Receiver operating characteristics and temporal integration in an insect auditory receptor cell

Abstract

Receiver operating characteristics (ROC) analysis was applied to the problem of temporal integration in the A1 auditory receptor of the noctuid moth Noctua pronuba. The index of detectability (d′) was calculated either from ROC curves or from a procedure equivalent to a two-alternatives forced-choice paradigm of psychophysics. Stimuli of six different durations (1–40 ms) were used. The detectability increased exponentially with intensity for all signals and with the rate of increase independent of duration. This allowed for an evaluation of the influence of stimulus duration on detectability (duration/intensity trade-off). A model of statistical threshold improvement (the “multiple looks” model) could be applied and the influence of statistics on thresholds could be separated from the influence of intensity integration. For stimulus durations significantly shorter than the time constant of the receptor (3.4 ms for N. pronuba), intensity integration was the main factor determining thresholds and thus an energy detector model was applicable to the data. For durations significantly longer than the time constant, the multiple look model alone could account for changes in thresholds with duration. For durations in-between, a mixture of both models was applicable, making specific predictions difficult.