Objective: To present a new methodology of recording STN local field potential (LFP) activity.

Background: Recordings of LFPs from the subthalamic nucleus (STN) of patients with PD have revealed pathologically prominent and synchronised oscillatory activity in the beta-band frequency (13–35 Hz) [1]. These oscillations are involved in movement preparation, execution and recovery and have been shown to have an anti-kinetic effect [1,2]. While frequency specific STN activity has been investigated in various voluntary movement paradigms [2-5], the relationship between STN oscillations and sustained motor control and dual-task performance has not been explored.

Method: We record LFP activity using externalized DBS electrodes from PD patients during the performance of a continuous motor task, using a previously published sustained visuo-manual tracking paradigm in which the participants operate a joystick to track the movements of a visual stimulus on a screen. We employ a double-stimulus paradigm, used to measure cognitive processing of two sequential reaction time tasks which are presented at varying delay intervals. A psychological refractory period (PRP) is identified: the delay interval between the tasks impairs performance in the second task [6]. Control of sustained human movement is understood incompletely. The continuous control paradigm – which assumes a continuous biofeedback loop of sensory input, predictive modelling and motor output – fails to account for the existence of the PRP. The alternative paradigm of intermittent control, postulating the existence of refractory periods during which motor output continues without sensory updates, resolves these issues and provides a more general framework for understanding human movement [7].

Results: We describe using a new testing methodology which applies the principles of intermittent motor control. The relationship between the target signal and the subsequent motor response is modelled using an autoregressive moving average (ARMA) process [7].This allows us to pinpoint when motor processing becomes refractory (ie response to the second step is significantly delayed as compared to the first step). Using LFP power spectrum analysis and event related LFP power, we can characterize the neuronal oscillations underlying motor refractoriness.

Conclusion: We present a novel methodology to explore LFP activity in the basal ganglia related to a continuous motor task.

References: 1. Kühn AA, Williams D, Kupsch A, Limousin P, Hariz M, Schneider GH, Yarrow K, Brown P (2004). Event-related beta desynchronization in human subthalamic nucleus correlates with motor performance. Brain 127:735–746. 2. Foffani G, Bianchi AM, Baselli G, Priori A (2005). Movement-related frequency modulation of beta oscillatory activity in the human subthalamic nucleus. J. Physiol 568:699–711. 3. Quinn EJ, Blumenfeld Z, Velisar A, Koop MM, Shreve LA, Trager MH, Hill BC, Kilbane C, Henderson JM, Bronte-Stewart H (2015). Beta oscillations in freely moving Parkinson’s subjects are attenuated during deep brain stimulation. Mov. Disord.;30:1750–1758. 4. Tan H, Pogosyan A, Ashkan K, Green AL, Aziz T, Foltynie T, Limousin P, Zrinzo L, Hariz M, Brown P (2016). Decoding gripping force based on local field potentials recorded from subthalamic nucleus in humans. 5. Hell F, Plate A, Mehrkens JH, Bötzela K (2018). Subthalamic oscillatory activity and connectivity during gait in Parkinson’s disease. Neuroimage Clin 19: 396–405. 6. Pashler, H. (1994). Dual-task interference in simple tasks: Data and theory. Psychol Bull 116, 220-244. 7. van de Kamp C, Gawthrop P, Gollee H, Loram ID (2013). Refractoriness in sustained visuo-manual control: is the refractory duration intrinsic or does it depend on external system properties? PLoS Comput Biol 9(1):e1002,843.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/a-novel-intermittent-control-paradigm-to-investigate-oscillatory-neuronal-activity-in-the-stn/