Slow phase-locked endogenous modulations support selective attention to sound

To make sense of complex soundscapes, listeners must select and attend to task-relevant streams while ignoring uninformative sounds. One possible neural mechanism underlying this process is alignment of endogenous oscillations with the temporal structure of the target sound stream. Such a mechanism has been suggested to mediate attentional modulation of neural phase-locking to the rhythms of attended sounds. However, such modulations are compatible with an alternate framework, where attention acts as a filter that enhances exogenously-driven neural auditory responses. Here we attempted to adjudicate between theoretical accounts by playing two tone steams varying across condition in tone duration and presentation rate; participants attended to one stream or listened passively. Attentional modulation of the evoked waveform was roughly sinusoidal and scaled with rate, while the passive response did not. This suggests that auditory attentional selection is carried out via phase-locking of slow endogenous neural rhythms.

Effects of tone duration on three psychophysical measures of temporal integration in rhesus macaques

The relationship between sound duration and detection performance has long been thought to reflect temporal integration, and has been well studied in both humans and animal models. Reports of species differences are equivocal, with some metanalyses reporting no species differences, and others reporting substantial differences. This renders translational work in animals problematic. To re-evaluate this issue, tone detection performance was measured in rhesus macaques using a Go/No-Go reaction time detection task at various stimulus durations, and in the presence of broadband noise (BBN). Detection thresholds, reaction times (RT), and psychometric function slopes were calculated. All three measures were sensitive to tone duration, consistent with temporal integration. The rate of threshold change with duration was similar to human data, and was equally well fit by power law and exponential functions. The effect of tone duration on RT is the first reported in animals. BBN significantly affected how slopes changed with duration, and elevated thresholds, but did not affect how threshold or RT changed with duration. To begin investigating what processes may underlie these behavioral measures, the data were then compared to data generated using a probabilistic Poisson process model, previously compared to human data. The Poisson model recapitulated the effects of duration on threshold and psychometric slope. These behavioral data provide evidence that macaques are an exceptional model of human temporal integration, and the modeling results point the way forward for future neurophysiological studies.

Perception of Pitch and Time in the Structurally Isomorphic Standard Rhythmic and Diatonic Scale Patterns

The three experiments reported here investigate how pitch and time interact in perception using the standard rhythmic pattern and the diatonic scale pattern, which share the intervallic structure of 2 2 1 2 2 2 1. They share a number of theoretical properties, including being cyclic with seven unique rotations. Experiment 1 measured rhythmic stability by dynamically accenting each of the events in each rhythm, called the probe accent; listeners rated how well the probe accent fit the rhythm. Listeners heard the rhythms in subgroups and with reference to a syncopation-shifted metrical hierarchy. Experiment 2 used the probe tone technique to measure the tonal stability of each tone in each mode beginning and ending on C. Higher ratings were given to tones earlier in the contexts and tones closer to C on both the chroma circle and the circle of fifths; influences were also found of tonal hierarchies of diatonic scales with corresponding accidentals. A measure of similarity derived from the probe ratings found the same order for the rhythms and modes which matched theoretical proposals of inter-rhythm and inter-mode distances. Experiment 3 presented all combinations of rhythms and modes; listeners judged how well the rhythm fit the mode. These judgments did not depend on the intervallic isomorphism between tone duration and interval size. Instead, the judgments depended on whether tonally stable events occurred where accents were judged as fitting well with the rhythm. Overall, the standard and diatonic patterns follow different perceptual hierarchies while sharing similar cognitive principles between rhythms, between modes, and across dimensions.