FIG. 7.

Plot of the difference among mean group spectra. Top: Raw mean population spectra. Middle: Smoothed mean population spectra with Gaussian filter (σ = 2). Bottom: Blue denotes the subtraction of Old–Young, Green denotes the subtraction of Subacute–Young, and Purple denotes the subtraction of Subacute–Old. Rectangular boxes at the bottom represent series of statistical tests carried out between the population spectra for specific frequency bins, from 0.009 to 0.027 Hz (frequencies in the slow-5 range), and beyond from 0.027 to 0.045 Hz (some frequencies in the slow-4 range) in steps of ∼0.0015 Hz. Darkly colored boxes (blue, green, purple) denote statistical significance at p < 0.05, and lightly colored boxes (light green, pink) denote statistical significance trending toward 0.05 < p < 0.10, with p-values uncorrected for multiple comparisons. There is a significant reduction in amplitude in slow-5 range in Old versus Young, with even greater reductions in amplitude noted in Subacute versus Young, and in Subacute versus Old. There is a trend toward significance and a significant increase in amplitude in the slow-4 range in Subacute versus Young, and in Subacute versus Old with no significant difference in amplitude noted in the Old versus Young comparison. The change from reduction in amplitude to an increase in amplitude when comparing Subacute versus Young and Subacute versus Old occurs at ∼0.024 Hz (near 0.027 Hz, the border of slow-5 vs. slow-4 range).