Generators of the gamma-band activities in response to rare and novel stimuli during the auditory oddball paradigm.

In this study, we report the cortical sources of the gamma-band activity emitted during the auditory oddball paradigm using the adaptive beamformer algorithm and non-parametric permutation test and then compare them with those of the P3a and P3b components. The results of the gamma-band current sources revealed that the same gamma-band activities are in process during the rare target and novelty task. In the low (30-55 Hz) gamma-band activity, the common sources were localized in the (inferior) anterior cingulate and adjacent inferior frontal cortex. In the high (65-85 Hz) gamma-band activity, the generator was represented in the superior frontal cortex. On the other hand, the P3a and P3b generators showed widespread distributions including the well-known fronto-parietal network [J. Polich, Theoretical overview of P3a and P3b, in: J. Polish (Ed.), Detection of Change: Event-Related Potential and fMRI Findings, Kluwer Academic Press, Boston, 2003, pp. 83-98]. In conclusion, the same frontal generators of gamma-band activities in the present study may be associated with the functions of attentional control for the binding of consecutive cognitive stages corresponding to earlier P3a and later P3b components, which have distinct source distributions except for some overlaps.