Related Experiment Videos
Temporal and extratemporal BOLD responses to temporal lobe interictal spikes
Eliane Kobayashi1, Andrew P Bagshaw, Christian-George Bénar
1Montreal Neurological Institute and Hospital, McGill University, 3801 University Street, Montreal, Quebec, Canada H3A 2B4. eliane.kobayashi@mail.mcgill.ca
Epilepsia
|February 28, 2006
Summary
Simultaneous EEG-fMRI revealed blood oxygenation level-dependent (BOLD) responses to temporal lobe (TL) spikes in 83% of epilepsy patients. These responses, including activation and deactivation, often extended beyond the spiking temporal lobe, indicating widespread neuronal network involvement.
Area of Science:
- Neuroscience
- Epileptology
- Medical Imaging
Background:
- Simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) offer a powerful method to investigate brain activity during epileptic events.
- Temporal lobe epilepsy (TLE) is characterized by interictal spikes, which are brief, abnormal electrical discharges originating in the temporal lobe.
Purpose of the Study:
- To investigate the blood oxygenation level-dependent (BOLD) responses associated with temporal lobe (TL) spikes using simultaneous EEG-fMRI.
- To characterize the spatial extent and nature (activation/deactivation) of BOLD responses to TL spikes.
Main Methods:
- 35 patients diagnosed with TLE and exhibiting active TL spiking on routine EEG were included.
- Continuous 2-hour EEG-fMRI sessions were recorded, with identified spikes serving as events for fMRI analysis.
- Significant positive (activation) and negative (deactivation) BOLD responses were determined for each spike type.
Main Results:
- 27 patients (83%) showed BOLD responses to TL spikes during scanning.
- Responses included both activations and deactivations in 14 studies, activations only in 12, and deactivations only in 3.
- Neocortical TL activation was common, often involving the contralateral TL and extratemporal regions, while deactivations were frequently extratemporal.
Conclusions:
- BOLD responses to TL spikes are frequent (83%), predominantly occurring in the spiking temporal lobe.
- These responses manifest as both activation and deactivation, frequently involving contralateral homologous cortex and extratemporal regions.
- The findings suggest that TL epileptic spikes can influence neuronal activity at distant sites via synaptic connections, highlighting network involvement in epilepsy.