Abstract:

Temporal resolution of the dolphin's auditory system was studied using the auditory brain-stem-evoked response (ABR) recording in paradigms as follows: (i) paired click and pip stimulation; (ii) rhythmic click and pip stimulation; (iii) sinusoidally amplitude-modulated tones; (iv) noise burst of various duration (the temporal summation test); and (v) gap in noise detection. An integration temporal transfer function was derived from the data of all the listed experiments using a model of a linear integrator with subsequent nonlinear transform to ABR amplitude. All the experiments listed above gave strictly corresponding results. The integration transfer function consisted of an initial high-level part about 0.3-ms long and the subsequent low-level part with a decay of around 40 dB per time decade. The short initial part of the integration transfer function makes it possible to respond to paired stimuli with interstimulus intervals down to 0.2 ms, to follow rhythmic stimuli of a rate of more than 2000 Hz, and to detect gaps in noise as short as 0.1 ms. The subsequent low-level part is also important; it dictates response properties at interstimulus intervals and gap durations as loud as dozens of ms.