Enhancement of Resting-State fcMRI Networks by Prior Sensory Stimulation

Abstract

It is important to consider the effect of a previous experimental condition when analyzing resting-state functional connectivity magnetic resonance imaging (fcMRI) data. In this work, a simple sensory stimulation functional MRI (fMRI) experiment was conducted between two resting-state fcMRI acquisitions in anesthetized rats using a high-field small-animal MR scanner. Previous human studies have reported fcMRI network alteration by prior task/stimulus utilizing similar experimental paradigms. An anesthetized rat preparation was used to test whether brain regions with higher level functions are involved in post-task/stimulus fcMRI network alteration. We demonstrate significant fcMRI enhancement poststimulation in the sensory cortical, limbic, and insular brain regions in rats. These brain regions have been previously implicated in vigilance and anesthetic arousal networks. We tested their experimental paradigm in several inbred strains of rats with known phenotypic differences in anesthetic susceptibility and cerebral vascular function. Brown Norway (BN), Dahl Salt-Sensitive (SS), and consomic SSBN13 strains were tested. We have previously shown significant differences in blood oxygen level-dependent fMRI activity and fcMRI networks across these strains. Here we report statistically significant interstrain differences in regional fcMRI poststimulation enhancement. In the SS strain, poststimulation enhancement occurred in posterior sensory and limbic cortical brain regions. In the BN strain, poststimulation enhancement appeared in anterior cingulate and subcortical limbic brain regions. These results imply that a prior condition has a significant impact on fcMRI networks that depend on intersubject difference in genetics and physiology.

Mapping of the brain hemodynamic responses to sensorimotor stimulation in a rodent model: A BOLD fMRI study

“…Stimulation parameters were adapted from N. Van Camp et al [23] and included current pulses with a 1.7 mA amplitude, 10 ms duration and 8 Hz frequency applied in a block-design. In a separate experiment outside the magnet, 1.7 mA-current intensity was found to be below the threshold of nociception (S1 Table), where no significant changes in cardiac frequency and pulse oximetry were observed while applying stimulation under our conditions of anesthesia [12,35,36]. As reported by N. Van Camp et al [23] and observed in the present study, this set of electrical stimulation parameters resulted both in somatosensory and proprioceptive inputs owing to visible movement in the hindpaw's digits (S1 Video).…”

Evaluation of nuisance removal for functional MRI of rodent brain

“…In this study, task fMRI was conducted before resting fMRI. A previous study suggested that sensory stimulation prior to resting fMRI could enhance functional connectivity between the sensory, insular and limbic cortices (Li et al, 2014). Therefore the observed connectivity may have been modulated by the somatosensory stimulation applied.…”

Evaluation of drug effects on cerebral blood flow and glucose uptake in un-anesthetized and un-stimulated rats

“…To avoid this problem, there have been some reports of preclinical imaging using pharmacological MRI, fluorine-18-fluorodeoxyglucose ( 18 F-FDG)-PET and 99m Tc-hexamethylpropylene amine oxime (HMPAO)-SPECT in conscious animals 11 – 14 . However, in most of these studies, the animals are exposed to the stress of physical restraint, which has a huge effect on the brain function 15 – 17 .…”