Detection of tones of unexpected frequency in amplitude-modulated noise

Forward entrainment: Psychophysics, neural correlates, and function

We define forward entrainment as that part of behavioral or neural entrainment that outlasts the entraining stimulus. In this review, we examine conditions under which one may optimally observe forward entrainment. In Part 1, we review and evaluate studies that have observed forward entrainment using a variety of psychophysical methods (detection, discrimination, and reaction times), different target stimuli (tones, noise, and gaps), different entraining sequences (sinusoidal, rectangular, or sawtooth waveforms), a variety of physiological measures (MEG, EEG, ECoG, CSD), in different modalities (auditory and visual), across modalities (audiovisual and auditory-motor), and in different species. In Part 2, we describe those experimental conditions that place constraints on the magnitude of forward entrainment, including an evaluation of the effects of signal uncertainty and attention, temporal envelope complexity, signal-to-noise ratio (SNR), rhythmic rate, prior experience, and intersubject variability. In Part 3 we theorize on potential mechanisms and propose that forward entrainment may instantiate a dynamic auditory afterimage that lasts a fraction of a second to minimize prediction error in signal processing.

Improving older adults' understanding of challenging speech: Auditory training, rapid adaptation and perceptual learning

The literature surrounding auditory perceptual learning and auditory training for challenging speech signals in older adult listeners is highly varied, in terms of both study methodology and reported outcomes. In this review, we discuss some of the pertinent features of listener, stimulus, and training protocol. Literature regarding the elicitation of auditory perceptual learning for time-compressed speech, non-native speech, and noise-vocoded speech is reviewed, as are auditory training protocols designed to improve speech-in-noise recognition. The literature is synthesized to establish some over-arching findings for the aging population, including an intact capacity for auditory perceptual learning, but a limited transfer of learning to untrained stimuli.

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 postmodulation detection of probe signals. Hickok, Farahbod, and Saberi (Psychological Science, 26, 1006-1013, 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 two 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.