A PET investigation of lexicality and phonotactic frequency in oral language processing.

Lexicality and phonotactic frequency effects are observed in many cognitive studies on language processing, but little is known about their underlying neural substrates, especially with regard to phonotactic frequency effects. Here, we conducted a positron emission tomography (PET) study in which 11 right-handed volunteers had either to repeat or to listen to lists of words, high phonotactic frequency nonwords, and low phonotactic frequency nonwords. The comparison of word versus nonword processing consistently confirmed previous findings of left temporal and prefrontal activations classically ascribed to lexicosemantic processing. Higher activation was found in the right posterior superior temporal gyrus when comparing high phonotactic frequency nonwords to words, but not when comparing low phonotactic frequency nonwords to words. We propose that this region is implicated in the formation of temporary phonological representations for high-probability phonological events, which may support processing of high phonotactic frequency nonwords.