DOI: 10.5061/dryad.280gb5mwz
title: Data from: Diurnal variation of brain activity in the human suprachiasmatic nucleus

description: The suprachiasmatic nucleus (SCN) is the central clock for circadian
 rhythms. Animal studies have revealed daily rhythms in the neuronal
 activity in the SCN. However, the circadian activity of the human SCN has
 remained elusive. In this study, to reveal the diurnal variation of the
 SCN activity in humans, the SCN was localized, and its activity was
 investigated using perfusion imaging. We scanned each participant four
 times a day, every six hours, and higher activity was observed at noon
 while lower activity was recorded in the early morning. The SCN activity
 was then measured every thirty minutes for six hours from midnight to dawn
 and showed a decreasing trend and was comparable with the rodent SCN
 activity after switching off the lights. These results suggest that the
 diurnal variation of the human SCN follows the zeitgeber cycles of mammals
 and is modulated by physical lights rather than the local time.
description: In this study, two experiments were conducted, wherein the first
 investigated the whole cycle of the diurnal activity of the SCN in humans.
 Participants were scanned four times within 24 hours (18:00, 24:00, 6:00,
 and 12:00 local time). In the second experiment, we investigated the human
 SCN activity in more detail during the night. Participants stayed in the
 scanner throughout the night, except for brief unavoidable interruptions,
 and were scanned every 30 min from 24:00 to 6:00. Perfusion images of
 pseudo-continuous arterial spin labeling (pCASL) in each participant were
 acquired. Twenty-seven and twenty right-handed participants without
 neurological/psychiatric illness or sleep disorders participated in the
 first and second experiments. Whole brain perfusion
 images were acquired using pCASL imaging with multiband-EPI (number of
 measurements = 90, repetition time = 4.0 s, echo time = 25.2 ms, partial
 Fourier = 6/8, flip angle = 90°, labeling duration = 1.5 s, post labeling
 delay = 1.64 s, slice thickness = 1.82 mm, distance factor = 10%, number
 of slices = 72, slice acquisition order = ascending, in-plane field of
 view = 212 × 212 mm<sup>2</sup>, matrix size = 106 × 106,
 multiband acceleration factor = 6). Two M0 images, which were included in
 the pCASL sequence, were also acquired after the label/control images
 series. The perfusion images were corrected for motion and distortion. The
 cerebral blood flow (CBF) images in the standard MNI space were calculated
 using a command line interface of oxford_asl included in FSL software.
 Spatially minimal smoothing was applied to the CBF images (FWHM = 2.0 mm),
 and the absolute CBF values [ml/100mg/min] of the regions of interest were
 extracted and sent for statistical analyses.
description: # Diurnal variation of brain activity in the human suprachiasmatic nucleus
 **Oka et al. (2024) Journal of Neuroscience** This study investigated the
 diurnal variation of brain activity in the suprachiasmatic nucleus (SCN)
 in humans. In the first experiment, the SCN activity was measured four
 times a day, every six hours, using perfusion imaging. In the second
 experiment, the SCN activity was measured every thirty minutes for six
 hours from midnight to dawn, from 24:00 to 6:00. The results showed that
 the diurnal variation of the human SCN activity follows the zeitgeber
 cycles of mammals. Nifti files showing the regions of interest (ROIs) of
 the hypothalamus and hypothalamic nucleus and the boundary probability map
 in the hypothalamus are provided. CSV files showing the data of brain
 activity in the SCN, MPO, SO, and PVH, which were used to make the line
 and bar graphs, are provided. ## The ROIs of the hypothalamus and
 hypothalamic nuclei and the boundary probability map The areal boundary
 mapping technique was used to generate the probabilistic boundary map,
 where the probability value represented how likely the voxel is a boundary
 of a functional area. We identified the human SCN above the optic chiasm
 and lateral to the third ventricle. The surrounding nuclei (medial
 preoptic nucleus: MPO, supraoptic nucleus: SO, paraventricular nucleus:
 PVH) were also localized. These nuclei were ROIs in this study. The file
 of ROIs: ROIs.zip The file of boundary probability map: bpmap.nii The
 probability map can be overlaid on the truncated structure image
 (ravg152T1.nii). ## The data of brain activity in the SCN, MPO, SO, and
 PVH The brain activity in the hypothalamus nuclei (ROIs) was extracted for
 further analysis. In the first experiment, the activity in the SCN was
 highest at 12:00 in the daytime and lowest at 6:00 in the morning. The
 file of the data of brain activity in the SCN in the first experiment:
 Fig3A.csv and Fig3B.csv The file of the data of brain activity in the MPO
 in the first experiment: Fig3-1A.csv The file of the data of brain
 activity in the SO in the first experiment: Fig3-1B.csv The file of the
 data of brain activity in the PVH in the first experiment: Fig3-1C.csv In
 the second experiment, the SCN activity gradually decreased from midnight
 to dawn. The file of the data of brain activity in the SCN in the second
 experiment: Fig4A.csv The file of the data of brain activity in the MPO in
 the second experiment: Fig4-1A.csv The file of the data of brain activity
 in the SO in the second experiment: Fig4-1B.csv The file of the data of
 brain activity in the PVH in the second experiment: Fig4-1C.csv NaN
 indicate the lacking data due to technical issues. ## Softwares The Nifti
 files can be opened using SPM, MRIcron, and FSL.