Our work examines the processing interactions between different levels of representation (mostly phonetic and lexical) during the perception of spoken language.  The approach is strongly interdisciplinary, embracing theory and experimental paradigms ranging from acoustic-phonetic analysis to formal linguistics, psycholinguistics and cognitive neuroscience.  Our current work relies on the use of Granger causality analysis of high spatiotemporal resolution MRI constrained movies of cortical activation to observe patterns of directional functional interaction between localized brain regions during spoken language perception.  Drawing on a broad experimental localization literature, we can use these analyses to develop highly articulated, empirically grounded models of cognitive processing architecture. Our work suggests that speech perception is a highly interactive process involving bidirectional connections to between brain regions associated with phonetic processing and higher regions associated with representations of articulation, phonological wordform, semantics and working memory