Modular organization of frequency integration in primary auditory cortex

Two fundamental aspects of frequency analysis shape the functional organiza tion of primary auditory cortex. For one, the decomposition of complex soun ds into different frequency components is reflected in the tonotopic organi zation of auditory cortical fields. Second, recent findings suggest that th is decomposition is carried out in parallel for a wide range of frequency r esolutions by neurons with frequency receptive fields of different sizes (b andwidths). A systematic representation of the range of frequency resolutio n and, equivalently, spectral integration shapes the functional organizatio n of the iso-frequency domain. Distinct subregions, or "modules," along the iso-frequency domain can be demonstrated with various measures of spectral integration, including pure-tone tuning curves, noise masking, and electri cal cochlear stimulation. This modularity in the representation of spectral integration is expressed by intrinsic cortical connections. This organizat ion has implications for our understanding of psychophysical spectral integ ration measures such as the critical band and general cortical coding strat egies.