Atypical Functional Connectivity Subspaces Reflect Declarative Retrieval Impairments
in Temporal Lobe Epilepsy
Abstract number :
2.189
Submission category :
5. Neuro Imaging / 5B. Functional Imaging
Year :
2022
Submission ID :
2204367
Source :
www.aesnet.org
Presentation date :
12/4/2022 12:00:00 PM
Published date :
Nov 22, 2022, 05:24 AM
Authors :
Cabalo Donna Gift, RN, PhD Trainee – McGill University, Multimodal Imaging and Connectome Analysis Laboratory, McConnell Brain Imaging Centre, Montreal Neurological Institute and Hospital, McGill University,; Andrea Bernasconi, MD – Montreal Neurological Institute and Hospital; Neda Bernasconi, MD – Montreal Neurological Institute and Hospital; Boris Bernhardt, PhD – McGill University; Lorenzo Caciagli, PostDoc – University of Pennsylvania; Elizabeth Jefferies, PhD – University of York; Raul Rodriguez-Cruces, PostDoc – McGill University; Jessica Royer, PhD Candidate – McGill University; Jonathan Smallwood, PhD – Queens University; Shahin Tavakol, PhD Candidate – McGill University; Ke Xie, PhD Student – McGill University; Reinder Vos de Wael, PhD – McGill University
Rationale:: Temporal lobe epilepsy (TLE), the most common drug-resistant epilepsy in adults, is known to adversely affect declarative memory processes. Converging cognitive neuroscience research in healthy and diseased populations has led to largely divide declarative memory processes into episodic and semantic components.1 However, whether networks subserving such function in TLE may undergo shared or selective reorganization remains incompletely understood. In this study, we probe the organization of semantic and episodic memory networks in people with TLE relative to healthy controls, capitalizing on advanced connectome analyses of task-based functional MRI data._x000D_
Methods: We studied 18 TLE (left/right=14/4, age=36±12 years; F/M: 9/9) as well as 52 controls (age=34±8 years, F/M: 26/26). All participants underwent an episodic and semantic retrieval task-fMRI in a 3T Siemens Prisma MRI (Figure 1A). Following surface-based fMRI processing with micapipe,2 we generated task-based functional connectomes. Low-dimensional connectome spaces were derived using non-linear dimensionality reduction implemented in Brainspace3 and aligned to a normative gradient derived from resting-state fMRI data4 (Figure 1B). Gradient scores were z-normalized relative to controls, and data in TLE patients were sorted relative to the ipsilateral hemisphere. We then assessed group differences with surface-based multivariate analysis, controlling for age and sex, and corrected for multiple comparisons using the FDR procedure. _x000D_
Results: In both memory states, the first two eigenvectors explained the largest variance in the data and followed a similar sensory-to-transmodal and visual-to-somatomotor pattern, as in prior work.4 In TLE, we found a reduced sensory-transmodal differentiation for both memory tasks. Between-group differences were more marked and significant after multiple comparisons for episodic memory state (Figure 1C). Atypical gradient alterations were primarily localized in the bilateral posterior cingulate cortex, inferior frontal cortex, and angular gyrus, superior, and inferior temporal cortex. _x000D_
Conclusions: Our data-driven analysis of task fMRI data reveals an atypical organization of declarative memory systems in TLE, which mostly encompasses areas of the default mode network, and appears more marked for episodic memory than for semantic tasks. These findings provide novel insights into the state-dependent reorganization of memory systems in TLE. _x000D_
_x000D_
References:_x000D_
1. Irish et al., 2020.Curr Opin Behav Sci,32,43-49_x000D_
2. Cruces et al., 2022. bioRxiv 2022.01.31.478189_x000D_
3. Vos de Wael et al., 2020. Commun Biol 3,103_x000D_
4. Margulies et al., 2016. PNAS, 201608282
Funding: Canadian Institute of Health Research- Foundation Grant Program (CIHR FDN 154298)
Neuro Imaging