(a–e) Left: Individual hypothalamic centres derived from functional connectivity presented as mixture model thresholded probability maps. Centre: Normalised spectral BOLD signal changes (n = 22, paired t-test, p≤0.05). Right: Functional connectivity (fc) changes to the hypothalamus and lower brainstem (thresholded statistical maps, n = 22, paired t-test, p≤0.05 family-wise error corrected). Warm/cold colours indicate an increase/decrease in fc during LBNP. A hypothalamic system of five regions showed both spectral BOLD and fc changes during LBNP. These cardiovascular centres included (a) the anterior part of the right lateral hypothalamic region (LH)/supraoptic nucleus (SON) showing reduced HF power (t = −2.2, p≤0.05) and increased fc with the dorsal lower brainstem including the nucleus of the solitary tract (NTS); (b–c) the bilateral tuberal part of the LH/SON showing reduced HF (tright = −2.93 pright ≤0.01, tleft = −2.28 pleft ≤0.05) and LF power (tright = −2.24 pright ≤0.05) and increased within-nucleus fc (both sides) as well as reduced fc with the arcuate nucleus (Arc, left side only); (d) the tuberal part of the paraventricular nucleus (PVN) showing increased HF power (t = 2.69, p≤0.05) and reduced within-nucleus fc as well as increased fc with the right lateral lower brainstem including nucleus ambiguus (Amb) and rostral ventrolateral medulla (RVLM); and (e) the Arc showing reduced LF power (t = −2.05, p≤0.05) and increased fc with the dorsal and midline lower brainstem including the NTS, dorsal motor nucleus of the vagal nerve (DMN) and nucleus raphe obscurus (ROb). (f) T1-weighted study template showing slice localisation in the hypothalamus and brainstem. Spectral data in a-e are presented as mean with 95% confidence interval. All coordinates are in Montreal Neurological Institute (MNI) standard space. Atlas slices modified after Mai et al., 2016 and Paxinos et al., 2012 (with permission from the authors). *p≤0.05, **p≤0.01. Abbreviations: 3V, third ventricle; 4V, fourth ventricle; DPGi, Dorsal paragigantocellular nucleus; DMN, dorsal motor nucleus; fc, functional connectivity; fx, fornix; Hyp, hypoglossal nucleus; IO, inferior olivary nucleus; IRt, intermediate reticular nucleus; MdRt, medullary reticular nucleus; opt, optic tract; PCRt, parvicellular reticular nucleus; PH, posterior hypothalamic area; Sp5, spinal trigeminal nucleus.
© 2016 Academic Press. All rights reserved. Atlas slices modified from Mai et al., 2016. They are not covered by the CC-BY 4.0 licence and further reproduction of this panel would need permission from the copyright holder.
© 2012 Academic Press. All rights reserved. Atlas slices modified from Paxinos et al., 2012. They are not covered by the CC-BY 4.0 licence and further reproduction of this panel would need permission from the copyright holder.