title: Loss of resting-state posterior cingulate flexibility is associated with memory disturbance in left temporal lobe epilepsy.
abstract: The association between cognition and resting-state fMRI (rs-fMRI) has been the focus of many recent studies, most of which use stationary connectivity. The dynamics or flexibility of connectivity, however, may be seminal for understanding cognitive functioning. In temporal lobe epilepsy (TLE), stationary connectomic correlates of impaired memory have been reported mainly for the hippocampus and posterior cingulate cortex (PCC). We therefore investigate resting-state and task-based hippocampal and PCC flexibility in addition to stationary connectivity in left TLE (LTLE) patients. Sixteen LTLE patients were analyzed with respect to rs-fMRI and task-based fMRI (t-fMRI), and underwent clinical neuropsychological testing. Flexibility of connectivity was calculated using a sliding-window approach by determining the standard deviation of Fisher-transformed Pearson correlation coefficients over all windows. Stationary connectivity was also calculated. Disturbed memory was operationalized as having at least one memory subtest score equal to or below the 5th percentile compared to normative data. Lower PCC flexibility, particularly in the contralateral (i.e. right) hemisphere, was found in memory-disturbed LTLE patients, who had up to 22% less flexible connectivity. No significant group differences were found with respect to hippocampal flexibility, stationary connectivity during both rs-fMRI and t-fMRI, or flexibility during t-fMRI. Contralateral resting-state PCC flexibility was able to classify all but one patient with respect to their memory status (94% accuracy). Flexibility of the PCC during rest relates to memory functioning in LTLE patients. Loss of flexible connectivity to the rest of the brain originating from the PCC, particularly contralateral to the seizure focus, is able to discern memory disturbed patients from their preserved counterparts. This study indicates that the dynamics of resting-state connectivity are associated with cognitive status of LTLE patients, rather than stationary connectivity.
authors.affiliation: Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States of America; Department of Radiology, Harvard Medical School, Boston, MA, United States of America; Department of Anatomy and Neurosciences, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Linda
authors.initials: L
authors.lastname: Douw
authors.affiliation: Department of Psychiatry, Massachusetts General Hospital, Boston, MA, United States of America.
authors.forename: Catherine L
authors.initials: CL
authors.lastname: Leveroni
authors.affiliation: Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States of America; Department of Radiology, Harvard Medical School, Boston, MA, United States of America.
authors.forename: Naoaki
authors.initials: N
authors.lastname: Tanaka
authors.affiliation: Department of Psychiatry, Massachusetts General Hospital, Boston, MA, United States of America.
authors.forename: Britt C
authors.initials: BC
authors.lastname: Emerton
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Cole
authors.affiliation: Department of Neurology, Massachusetts General Hospital, Boston, MA, United States of America.
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Cole
authors.affiliation: Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States of America; Department of Neurology, Brigham and Women's Hospital, Boston, MA, United States of America; Institute of Sports Medicine, Faculty of Science, University of Paderborn, Paderborn, Germany.
authors.forename: Claus
authors.initials: C
authors.lastname: Reinsberger
authors.affiliation: Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States of America; Department of Radiology, Harvard Medical School, Boston, MA, United States of America.
authors.forename: Steven M
authors.initials: SM
authors.lastname: Stufflebeam
mesh_terms: D000328:Adult; D004833:Epilepsy, Temporal Lobe / Q000150:complications / Q000503:physiopathology* / Q000523:psychology; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006179:Gyrus Cinguli / Q000503:physiopathology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008568:Memory / Q000502:physiology*; D008569:Memory Disorders / Q000150:complications / Q000503:physiopathology* / Q000523:psychology; D008875:Middle Aged; D009483:Neuropsychological Tests; D013702:Temporal Lobe / Q000503:physiopathology*; D055815:Young Adult