Structures involved at the time of temporal lobe spikes revealed by interindividual group analysis of EEG/fMRI data

Epilepsia. 2009 Dec;50(12):2549-56. doi: 10.1111/j.1528-1167.2009.02180.x. Epub 2009 Jun 22.


Purpose: We measured metabolic changes associated with temporal lobe (TL) spikes using combined electroencephalography (EEG) and functional magnetic resonance imaging (fMRI). We selected 18 patients with temporal lobe epilepsy (TLE) who underwent a 2-h simultaneous EEG-fMRI and had unilateral or bilateral independent TL spikes for interindividual group analysis, in order to identify consistent blood oxygenation level dependent (BOLD) responses to TL spikes.

Methods: EEG was postprocessed and spikes were visually identified. fMRI data were preprocessed with motion correction, spatial smoothing, and removal of low frequency drifts. Spike timings were used as events for fMRI statistical analysis. Four hemodynamic response functions were used to account for variability in the BOLD response.

Results: Group analysis revealed common areas of BOLD activations and deactivations. The hemodynamic response function (HRF) peaking 3 s after the spike showed activation involving ipsilaterally the mesial temporal structures (presumably the hippocampus), putamen/globus pallidus, inferior insula, and superior temporal gyrus. The HRF peaking at 5 s showed activations involving ipsi- and contralaterally the superior temporal gyrus and inferior insula. Both HRFs showed bilateral posterior cingulate deactivations.

Discussion: We disclosed involvement of a network of activated areas during unilateral TL spikes, including ipsilateral mesial temporal structures, basal ganglia, and bilateral neocortical temporal regions. Despite the low temporal resolution of fMRI we demonstrated that contralateral temporal involvement occurred later than ipsilateral activation. This contralateral change took place in the absence of visible EEG changes. The posterior cingulate deactivation may reflect the interconnections between this region and other limbic structures. It may also partially correspond to a suspension of the default mode network, as previously described for TL spikes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Brain Mapping
  • Cerebral Cortex / physiopathology
  • Cluster Analysis
  • Electroencephalography / methods
  • Electroencephalography / statistics & numerical data*
  • Epilepsy, Temporal Lobe / diagnosis*
  • Epilepsy, Temporal Lobe / physiopathology*
  • Functional Laterality / physiology
  • Gyrus Cinguli / blood supply
  • Gyrus Cinguli / physiopathology
  • Hemodynamics / physiology
  • Hippocampus / blood supply
  • Hippocampus / physiopathology
  • Humans
  • Image Processing, Computer-Assisted
  • Magnetic Resonance Imaging / methods
  • Magnetic Resonance Imaging / statistics & numerical data*
  • Neocortex / physiopathology
  • Neural Pathways / physiopathology
  • Oxygen / blood
  • Temporal Lobe / blood supply
  • Temporal Lobe / physiopathology*


  • Oxygen