Artefact-free recording of local field potentials with simultaneous stimulation for closed-loop Deep-Brain Stimulation

Abstract

Continuous high frequency Deep Brain Stimulation (DBS) is a standard therapy for several neurological disorders. Closed-loop DBS is expected to further improve treatment by providing adaptive, on-demand therapy. Local field potentials (LFPs) recorded from the stimulation electrodes are the most often used feedback signal in closed-loop DBS. However, closed-loop DBS based on LFPs requires simultaneous recording and stimulating, which remains a challenge due to persistent stimulation artefacts that distort underlying LFP biomarkers. Here we first investigate the nature of the stimulation-induced artefacts and review several techniques that have been proposed to deal with them. Then we propose a new method to synchronize the sampling clock with the stimulation pulse so that the stimulation artefacts are never sampled, while at the same time the Nyquist-Shannon theorem is satisfied for uninterrupted LFP recording. Test results show that this method achieves true uninterrupted artefact-free LFP recording over a wide frequency band and for a wide range of stimulation frequencies.Clinical relevance-The method proposed here provides continuous and artefact-free recording of LFPs close to the stimulation target, and thereby facilitates the implementation of more advanced closed-loop DBS using LFPs as feedback.

Figure 1

Classical approach of LFP recording for closed-loop DBS

Figure 2

Stimulation artefact in LFPs measured from the subthalamic nucleus in one human patient while biphasic stimulation pulses (A) were delivered at 130 Hz. B) LFP recordings in the temporal domain with either a SAR ADC at 83 kHz (Amplifier1902 +CED1401, green lines) or a Sigma-Delta ADC at 2048 Hz (TMSi Porti, blue lines). (C) Artefacts sampled at 2048 Hz using a Sigma-Delta ADC in frequency domain.

Figure 3

Proposed approach for LFP recording for closed-loop DBS

Figure 4

Synchronisation logic function of the proposed method

Figure 5

Illustrative chronogram of the different clocks

Figure 6

Recording without clock synchronization in the temporal-domain (A) and frequency-domain (B).

Figure 7

Recording with clock synchronization in the temporal domain (A) and the frequency domain (B).