Electrophysiology Studies in Normal Population

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. On the other hand, the P3a and P3b generators showed widespread distributions including the well-known fronto-parietal network.

Grand-average ERP waveforms at Fz, Cz and Pz in each condition.


Scalp topographical and cortical current source maps for potential differences of grand-average ERPs.
a) maximal distribution of P3a in fronto-central area and the corresponding cortical generators in anterior cingulate and superior frontal gyrus; b) maximal distribution of P3b in centro-parietal area and the corresponding cortical generators in precuneus/cingulate gyrus and superior frontal gyrus.

Lee et al., 2007, Neurosci Letters


Activity of left inferior frontal gyrus related to word repetition effects: LORETA imaging with 128-channel EEG and individual MRI

We investigated the brain substrate of word repetition effects on the implicit memory task using low-resolution electromagnetic tomography (LORETA). The subjects exhibited word repetition effects with respect to the behavioral data, in which a faster reaction time was observed to the repeated word (old word) than to the first presentation of the word (new word). We found that the source elicited by the old words exhibited a reduced current density in the left inferior frontal gyrus.

Statistical parametric map of ERP generator elicited by old (a) and new words (b) at the latency of 400 ms.


Statistical parametric maps displaying decreased current density by word repetition effects at 400 ms post-stimulus.

Kim et al., 2006, Neuroimage