Scopolamine effects on functional brain connectivity: a pharmacological model of Alzheimer's disease.

Scopolamine administration may be considered as a psychopharmacological model of Alzheimer's disease (AD). Here, we studied a group of healthy elderly under scopolamine to test whether it elicits similar changes in brain connectivity as those observed in AD, thereby verifying a possible model of AD impairment. We did it by testing healthy elderly subjects in two experimental conditions: glycopyrrolate (placebo) and scopolamine administration. We then analyzed magnetoencephalographic (MEG) data corresponding to both conditions in resting-state with eyes closed. This analysis was performed in source space by combining a nonlinear frequency band-specific measure of functional connectivity (phase locking value, PLV) with network analysis methods. Under scopolamine, functional connectivity between several brain areas was significantly reduced as compared to placebo, in most frequency bands analyzed. Besides, regarding the two complex network indices studied (clustering and shortest path length), clustering significantly decreased in the alpha band while shortest path length significantly increased also in alpha band both after scopolamine administration. Overall our findings indicate that both PLV and graph analysis are suitable tools to measure brain connectivity changes induced by scopolamine, which causes alterations in brain connectivity apparently similar to those reported in AD.

Right parietal activation during delusional state in episodic interictal psychosis of epilepsy: a report of two cases.

Magnetoencephalography (MEG) was used to image brain activity associated with delusions in episodic interictal psychosis of epilepsy. Two female patients aged 65 and 68 with temporal lobe epilepsy were studied during and after a delusional state. Topographic images of the excess kurtosis (g2), the statistical index of spikelike activity, were obtained from unaveraged MEG recordings using an analysis called "synthetic aperture magnetometry" (SAM). For both patients, MEG waveforms and excess kurtosis images revealed spiky activity in the right inferior parietal region during the delusional state. A second MEG measurement after delusions were resolved with antipsychotic therapy revealed no excess kurtosis in the right parietal area. Likewise, the sharp waves on MEG recordings disappeared as well. Our results suggest association of the right inferior parietal cortex, including the supramarginal gyrus, with the delusional state of episodic interictal psychosis of epilepsy.