Rapid information processing in the human brain is vital to survival in a highly dynamicenvironment. The key tool humans use to exchange information is spoken language, but the exactspeed of the neuronal mechanisms underpinning speech comprehension is still unknown. Herewe investigate the time course of neuro-lexical processing by analyzing neuromagnetic brainactivity elicited in response to psycholinguistically and acoustically matched groups of wordsand pseudowords. We show an ultra-early dissociation in cortical activation elicited by thesestimulus types, emerging ~50ms after acoustic information required for word identification firstbecomes available. This dissociation is the earliest brain signature of lexical processing of wordsso far reported, and may help explain the evolutionary advantage of human spoken language.
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