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subcortical regions). By contrast, tremor improvement ABSTRACT An emerging perspective describes beta-
did not correlate with changes in functional connectiv- band (15-28 Hz) activity as consisting of short-lived
ity. Our results highlight the distributed effects of DBS high-amplitude events that only appear sustained in
on the resting-state brain and suggest that DBS-related conventional measures of trial-average power. This has
improvements in rigidity and bradykinesia, but not important implications for characterising abnormali-
tremor, may be mediated by an increase in alpha2 ties observed in beta-band activity in disorders like
and low-beta functional connectivity. Beyond the Parkinson's disease. Measuring parameters associated
local effects of DBS in and around the STN, functional with beta-event dynamics may yield more sensitive
connectivity changes in these frequency bands might measures, provide more selective diagnostic neural
therefore be considered as "pro-kinetic". markers, and provide greater mechanistic insight into
the breakdown of brain dynamics in this disease. Here,
Keywords: Deep brain stimulation, Magnetoencephalog- we used magnetoencephalography in eighteen Parkin-
raphy, Motor symptoms, Parkinson's disease, Resting-state son's disease participants off dopaminergic medication
and eighteen healthy control participants to investigate
NeuroImage. Clinical (2020), Vol. 26 (32120294) (7 beta-event dynamics during timed movement prepa-
citations) ration. We used the Hidden Markov Model to classify
event dynamics in a data-driven manner and derived
three parameters of beta events: (1) beta-state ampli-
Dissecting beta-state changes during timed tude, (2) beta-state lifetime, and (3) beta-state interval
movement preparation in Parkinson's disease time. Of these, changes in beta-state interval time
(2020) explained the overall decreases in beta power during
timed movement preparation and uniquely captured
Heideman, Simone G; Quinn, Andrew J; Woolrich, Mark the impairment in such preparation in patients with
W; van Ede, Freek; Nobre, Anna C Parkinson's disease. Thus, the increased granularity of
the Hidden Markov Model analysis (compared with
Oxford Centre for Human Brain Activity, Wellcome Centre conventional analysis of power) provides increased sen-
for Integrative Neuroimaging, Department of Psychiatry, sitivity and suggests a possible reason for impairments
University of Oxford, Oxford, United Kingdom; Oxford Centre of timed movement preparation in Parkinson's disease.
for Human Brain Activity, Wellcome Centre for Integrative
Neuroimaging, Department of Psychiatry, University of Ox- Keywords: Beta oscillations, Burst-events, Movement,
ford, Oxford, United Kingdom; Department of Experimental Parkinson’s disease, Timing
Psychology, University of Oxford, Oxford, United Kingdom.
Electronic address: [email protected] Progress in neurobiology (2020), Vol. 184 (31778771) (14
citations)

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