These results are in striking agreement with the reduced left inferior parietotemporal P3 source found during visual word encoding in schizophrenia (Kayser et al., 2006). In their meta-analysis of P3 asymmetry in schizophrenia for auditory oddball data, Jeon and Polich (2001) reported no reliable effect sizes for lateral temporal (T7/8) scalp locations, but instead for homologous sites located more posteriorly, towards the medial-parietal regions (referred to as TCP1/2), which more closely matches the present results. It is generally well-known that multiple generators contribute to the scalp recorded P3 potential, and although task-specific requirements, including stimulus modality and response mode, critically affect and modulate its topography, temporal-parietal activity is considered a main source contributing to stimulus-driven P3b (e.g., Picton, 1992; Halgren et al., 1995a, 1995b; Molnar, 1994; Brazdil et al., 2003; Polich, 2007). Tenke et al. (2008) recently supplemented the current CSD-PCA approach with a hemispatial PCA to disentangle parietal and temporal neuronal generators as contributors to P3 source activity during a dichotic oddball task. Interestingly, by tackling the recording reference conundrum of auditory oddball data with CSD transformations and spatial
