Yunru looked at harmonic sensitivity in A1 and A2. She found harmonic-sensitive neurons (HNs) responding only to harmonic stacks but not to individual frequencies in all areas at similar proportions. Thus, harmonic sensitivity is already established in A1 L4. Thus, tuning to sounds of complex spectral contents might be a fundamental processing function of the auditory cortex and is already established in A1 L4, which receives major thalamic inputs. Read more here eNeuro 2026.