Analyzing the Effect of Weak External Transcranial Magnetic Stimulation on the Primary Dominant Frequencies of Alzheimer Patients Brain by Using MEG Recordings

Backround and Objectives: Alternative, non-invasive, and non-pharmaceutical options are gaining place in the battle of Alzheimer’s Disease treatment control. Lately, the magnetic stimulation of the brain is the most prevalent technique with encouraging results. The aim of this study is to establish any possible change on the Primary Dominant Frequencies (PDF) (range 2–7 Hz) of the affected brain regions in Alzheimer Disease (AD) patients after applying extremely weak Transcranial Magnetic Stimulation. Materials and Methods: For this purpose, all AD patients were scanned with the use of MagnetoEncephaloGraphy (MEG) recordings through a whole-head 122–channel MEG system. Results: Our results exerted statistically significant PDF changes due to weak TMS accompanied by rabid attenuation of clinical symptoms. Conclusion: Thus, this is the first time that a positive therapeutic effect is being demonstrated even at pico-Tesla range magnetic fields in a small clinical group of studies for AD.

Slowing of Hippocampal Activity Correlates with Cognitive Decline in Early Onset Alzheimer's Disease. An MEG Study with Virtual Electrodes

Pathology in Alzheimer's disease (AD) starts in the entorhinal cortex and hippocampus. Because of their deep location, activity from these areas is difficult to record with conventional electro- or magnetoencephalography (EEG/MEG). The purpose of this study was to explore hippocampal activity in AD patients and healthy controls using "virtual MEG electrodes". We used resting-state MEG recordings from 27 early onset AD patients [age 60.6 ± 5.4, 12 females, mini-mental state examination (MMSE) range: 19-28] and 26 cognitively healthy age- and gender-matched controls (age 61.8 ± 5.5, 14 females). Activity was reconstructed using beamformer-based virtual electrodes for 78 cortical regions and 6 hippocampal regions. Group differences in peak frequency and relative power in six frequency bands were identified using permutation testing. For the patients, spearman correlations between the MMSE scores and peak frequency or relative power were calculated. Moreover, receiver operator characteristic curves were plotted to estimate the diagnostic accuracy. We found a lower hippocampal peak frequency in AD compared to controls, which, in the patients, correlated positively with MMSE [r(25) = 0.61; p < 0.01] whereas hippocampal relative theta power correlated negatively with MMSE [r(25) = -0.54; p < 0.01]. Cortical peak frequency was also lower in AD in association areas. Furthermore, cortical peak frequency correlated positively with MMSE [r(25) = 0.43; p < 0.05]. In line with this finding, relative theta power was higher in AD across the cortex, and relative alpha and beta power was lower in more circumscribed areas. The average cortical relative theta power was the best discriminator between AD and controls (sensitivity 82%; specificity 81%). Using beamformer-based virtual electrodes, we were able to detect hippocampal activity in AD. In AD, this hippocampal activity is slowed, and correlates better with cognition than the (slowed) activity in cortical areas. On the other hand, the average cortical relative power in the theta band was shown to be the best diagnostic discriminator. We postulate that this novel approach using virtual electrodes can be used in future research to quantify functional interactions between the hippocampi and cortical areas.

MEG as a Medical Diagnostic Tool in the Greek Population

Magnetoencephalography (MEG) is the recording of the magnetic field produced by the flowing of ions in the brain. This article reports our experience in the application of MEG in patients and healthy volunteers in the Greek population. We provide a brief description of our research work. The MEG data were recorded in a magnetically shielded room with a whole-head 122 channel or an one-channel biomagnetometer. Our results lead us to believe that the MEG is an important research field which is evolving quickly with a number of interesting findings with respect to normal and abnormal functions of the human brain. It could provide clinical practice with an easy to perform non invasive method, which could be adjunct to conventional methods for the evaluation of brain disorders.

Magnetoencephalography in neuropsychiatry: ready for application?

PURPOSE OF REVIEW

Magnetoencephalography (MEG) has been available for over 30 years, but the past 10 years have seen serious investigation of its use as a clinical tool. It is therefore an opportune time to review how MEG is able to contribute to neuropsychiatric research and practice.

RECENT FINDINGS

We limit this review to the areas of dementia, schizophrenia, depression and autism. MEG can achieve correct classification of individuals with mild cognitive impairment versus Alzheimer's disease, may identify a marker of early disease in schizophrenia, can distinguish bipolar from major depressive disorder, and has been used to study cognitive and other deficits in autism. It provides a valuable tool to study cognitive dysfunction.

SUMMARY

The most important aspect of MEG is the ability to record neural activity with millisecond precision, allowing coherence analysis of neural data to examine how brain areas are synchronized. Such synchrony is thought to underlie cognitive processes. As cognitive dysfunction is a common marker of neuropsychiatric disorders, MEG is emerging as an important investigatory tool in neuropsychiatry. It may also be useful clinically for early or differential diagnosis of some neuropsychiatric disorders, or for the prediction of drug effects, but more research is necessary before this becomes a clinical reality.