Early development of a somatosensory fovea: a head start in the cortical space race?

Star-nosed moles have 11 mechanosensory appendages surrounding each nostril, and primary afferents from a single appendage-the tactile fovea-are greatly over-represented in somatosensory cortex. It was found that the foveal appendage led development in the periphery, had the greatest innervated surface area in embryos, and developed mature nerve terminals and epidermal sensory organs first; also, in developing cortex, markers for metabolic activity (cytochrome oxidase) appeared first in the fovea representation. This developmental sequence may provide the fovea with an advantage in a competition for cortical space, and account for the much larger areas of cortex devoted to foveal afferents.