title: Frequency characteristics of neuromagnetic auditory steady-state responses to sinusoidally amplitude-modulated sweep tones.
abstract: OBJECTIVE
  This study aimed to capture the neuronal frequency characteristics, as indexed by the auditory steady-state response (ASSR), relative to physical characteristics of constant sound pressure levels (SPLs). Relationship with perceptual characteristics (loudness model) was also examined.
  
  
  METHODS
  Neuromagnetic 40-Hz ASSR was recorded in response to sinusoidally amplitude-modulated sweep tones with carrier frequency covering the frequency range of 0.1-12.5kHz. Sound intensity was equalized at 50-, 60-, and 70-dB SPL with an accuracy of ±0.5-dB SPL at the phasic peak of the modulation frequency. Corresponding loudness characteristics were modeled by substituting the detected individual hearing thresholds into a standard formula (ISO226:2003(E)).
  
  
  RESULTS
  The strength of the ASSR component was maximum at 0.5kHz, and it decreased linearly on logarithmic scale toward lower and higher frequencies. Loudness model was plateaued between 0.5 and 4kHz.
  
  
  CONCLUSIONS
  Frequency characteristics of the ASSR were not equivalent to those of SPL and loudness model. Factors other than physical and perceptual frequency characteristics may contribute to characterizing the ASSR.
  
  
  CONCLUSIONS
  The results contribute to the discussion of the most efficient signal summation for the generation of the ASSR at 0.5kHz and efficient neuronal processing at higher frequencies, which require less energy to retain equal perception.
authors.affiliation: Biomedical Research Institute, The National Institute of Advanced Industrial Science and Technology (AIST), Osaka, Japan; Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Asuka
authors.initials: A
authors.lastname: Otsuka
authors.affiliation: Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Yumoto
authors.affiliation: Research Center for Science and Technology, Tokyo Denki University, Chiba, Japan.
authors.forename: Shinya
authors.initials: S
authors.lastname: Kuriki
authors.affiliation: Biomedical Research Institute, The National Institute of Advanced Industrial Science and Technology (AIST), Osaka, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Hotehama
authors.affiliation: Biomedical Research Institute, The National Institute of Advanced Industrial Science and Technology (AIST), Osaka, Japan. Electronic address: s-nakagawa@aist.go.jp.
authors.forename: Seiji
authors.initials: S
authors.lastname: Nakagawa
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods*; D000328:Adult; D001303:Auditory Cortex / Q000502:physiology*; D001307:Auditory Perception / Q000502:physiology*; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D006801:Humans; D015225:Magnetoencephalography / Q000379:methods*; D008297:Male; D008875:Middle Aged
keywords: Auditory steady-state response (ASSR); Frequency characteristics; Loudness modeling; Magnetoencephalography (MEG); Sinusoidally amplitude-modulated (SAM) sweep tone; Sound intensity calibration