Adaptive categorization of sound frequency does not require the auditory cortex in rats.

A defining feature of adaptive behavior is our ability to change the way we interpret sensory stimuli depending on context. Rapid adaptation in behavior has been attributed to frontal cortical circuits, but it is not clear if sensory cortexes also play an essential role in such tasks. In this study we tested whether the auditory cortex was necessary for rapid adaptation in the interpretation of sounds. We used a two-alternative choice sound-categorization task for rats in which the boundary that separated two acoustic categories changed several times within a behavioral session. These shifts in the boundary resulted in changes in the rewarded action for a subset of stimuli. We found that extensive lesions of the auditory cortex did not impair the ability of rats to switch between categorization contingencies and sound discrimination performance was minimally impaired. Similar results were obtained after reversible inactivation of the auditory cortex with muscimol. In contrast, lesions of the auditory thalamus largely impaired discrimination performance and, as a result, the ability to modify behavior across contingencies. Thalamic lesions did not impair performance of a visual discrimination task, indicating that the effects were specific to audition and not to motor preparation or execution. These results suggest that subcortical outputs of the auditory thalamus can mediate rapid adaptation in the interpretation of sounds.