Measurement of auditory evoked brain responses elicited by ipsilateral and contralateral ear stimulation with a high-sensitivity SQUID system

The effects of the stimulation side on human middle latency auditory evoked responses (MLR) were investigated with a high-sensitivity 7-channel DC SQUID system. We recorded middle latency auditory evoked magnetic fields elicited by ipsilateral and contralateral ear stimuli, and compared the amplitudes and latencies of the magnetic equivalents of Pa and Pb responses, which are the two main components of MLR. The amplitude of the contralateral Pa response was found to be significantly larger than the ipsilateral Pa response. On the other hand, no significant difference was observed in the latencies of Pa and Pb between the ipsi- and contralateral responses