REPLICABILITY OF MEG AND EEG MEASURES OF THE AUDITORY N1 N1M-RESPONSE/

We investigated the replicability of the source location, amplitude an d latency measures of the auditory evoked N1 (EEG) and Nlm (MEG) respo nses. Each of the 5 subjects was measured 6 times in two recording ses sions. Responses to monaural stimuli were recorded from 122 MEG and 64 EEG channels simultaneously. The EEG data were modeled with a symmetr ically-located dipole pair. For the MEG data, one dipole in each hemis phere was located independently using a subset of channels. Standard d eviation (SD) was used as a measure for replicability. The average SD of the x, y and z coordinates of the contralateral Nlm dipole was abou t 2 mm, whereas the corresponding figures for the ipsilateral Nlm and the contra-and ipsilateral N1 were about twice as large. The SDs of th e dipole amplitudes and latencies were almost equal with MEG and EEG. The amplitude and latency measures of the MEG field gradient waveforms were almost as replicable as those of the dipole models. The results suggest that both MEG and EEG can be used for investigating the simult aneous activity of the left and right auditory cortices independently, MEG being superior in certain experimental setups. (C) 1998 Elsevier Science Ireland Ltd.