Brain Conflict System Can Be Modulated By Working Memory Load And Selective Attention: An ERP Study

Purpose: To study the effects of working memory load and selective attention on conflict system, mainly through the event related potential, and investigate the mechanism of conflict system.Method: The study orderly examined the electroencephalic response in S1-S2 and cross modal paradigms, while 24 subjects with normal visual function were receiving different stimulus types with the other eye covered. According to the difference of stimulus types, the study were divided visual attended group(VA) and visual unattended group(VU), and three working memory loads were recorded for each group.Results:(1) The N1 mainly located at temporal-occipital area.There was no statistical significance among the latencies of N1 component for different conditions.(2) N1-difference did not differ from the activity within the three working memory loads for VU.(3) Meanwhile, the N1-difference was distributed over the three working memory loads for VA. Post-hoc comparisons on VA showed that the N1-difference recorded in the low memory load did not differ from the activation in the middle memory load, while significantly differed from the activity of the high memory load. What’s more, there was statistically significant difference between the middle memory load and high memory load.(4) In VA: N270 appeared on the regions within F3, F4 and C3 sites in the low memory load, while distributed on the F3 and C4 sites under the middle memory load. For VU, N270 was evoked on the F3 and F4 sites in the low memory load and distributed only on the F3 region in the middle memory load.(5) We considered the time window 230-340 ms on F3 site to compare the N270d(mismatches minus matches) across the two groups. Statistical analysis told us that there was a main effect of working memory load. Post-hoc analyses revealed a N270 d of lager amplitude in the low memory load compared to the high memory load, and also the N270 d of middle memory load was larger N270 d than the high memory load. Similar ANOVA for the difference between the low memory load and middle memory load did not yield meaning results.(6) N270 was absent in the high memory load for both groups.Conclusions: The present data revealed different working memory loads and selective attention on the EEG evoked activity. In summary, the conflict system is sensitive to the amount of attentional allocation, and can be affected by the working memory load. Interestingly, the effect here seemed to have similar effect on the cognitive process not only at the early cortex processing N1, but also at later cognitive process N270. These results suggest that conflict detection could be modulated under different working memory loads for attended and non-attended groups.