Auditory brainstem responses recorded at fast stimulation rates using maximum length sequences.

There are now commercially available systems which can provide maximum length sequence averaging techniques. This study examines the effects on auditory brainstem response amplitude and latency of using such a system and stimulating at rates from 9 to 1000 clicks/s. As expected there is considerable adaptation of the response such that at 1000 clicks/s wave V amplitude is only approximately 8% of its low stimulation rate value. As the stimulation rate is increased so the test time taken to obtain a response of the same signal-to-noise ratio as a conventional recording decreases. This process continues up to a maximum click rate of about 200 clicks/s. Thereafter, the response adapts so rapidly that further increases of rate lead to a worsening of performance. Thus, the optimum stimulation rate appears to be of the order of 200 clicks/s and this can give a speed improvement by a factor of approximately 2.8 over conventional recordings taken at 9 or 10 clicks/s.