超伝導磁気シールド環境下の短·中潜時聴性誘発脳磁界の計測

抄録

A superconducting magnetic shielding enclosure made of a bithmus-strontium-based high-critical-temperature superconducting material was formed to have better magnetic noise rejection at low frequencies than conventional magnetic shielding. To evaluate its efficiency, short- and middle-latency auditory evoked fields (SLAEFs and MLAEFs), which have weak amplitudes compared with other longlatency auditory evoked fields such as N1m, were measured. Measurements were made for three subjects with normal hearing in response to auditory clicks in the left ear. Multiple recordings were made at different locations over both lateral sides of the head, using a 7-ch SQUID with magnetometer coils. SLAEF and MLAEF components were observed at latencies of 6(M6), 10, 15, 20, and 30 ms in all subjects. Calculation of an equivalent current dipole source suggested that the source of M6 is located deep in the brain. The results are discussed alone with previous measurements of SLAEFs in terms of the response from the brainstem.