Article Figures & Data
Figures
- Figure 1.
Data acquisition. a, b, MRS voxel placement for visual (a) and posterior cingulate (b) cortices on a T1-weighted structural image and probabilistic partial volume voxel maps following tissue segmentation for a representative participant. Corresponding tissue proportions of gray matter (GM), white matter (WM), and CSF are shown. c, d, Average spectra across all subjects for visual (c) and posterior cingulate (d) cortices; the number of subjects comprising each average spectrum is shown, and gray shaded regions indicate SD. Note the nonuniform baseline in d, which resulted from the incomplete removal of the water peak (which was suppressed in the visual but not in the posterior cingulate cortex data) in the difference spectra; importantly, this nonuniformity was modeled and removed during neurometabolite quantification.
- Figure 2.
Static analysis. Distribution of gray matter (GM), white matter (WM), and CSF voxel tissue proportions, and neurometabolite (GABA+, Glx, tNAA) concentrations across participants for visual and posterior cingulate cortices. Neurometabolite concentrations are tissue corrected and expressed as a ratio to tCr. Triangles indicate distribution means.
- Figure 3.
Low-resolution temporal dynamics of neurometabolites in visual and posterior cingulate cortices. a, Top, Individual traces showing change in GABA+, Glx, and tNAA (all referenced to tCr) measured from an MRS voxel targeting visual cortex. Bottom, Same as top, but averaged across participants. b, Same as a, but from a voxel targeting posterior cingulate cortex. Shaded regions indicate SEM, and horizontal colored bars at the top and bottom of a indicate (cluster-corrected) periods of significant difference from zero. Note, the scale of change was smaller for tNAA:tCr than the other two neurometabolites, so it is closely overlaid with the dashed “zero” line.
- Figure 4.
High-resolution temporal dynamics of neurometabolites in visual and posterior cingulate cortices. a, b, Changes in GABA+ and Glx concentrations, proportional to the average, measured from voxels targeting visual (a) and posterior cingulate (b) cortices. Semitransparent lines indicate raw concentration estimates; for illustrational purposes, opaque lines indicate data smoothed using a window of eight time points. c, d, Cross-correlations between GABA+ and Glx concentrations measured from voxels targeting visual (c) and posterior cingulate (d) cortices. Lag values indicate the duration between when the GABA+ measurements were acquired and the Glx measurements were acquired. Correlations at negative lags indicate that GABA+ concentration predicts Glx concentration, and correlations at positive lags indicate that Glx predicts GABA+ concentration. Vertical lines indicate 95% confidence intervals; cluster-corrected correlations that are significantly different from zero are highlighted in green. All values are referenced to tCr.
- Figure 5.
Controls for high-resolution analyses. a, Cross-correlations between GABA+ and Glx, referenced to tNAA, measured from voxels targeting visual cortex. Vertical lines indicate 95% confidence intervals; cluster-corrected correlations that are significantly different from zero are highlighted in green, correlations at negative lags indicate that GABA+ predicts Glx, and correlations at positive lags indicate that Glx predicts GABA+. b, Comparison between results from the sliding window method used in the low-temporal resolution analysis (dashed lines) and sliding window applied to results from the high-resolution analysis (solid lines) for visual (top) and posterior cingulate (bottom) cortices.
Tables
Location FWHM (Hz) Frequency drift (ppm SD) Fit error (%) GABA+ Glx tNAA tCr GABA+ Glx tNAA tCr VC 24.9 ± 1.7 17.8 ± 0.4 8.4 ± 0.9 8.5 ± 0.7 0.0088 ± 0.0044 7.6 ± 2.1 1.3 ± 0.3 3.3 ± 0.3 3.6 ± 0.2 PCC 20.5 ± 1.7 16.8 ± 0.7 8.2 ± 0.8 7.6 ± 0.7 0.0065 ± 0.0061 6.9 ± 1.7 2.1 ± 1.5 3.1 ± 1.3 4.5 ± 0.5 Values indicate across-subject averages ± SD. PCC, Posterior cingulate cortex; VC, visual cortex.
- Table 2
Correlation coefficients between neurometabolites measured from visual and posterior cingulate cortices
Location GABA+and Glx GABA+and tNAA Glxand tNAA ΔGABA+and ΔGlx ΔGABA+and ΔtNAA ΔGlxand ΔtNAA VC −0.16 0.33* 0.33* 0.06 0.10 −0.17 PCC 0.25*** 0.50*** 0.17* 0.03 −0.18* 0.04 Correlation coefficients are Pearson linear partial coefficients after controlling for the common reference neurometabolite tCr. All neurometabolites are referenced to tCr and are tissue corrected. PCC, Posterior cingulate cortex; VC, visual cortex.
*p < 0.05; ***p < 0.001.
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