The neural basis of autobiographical memory deficits in transient epileptic amnesia

Transient epileptic amnesia (TEA) is a recently recognized form of temporal lobe epilepsy which is often associated with persistent interictal impairment of autobiographical memory. We used fMRI to investigate the neural basis of this deficit. Eleven patients with TEA, who had no significant deficits on standard tests of anterograde memory, and 17 age and IQ matched healthy controls retrieved memories from across the lifespan. Both groups engaged the autobiographical memory network, but activation in patients was less extensive than in controls. Direct comparison revealed hypoactivation of regions in the right hemisphere. Specifically, patients showed reduced activation of the posterior parahippocampal gyrus (pPHG), especially for mid-life and recent memories, with decreased engagement of the right temporoparietal junction and the cerebellum. In addition, we found reduced effective connectivity in patients between the right pPHG and the right middle temporal gyrus. Our results are consistent with other evidence that TEA is a syndrome of medial temporal lobe epilepsy and indicate that it affects the function and connectivity of regions within the autobiographical memory network.