A layer-specific model of cortical sensory aging

The segregation of processes into cortical layers is a convergent feature in animal evolution. However, it remains unclear how changes in the cortical layer architecture affect sensory system function and dysfunction. To address this, we conducted layer-specific in-vivo 7T-MRI of the primary somatosensory cortex in younger and older adults and in an adult with congenital arm loss. Input layer IV was enlarged and more myelinated in older adults, which drove extended sensory input signals, whereas with congenital arm loss, input layer IV contralateral to the missing limb had shrunk. Age-related cortical thinning was driven by deep layers, and accompanied by altered functional modulation and behavioral readouts. Neuronal calcium imaging and histology across aging mice revealed altered excitatory/inhibitory balance, with deep-layer cell loss and overall increased parvalbumin cell density as potential neural underpinnings. We here uncover the segregation of processes into cortical layers and its unique age-related profile. ### Competing Interest Statement The authors have declared no competing interest.