1. ^*Department of Neurology, Section of Bioimaging Science, Yale University School of Medicine, New Haven, Connecticut, U.S.A.
2. Department of Neurobiology, Section of Bioimaging Science, Yale University School of Medicine, New Haven, Connecticut, U.S.A.
3. ^†Magnetic Resonance Research Center, Section of Bioimaging Science, Yale University School of Medicine, New Haven, Connecticut, U.S.A.
4. ^‡Department Diagnostic Radiology and Biomedical Engineering, Section of Bioimaging Science, Yale University School of Medicine, New Haven, Connecticut, U.S.A.
5. ^§Department of Neurosurgery, Gulhane Medical School, Etlik-Ankara, Turkey

Correspondence: Hal Blumenfeld, Yale University School of Medicine, Department of Neurology, LLCI 1007, 333 Cedar Street, New Haven, CT 06520, U.S.A.; E-mail: hal.blumenfeld@yale.edu

Received 22 December 2003; Revised 6 April 2004; Accepted 13 April 2004.

Abstract

There is broad agreement that generalized tonic-clonic seizures (GTCS) and normal somatosensory stimulation are associated with increases in regional CBF. However, the data regarding CBF changes during absence seizures are controversial. Electrophysiologic studies in WAG/Rij rats, an established animal model of absence seizures, have shown spike-wave discharges (SWD) that are largest in the perioral somatosensory cortex while sparing the visual cortex. Recent functional magnetic resonance imaging (fMRI) studies in the same model have also shown localized increases in fMRI signals in the perioral somatosensory cortex during SWD. Because fMRI signals are only indirectly related to neuronal activity, the authors directly measured CBF and neuronal activity from specific microdomains of the WAG/Rij cortex using a specially designed probe combining laser-Doppler flowmetry and extra-cellular microelectrode recordings under fentanyl/haloperidol anesthesia. Using this approach, parallel increases in neuronal activity and CBF were observed during SWD in the whisker somatosensory (barrel) cortex, whereas the visual cortex showed no significant changes. For comparison, these measurements were repeated during somatosensory (whisker) stimulation, and bicuculline-induced GTCS in the same animals. Interestingly, whisker stimulation increased neuronal activity and CBF in the barrel cortex more than during SWD. During GTCS, much larger increases that included both the somatosensory and visual cortex were observed. Thus, SWD in this model produce parallel localized increases in neuronal activity and CBF with similar distribution to somatosensory stimulation, whereas GTCS produce larger and more widespread changes. The normal response to somatosensory stimulation appears to be poised between two abnormal responses produced by two physiologically different types of seizures.