TEMPORAL-MODULATION TRANSFER-FUNCTIONS IN THE EUROPEAN STARLING (STURNUS-VULGARIS) .2. RESPONSES OF AUDITORY-NERVE FIBERS

The temporal resolution of cochlear-nerve fibres in the European starl ing was determined with sinusoidally amplitude-modulated noise stimuli similar to those previously used in a psychoacoustic study in this sp ecies (Klump and Okanoya, 1991). Temporal modulation transfer curves ( TMTFs) were constructed for cochlear afferents allowing a direct compa rison with the starling's behavioural performance. On average, the neu ron's detection of modulation was less sensitive than that obtained in the behavioural experiments, although the most sensitive cells approa ched the values determined psychophysically. The shapes of the neural TMTFs generally resembled low-pass or band-pass filter functions, and the shapes of the averaged neural functions were very similar to those obtained in the behavioural study for two different types of stimuli (gated and continuous carrier). Minimum integration times calculated f rom the upper cut-off frequency of the neural TMTFs had a median of 0. 97 ms with a range of 0.25 to 15.9 ms. The relations between the minim um integration times and the tuning characteristics of the cells (tuni ng curve bandwidth, Q(10) dB-value, high- and low-frequency slopes of the tuning curves) are discussed. Finally, we compare the TMTF data re corded in the starling auditory nerve with data from neurophysiologica l and behavioural observations on temporal resolution using other expe rimental paradigms in this and other vertebrate species.