Conversely, in defence of the P600-as-P3 hypothesis, Coulson et al. (1998a) argued that P3 magnitude correlates with item salience and subjective categorisation confidence, and double violations are presumably more salient. Further studies arguing against the P600-as-P3 perspective report that basal ganglia (Frisch, Kotz, Cramon, & Friederici, EGFR inhibitor 2003) or Broca’s area (Wassenaar, Brown, & Hagoort, 2004) lesions eliminate a linguistic P600, yet not an oddball P3 (though several studies also report a P600 after left-hemispheric or basal ganglia lesions; Kielar et al., 2012 and Kotz and Friederici, 2003, indicating that task peculiarities may be responsible rather
than a specific role of the lesioned area in P600 generation). In these studies, linguistic but not oddball task Selleckchem ABT199 performance was drastically impaired in the lesion group compared to controls, thus in fact strengthening the link between the P600 and behaviour, and thereby, the P3. The missing P600 here may simply reflect that participants were not able to reliably realise that an item should be categorised as ungrammatical. A recent account of the P3 side-steps many of these issues (e.g.
co-localisation of P3 and P600 to common cortical or subcortical generators), while at the same time entailing a novel range of predictions under the assumption that it also applies to the P600. In contrast to models explaining ERP generation by the evoked synchronisation of independent cortical generators, Nieuwenhuis et al. (2005) connect the P3 to phasic activity of the brainstem Locus Coeruleus/LC (Aston-Jones and Cohen, 2005 and Bouret and Sara, 2005). They thus associate it with a neuromodulator system
affecting multiple cortical sites with a distinct time course. The LC diffusely releases norepinephrine/NE, which facilitates general cortical state transitions, supporting cognitive reorientation (like response execution or inhibition). The P3 is mostly insensitive to the sensory qualities of the stimulus and reflects contextually evoked subjective significance: surprising or expected, task relevant or intrusive stimuli may all result in a P3, since they all require Progesterone cortical reorientation. Accordingly, the P3 has also been connected to the Ventral Attention Network (Corbetta, Patel, & Shulman, 2008), which governs effective stimulus-driven reorienting. This system is activated by stimuli such as task-critical targets, which, by their subjective importance, capture the subject’s attention. This strict association between the timing of the P3 and that of overt behavioural responses is emphasised in the LC/NE-P3 theory, since this same alignment between overt, behavioural manifestations of reorientation mirrors that of LC neurons, which are known to be better aligned with response than with stimulus timing (Rajkowski, 2004).