Functional networks in the anesthetized rat brain revealed by independent component analysis of resting-state FMRI.
The rodent brain is organized into functional networks that can be studied through examination of synchronized low-frequency spontaneous fluctuations (LFFs) of the functional magnetic resonance imaging -blood-oxygen-level-dependent (BOLD) signal. In this study, resting networks of LFFs were estimated from the whole-brain BOLD signals using independent component analysis (ICA). ICA provides a hypothesis-free technique for determining the functional connectivity map that does not require a priori selection of a seed region. Twenty Long-Evans rats were anesthetized with isoflurane (1%, n = 10) or ketamine/xylazine (50/6 mg . kg(-1) . h(-1) ip, n = 10) and imaged for 5-10 min in a 9.4 T MR scanner without experimental stimulation or task requirement. Independent, synchronous LFFs of BOLD signals were found to exist in clustered, bilaterally symmetric regions of both cortical and subcortical structures, including primary and secondary somatosensory cortices, motor cortices, visual cortices, posterior and anterior cingulate cortices, hippocampi, caudate-putamen, and thalamic and hypothalamic nuclei. The somatosensory and motor cortices typically demonstrated both symmetric and asymmetric components with unique frequency profiles. Similar independent network components were found under isoflurane and ketamine/xylazine anesthesia. The report demonstrates, for the first time, 12 independent resting networks that are bilaterally synchronous in different cortical and subcortical areas of the rat brain.
Hutchison
R Matthew
RM
Department of Physiology and Pharmacology, University of Western Ontario, Medical Sciences Bldg. Rm. 236, London, Ontario, N6A 5C1, Canada.
Mirsattari
Seyed M
SM
Jones
Craig K
CK
Gati
Joseph S
JS
Leung
L Stan
LS
D000758:Anesthesia; D000818:Animals; D001921:Brain / Q000098:blood supply*; D001931:Brain Mapping; D007839:Functional Laterality; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging; D008297:Male; D010100:Oxygen / Q000097:blood; D025341:Principal Component Analysis; D051381:Rats; D020318:Rats, Long-Evans; D012146:Rest / Q000502:physiology*
D010100:Oxygen