In Brief:
The amplitude modulation following response (AMFR, a.k.a ASSR) is a promising tool for assessing hearing on a frequency-by-frequency basis. Here we report procedures that serve to enhance the detection of this scalp potential in neonates. Scalp recordings were made between the forehead and linked mastoids in full term and premature babies (n 149) that were usually asleep. The presence of the AMFR was based on the magnitude squared coherence algorithm. Using tonal carriers we assessed the effect of envelope shape on the AMFR. Specifically, we compared a sinusoidal envelope with a transposed (i.e., half-wave rectified) envelope. The transposed envelopes evoked AMFRs that were detected faster than those to the sinusoidal envelope. Then, using the transposed envelope, we found that the time to detect the AMFR was similar for a broad range of modulation frequencies (~40 to 90 Hz). Next, using bandpass noise as a carrier, we found that these transposed, noise stimuli evoked larger and faster AMFRs than those to transposed tones. We conclude that the AMFR can be efficiently evoked over a wide range of modulation frequencies. Moreover, the use of transposed envelopes and band pass noise serve to increase the efficiency of detecting the AMFR.
