Abstracts

RATIONALE: Previous studies demonstrate that absence seizures are generated by enhanced burst firing in both cortical and thalamic neurons. However, FDG-PET imaging studies during human absence seizures have provided contradictory results about whether or not cerebral activity increases during absence seizures. We have used blood oxygenation level-dependent (BOLD) fMRI in a rodent model of absence seizures to map cortical and subcortical activity during seizures, and we seek to relate these signals to neuronal firing recorded electrophysiologically.
METHODS: WAG/Rij rats under fentanyl/haloperidol anesthesia exhibit spontaneous spike-wave seizures. BOLD fMRI measurements were performed in a 7T horizontal bore spectrometer and superimposed on high resolution anatomical images in the coronal plane. EEG was recorded simultaneously using carbon filament electrodes. Single unit recordings were performed separately under stereotactic guidance.
RESULTS: Comparison of ictal and interictal epochs revealed a symmetrical increase of the BOLD fMRI signal in both cortical and subcortical regions during spike-wave discharges. Increased neuronal firing during spike-wave seizures was also seen in these regions with electrophysiological recordings.
CONCLUSIONS: Spike-wave seizures are accompanied by an increase in neuronal firing and in fMRI BOLD signals in both cortical and subcortical structures, likely representing an increase in cerebral blood flow (CBF) during these seizures. This study represents the first reported use of BOLD fMRI to map ongoing seizure activity in a human or animal model. Further studies will quantify the relationship between neuronal firing, CBF and metabolism in this model.
[Supported by: NIH NS02060 and the Patterson Trust.]