Figure 5.

Example of CBV increases and decreases measured using fMRI during electrically stimulated partial and secondarily generalized limbic seizures. A, During partial limbic seizures, CBV signal increases are observed in the hippocampus, thalamus, and septal nuclei, whereas decreases are seen in the orbitofrontal, anterior cingulate, and retrosplenial cortices. The arrow signifies hippocampal electrode artifact. B, During secondarily generalized limbic seizures, CBV increases are observed in the hippocampus, thalamus, and septal region, as well as in widespread cortical regions, including the orbitofrontal, cingulate, and primary somatosensory cortices. Few CBV decreases are seen. CBV changes during both seizure types closely mirror BOLD signal changes (Fig. 4). t-Maps are shown for the first 30 s of seizure activity (10 consecutive fMRI images acquired every 3 s) versus 30 s baseline, and are superimposed on high-resolution anatomical images. Slices are shown from anterior to posterior, with approximate coordinates relative to bregma (Paxinos and Watson, 1998). Color bars indicate t values for increases (warm colors) and decreases (cold colors). Note that although intravenous paramagnetic contrast results in decreased signal with increased CBV, color-labeled changes have been inverted for clarity so that warm colors indicate CBV increases. The display threshold is t = 2. Cg1, Anterior cingulate cortex; HC, hippocampus; OFC, orbitofrontal cortex; RSC, retrosplenial/posterior cingulate cortex; Septum, septal nuclei; S1, primary somatosensory cortex; Thal, thalamus.