The Cortical Topography of Tonal Structures

Here's an interesting experimental result, from Per Janata's article The Cortical Topography of Tonal Structures Underlying Western Music in the December 2002 edition of Science:

In contrast to distributed cortical representations of classes of complex visual objects that appear to be topographically invariant (26), we found that the mapping of specific keys to specific neural populations in the rostromedial prefrontal cortex is relative rather than absolute.

Within a reliably recruited network, the populations of neurons that represent different regions of the tonality surface are dynamically allocated from one occasion to the next. This type of dynamic topography may be explained by the properties of tonality structures. In contrast to categories of common visual objects that differ in their spatial features, musical keys are abstract constructs that share core properties. The internal relationships among the pitches defining a key are the same in each key, thereby facilitating the transposition of musical themes from one key to another.

Two observations about this:

1. The brain may recognize individual pitches using "fixed Do," but it recognizes tonal relationships using "movable Do with a La-based minor."
2. The neural topography revealed by this experiment is compatible with an isomorphic note-layout, and therefore it ought to be tuning invariant. This observation could enable the experiment's results to be generalized beyond 12-tet to include not only 12-tet, but nearly all of the pre-modern and non-Western tunings ever used by humankind.