Data from: Dissociable neural response signatures for slow amplitude and frequency modulation in human auditory cortex

Natural auditory stimuli are characterized by slow fluctuations in
amplitude and frequency. However, the degree to which the neural responses
to slow amplitude modulation (AM) and frequency modulation (FM) are
capable of conveying independent time-varying information, particularly
with respect to speech communication, is unclear. In the current
electroencephalography (EEG) study, participants listened to amplitude-
and frequency-modulated narrow-band noises with a 3-Hz modulation rate,
and the resulting neural responses were compared. Spectral analyses
revealed similar spectral amplitude peaks for AM and FM at the stimulation
frequency (3 Hz), but amplitude at the second harmonic frequency (6 Hz)
was much higher for FM than for AM. Moreover, the phase delay of neural
responses with respect to the full-band stimulus envelope was shorter for
FM than for AM. Finally, the critical analysis involved classification of
single trials as being in response to either AM or FM based on either
phase or amplitude information. Time-varying phase, but not amplitude, was
sufficient to accurately classify AM and FM stimuli based on single-trial
neural responses. Taken together, the current results support the
dissociable nature of cortical signatures of slow AM and FM. These
cortical signatures potentially provide an efficient means to dissect
simultaneously communicated slow temporal and spectral information in
acoustic communication signals.