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Auditory temporal integration in the rhesus macaque (Macaca mulatta)
K N O'Connor1, P Barruel, R Hajalilou
1Center for Neuroscience, University of California, Davis 95616, USA.
Abstract:
Temporal integration for pure tones was examined in two rhesus macaques. The subjects were required to respond to a brief sound (a tone burst) that deviated from a previous series of sounds (noise bursts) on a trial (a deviant-stimulus detection paradigm). Psychometric functions and thresholds were determined from correct detections (hit proportions) alone, and from d' scores. Two models describing the decline in threshold as a function of stimulus duration, one a power function the other an exponential, were tested against the data. When the decline (slope) in threshold per log stimulus duration is used as a rate measure, our results yield a lower estimate of temporal integration rate in rhesus than did a previous study [Clack, J. Acoust. Soc. Am. 40, 1140-1146 (1966)]. Both studies, however, gave slope estimates of integration rate that were higher than in most other species. Comparison of the models using data from several species, revealed that the exponential, but not the power model, could account for two sources of variation in threshold measurement. One source is due to the range across threshold as a function of duration (the linear rate component), and is described by the constant of proportionality Ik in the model. The other source of variation arises from the rate of decline within this range (the nonlinear rate component), and is described by the time constant tau. In terms of this model, differences in rate estimates between Clack's study and ours (and between rhesus and other species) are primarily due to the linear component. The nonlinear rate component was about equal for our study and Clack's (tau = approximately 150 ms): a time constant that is just slightly larger (indicating a rate of temporal integration slightly slower) than for most other species examined.
Insights
This study investigated temporal integration in rhesus macaques, finding their auditory systems integrate sound duration differently than previously estimated. Results suggest variations in integration rates across species may stem from linear components of auditory processing.
Area of Science:
- Auditory Neuroscience
- Psychoacoustics
- Comparative Psychology
Background:
- Temporal integration, the ability of the auditory system to combine sound information over time, is crucial for perceiving acoustic signals.
- Previous research has estimated temporal integration rates in various species, but species-specific differences and underlying mechanisms require further investigation.
Purpose of the Study:
- To examine temporal integration for pure tones in rhesus macaques using a deviant-stimulus detection paradigm.
- To compare the effectiveness of power and exponential models in describing the relationship between stimulus duration and auditory threshold.
- To investigate species-specific differences in auditory temporal integration rates.
Main Methods:
- Two rhesus macaques were trained on a task requiring detection of brief tone bursts amidst noise bursts.
- Psychometric functions and thresholds were determined using hit proportions and d' scores.
- Data were analyzed using power and exponential models to assess temporal integration rates.
Main Results:
- Rhesus macaques exhibited a lower temporal integration rate compared to a previous study, though still higher than most other species.
- An exponential model provided a better fit to the data than a power model, accounting for linear and nonlinear components of threshold variation.
- Differences in integration rate estimates between species were primarily attributed to the linear component of the exponential model.
Conclusions:
- The findings refine estimates of auditory temporal integration in rhesus macaques and highlight the utility of the exponential model for cross-species comparisons.
- Variations in auditory temporal integration rates across species are influenced by both linear and nonlinear processing components.
- The nonlinear component of temporal integration in rhesus macaques is comparable to that in humans, suggesting conserved underlying mechanisms.