Stability of Source Localization with LORETA of Visual Target Processing

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Abstract
This study investigates whether LORETA, a method of source localization of EEG data, reveals replicable and valid sources of event-related potentials (ERPs), which are supposed to be generated in a widespread cortical network. For that purpose, the ERPs in a rare primer (= target) and a frequent distractor condition (= nontarget) of a visually presented Continuous Performance Test (CPT) were analyzed in two independent samples of healthy subjects (n1 = 49, n2 = 38). At about 420ms significantly higher global field power values (GFP) were observed in the target condition as compared to the nontarget condition. For both samples the LORETA source localization revealed significantly higher activation for the target-condition as compared to the nontarget condition in the anterior cingulum, the precuneus and superior-posterior parietal cortex (parietal lobe), the insula, and the fusiform gyrus (temporal lobe). Only in the second sample were widespread areas in the frontal cortex also activated. The results indicate that LORETA localizes widespread cortical areas involved in target processing similar to results of fMRI studies.