Functional connectivity of hippocampal networks in temporal lobe epilepsy

Epilepsia. 2014 Jan;55(1):137-45. doi: 10.1111/epi.12476. Epub 2013 Dec 6.


Objective: Temporal lobe epilepsy (TLE) affects brain areas beyond the temporal lobes due to connections of the hippocampi and other temporal lobe structures. Using functional connectivity magnetic resonance imaging (MRI), we determined the changes of hippocampal networks in TLE to assess for a more complete distribution of abnormality.

Methods: Regions of interest (ROIs) were defined in the right and left hippocampi in three groups of participants: left TLE (n = 13), right TLE (n = 11), and healthy controls (n = 16). Brain regions functionally connected to these ROIs were identified by correlating resting-state low-frequency functional MRI (fMRI) blood oxygenation level-dependent (BOLD) signal fluctuations. The grouped results were compared using independent sample t-test.

Results: TLE was associated with increased hippocampal connectivity involving several key areas of the limbic network (temporal lobe, insula, thalamus), frontal lobes, angular gyrus, basal ganglia, brainstem, and cerebellum, along with reduced connectivity involving areas of the sensorimotor cortex (visual, somatosensory, auditory, primary motor) and the default mode network (precuneus). Left TLE had more marked connectivity changes than right TLE.

Significance: The observed connectivity changes in TLE indicate dysfunctional networks that underlie widespread brain involvement in TLE. There are identifiable differences in the connectivity of the hippocampi between left and right TLE.

Keywords: Epilepsy psychopathology; Epileptic networks; Functional connectivity; Hippocampal networks; Temporal lobe epilepsy; fMRI.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Epilepsy, Temporal Lobe / physiopathology*
  • Female
  • Functional Laterality / physiology
  • Functional Neuroimaging
  • Hippocampus / physiopathology*
  • Humans
  • Magnetic Resonance Imaging
  • Male
  • Middle Aged
  • Nerve Net / physiopathology*
  • Young Adult