization during listening to continuous speech and musical training: Spearman correlation (one-tailed) showed a positive association between the duration of individual musical training and the magnitude of alpha-band phase locking between auditory cortex seed time courses and various brain regions in frontal and temporal cortices, and along the midline (at p < 0.05, FDR correction). Brain regions for which stimulus-driven interregional phase synchronization was positively associated with musical training included the superior (STG), middle (MTG) and inferior temporal gyri (ITG); the insula (INS); the orbitofrontal (OFC) and medial orbitofrontal (mOFC) cortices; the inferior (IFG) and middle frontal (MFG) gyri; the precentral (PrCG) gyrus; the angular gyrus (AnG); the precuneus (PCUN); and the anterior cingulate cortex (ACC).
