Rivastigmine effects on EEG spectra and three-dimensional LORETA functional imaging in Alzheimer’s disease
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The objective of the study is to investigate the electrocortical and the global cognitive effects of 3 months rivastigmine medication in a group of mild to moderate Alzheimer’s disease patients.
Materials and methods
Multichannel EEG and cognitive performances measured with the Mini Mental State Examination in a group of 16 patients with mild to moderate Alzheimer’s Disease were collected before and 3 months after the onset of rivastigmine medication.
Spectral analysis of the EEG data showed a significant power decrease in the delta and theta frequency bands during rivastigmine medication, i.e., a shift of the power spectrum towards ‘normalization’. Three-dimensional low resolution electromagnetic tomography (LORETA) functional imaging localized rivastigmine effects in a network that includes left fronto-parietal regions, posterior cingulate cortex, bilateral parahippocampal regions, and the hippocampus. Moreover, a correlation analysis between differences in the cognitive performances during the two recordings and LORETA-computed intracortical activity showed, in the alpha1 frequency band, better cognitive performance with increased cortical activity in the left insula.
The results point to a ‘normalization’ of the EEG power spectrum due to medication, and the intracortical localization of these effects showed an increase of cortical activity in frontal, parietal, and temporal regions that are well-known to be affected in Alzheimer’s disease. The topographic convergence of the present results with the memory network proposed by Vincent et al. (J. Neurophysiol. 96:3517–3531, 2006) leads to the speculation that in our group of patients, rivastigmine specifically activates brain regions that are involved in memory functions, notably a key symptom in this degenerative disease.
KeywordsAlzheimer’s disease Rivastigmine Cholinesterase inhibitors EEG Spectral analysis Source localization LORETA functional imaging
The authors thank Mr. M. Manske and Mr. P. Lirgg for technical collaboration. The authors declare that this work was in part supported by NOVARTIS foundation (Grant no. CENA713IN01). PLF declares that in 2005 has received a 5% time compensation from NOVARTIS foundation, the manufacturer of rivastigmine, besides the 60% time income received from his primary employer.
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