title: A practice of caution: spontaneous action potentials or artifactual spikes?
abstract: BACKGROUND
  High density surface electromyogram (EMG) techniques with electrode arrays have been used to record spontaneous muscle activity, which is important, both for supporting the diagnosis of neuromuscular diseases and for laboratory based neurophysiological investigations. This short report addresses a practical issue we have experienced during recording of spontaneous muscle activity using electrode arrays from subjects with major neuromuscular disorders.
  
  
  RESULTS
  We show that recording artifacts can appear similar to spontaneous action potential spikes. Moreover, a causal filter may induce asymmetric distortions of an artifact and thus confuse it with a real action potential spike. As a consequence, for a single channel surface EMG recording, it might be difficult to judge whether a voltage transient is a real action potential or an artifact. Further investigation of the signal distributions among other channels of the array can be used to reach a more confident judgment.
  
  
  CONCLUSIONS
  During examination of spontaneous muscle activity using electrode arrays, caution is required for differentiation of physiological signals from artifactual spikes, which is important for accurate extraction of diagnostic or investigatory information.
authors.forename: Faezeh
authors.initials: F
authors.lastname: Jahanmiri-Nezhad
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Li
authors.forename: William Zev
authors.initials: WZ
authors.lastname: Rymer
authors.affiliation: Department of Physical Medicine and Rehabilitation, University of Texas Health Science Center at Houston; TIRR Memorial Hermann Research Center, 1333B Moursund St, Room 230, Houston, TX 77030, USA. dr.ping.zhou@ieee.org.
authors.forename: Ping
authors.initials: P
authors.lastname: Zhou
mesh_terms: D000200:Action Potentials; D000328:Adult; D016477:Artifacts; D004566:Electrodes; D004576:Electromyography / Q000379:methods* / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D008297:Male; D018485:Muscle Fibers, Skeletal; D018482:Muscle, Skeletal / Q000503:physiopathology; D009468:Neuromuscular Diseases / Q000175:diagnosis* / Q000503:physiopathology; D012815:Signal Processing, Computer-Assisted; D055815:Young Adult