AUDITORY SPATIAL TUNING OF CORTICAL-NEURONS IS SHARPENED IN CATS WITHEARLY BLINDNESS

1. The specificity for the location of a sound source in azimuth was m easured in single neurons of the anterior ectosylvian (AE) region of t he cat's cortex, which includes the anterior auditory field (AAF) and the anterior ectosylvian auditory field (AEA). 2. The influence of vis ual experience on auditory spatial tuning of these neurons was determi ned by comparing responses in cats with binocular deprivation from bir th with those in normal control cats. 3. Spatial tuning was measured u nder near free-field conditions by presenting broadband sounds through a speaker in seven different azimuthal locations, from -60 to +60-deg rees at 20-degrees intervals. Elevation was constant at the cats' ears . 4. In normal cats, a little over one-half of the neurons in the AE r egion (82/146 = 56%) showed some degree of azimuthal spatial tuning, a s defined by at least a 2:1 ratio of responses between best and worst location. The rest (44%) were omnidirectional. 5. In binocularly depri ved cats, a significantly higher proportion (70/82 = 86%) of the neuro ns in the AE region were spatially tuned. Only 14% were omnidirectiona l. Median spatial tuning width was significantly sharper than in norma l cats. 6. We conclude that visual deprivation from birth induces inte rmodal changes that enhance the response specificity of neurons in the auditory cortex. These modifications may constitute the neural basis of behavioral compensation for early blindness.