ABSTRACT
House mice (Mus musculus, outbred strain NMRI) were trained to locate loudspeakers at the margin of a wire-mesh covered circular platform. Sound signals were tone bursts of 1, 15, 50 and 80 kHz and noise bursts (bandwidth 15–80 kHz). Localization acuity as represented by orientation angles (α) toward the speaker was determined at 5 radial distances from the centre of the platform. If the animals could localize under closed-loop conditions (with repetitive stimulation), the distributions of (α) showed a significant peak at the speaker position (0°) and mean orientation angles 
for the different stimuli all varied around 0°. Distributions of (α) from open-loop tests were not peaked, i.e. mice did not localize the sound source. We calculated the median angle (β) of the distributions of orientated runs and used (β) as a measure for the accuracy of localization. Smallest values of α were 12° for 1 kHz, 15 ° for 15 kHz, 9·5 ° for 50 kHz, 8·5 ° for 80 kHz tone bursts and 7 ° for the noise bursts. The results are discussed in relation to possible localization mechanisms in mice.
