Resting State Functional Connectivity Subserving The Individual Difference In Perceptual Load Effect

Selective attention is a process whereby the brain selectively filters out large amounts of sensory stimuli and enables people to allocate the limited resources to just one aspect. This allows the brain to pay attention to what is vital for individuals while reduce the interference from distractors, and it is significant for person to perceive and adapt to the new circumstance. The issue on attention has attracted many researchers from long ago, and they mainly concerned about whether the selective attention occurred at early stage of perception or the late stage(early selection or late selection).Although this question has been widely studied, the results were not consistent. Perceptual load theory came up with a solution to the controversy on the locus of selective attention. The theory states that perception is a limited capacity process and proceeds automatically until that capacity is filled. When a task imposes high perceptual load, capacity is run out and distractors cannot be processed(in line with early selection views). However, when a task involves low perceptual load, all available stimuli are processed, distractors and targets alike, appropriate response necessitating selective attention at late selection(in line with late selection views). The perceptual load theory has acquired a wide range of support from previous researches on behavior and neuroscience domains. However, these researches mainly focused on the demonstration of the perceptual load theory; little of them attach importance to inter-subjects variability of perceptual load effect(PLE) and the mechanism behind the phenomenon of perceptual load. On the basis of earlier studies which concentrated on perceptual load, current study planned to adopt behavioral experiment and resting-state functional magnetic resonance imaging(rs-fMRI) measures to explore the individual differences of PLE and neural mechanism related to PLE.In Experiment 1, we adopted the letter search task, which was involved in response competition paradigm, to explore the role of perceptual load in modulating the interference from irrelevant stimulus, and we had put forward a simple expression to calculate perceptual load effect(PLE),then we studied the individual difference of PLE. Our results repeated the classic findings of studies regarding perceptual load theory: the perceptual load can significantly modulate the interference from irrelevant stimulus, in the high perceptual load condition the interference from irrelevant stimulus was reduced significantly compared to the low perceptual load condition. Moreover, the normality test of PLE showed that perceptual load effect was approximately normal distribution across participants, which imply that there existed individual difference in PLE.In Experiment 2, we took advantage of rs-fMRI measures, including the fractional regional amplitude of spontaneous low frequency fluctuation(fALFF) and resting state functional connectivity(RSFC), to explore PLE-related brain areas and functional connectivity network. The results were as follows:(1) fALFF-PLE correlation analysis showed that individuals with higher fALFF in left superior frontal gyrus/frontal eye field(SFG/FEF) and left insula may have a higher PLE, while the higher spontaneous activity in left middle temporal gyrus(MTG), left precentral/postcentral gyrus, right precentral/postcentral gyrus and right lingual gyrus(LG) negatively associated with the individual’s behavioral performance in PLE.(2) RSFC analysis revealed that: for seed region of left SFG/FEF, the synchronization between left SFG and left middle frontal gyrus, left superior frontal gyrus, left inferior parietal lobule, left superior/middle frontal gyrus and right superior parietal lobule/angular were positively correlated with PLE; with left MTG as seed region, however, the strength of functional connectivity between left MTG and right middle frontal gyrus, right inferior temporal gyrus, bilateral middle cingulum, right inferior parietal lobule and right inferior parietal lobule/supramarginal negatively associated with PLE, moreover, for seed region of left insula, the connections between left insula and right precuneus/post cingulum, right superior frontal gyrus and left middle temporal gyrus/angular were negatively related to PLE.In short, there are large individual differences in PLE, in addition, the reduction of interference from irrelevant stimulus in high perceptual load may be due to the top down attentional control. The results of present research have enriched the studies of perceptual load theory in behavioral and cognitive neuroscience domain, and deepened our understanding on the cognitive neuroscience mechanism of perceptual load.