Critical period for neural representation of musical chords in the auditory cortex of rats

It is previously reported that human preference for consonant chords or intervals is affected by experience with Western music. This study used rats as an animal model to investigate whether the acoustic critical period influences the formation of harmony perception and preference through acoustic experience. Five groups of rats were tested. Two groups were exposed to consonant or dissonant chords for approximately 3 weeks during the critical period, and other two groups were exposed to consonant or dissonant chords after the critical period. The remaining group was kept naïve. All groups were allowed to grow until 8 weeks of age, and chord preferences were quantified based on active listening behavior. Additionally, we measured multi-unit activity in response to chords using a microelectrode array under anesthesia and quantified specific activity in response to chords. The results showed that only chord exposure during the critical period biased post-developmentalchord preference and that exposure to dissonant chord also influenced the characteristics of neural activity in the auditory cortex. These findings suggest that the neural basis for processing chord information may be acquired through experiences during the critical period. [Work supported by JSPS KAKENHI (23H03465, 23H04336, 24H01544, 25H02600), AMED (24wm0625401h0001), JST (JPMJPR22S8), the Asahi Glass Foundation, and the Secom Science and Technology Foundation.]