Descamps, Benedicte

Fias, Wim

Marinazzo, Daniele

Raedt, Robrecht

Siugzdaite, Roma

Van Den Berge, Nathalie

van Mierlo, Pieter

Wu, G

English

Ghent University Academic Bibliography

increases as expected; also, the variance decreases for strongercorrelation coefficients. The behaviors of the correlation betweenstationary signals were similar to in vivo monkey data whenusing smaller window sizes, such as 45 s.For example, figure 1 shows the probability density functions(pdf) of the cross-correlations between two sub-regions of SI forfMRI data obtained from one monkey, along with the pdf of twostationary simulated signals with the same mean correlation, forwindow sizes 45 s and 180 s, respectively. For statistical com-parison, the Kolmogorov-Smirnov (K-S) test shows that corre-lations between functionally related regions 3a and 3b in themonkey data are distributed similarly to the correlations derivedfrom simulated stationary data at short window sizes (smaller ks-value indicates less difference), but depart substantially at largerwindow sizes. The correlations between functionally unrelatedregions 3a and control are distributed similarly to the stationarydata from the simulation at all window sizes (Fig 2).Conclusions: Sliding window estimates of variations in correla-tion between non-stationary signals may reveal dynamic changesbut also may be confounded by statistical variations.Whether thereare additional features within the real monkey fMRI data that arenot present in simulated stationary data remains unclear, but ex-ploration of additional statistical metrics is underway.P47B Lesion to left hippocampus changes functionalconnectivity according to changes in structureR. Siugzdaite1,3, B. Descamps2, N. Van Den Berge3,P. Van Mierlo3, G. Wu4, W. Fias5, R. Raedt6, D. Marinazzo11Data analysis department, Faculty of Psychology, GhentUniversity, Ghent, Belgium, 2Infinity, Ghent University, Ghent,Belgium, 3MEDISIP, Ghent University, Ghent, Belgium, 4KeyLaboratory for NeuroInformation of Ministry of Education,School of Life Science and Technology, University of ElectronicScience and Technology of China, Chengdu, China, 5Faculty ofPsychology, Ghent University, Ghent, Belgium, 6Laboratory forClinical and Experimental Neurophysiology, Neurobiology andNeuropsychology, Department of Neurology, Ghent UniversityHospital, Ghent, BelgiumBackground: Resting-state functional connectivity (rsFC) notonly reflects structural connectivity in default mode network(Greicius et al 2009), but also allows exploring interactions be-tween remote regions. For this, several recent fMRI studies bothin animals and in humans used it as a convenient and non-invasive tool to systematically investigate the connectional ar-chitecture of selected brain networks (Zhang et al 2010). Thepurpose of this study is to trace changes in rsFC after inducing aunilateral hippocampal lesion in rats.Methods: Male Sprague Dawley rats (n= 20, 250–275 g) wereanesthetized (induction 5% isoflurane, s.c. bolus medetomidine(0.05mg/kg), followed by continuous s.c. infusion medetomidine(0.1mg/kg/h)) and were inserted into the MR scanner (7T BrukerPharmascan, Ettlingen, Germany). Anatomical (voxel size 0.156·0.156· 0.156mm3) and resting state fMRI (voxel size 0.375·0.375· 1.1mm3) data were acquired. Afterwards, kainic acid(0,4lg/0,1ll) was injected into the right hippocampus underisoflurane anesthesia (5% induction, 2% sustenance). This re-sulted in lesions to ipsilateral or bilateral hippocampus, and othercortexes. Four days and three months after the injection animalswere scanned again using the protocol described above.Results: The rsFC analysis found generally reduced functionalconnectivity between different areas, ipsilateral but also contralat-eral to the lesion. It is worth to mention that the connectivity patternvaried across rats based on structural changes due to the lesion.Conclusions: We conclude that functional networks in restingstate are a valuable tool to map brain dynamics when we act onsome specific nodes via targeted lesions.P48B Phase-amplitude coupling indicates independenceof infraslow versus high frequency neural electrical activityregarding their relationship to resting state fMRI in ratsG.J. Thompson1, W.J. Pan1, J.C.W. Billings1, J.K. Grooms1,S. Shakil2, D. Jaeger3, S.D. Keilholz11Biomedical Engineering, Emory University and GeorgiaInstitute of Technology, Atlanta, GA, USA, 2Electrical andComputer Engineering, Georgia Institute of Technology,Atlanta, GA, USA, 3Biology, Emory University, Atlanta, GA, USABackground: Fluctuations in the resting state functional magneticresonance imaging (fMRI) signal have been linked to electricalpotential changes in the brain, both band-limited power of highfrequency activity (>1Hz) but also to local field potentials (LFPs)in infraslow (<1Hz) frequencies. One testable hypothesis for theneural basis of resting state fMRI is that power fluctuations inhigher frequency neural activity correspond to the phase of theinfraslow neural activity, and this relates directly to the infraslowchanges seen in resting state fMRI. To test this hypothesis, we usedan invasive LFP/fMRI rat model and quantified coupling betweeninfraslow phases and high frequency amplitudes.Methods: Data were recorded from 10 anesthetized Sprague-Dawley rats under a simultaneous infraslow LFP/fMRI protocol,and from 10 different rats under similar conditions except on thebench without fMRI scanning performed. The anesthesia usedwas either*2.0% isoflurane (iso, 8 rats in total) or subcutaneousdexmedetomidine infusion (dex, 11 rats in total) or both in series(1 rat). Infraslow (0–1Hz) phases from LFP and fMRI werecompared to amplitude changes in simultaneously recorded highfrequency (1–50Hz) LFP power. Correlation between fMRI andLFP was also calculated.Results: The only consistent phase-amplitude coupling was seenunder iso and was due to the neural suppression burst condition thatexisted (Figure 1). No consistent phase-amplitude coupling was seenunder dex. In addition, while both infraslow and high frequencypower from the LFP correlated with the fMRI, these correlationswere statistically independent, indicating that the high and lowfrequencies had independent relationships with resting state fMRI.A78 POSTER PRESENTATIONS

Lesion to left hippocampus changes functional connectivity according to changes in structure

https://biblio.ugent.be/publication/6935650/file/6935659.pdf

Lesion to left hippocampus changes functional connectivity according to changes in structure

Abstract

Similar works

Full text

Available Versions

Ghent University Academic Bibliography