Biology subjects

Oghabian, M. A.

Publications and source records attributed to Oghabian, M. A..

3 recordsLinked to original sources

bioRxiv2020

Evaluation and Optimization of Motion Correction in Spinal Cord fMRI Preprocessing

Motion correction is an essential step in the preprocessing of functional magnetic resonance imaging (fMRI) data, improving the temporal signal to noise ratio (tSNR) and removing unwanted variance. Because of the characteristics of the spinal cord (non-rigidity, surrounded by moving organs), motion correction becomes especially challenging. We compared the efficiency of different motion correction protocols and suggest a preferred method for spinal cord fMRI data. Here we acquired gradient-echo echo-planar-imaging axial lumbar spinal cord fMRI data during painful mechanical stimulation of the left lower extremity of 15 healthy volunteers on a 3T scanner. We compared multiple motion correction techniques: 2D and 3D FLIRT realignment with and without slice-wise regulation, SliceCorr (implemented in the Spinal Cord Toolbox) and proposed a method 3D FLIRT in addition to Slice Regulation (SLiceReg) along the spinal cord. TSNR, image entropy, DVARS, image Sum of Absolute Differences and number of activated voxels in the spinal cord from GLM analysis to evaluate the performance of multiple motion correction procedures. The tSNR and DVARS 3D FLIRT + SLiceReg were significantly improved over other realignment methods (p<0.001). In comparison, tSNR=14.20{+/-}0.02 and DVARS=165.77{+/-}1.54 were higher than other methods. Additionally, the number of activated voxels of the statistical map in our suggested method was higher than the other realignment methods (p<0.05). Our results illustrated the proposed motion correction algorithm that integrated 3D motion correction and 2D slicewise regularization along spinal cord curvature could improve subject-level processing outputs by reducing the effects of motions. Our proposed protocols can improve subject-level analysis, especially in lumbar region that suffers from involuntary motions and signal loss due to susceptibility effect more than other spinal cord regions.

neuroscience↗

bioRxiv2019

How Top-Down and Bottom-Up Regulation in Fronto-Amygdalar Network Changes over Time during Drug Cue-Exposure: An fMRI Study among Abstinent Heroin User

Top-down regulation is one of the major neural cores in drug-craving management and relapse prevention. The dynamic temporal behavior of top-down regulation between the dorso-lateral and ventro-medial prefrontal cortices (DLPFC and VMPFC) and amygdala during drug cue-exposure has not been studied yet. Fifteen abstinent participants with heroin use disorder were scanned using drug cue-induced craving fMRI task. Using Dynamic Causal Modelling (DCM), the winning model showed a significant reciprocal connection between the VMPFC and DLPFC while there was a one-way effect of the VMPFC on the amygdala. There is also a top-down modulation by DLPFC on the VMPFC-Amygdala connection. Craving contrast input only modulated amygdala directly. Using sliding-window for temporal evaluation, craving input to amygdala increased over time, simultaneously, DLPFC top-down modulatory effect on VMPFC-amygdala connection decreased. Temporal changes in the network connectivity during cue exposure with enhancement in craving input to amygdala and reduction in top-down modulatory effects of DLPFC, could provide us with new insights towards the dynamic nature of the cue-reactivity and failure to control its motivational consequences. Dynamic response of top-down regulatory networks during cue exposure can be considered as a new potential biomarker in the future addiction fMRI studies.

neuroscience↗

bioRxiv2016

fMRI Correlates of Reaction Time Prolongation during intentional False Responding; an inter-individual difference study

Reaction time (RT) is chiefly longer when people lie. However, the baseline speed in answering questions and the amount of RT prolongation during lying show considerable amount of inter-individual variability. In the current study, we exploited this fact to glean insights on the contribution of each lie-related brain region to hampering of response speeds when people try to be deceitful. In an event-related fMRI session, participants were interrogated by yes-no autobiographical questions and were instructed to intentionally provide false responses to a pre-selected subset of questions. Data from twenty healthy volunteers were analyzed. Baseline speed [RTtruth] and relative appended lie RT [(RTlie - RTtruth) / RTtruth] measures were calculated for each participant and were included in the group level analysis of [lie > truth] BOLD contrasts. Lying RTs were significantly longer than truth telling RTs. Lie-related increase in activity of right ventrolateral prefrontal cortex (VLPFC) and bilateral paracingulate cortex correlated with the baseline speed of participants, while the increase in activity of Left VLPFC, left lateral occipital cortex and bilateral anterior cingulate areas directly correlated with the amount of lying reaction time cost. Activity within bilateral posterior cingulate cortex and right insular cortex inversely correlated with lying RT-cost. Bilateral supplementary motor areas, internal capsule white matter and left angular gyrus showed lie-related increase in activity but did not correlate with either of behavioral measures. Provisional implications regarding the contribution of these regions to RT prolongation and their cognitive role in deceitful behavior are discussed.

neuroscience↗