ERP effects of mismatch in word fragment priming

Friedrich, C. K.1,2, Alter, K.2, and Friederici, A. D.2
1Department of Linguistics, University of Konstanz, Germany; 2Department of Neuropsychology, MPI of Cognitive Neuroscience, Leipzig, Germany

Onset fragments of spoken and visual words modulate the processing of subsequently presented visual targets. For example, the string 'kon' facilitates responses to a matching target like 'Konto' (Engl. account), but not to an unrelated target like 'Salto' (Eng. somersault). The behavioral facilitation is accompanied by a reduced amplitude of a left-posterior positive going ERP deflection, named P350, and a reduced N400 component for matching targets. The former effect, peaking at 350 ms, has been related to the activation of modality-independent lexical representations. In contrast, the N400 peaking at 500 ms has been related to strategic mechanisms (Friedrich, Kotz, Friederici & Gunter, Journal of Cognitive Neuroscience, in press). In the present experiment we tested ERP effects of partial mismatch for prime - target pairs like 'kon' - 'Kante' (Engl. edge), being different in syllable nucleus. Responses to partially mismatching targets were longer than responses to matching targets, but shorter than responses to unrelated targets. However, the amplitude of the P350 was only reduced for matching targets, but not for partially mismatching targets. In contrast, the amplitude of the N400 showed the same pattern as the reaction times. Partially mismatching targets elicited an enhanced amplitude of the N400 as compared to matching targets, but a reduced amplitude of the N400 as compared to unrelated targets. The present results may indicate that lexical representations of partially mismatching targets do not receive activation from the preceding primes. The behavioral facilitation appears to be an artifact of strategic mechanisms underlying the N400 priming effect.