A Thalamocortical Pathway for Decoding Communicative Syllables

Social communication in rodents depends on ultrasonic vocalizations, yet the neural circuits that selectively process these complex acoustic signals remain poorly defined. Here, using wide-field calcium imaging in awake mice, we identify a previously unknown region of the auditory cortex that we termed communicative auditory field (CAF). CAF is located between the anterior auditory field and ultrasonic field and responds selectively to ultrasonic syllables. Two-photon imaging revealed that individual CAF neurons are tuned to distinct syllable categories. Transsynaptic tracing showed that CAF receives its predominant thalamic input from the posterior nucleus (POL), defining a pathway in parallel to the canonical lemniscal pathway from the ventral medial geniculate body to the primary auditory cortex. Chemogenetic inhibition of either CAF or POL neurons projecting to CAF impaired innate social behaviors, including pup retrieval and courtship, whereas inhibition of A1 was ineffective. These findings define a specialized thalamocortical circuit for decoding ethologically relevant communication sounds.