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Signal processing methods for reducing artifacts in microelectrode brain recordings caused by functional electrical stimulation.

ABSTRACT: OBJECTIVE:Functional electrical stimulation (FES) is a promising technology for restoring movement to paralyzed limbs. Intracortical brain-computer interfaces (iBCIs) have enabled intuitive control over virtual and robotic movements, and more recently over upper extremity FES neuroprostheses. However, electrical stimulation of muscles creates artifacts in intracortical microelectrode recordings that could degrade iBCI performance. Here, we investigate methods for reducing the cortically recorded artifacts that result from peripheral electrical stimulation. APPROACH:One participant in the BrainGate2 pilot clinical trial had two intracortical microelectrode arrays placed in the motor cortex, and thirty-six stimulating intramuscular electrodes placed in the muscles of the contralateral limb. We characterized intracortically recorded electrical artifacts during both intramuscular and surface stimulation. We compared the performance of three artifact reduction methods: blanking, common average reference (CAR) and linear regression reference (LRR), which creates channel-specific reference signals, composed of weighted sums of other channels. MAIN RESULTS:Electrical artifacts resulting from surface stimulation were 175??×??larger than baseline neural recordings (which were 110 µV peak-to-peak), while intramuscular stimulation artifacts were only 4??×??larger. The artifact waveforms were highly consistent across electrodes within each array. Application of LRR reduced artifact magnitudes to less than 10 µV and largely preserved the original neural feature values used for decoding. Unmitigated stimulation artifacts decreased iBCI decoding performance, but performance was almost completely recovered using LRR, which outperformed CAR and blanking and extracted useful neural information during stimulation artifact periods. SIGNIFICANCE:The LRR method was effective at reducing electrical artifacts resulting from both intramuscular and surface FES, and almost completely restored iBCI decoding performance (>90% recovery for surface stimulation and full recovery for intramuscular stimulation). The results demonstrate that FES-induced artifacts can be easily mitigated in FES??+??iBCI systems by using LRR for artifact reduction, and suggest that the LRR method may also be useful in other noise reduction applications.

SUBMITTER: Young D

PROVIDER: S-EPMC5818316 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature

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Signal processing methods for reducing artifacts in microelectrode brain recordings caused by functional electrical stimulation.

Young D D Willett F F Memberg W D WD Murphy B B Walter B B Sweet J J Miller J J Hochberg L R LR Kirsch R F RF Ajiboye A B AB

Journal of neural engineering 20180401 2

<h4>Objective</h4>Functional electrical stimulation (FES) is a promising technology for restoring movement to paralyzed limbs. Intracortical brain-computer interfaces (iBCIs) have enabled intuitive control over virtual and robotic movements, and more recently over upper extremity FES neuroprostheses. However, electrical stimulation of muscles creates artifacts in intracortical microelectrode recordings that could degrade iBCI performance. Here, we investigate methods for reducing the cortically ...[more]

PMID: 29199642

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Project description:BackgroundElectrical slow waves drive peristaltic contractions in the stomach and facilitate gastric emptying. In gastroparesis and other disorders associated with altered gastric emptying, motility defects have been related to altered slow wave frequency and disordered propagation. Experimental and clinical measurements of slow waves are made with extracellular or abdominal surface recording.MethodsWe tested the consequences of muscle contractions and movement on biopotentials recorded from murine gastric muscles with array electrodes and pairs of silver electrodes.Key resultsPropagating biopotentials were readily recorded from gastric sheets composed of the entire murine stomach. The biopotentials were completely blocked by nifedipine (2 μmol L(-1) ) that blocked contractile movements and peristaltic contractions. Wortmannin, an inhibitor of myosin light chain kinase, also blocked contractions and biopotentials. Stimulation of muscles with carbachol increased the frequency of biopotentials in control conditions but failed to elicit biopotentials with nifedipine or wortmannin present. Intracellular recording with microelectrodes showed that authentic gastric slow waves occur at a faster frequency typically than biopotentials recorded with extracellular electrodes, and electrical slow waves recorded with intracellular electrodes were unaffected by suppression of movement. Electrical transients, equal in amplitude to biopotentials recorded with extracellular electrodes, were induced by movements produced by small transient stretches (<1 mm) of paralyzed or formalin fixed gastric sheets.Conclusions & inferencesThese data demonstrate significant movement artifacts in extracellular recordings of biopotentials from murine gastric muscles and suggest that movement suppression should be an obligatory control when monitoring electrical activity and characterizing propagation and coordination of electrical events with extracellular recording techniques.

Project description:ObjectiveTo determine if Functional Electrical Stimulation (FES) would improve ischemic pain, walking distance, and quality of life of patients with intermittent claudication.DesignSingle blind, randomized block, two factorial design.PatientsPatients diagnosed with Peripheral Artery Disease (PAD) and intermittent claudication (IC). Ankle Brachial Index ranged 0.4-0.9 on at least one leg. Patients were randomly assigned to experimental (FES+Walk, N=13) or control (WALK, N=14) groups.InterventionExperimental group patients received FES to the dorsiflexor and plantarflexor muscles while walking for 1h/day, six days/week for eight weeks. Control group patients received similar intervention without FES. A Follow-up period of both groups lasted eight weeks.Outcome measuresOutcome measures were taken at baseline (T0), after intervention (T1), and after follow-up (T2). Primary measures included Perceived Pain Intensity (PPI), Six minute walk (6MW), and Peripheral Arterial Disease Quality of Life (PADQOL). Secondary measures included Intermittent Claudication Questionnaire (ICQ) and Timed Up and Go (TUG).ResultsGroup by time interactions in PPI were significant (P<0.001) with differences of 27.9 points at T1 and 36.9 points at T2 favoring the FES+Walk group. Groups difference in Symptoms and Limitations in Physical Function of the PADQOL reached significance (T1=8.9, and T2=8.3 improvements; P=0.007). ICQ was significant (T1=9.3 and T2=13.1 improvements; P=0.003). Improvement in 6MW and TUG tests were similar between groups.Conclusions and relevanceWalking with FES markedly reduced ischemic pain and enhanced QOL compared to just walking. FES while walking may offer an effective treatment option for the elderly with PAD and Intermittent Claudication.Trial registrationNIH-NIA 1R21AG048001 https://projectreporter.nih.gov/project_info_description.cfm?aid=8748641&icde=30695377&ddparam=&ddvalue=&ddsub=&cr=1&csb=default&cs=ASC. https://clinicaltrials.gov/ct2/show/NCT02384980?term=David+Embrey&rank=1.

Dataset Information

Signal processing methods for reducing artifacts in microelectrode brain recordings caused by functional electrical stimulation.

Publications

Signal processing methods for reducing artifacts in microelectrode brain recordings caused by functional electrical stimulation.

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