Page 245 - MEGIN Book Of Abstracts - 2023

Hokkaido University, Sapporo, Hokkaido, Japan; Department Identification of nonlinear features in cortical and
of Pediatrics, Hokkaido University Hospital, Sapporo, Hok- subcortical signals of Parkinson's Disease patients
kaido, Japan via a novel efficient measure (2020)

ABSTRACT Studies on evoked responses in Parkinson's Özkurt, Tolga Esat; Akram, Harith; Zrinzo, Ludvic;
disease (PD) may be useful for elucidating the etiology Limousin, Patricia; Foltynie, Tom; Oswal, Ashwini; Litvak,
and quantitative evaluation of PD. However, in previ- Vladimir
ous studies, the association between evoked responses
and detailed motor symptoms or cognitive functions Wellcome Trust Centre for Neuroimaging, UCL Institute of
has not been clear. This study investigated the charac- Neurology, London, UK; Middle East Technical University,
teristics of the visual (VEF), auditory (AEF), and somato- Department of Health Informatics, Graduate School of
sensory (SEF) evoked magnetic fields in patients with Informatics, Ankara, Turkey. Electronic address: tolgaozkurt@
Parkinson's disease (PD), and the correlations between gmail.com; Department of Clinical and Movement Neurosci-
evoked fields and the patient's clinical characteristics, ences, UCL Institute of Neurology and The National Hospital
motor symptoms, and cognitive functions. Twenty for Neurology and Neurosurgery, Queen Square, London, UK;
patients with PD and 10 healthy controls (HCs) were Wellcome Trust Centre for Neuroimaging, UCL Institute of
recruited as participants. We recorded VEF, AEF, and SEF, Neurology, London, UK; Department of Clinical Neurology,
collected clinical characteristics, performed physical John Radcliffe Hospital, Oxford, UK
examinations, and administered 10 cognitive tests. We
investigated differences in the latencies of the evoked ABSTRACT This study offers a novel and efficient mea-
fields between patients with PD and HCs. We also sure based on a higher order version of autocorrelative
evaluated the correlation of the latencies with motor signal memory that can identify nonlinearities in a
symptoms and cognitive functioning. There were sig- single time series. The suggested method was applied
nificant differences between the two groups in 6 of the to simultaneously recorded subthalamic nucleus (STN)
cognitive tests, all of which suggested mild cognitive local field potentials (LFP) and magnetoencephalog-
impairment in patients with PD. The latencies of the raphy (MEG) from fourteen Parkinson's Disease (PD)
VEF N75m, P100m, N145m, AEF P50m, P100m, and SEF patients who underwent surgery for deep brain stimu-
P60m components were greater in the patients with lation. Recordings were obtained during rest for both
PD than in the HCs. The latencies mainly correlated OFF and ON dopaminergic medication states. We ana-
with medication and motor symptoms, less so with lyzed the bilateral LFP channels that had the maximum
cognitive tests, with some elements of the correlations beta power in the OFF state and the cortical sources
remaining significant after Bonferroni correction. In that had the maximum coherence with the selected
conclusion, the latencies of the VEF, AEF, and SEF were LFP channels in the alpha band. Our findings revealed
greater in PD patients than in HCs and were mainly cor- the inherent nonlinearity in the PD data as subcorti-
related with medication and motor symptoms rather cal high beta (20-30 Hz) band and cortical alpha (8-12
than cognitive functioning. Findings from this study Hz) band activities. While the former was discernible
suggest that evoked fields may reflect basal ganglia without medication (p=0.015), the latter was induced
functioning and are candidates for assessing motor upon the dopaminergic medication (p<6.10[-4]). The
symptoms or the therapeutic effects of medication in degree of subthalamic nonlinearity was correlated with
patients with PD. contralateral tremor severity (r=0.45, p=0.02). Con-
versely, for the cortical signals nonlinearity was present
PloS one (2020), Vol. 15, No. 9 (32941428) (1 citation) for the ON medication state with a peak in the alpha
band and correlated with contralateral akinesia and
rigidity (r=0.46, p=0.02). This correlation appeared to
be independent from that of alpha power and the two
measures combined explained 34 % of the variance in

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