Aberrant functional connectivity in dissociable hippocampal networks is associated with deficits in memory.
In the healthy human brain, evidence for dissociable memory networks along the anterior-posterior axis of the hippocampus suggests that this structure may not function as a unitary entity. Failure to consider these functional divisions may explain diverging results among studies of memory adaptation in disease. Using task-based and resting functional MRI, we show that chronic seizures disrupting the anterior medial temporal lobe (MTL) preserve anterior and posterior hippocampal-cortical dissociations, but alter signaling between these and other key brain regions. During performance of a memory encoding task, we found reduced neural activity in human patients with unilateral temporal lobe epilepsy relative to age-matched healthy controls, but no upregulation of fMRI signal in unaffected hippocampal subregions. Instead, patients showed aberrant resting fMRI connectivity within anterior and posterior hippocampal-cortical networks, which was associated with memory decline, distinguishing memory-intact from memory-impaired patients. Our results highlight a critical role for intact hippocampo-cortical functional communication in memory and provide evidence that chronic injury-induced functional reorganization in the diseased MTL is behavioral inefficient.
FMRIB Centre, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom, Oxford Epilepsy Research Group, Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom, Oxford Centre for Human Brain Activity, University of Oxford, Warneford Hospital, Oxford OX3 7JX, United Kingdom, and Russell Cairns Unit and Departments of Neurosurgery and Neurology, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom.
Natalie L
NL
Voets
Giovanna
G
Zamboni
Mark G
MG
Stokes
Katherine
K
Carpenter
Richard
R
Stacey
Jane E
JE
Adcock
D000293:Adolescent; D000328:Adult; D001931:Brain Mapping; D004833:Epilepsy, Temporal Lobe / Q000150:complications*; D005260:Female; D006624:Hippocampus / Q000098:blood supply / Q000503:physiopathology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008569:Memory Disorders / Q000209:etiology* / Q000473:pathology*; D008875:Middle Aged; D009415:Nerve Net / Q000098:blood supply / Q000503:physiopathology*; D009483:Neuropsychological Tests; D010100:Oxygen / Q000097:blood; D012146:Rest; D013223:Statistics as Topic; D018709:Statistics, Nonparametric; D055815:Young Adult
D010100:Oxygen
fMRI; memory; plasticity; reorganization; temporal lobe epilepsy