Effects of stimulus rise-fall time and equivalent duration on middle components of AER

Tone bursts of 500, 1 000, or 3 000 Hz with rise/fall times of 3, 5, and 10 msec were combined with either a 'no plateau' duration or 'equivalent durations' of 10 or 30 msec. Electroencephalic activity (102.4 msec post-stimulus) from normal-hearing adults was recorded between the vertex and each earlobe. AER latencies and amplitudes decreased as frequency increased but effects of increasing rise/fall time and duration were similar at all frequencies. An increase in stimulus rise/fall time or equivalent duration results in increases of about 1-3 msec in latencies of all middle component peaks. Increasing either rise/fall time or equivalent duration produces a considerable reduction in middle component amplitude at all intensity levels. Any combination of rise/fall time and plateau duration that gives an equivalent duration of less than 10 msec. and results in narrow spectra stimuli, appears optimal for clinical EEA with middle components.