White matter functional connectivity.

<p>Functional connectivity of the white matter seed in the two lower frequency bands (<0.1 Hz and 0.1–0.25 Hz) in the low-TR (top) and high-TR (bottom) datasets. The colors represent z-transformed correlation coefficients.</p

Fractional amplitudes of fluctuations.

<p>Fractional amplitudes of fluctuations in four different frequency bands in the low-TR dataset (a), in two different frequency bands in the high-TR dataset (b), and in the two lower frequency bands combined in the low-TR dataset (c). All color bars are set to the same window width (0.15).</p

ROI locations.

<p>Location of ROI center voxels in MNI coordinates.</p

ROI power spectra.

<p>Power spectra of the center voxel time courses of selected ROIs for the low-TR dataset (left) and the high-TR dataset (right). Vertical red lines indicate 0.1 Hz and 0.25 Hz, dotted grey horizontal lines mark the minimum power in each plot. (mPFC stands for medial prefrontal cortex, PCC for posterior cingulate cortex).</p

White matter functional connectivity.

<p>Functional connectivity of the white matter seed in the two lower frequency bands (<0.1 Hz and 0.1–0.25 Hz) in the low-TR (top) and high-TR (bottom) datasets. The colors represent z-transformed correlation coefficients.</p

ROI power ratios.

<p>Ratio between peak low frequency power and minimum power to the right of the peak for various ROIs. (PCC stands for posterior cingulate cortex, mPFC for medial prefrontal cortex).</p

Fractional amplitudes of fluctuations.

<p>Fractional amplitudes of fluctuations in four different frequency bands in the low-TR dataset (a), in two different frequency bands in the high-TR dataset (b), and in the two lower frequency bands combined in the low-TR dataset (c). All color bars are set to the same window width (0.15).</p

Mean spectral power proportions.

<p>Mean spectral power proportions in the indicated frequency bands within grey matter, white matter and ventricle masks in the low-TR (top) and high-TR (bottom) datasets. Voxelwise spectra were calculated and averaged across all voxels within the respective masks. Row-wise maxima are highlighted in the table. In the low-TR dataset, low-frequency fluctuations up to 0.25 Hz are most pronounced in grey matter, while medium and high frequency oscillations have highest amplitude in white matter and in the ventricles, respectively. In the high-TR dataset, fluctuations below 0.1 Hz are present predominantly in grey matter, and fluctuations between 0.1 and 0.25 Hz in white matter and ventricles.</p

Functional connectivity of cortical regions in higher frequency bands.

<p>Each row shows the connectivity of the seed given on the left for the data band-passed to the frequency range noted there. The colors represent z-transformed correlation coefficients.</p

Platelet Serotonin Transporter Function Predicts Default-Mode Network Activity

<div><p>Background</p><p>The serotonin transporter (5-HTT) is abundantly expressed in humans by the serotonin transporter gene <i>SLC6A4</i> and removes serotonin (5-HT) from extracellular space. A blood-brain relationship between platelet and synaptosomal 5-HT reuptake has been suggested, but it is unknown today, if platelet 5-HT uptake can predict neural activation of human brain networks that are known to be under serotonergic influence.</p><p>Methods</p><p>A functional magnetic resonance study was performed in 48 healthy subjects and maximal 5-HT uptake velocity (V_max) was assessed in blood platelets. We used a mixed-effects multilevel analysis technique (MEMA) to test for linear relationships between whole-brain, blood-oxygen-level dependent (BOLD) activity and platelet V_max.</p><p>Results</p><p>The present study demonstrates that increases in platelet V_max significantly predict default-mode network (DMN) suppression in healthy subjects independent of genetic variation within <i>SLC6A4</i>. Furthermore, functional connectivity analyses indicate that platelet V_max is related to global DMN activation and not intrinsic DMN connectivity.</p><p>Conclusion</p><p>This study provides evidence that platelet V_max predicts global DMN activation changes in healthy subjects. Given previous reports on platelet-synaptosomal V_max coupling, results further suggest an important role of neuronal 5-HT reuptake in DMN regulation.</p></div