Fig. 6.

Cartoon schematic depicting spectral integration in A1, based on present results. Gaussians represent RFs in layers 2/3, 4, and 5/6 with subfields determined by thalamocortical (black) and intracortical (gray) synapses. Thalamic inputs (black arrows) mediating CF and near-CF responses enter the cortex via myelinated axons and may retain myelination through the deep layers. Intracortical horizontal projections (gray arrows) from regions with higher or lower CFs contribute to spectral integration in layers 2/3 and 4 but not layer 5/6. Similarly, local connections (vertical double arrows) amplify responses in layers 2/3 and 4 but not 5/6.