Figure 1 | Scientific Reports

Figure 1

From: States and traits of neural irregularity in the age-varying human brain

Figure 1

Trial structure, evoked responses, and entropy across age. (A) Trial structure and average responses. Two 650 Hz pure tones were presented separated by a fixed ISI of 900 ms and followed by the response screen (top panel). The middle panel shows the event-related potential (ERP) at electrode Cz (baseline −0.5 to 0 s) for trials during which the first (S1, purple) versus the second tone (S2, orange) was perceived as higher in pitch. Topographies correspond to the N1 time-windows after S1 and S2 (grey areas). Colors show average microvolt values. Entropy (WPE) is computed by taking small snippets of voltage data, transforming them to rank sequences and computing the entropy of their frequency of occurrence. This procedure is illustrated in the small inset boxes that connect ERP and WPE representations. In the bottom panel, average WPE time courses of both conditions are shown (baselined relative to −1.5 to −1 s). Colors on topographies correspond to average WPE. (B) Pre-stimulus entropy (WPE) across age. Trial-wise averages of entropy in a pre-stimulus time window (−0.4 to −0.1 s, electrode Cz; grey shaded area) are shown as clouds of dots per subject (upper panel, warmer colors code higher age), black bars indicate average entropy across trials. Average entropy increased with age (upper panel, inset, electrode Cz), colors on topography correspond to average correlation coefficients r. The standard deviation of entropy values across trials decreased with age (lower panel). (C), Same as B but for entropy data from whole trials (i.e., −2 to 2 s). *p < 0.05; *** p < 0.001.