The rhythm of attention: perceptual modulation via rhythmic entrainment is lowpass and attention mediated

Modulation patterns are known to carry critical predictive cues to signal detection in complex acoustic environments.  The current study investigated the persistence of masker modulation effects on post-modulation detection of probe signals.  Hickok et al. (2015) demonstrated that thresholds for a tone pulse in stationary noise follow a predictable periodic pattern when preceded by a 3-Hz amplitude modulated masker.  They found entrainment of detection patterns to the modulation envelope lasting for approximately 2 cycles after termination of modulation.  The current study extends these results to a wide range of modulation rates by mapping the temporal modulation transfer function for persistent modulatory effects.  We found significant entrainment to modulation rates of 2 and 3 Hz, a weaker effect at 5 Hz, and no entrainment at higher rates (8 to 32 Hz).  The effect seems critically dependent on attentional mechanisms, requiring temporal and level uncertainty of the probe signal.  Our findings suggest that the persistence of modulatory effects on signal detection is lowpass in nature and attention based.

Methods
Data were collected using Matlab software on a Sony Lenovo T400 computer in a steel-walled acoustically isolated chamber (Industrial Acoustics Company).  On each trial of a single-interval two-alternative forced-choice task, the subject was required to indicate (via a key press) whether a tonal signal was present during the unmodulated segment of a masking noise. Feedback was provided after each trial.  The data made available here is the raw data in a .mat file which includes results of every single trials of every run by every subject.  The files include the raw data without any postprocessing.