Objective: The study objective was to assess the changes in amplitude of low frequency fluctuations (ALFF) in patients with Parkinson´s disease (PD) as compared to healthy controls (HC). The differences in ALFF between PD and patients with mild Alzheimer disease (AD) were also evaluated.

Background: The neurons, although they are not involved in a specific task at the moment, show permanent activity, so called resting state activity. This activity can be detectable as low frequency fluctuations on various frequencies that are generated by neuronal oscillators with specific physiological functions [1]. Changes in ALFF have been observed in many diseases, including PD and AD.

Method: We performed resting state functional magnetic resonance imaging (rs-fMRI) in 134 subjects – 38 PD, 40 AD and 56 HC. The diagnosis was based on published clinical and research criteria and all subjects underwent detailed clinical and cognitive examination.  Imaging was performed using 3T MRI scanner. Acquired BOLD rs-fMRI data were preprocessed and ALFF was computed in 3 power bands: slow-5 (0.010 ÷ 0.027 Hz); slow-4 (0.027 ÷ 0.073 Hz); and slow-3 (0.073 ÷ 0.198 Hz) according to [2]. The data were corrected for gray matter atrophy. ANOVA with factor of group and covariates of age and gender was used for statistical analysis.

Results: The differences in given ALFF band in PD as compared to HC were present in following regions: 1) ALFF slow-5. Increased ALFF in bilateral middle occipital and middle temporal gyrus (MOG/MTG). 2) ALFF slow-4. Decreased ALFF in the right supplementary motor area (SMA) and putamen. Increased ALFF in the right MOG. 3) ALFF slow-3. Increased ALFF in bilateral MOG. Considering the AD group, the ALFF slow-5 increase in occipital-temporal regions and ALFF slow-4 decrease in the right SMA in PD were significant also as compared to AD, but were not present in AD as compared to HC. Therefore, it seems that these ALFF changes are specific for PD.

Conclusion: Changes in neuronal activity in PD as revealed by ALFF approach were present in regions involved in motor control (SMA, putamen) and visual processing (MOG/MTG), the main domains affected in PD. These changes were dependent on frequency band; analyzing oscillatory changes in various frequencies can thus be helpful in detecting specific PD-related alterations in neuronal activity and distinguishing between other pathologies.

References: 1. Buzsaki G, Draguhn A. Neuronal oscillations in cortical networks. Science 2004;304(5679):1926-1929. 2. Han Y, Wang JH, Zhao ZL, et al. Frequency-dependent changes in the amplitude of low-frequency fluctuations in amnestic mild cognitive impairment: A resting-state fMRI study. Neuroimage 2011;55(1):287-295.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/frequency-dependent-abnormalities-of-intrinsic-brain-activity-in-parkinsons-disease/