The Role Of Perceptual Load And Working Memory Content In Selective Attention

In daily life,to survive in a complex and dynamically changing world,selective attention maks people to focus on that which is relevant to our behavioural goals while ignoring or suppressing task-irrelevant information.The cognitive and neural mechanisms which underlie this process are a key topic of investigation in cognitive psychology.There are many factors which can affect the selective attention.One the one hand,the level of perceptual load in a relevant task is one of major determinant of selective attention.The perceptual load theory(Lavie,1995;Lavie & Tsal,1994)suggested that perception has limited capacity but processes all stimuli in an automatic mandatory fashion until it runs out of capacity.Tasks with high perceptual load engaging full capacity will simply leave no capacity for perception of irrelevant distractor.Therefore,there is no distracter interference effect.In contrast,in situations of low perceptual load,spare capacity remaining beyond the task-relevant processing spills over involuntarily to irrelevant distractor processing,and distracter interference effect is observed.On the other hand,the biased competition model suggests that the content of working memory is another factor to influence selective attention(Desimone,1998;Desimone & Duncan,1995;Duncan & Humphreys,1989).When we held a object in working memory,a attentional template was developed and attention is bias selection to those items matching the “template” held in memory for improving search efficiency.The current study focuses on the development of perceptual load study and working memory guidance study.Furthermore,this is also the first study to explore the competition mechanism between perceptual load and working memory guidance in selective attention.Firstly,we used behavior data to explore the essence of perceptual load effect(study 1)and adopt the resting state f MRI to investigate the individual differences of perceptual load effect and the corresponding neural mechanisms(study 2).Secondly,given that the high time resolution of event related potential(ERP),study 3 explored the influence from visual working memory content on selective attention in early visual processing.Finally,study 4 combined the perceptual load and working memory guidance,by using ERP technology and task state f MRI technology,to explore the competition mechanism between them in selective attention.Study 1 investigated the essence of reduced distracter interference in high perceptual load condition.Experiment 1 used the same design with Lavie et al.(2003)and the non-targets were pseudo-words,excepting that the materials were Chinese stimulus(Chinese famous faces and names).The result showed that the present data reflect a successful replication of previous study.Distracter faces interfered with target performance at both low-and high-load.Based on the Experiment 1,Experiment 2 introduced the dilution condition(same to high-load condition,but target marked in red)and block design was used.The result showed that similar to the result of Experiment 1,the distracter interference effect was observed in low-load,high-load and dilution condition.In Experiment 3,to increase domain-similarity,the non-targets were replaced by real Chinese words.The result showed that the distracter interference effect was significant at low-load and high-load,but eliminated at dilution condition.In Experiment 4,to get greater domain overlap between non-targets and distracters,the non-targets were replaced by true Chinese names.The result showed that the distracter interference effect was only observed in low-load condition and compeletly eliminated in both the high-load and dilution conditions.These results suggested that the decrease for distractor processing from the dilution effect of non-targets on distracter and which depends on the domain congruency between distractor and non-targets.Study 2 tried to explore the relation between perceptual load modulation effect and the intensity of spontaneous brain activity(Amplitude of Low Frequency Fluctuation,ALFF)and resting state functional connectivity(RSFC).Experiment 5 used classical perceptual load task paradigm.The result showed that perceptual load modulation effect was significantly associated with ALFF in the attention control network and the sensory cortex,including the supplementary motor area,left inferior occipital gyrus and left inferior frontal gyrus.Furthermore,the resting state functional connectivity between inferior occipital gyrus and inferior frontal gyrus was significantly associated with the individual differences of perceptual load modulation effect.These results suggested that the modulation of the interference from distraction stimulus depends on the attention control network.Study 3 investigated the role of visual working memory content in selective attention and the corresponding electrophysiological characteristics.Experiment 6 used delayed-match-to-sample tasks paradigm and the working memory content was meaningless images.Behavioral results