Tuesday, November 27, 2012

Orthogonal acoustic dimensions define auditory field maps in human cortex

Wow, this is the most blogging I've done in months.  This one is way off the topic of embodied cognition and mirror neurons (some of you will be relieved to hear) and in my view more important.  An interdisciplinary group of us here at UC Irvine have successfully mapped two orthogonal dimensions in human auditory cortex, tonotopy (which we knew about) and periodotopy (which most suspected but hadn't measured convincingly or showed its orthogonal relation to tonotopy in humans).  What's cool about this is it allows us to clearly define boundaries between auditory fields just like is commonly done in vision.  There are 11 field maps in the human auditory core and belt region.

Previous studies of auditory field maps disagreed about whether A1 lined up along Heschl's gyrus or is perpendicular to it.  The disagreements stemmed from the lack of an orthogonal dimension to define boundaries.  We show that A1 lines up along Heschl's gyrus, as the textbook model holds, and show how contradictory maps can be inferred if you don't have the periodotopic data.

What can we do with this?  We can map auditory fields in relation to speech activations.  We can measure magnification factors.  We can measure the distribution of ~receptive field preferences for different frequencies or periodicities between auditory fields and between hemispheres (can you say, definitive test of the AST hypothesis?).  We can determine which fields are affected by motor to sensory feedback, cross sensory integration, attention, and so on.  We use them as seeds for DTI studies or functional connectivity studies.  The floodgates are open.

The report was published online today in PNAS.  You can check it out here:


Barton, Venezia, Saberi, Hickok, and Brewer. Orthogonal acoustic dimensions define auditory field maps in human cortex. PNAS, November 27, 2012, doi:10.1073/pnas.1213381109


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