Effects of auditory cortical lesions on pure-tone sound localization by the albino rat.

Two-choice and three-choice tests were used to evaluate the effects of bilateral auditory cortical lesions on pure-tone sound localization by the albino rat. Both tests required that animals approach a distant sound source to obtain water reinforcement. Stimuli were single noise and tone bursts, 65 ms in duration including 20-ms rise and fall times. Tone frequencies were 2, 4, 8, 16, and 32 kHz adjusted to 40 dB (SPL) above the rat's absolute threshold. Five animals were tested in the two-choice situation following bilateral ablation of auditory cortex. Some reduction in performance was observed relative to normals, but impairments were not severe. Similar results were obtained for 2 brain-damaged animals tested in the three-choice situation. Thus, the ability to localize sounds in space remained intact after complete destruction of auditory cortex, and there was no indication of a frequency-dependent deficit.