What's beat got to do with it? The influence of meter on syntactic processing

Auditory ERP-data from patients with lesions (BG) or neurodegenerative change (PD) of the basal ganglia reveal that timing is crucial for syntax processing. As Friederici et al. (2003), Frisch et al. (2003) and Kotz et al. (2003) showed, patients do not elicit a P600-component when presentation rate is random during syntactic processing. This applies to several syntactic violation types which evoke a P600 in healthy participants. Recent evidence has demonstrated that external predictable rhythmic stimulation re-elicits the P600 in Parkinson patients during the auditory presentation of syntactically erroneous sentences (Kotz & Gunter, 2005). Based on these observations, it is assumed, that perceived metrical regularities of a given language should influence speech perception and, in turn, syntactic processing. As German is a stress-timed language, we hypothesized that stressed syllables should be the predictable speech internal rhythmic marker influencing auditory syntactic processing. Thus, we constructed metrically regular sentences, which were either grammatically, metrically, or doubly violated. Sentences only included words consisting of two syllables and first syllable stress (trochee), the default-meter in German. The grammatical violations were realized by morphosyntactic violations. Metrical violations were realized by putting stress on the second rather than first syllable of the critical item, while sentences remained grammatically correct. Furthermore, double violations were syntactically as well as metrically erroneous (see example below). Example: a) Correct: 'Gina 'hätte 'Peter 'gestern 'abend 'reizen 'können Gina could have provoked Peter yesterday evening." b) Syntax: *'Gina 'hätte 'Peter 'gestern 'abend 'reizte 'können *"Gina could have provoke Peter yesterday evening." c) Meter: 'Gina 'hätte 'Peter 'gestern 'abend rei'ZEN 'können d) Double: *'Gina 'hätte 'Peter 'gestern 'abend reiz'TE 'können If meter works as a rhythmic pacemaker during auditory syntactic processing, the P600 should be elicited by metric as well as syntactic violations. Data was collected in two sessions. In one session subjects judged metrical correctness, in session two they judged grammatical correctness (counterbalanced across subjects). In the metric task, metric violation as well as the double violation evoked a late posterior positivity. In the syntactic task, all of the three manipulations elicited a P600. Latency of the positivity varied across the tasks (earlier onset of the positivity when syntactically instructed compared to metrically instructed). The current data will be discussed in the context of a domain-specific or a domain-general explanation of the P600