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102 Episodic memory functional connectivity in temporal lobe epilepsy
  1. Sarah Buck1,2,
  2. Lorenzo Caciagli1,2,
  3. Sjoerd Vos1,2,
  4. John S Duncan1,2,
  5. Meneka Kaur Sidhu1,2
  1. 1National Hospital for Neurology and Neurosurgery
  2. 2Chalfont Centre for Epilepsy

Abstract

Purpose Functional magnetic resonance imaging (fMRI) has previously demonstrated functional reorganisation of memory representations in people with Temporal Lobe Epilepsy (TLE). Less is known about the changes in functional connectivity within the memory network.

Methods We studied 77 patients with unilateral TLE (37 left) and 27 controls. All participants performed a memory encoding fMRI paradigm of faces and words. Psychophysiological Interaction (PPI) analysis was conducted to examine brain regions that were time-correlated with activations in the left and right hippocampi.

Results During word encoding, left TLE patients showed reduced connectivity from the left hippocampus to the prefrontal cortex, compared to controls. During face encoding, right TLE patients showed reduced connectivity from the right hippocampus to the ipsilateral lateral temporal lobe and bilateral fusiform gyri. However, left and right TLE patients showed greater connectivity to posterior hippocampi bilaterally during word and face encoding.

Conclusion TLE is increasingly recognised as a network disease and correspondingly we demonstrate widespread memory network reorganisation in people with epilepsy. The reorganisation of eloquent functions has important implications in the planning of epilepsy surgery and a network approach may be helpful in the prediction of memory outcome after epilepsy surgery.

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