ABSTRACT
The brain activity associated with processing numerical end values has received limited research attention. The present study explored the neural correlates associated with processing semantic end values under conditions of automatic number processing. Event-related potentials (ERPs) were recorded while participants performed the numerical Stroop task, in which they were asked to compare the physical size of pairs of numbers, while ignoring their numerical values. The smallest end value in the set, which is a task irrelevant factor, was manipulated between participant groups. We focused on the processing of the lower end values of 0 and 1 because these numbers were found to be automatically tagged as the "smallest." Behavioral results showed that the size congruity effect was modulated by the presence of the smallest end value in the pair. ERP data revealed a spatially extended centro-parieto-occipital P3 that was enhanced for congruent versus incongruent trials. Importantly, over centro-parietal sites, the P3 congruity effect (congruent minus incongruent) was larger for pairs containing the smallest end value than for pairs containing non-smallest values. These differences in the congruency effect were localized to the precuneus. The presence of an end value within the pair also modulated P3 latency. Our results provide the first neural evidence for the encoding of numerical end values. They further demonstrate that the use of end values as anchors is a primary aspect of processing symbolic numerical information.
ABSTRACT
In a paradigm combining color-word Stroop and misspelled words processing, spelling mistakes were placed in half the Stroop stimuli. Participants were presented with words written in different ink colors and asked to identify the color of the ink while ignoring the word meaning. Importantly, whether the word was correctly spelled or not was completely irrelevant to the task. The spelling manipulation did not change the phonology or semantic meaning of the words. Congruency and spelling correctness were manipulated orthogonally and interacted at the behavioral level. Event-related potentials showed a very early processing of misspelled words. The present findings are in line with the idea of anterior cingulate cortex (ACC) involvement in cognitive monitoring, expressed mainly in the theta frequency band. The present study demonstrates that this monitoring mechanism is elicited automatically, in other words, this mechanism perceives erroneous stimuli even when they are absolutely irrelevant to the participant׳s task. At later processing stages, the same central monitoring mechanism is also involved in the detection/resolution of conflict.
