Rhythm of Attention

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.  We also investigated
whether entrainment extends to more complex periodic patterns by using
driving modulators comprising two simultaneous rates (2 & 3 Hz or
3 & 5 Hz).  No persistence was observed for these complex
patterns.  Our findings suggest that the persistence of
modulatory effects on signal detection is lowpass in nature and attention
based, extending only to simple envelope patterns.