A quantitative analysis of psychometric functions for different auditory tasks in gerbils

The psychometric function relates the probability of a correct response to the variation of a physical stimulus parameter. In many perceptual tasks one point on this function is defined by a more or less arbitrary threshold criterion and threshold is used to study the effects of various treatments or age. Besides threshold, the shape of the psychometric function provides additional information. The variability of internal (neural) noise and the sensorineural transduction function will affect the shape of the psychometric function and may, therefore, reveal important features in the processing of stimulus characteristics. Here we analyze the effect of age on psychometric functions from gerbils: (A) for the detection of a tone or noise pulse in silence which is generally regarded as a measure of cochlear function and (B) for a gap detection task, investigating aspects of temporal processing that involve the ascending auditory pathway. Our data show that the slope of the psychometric function for the detection of tone and noise pulses in silence is independent of age and threshold. In contrast, the steepness of the psychometric function is decreased in gerbils with impaired temporal resolution. We discuss these observations in the context of physiological data from young and old animals.