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Sensitivity of early and late neuromagnetic auditory activity to degenerative processes in MCI and Alzheimer disease

Magnetoencephalography (MEG) measurements with excellent millisecond time resolution offer a valuable noninvasive approach for assessing the pathological changes in neuronal activation pattern. In this study we used spatio-temporal source localization methods to identify the activated cortical networks evoked by simple auditory tone stimuli within an add-ball paradigm and a battery of neuropsychological tests in an effort to discriminate between patients diagnosed as potential MCI and AD compared to the age-matched controls. MEG brain cortical activation patterns were examined in 10 elderly controls (>64 years) and 10 elderly diagnosed as MCI or AD patients. MEG data were recorded with the CTF 275 channel whole-head system in a magnetically shielded room at the MIND Research Network in Albuquerque, New Mexico. Multiple dipole source localization and temporal dynamics estimation were conducted during both, early and late activity (30-200ms and 30-750ms time intervals) using MRVIEW Calibrated Start Spatio Temporal (CSST) algorithm [1].The findings revealed a main effect of pathological alternation in early neuroactivity: frontal current dipoles identified in healthy controls, generally lacking in AD patients for both stimuli. Also prominent differences were noted in dynamic patterns of early and late STG activation for AD/MCI subjects: distinct increases in the amplitude of the 40ms peak ; increases in amplitude and latency of M100 and M150 peaks with alerted late M300 activity [2]. Findings of the present study indicate that relatively easy task in auditory modality demonstrating sensitivity of early and late neuronal activity to degenerative processes and emphasized that early sensory regions not spared as previously thought. Lack of a frontal activity and prominent differences noted in the dynamic patterns of early and late STG activation is likely to be of a clinical value in discriminating between the subject categories. REFERENCE : [1] Ranken DM et al: MEG/EEG forward and inverse modeling using MRIVIEW ; Proceeding of Biomag 2002 785-787. [2] Supek, Selma ; Josef Golubic, Sanja ; Bryant, Jennifer ; Donahue, Chris ; Montañ o, Rebecca ; Adair, John ; Hart, Blaine ; Knoefel, Janice ; Stephen, Julia ; Aine, Cheryl: Neuromagnetic auditory activity reflects differences between normal aging, MCI and AD subjects: An oddball study ; Biomagnetism:Interdisciplinary Research and Exploration (Proceedings of Biomag 2008), R. Kakigi, K. Yokosawa, S. Kuriki (Eds), Hokkaido University Press, Sapporo, 2008, pp 171-173.

Magnetoencephalography (MEG); MCI patients; AD patients

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