Functional Connectivity In Rat Brain Research Articles

Lesion to Hippocampus Changes Resting State Functional Connectivity in Rat Brain Reflecting Structural Damage

Lesion to Hippocampus Changes Resting State Functional Connectivity in Rat Brain Reflecting Structural Damage

Functional connectivity in rat brain at 200 μm resolution.

The somatosensory functional magnetic resonance imaging (fMRI) response to electrical stimulation of the middle phalange of the second digit of four rats at a spatial resolution of 200 μm cubic at 9.4 T is reported. At high threshold (p<0.002), activated voxels encompass a penetrating vein that passes across the gray matter. These voxels lie mostly in three contiguous slices perpendicular to the pial surface. This activation is assigned to the representation in the forepaw barrel subfield (FBS) of a single cortical column of this phalange. In addition, the activation of the indusium griseum (IG) is visualized robustly. Voxels revealed by fMRI were used to observe functional connectivity to other voxels of the sensorimotor cortex using fcMRI. Results of this experiment were analyzed as a function of decreasing threshold, which exhibited spreading connectivity that revealed S2, M1/M2, and contralateral S1. Noting that every cubic millimeter of tissue contains 125 voxels, connectivity patterns are complex. It is hypothesized that they reflect connections within gray matter by association fibers. S2 and IG revealed connectivities with many voxels across the sensorimotor cortex. These regions also showed subregional variation of connectivity. A 1-cm-diameter surface coil with a local low-noise RF amplifier was used in these studies. The usual region of sensitivity (ROS) of such a coil is 1 cm diameter by 0.5 cm depth. Significant connectivity was observed between time courses of voxels that were within the ROS and voxels that were outside, which extends the volume of tissue that can be observed by the methods of this article.

Lesion to Hippocampus Changes Resting State Functional Connectivity in Rat Brain Reflecting Structural Damage

Temporal lobe epilepsy (TLE) is associated with pathologic changes in hippocampal physiology and morphology. Resting state functional connectivity (rsFC) is known to reflect structural connectivity, but also allows exploring interactions between remote regions. We will try to disambiguate the effect of the epileptogenic lesion from a normal surgery. The purpose of this study is to trace changes in rsFC using BOLD-­fMRI after inducing a unilateral left hippocampal lesion in rats. Male Sprague Dawley rats (n=19, 250-275 g) were anesthetized (induction 5% isoflurane, s.c. bolus medetomidine (0.05 mg/kg), followed by continuous s.c. infusion medetomidine (0.1 mg/kg/h)) and were inserted into the MR scanner (7T Bruker Pharmascan, Ettlingen, Germany). Anatomical (voxel size 0.156 x 0.156 x 0.156 mm3) and fMRI (voxel size 0.375 x 0.375 x 1.1 mm3) data were acquired. Afterwards, kainic acid (0,4 µg/0,1 µl) was injected into the right hippocampus under isoflurane anesthesia (5% induction, 2% sustenance). This resulted in lesions in ipsilateral hippocampus, thalamus and cortex. Four days and 3 months after the injection the animals were scanned again using the protocol described above. Seventeen ROIs were segmented in each rat using anatomical MRI: cingulate, retrosplenial and septum; and sensorimotor, auditory visual cortexes, striatum, hippocampus, thalamus, hypothalamus, colliculus and amygdala/enthorinal/piriform (AEP) cortex bilaterally. Mean time series were extracted from realigned, detrended and filtered (bandpass, 0.01~0.1HZ) rs-fMRI data in the ROIs before and after the lesion was induced. ROI based functional connectivity and voxel wise functional connectivity density was compared in each of these rats in pre- and two post-lesion scans (the first one after 4 days, the second one after 3 months). The rsFC analysis found generally reduced functional connectivity between different areas, ipsilateral but also contralateral to the lesion. Functional connectivity density revealed voxel-wise reorganization in rat brain where less connected voxels disappear 4 days post-lesion and a number of more dense connected voxels decreases 3 months post-lesion. We conclude that functional connectivity measures in resting state fMRI are a valuable tool to map brain dynamics and its reliability when we act on some specific nodes via targeted lesions.

How Lesions Change Resting State Functional Connectivity in Rat Brain

Frontiers Events is a rapidly growing calendar management system dedicated to the scheduling of academic events. This includes announcements and invitations, participant listings and search functionality, abstract handling and publication, related events and post-event exchanges. Whether an organizer or participant, make your event a Frontiers Event!