David Gow has published a series of papers on the cortical basis of speech perception using pretty sophisticated analytic tools that do not often get applied to the type of data we are used to.
For example, in this Cognition paper: "Articulatory mediation of speech perception: A causal analysis of multi-modal imaging data" (2009) by Gow and Segawa, Granger causality analyses are used to support the Motor Theory.
And in this NeuroImage paper: "Lexical influences on speech perception: A Granger causality analysis of MEG and EEG source estimates" by Gow, Segawa, Ahlfors, and Lin (2008), top-down effects demonstrated by Granger causality analysis appear to have a lexical origin and compelling effects on phonetic perception. This is a longstanding battle in spoken word recognition, and I'm pretty enthused to see new data of this type addressing this controversy.
Common to some of David's recent work is a demonstration of the pretty compelling contribution of top-down factors in the analysis of the speech signal. One thing that is a little less obvious is why these top-down effects should have the supramarginal gyrus as a critical ingredient. It's my homework this week to work through these papers in sufficient detail to really get my head around them. I am already predisposed to the top-down part, but I do need to understand why the SMG would be the critical node. What's really impressive is the thoughtful integration of EEG, MEG and MRI data.
David, if you're reading this, it would be great to get a bit of discussion going on this issue. For example, how deeply held is your commitment to the SMG? Did you guys find any data that challenge that conclusion, or are you willing to bet something substantial?