From point to plane in the brain: dimensional expansion.
“But, interestingly, tonotopic projections are not point to-point. Each characteristic frequency point on basilar membrane projects to an iso-frequency plane across the extent of the cochlear nucleus.
Thus cochlear place representation is expanded into a second dimension in brain.
These tonotopic sheets are preserved in projections all the way to cortex. We contrast this with the visual and somatosensory systems, where maps reflect a location of stimulus in space and the representations are point to point. “