Figure 3.

Effects of chronic monaural occlusion in infancy on auditory localization. (A) Schematic view of chamber used to measure the spatial identification ability of ferrets. The animals were trained to stand on the start platform and initiate a trial by licking the center spout. Each trial consisted of a Gaussian noise burst (0–30 kHz, 100-ms duration) presented quasirandomly from 1 of 12 speakers placed at 30° intervals in the azimuthal plane. Within each testing session, five sound levels ranging randomly from 56 to 84 dB sound pressure level were used to minimize loudness cues. Ferrets were rewarded for approaching and licking the spout associated with the speaker that had been triggered. (B) Stimulus-response plots showing the combined data of three normal adult ferrets (Normals) and three ferrets that had been raised and tested with the left ear occluded with a plug that produced 30–50 dB attenuation (Infant plug). These plots illustrate the distribution of responses (ordinate) as a function of stimulus location (abscissa). The size of the dots indicates, for a given speaker angle, the proportion of responses made to different spout locations. deg, degree. (C) Polar plots showing the percentage of correct responses made to each of the 12 speaker locations. Comparison of the percentage scores and error magnitudes showed that ferrets reared with a plug in one ear perform as well as normally reared animals.