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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.

Original publication

DOI

10.1523/JNEUROSCI.4281-13.2014

Type

Journal article

Journal

J Neurosci

Publication Date

02/04/2014

Volume

34

Pages

4920 - 4928

Keywords

fMRI, memory, plasticity, reorganization, temporal lobe epilepsy, Adolescent, Adult, Brain Mapping, Epilepsy, Temporal Lobe, Female, Hippocampus, Humans, Image Processing, Computer-Assisted, Male, Memory Disorders, Middle Aged, Nerve Net, Neuropsychological Tests, Oxygen, Rest, Statistics as Topic, Statistics, Nonparametric, Young Adult