Objective: To characterize deep brain stimulation (DBS) parameters for bilateral induction of cortical finely tuned gamma (FTG) via unilateral stimulation.

Background: FTG oscillations are reported to be associated with a prokinetic state in Parkinson’s disease (PD) [1]. We have previously described cortical gamma entrainment, or induction of FTG at a subharmonic of the stimulation frequency [1]. Entrainment of FTG by DBS may be related to therapeutic benefit [2].

Method: We collected local field potential data from basal ganglia and sensorimotor cortex in-clinic from six hemispheres of three PD patients bilaterally implanted with an investigational bi-directional DBS device in the subthalamic nucleus (STN; n=2) or globus pallidus internus (GPi; n=1). All patients had bilateral permanent subdural electrocorticography leads. In each patient, we performed frequency-amplitude titrations in one hemisphere only, keeping contralateral DBS therapy off.  Patients performed a standardized finger-tapping task at each frequency-amplitude combination. We determined the amplitude of gamma entrainment present in both hemispheres using the FOOOF algorithm [3].

Results: In all patients, we observed cortical FTG entrainment at half the stimulation frequency at a select set of frequency-amplitude combinations. Entrainment was present in both pre- and postcentral gyri but had the highest amplitude in the former. Entrainment was of highest amplitude at the subjects’ clinical stimulation frequency in both STN patients (130 Hz), while in the GPi patient it was most prominent during stimulation at 80-90 Hz. In general, entrainment was not linearly related to stimulation amplitude, since the amplitude of entrainment decreased with increasing stimulation amplitudes at select frequencies. All subjects showed beta entrainment at half stimulation frequency when delivering stimulation between 4 and 6 mA at 60 Hz and lower. Further, we report contralateral FTG entrainment in both STN patients, at a narrower range of frequencies than ipsilateral entrainment.

Conclusion: We showed co-occurrence, spatial specificity, and stimulation target-specific characteristics of ipsi- and contralateral FTG entrainment region. Next, we will assess if suppression of PD symptoms correlates with amplitude of entrainment to identify therapeutic DBS parameters.

References: [1] Swann et. Al, J. Neurosci., 2016
[2] Muthuraman et al., Brain, 2020
[3] Donoghue et al., Nat. Neurosci., 2020

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MDS Abstracts - https://www.mdsabstracts.org/abstract/cortical-gamma-oscillations-in-parkinsons-disease-ipsi-and-contralateral-deep-brain-stimulation-induced-entrainment/