How does structure inform the function of the nucleus accumbens in the context of chronic pain?
Poster No:
1574
Submission Type:
Abstract Submission
Authors:
Paul Bautin1, Marc-Antoine Fortier1, Monica Sean1, Graham Little1, Pascal Tétreault1
Institutions:
1Université de Sherbrooke, Sherbrooke, Quebec
First Author:
Co-Author(s):
Introduction:
Chronic pain (CP) is a pervasive condition with increasing implications for public health, affecting approximately 1 in 5 people globally. Recent human neuroimaging studies, complemented by behavioral and animal investigations, have begun to elucidate the role of the brain corticolimbic system in chronic pain across various clinical populations. Notably, abnormalities in the nucleus accumbens (NAc) structure and function have consistently been reported [1, 2]. However, due to the challenges it presents, the NAc white matter connectivity has rarely been investigated in the context of CP. This study employs diffusion MRI to explore the link between structure and function of the NAc in the context of CP.
Methods:
As presented in figure 1, we evaluate and compare the NAc structural and functional projections in both chronic low back pain (CLBP) participants (n=27) and healthy controls (n=25) at 3 time points (0, 2 and 4 months) with fully automated pipelines. Structural connectomes were reconstructed using Tractoflow [3] and Connectflow, BOLD images were processed using fMRIprep [4] and RapidTide [5] and seed based functional connectivity was performed with Nilearn. The NAc projections to the cortex were first reconstructed using an atlas free approach to generate an average heatmap of the regions where NAc projected the most across subjects (figure 1A). Then in an attempt to benchmark the link between structure and function projections of the NAc projections, structural and functional connectivity surface projections were correlated and compared between groups (control and CLBP) – significance was measured with neuromaps [6] spatial null spin tests (figure 1D).
Results:
Figure 2) presents the results of the comparison of structural NAc projections using communication models with functional NAc projections on the cortical surface using the Schaefer 200 atlas. Different structural connectivity metrics (streamline count, COMMIT2 [7] and fiber length) associated with communication models (inverse shortest path, inverse mean first passage time, search information) present different capacities to represent the functional connectivity. In the preliminary results, correlation between structure and function was on average across subjects highest using COMMIT2 associated with shortest path. That said, the results have a large inter-subject variability and unexpected negative correlations appear. As seen in figure 1B (bottom) in grey, a signal dropoff due to susceptibility artifacts in the orbitofrontal cortex could explain the negative correlations as these regions are also the most structurally connected to the NAc. Figure 1A) presents the cortex surface streamline count heatmap measured on 1 subject reconstructed with PFT tracking and connectome spatial smoothing (CSS) [8] to show the cortical regions most structurally connected to the NAc. The nucleus accumbens projections fall reliably in the mPFC regions which is aligned with prior results showing the segmentation of the accumbofrontal tract [9]. Figure 1C, presents the results of the investigation to determine if the streamline count is dependent on the cortex geometry. Absolute value of the gyral curvature map was significantly correlated to streamline count for this subject (aligned with the known tractography gyral bias).
Conclusions:
The aim of the project is to investigate if the functional connectivity differences, described in the CP literature, could be attributed to underlying structural white matter connectivity. Whilst investigating the link between structure and function of specific ROIs is promising, linking tractography reconstructions to fMRI bold images remains challenging. Therefore, we plan to further validate these results by: i) using age/sex matched subjects from the the human connectome project (HCP) dataset [10]; ii) investigating potential biases of high resolution connectomes; iii) and exploring the definition of the mPFC ROI to individualize segmentation of the accumbofrontal tract.
Modeling and Analysis Methods:
Connectivity (eg. functional, effective, structural) 1
Diffusion MRI Modeling and Analysis
fMRI Connectivity and Network Modeling
Neuroanatomy, Physiology, Metabolism and Neurotransmission:
White Matter Anatomy, Fiber Pathways and Connectivity
Perception, Attention and Motor Behavior:
Perception: Pain and Visceral 2
Keywords:
FUNCTIONAL MRI
Limbic Systems
MRI
Pain
White Matter
WHITE MATTER IMAGING - DTI, HARDI, DSI, ETC
1|2Indicates the priority used for review
Provide references using author date format
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