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Comparison of brain magnetic fields evoked by air-conducted sounds, bone-conducted audible sounds, and bone-conducted ultrasounds
NemoImage
13, Number
6, 2001, Part 2 of 2 Parts 1 D E al@
PERCEPTION
Comparison of brain magnetic fields evoked by air-conducted sounds, bone-conducted audible sounds, and bone-conducted ultrasounds Seiji Nakagawa*, Taichi Nigoro*t, Masahiko Yamaguchi”, Mitsuo Tonoike*, Hiroshi HosoiS, Yoshiaki Watanabe& Satoshi Imaizumi’ *Electrotechnical
Laboratory, National Institute of Advanced Industrial Science and Technology, tFaculty of Engineering Science, Kinki University SDept. of Otolaryngology, Nara Medical University §Dept. of Electronic Engineering, Doshisha University
‘Dept. of Speech and Cognitive Science, Graduate School of Medicine, University of Tokyo Several studies have reported that ultrasounds were perceived through bone conduction in deaf as well as normal-hearing subjects, and suggested that ultrasonic hearing aids might enable the profoundly deaf to detect environmental sounds and possibly even spoken words, without surgery. However, most of characteristics and mechanisms of bone-conduction hearing, not only ultrasound but also audible sounds, are still unclear. In this study, we investigated the brain activity evoked by air-conducted sounds, bone-conducted audible sounds, and bone-conducted ultrasounds using neuromagnetic measurements. 10 normal hearing volunteers (8 males, 21-52 years, right-handed) took part in this experiment. Measurements of brain magnetic fields were carried out using 122ch whole-head neuromagnetometer (Neuromag-122TM) in a magnetically shielded room. Nlm elicited by air-conducted sounds, bone-conducted audible sounds (1000, 2000, and 4000 Hz tone burst, 50 ms duration with 10 ms linear rising/falling ramps, 50 dBHL), and bone-conducted ultrasounds (22000, 27000, 32000, and 37000 Hz tone burst, 50 ms duration with 10 ms linear rising/falling ramps, 10 dBSL) at ipsilateral and contralateral ear/mastoid were measured. Boneconducted sounds were presented by ceramic vibrators. ECDs (equivalents current dipoles) of Nlm were estimated in the both hemisphere at Nlm peak latencies. For all kinds of stimuli, substantial Nlm were observed, and ECDs were localized in the auditory cortex, superior surface of the temporal lobe. Nlm ECD moments and Nlm latencies of bone-conducted ultrasounds were significantly smaller than that of air-conducted and bone-conducted audible sounds. Nlm evoked by contralateral stimuli was larger in ECD moment and shorter in latency than that evoked by ipsilateral stimuli, for all stimuli. These results suggest that bone-conducted sounds, as well as air-conducted sound, are processed in the auditory cortex. It is also suggested that bone-conducted ultrasounds enter the auditory pathway at more peripheral part than superior olivary nucleus.
s915
13, Number
6, 2001, Part 2 of 2 Parts 1 D E al@
PERCEPTION
Comparison of brain magnetic fields evoked by air-conducted sounds, bone-conducted audible sounds, and bone-conducted ultrasounds Seiji Nakagawa*, Taichi Nigoro*t, Masahiko Yamaguchi”, Mitsuo Tonoike*, Hiroshi HosoiS, Yoshiaki Watanabe& Satoshi Imaizumi’ *Electrotechnical
Laboratory, National Institute of Advanced Industrial Science and Technology, tFaculty of Engineering Science, Kinki University SDept. of Otolaryngology, Nara Medical University §Dept. of Electronic Engineering, Doshisha University
‘Dept. of Speech and Cognitive Science, Graduate School of Medicine, University of Tokyo Several studies have reported that ultrasounds were perceived through bone conduction in deaf as well as normal-hearing subjects, and suggested that ultrasonic hearing aids might enable the profoundly deaf to detect environmental sounds and possibly even spoken words, without surgery. However, most of characteristics and mechanisms of bone-conduction hearing, not only ultrasound but also audible sounds, are still unclear. In this study, we investigated the brain activity evoked by air-conducted sounds, bone-conducted audible sounds, and bone-conducted ultrasounds using neuromagnetic measurements. 10 normal hearing volunteers (8 males, 21-52 years, right-handed) took part in this experiment. Measurements of brain magnetic fields were carried out using 122ch whole-head neuromagnetometer (Neuromag-122TM) in a magnetically shielded room. Nlm elicited by air-conducted sounds, bone-conducted audible sounds (1000, 2000, and 4000 Hz tone burst, 50 ms duration with 10 ms linear rising/falling ramps, 50 dBHL), and bone-conducted ultrasounds (22000, 27000, 32000, and 37000 Hz tone burst, 50 ms duration with 10 ms linear rising/falling ramps, 10 dBSL) at ipsilateral and contralateral ear/mastoid were measured. Boneconducted sounds were presented by ceramic vibrators. ECDs (equivalents current dipoles) of Nlm were estimated in the both hemisphere at Nlm peak latencies. For all kinds of stimuli, substantial Nlm were observed, and ECDs were localized in the auditory cortex, superior surface of the temporal lobe. Nlm ECD moments and Nlm latencies of bone-conducted ultrasounds were significantly smaller than that of air-conducted and bone-conducted audible sounds. Nlm evoked by contralateral stimuli was larger in ECD moment and shorter in latency than that evoked by ipsilateral stimuli, for all stimuli. These results suggest that bone-conducted sounds, as well as air-conducted sound, are processed in the auditory cortex. It is also suggested that bone-conducted ultrasounds enter the auditory pathway at more peripheral part than superior olivary nucleus.
s915