title: Neural adaptation to silence in the human auditory cortex: a magnetoencephalographic study.
abstract: BACKGROUND
  Previous studies demonstrated that a decrement in the N1m response, a major deflection in the auditory evoked response, with sound repetition was mainly caused by bottom-up driven neural refractory periods following brain activation due to sound stimulations. However, it currently remains unknown whether this decrement occurs with a repetition of silences, which do not induce refractoriness.
  
  
  METHODS
  In the present study, we investigated decrements in N1m responses elicited by five repetitive silences in a continuous pure tone and by five repetitive pure tones in silence using magnetoencephalography.
  
  
  RESULTS
  Repetitive sound stimulation differentially affected the N1m decrement in a sound type-dependent manner; while the N1m amplitude decreased from the 1st to the 2nd pure tone and remained constant from the 2nd to the 5th pure tone in silence, a gradual decrement was observed in the N1m amplitude from the 1st to the 5th silence embedded in a continuous pure tone.
  
  
  CONCLUSIONS
  Our results suggest that neural refractoriness may mainly cause decrements in N1m responses elicited by trains of pure tones in silence, while habituation, which is a form of the implicit learning process, may play an important role in the N1m source strength decrements elicited by successive silences in a continuous pure tone.
authors.affiliation: Department of Integrative Physiology, National Institute for Physiological Sciences Okazaki, Japan ; Department of Physiological Sciences, The Graduate University for Advanced Studies Hayama, Japan.
authors.forename: Hidehiko
authors.initials: H
authors.lastname: Okamoto
authors.affiliation: Department of Integrative Physiology, National Institute for Physiological Sciences Okazaki, Japan ; Department of Physiological Sciences, The Graduate University for Advanced Studies Hayama, Japan.
authors.forename: Ryusuke
authors.initials: R
authors.lastname: Kakigi
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods; D000222:Adaptation, Physiological / Q000502:physiology*; D001303:Auditory Cortex / Q000502:physiology*; D001307:Auditory Perception / Q000502:physiology*; D005260:Female; D006801:Humans; D015225:Magnetoencephalography; D008297:Male; D055815:Young Adult
keywords: Habituation; magnetoencephalography; refractoriness