showed that response times were longer when the distractor in the visual search task was held in WM.ERP results showed that both in the P1 and N1 component,match trials elicited larger amplitude than mismatch trials.s LORETA showed that the P1-related activation occurred in the occipital lobe and the N1-related activation occurred in the parietal gyrus.Time-frequency data suggested that alpha-band event-related spectral perturbation(ERSP)magnitudes increased under the match condition compared with the mismatch condition.These results suggested that the reappearance of a stimulus held in WM enhanced activity in the occipital area.Subsequently,in N1 stage,this initial capture of attention by WM could be inhibited by competing visual inputs through attention re-orientation,reflecting by the alpha-band rhythm.Study 4 explored the time dynamic and neutral mechanism when selective attention is influenced by both perceptual load and WM guidance.On the basis of the Experiment 6,Experiment 7 increased the perceptual load and the distracter stimulus was high salience.Behavioural data showed that response times were longer when the distractor in the visual search task was held in WM at low-load and high-load eliminated this effect.The ERP results revealed that match trials eliciting larger P1 than mismatch trials,regardless of the level of perceptual load.In contrast,match trials eliciting larger N1 than mismatch trials only at low-load condition and the difference eliminated by high perceptual load.s LORETA showed that the P1-related activation occurred in the occipital lobe and the N1-related activation occurred in the parietal gyrus.These results suggest that in selective attention,the information held in WM could capture attention at the early stage of visual processing in the occipital cortex.Interestingly,this initial capture of attention by WM could be modulated by the level of perceptual load and the working memory guidance eliminated by high perceptual load.Experiment 8 used the classical delayed-match-to-sample tasks paradigm,but the distracter and target stimuli was tied together,which was not high salience.Behavioural data showed that at low-load condition,the RT of memory match trials have no difference with neutral trials.However,at high-load condition,the RTs of memory match trials were longer than neutral trials.f MRI results showed that the main effect of perceptual load activated areas were mainly distributed in thefrontal lobe,temporal lobe and occipital lobe area.The main effect of validity activated occipital lobe and the interaction effect between perceptual load and validity activated precuneus area.Function connection results showed that at low-load condition,precuneus was positively coupled with occipital area;at high-load condition,precuneus and occipital lobe and frontal lobe were positively coupling.The coupling between precuneus and frontal lobe was only observed in high perceptual load condition,and not in low-load condition.These results suggested that the development of frontal-parietal-occipital pathway is the neural basis of working memory guidance.Through four closely connected researches,the current study revealed the role of perceptual load and working memory guidance in selective attention respectively.And more importantly,the competitive interaction mechanism between them in selective attention was also explored.By this,we can expand the existing research and integrate this two research areas.Firstly,we confirmed that the eliminated distracter interference effect in high-load condition was due to the dilution effect from non-targets to distracter,which supported the dilution effect.Secondly,it is pointed out that spontaneous brain activity can reflect the individual differences of perceptual load modulation effect and the stronger the functional connectivity between inferior occipital gyrus and inferior frontal gyrus,the greater perceptual load modulation effect,and the smaller distracter interference effect.Thirdly,we found that the visual working memory could guide attention automatically,which occurred in the early perceptual processing stage.Finally,it showed that the working memory guidance influenced by the level of perceptual load and the corresponding interaction result was related to the salience of distracter.When the memory matching distracter own high salience,it can automatically capture attention priority,both in low-and high-load condition.However,this effect was eliminated by the high perceptual load.In contrast,when the memory matching distracter has no salience,at high-load condition,the development of frontal-parietal-occipital pathway made working memory guidance observed;at low-load condition,the coupling between precuneus and occipital area was not enough to produce working memory guidance.These findings make a deeply understanding to perceptual load effect and working memory guidance.This is also the first study to explore the time dynamic and neutral mechanism when selective attention is influenced by both perceptual load and WM guidance,filling the gap in the cross field.