Neural Mechanisms Underlying The Interaction Between Attention And Working Memory

Attention refers to the ability to selectively note some information while ignoring other information,which is commonly studied by visual search tasks.Working memory(WM)refers to the online maintenance and manipulation of information that is no longer available to the senses,including information encoding,information maintenance,and information retrieval.Evidence showed that an actively maintained WM representation can bias attentional processing in favor of matching items over other,competing objects.In this thesis,based on the classic delayed match to sample & visual search dual task paradigm,we will explore the brain mechanism of the interaction between attention and working memory from the following three aspects,by using high-time-resolution electroencephalogram(EEG)recording,non-invasive transcranial magnetic stimulation technology(TMS)and high-spatial-resolution functional magnetic resonance imaging(fMRI).1.Exploring the resource allocation between WM maintenance and search processing from the time dimension.Previous evidence showed that attention and WM rely on a common cognitive resource,and irrelevant WM contents affect the early target selection and the later stage of target identification during the visual search.The present study used the dual task paradigm and event-related potentials(ERP).Subjects maintained a color in WM while performing a search task.The color cue contained the target(valid)or the distractor(invalid).The behavior shows faster search reaction times(RTs)and higher search accuracies(ACC)during the valid than the invalid conditions.In the valid condition,efficient target selection was indicated by the N2-posterior contralateral component(N2pc)and sustained posterior contralateral negativity(SPCN).Furthermore,the search RTs were faster and the amplitudes of N2 pc and SCPN were larger in the valid &incorrect WM condition than the valid & correct WM condition.These findings suggest that the maintained WM representation facilitated search processes,and the two compete for processing resources.When subjects did not actively attend to the memorized color during the maintenance interval,resulting in an incorrect response,more resources were available to the search task.2.Exploring the causal role of the dorsolateral prefrontal cortex and posterior parietal cortex in controlling the resource allocation between the WM maintenance and the search processing from the spatial dimension.The foregoing work found that the search was facilitated when the search target is spatially consistent with the WM stimulus.The right dorsolateral prefrontal cortex(rDLPFC)and the right posterior parietal cortex(rPPC)have been suggested to be associated with the interaction between the WM maintenance and the search processing.Thus,in the present study,online repetitive transcranial magnetic stimulation(rTMS)was delivered at rDLPFC and rPPC,concurrent with the search onset,inducing cortical inhibition at the site of stimulation.Results show that relative to rTMS over the control site,rTMS over rPPC and rDLPFC further decreased the search RTs in the valid condition.These findings suggest that rDLPFC and rPPC are critical for controlling the allocation of attention resources between the WM maintenance and the search processing in the valid condition.3.Exploring the neural substrates underlying the influence of the maintained WM representation on attentional processing during visual search from the time-spatial integrative dimension.The foregoing work finds that irrelevant WM contents affect the early target selection and the later stage of target identification during the visual search,and the processing of these two stages is modulated by the resource allocation between the WM maintenance and the search processing.Meanwhile,it is found that rDLPFC and rPPC are critical to controlling the resource allocation between the WM maintenance and the search processing,but lack of direct neural evidence.In the present study,simultaneous ERP-fMRI recordings were used to determine the neutral basis of the WM biases on the early attentional selection and the late target processing.Results show that the search RTs were faster and the amplitudes of target-related N1 component were larger in the valid relative to the neutral conditions in which the memory stimuli did not appear in the search display.These findings suggest that the maintained WM representation enhances the visual perception of the search target at an earlier stage.The fMRI results revealed that the activation of bilateral parietal cortex was associated with the beneficial effects from WM representation on attentional selection of the search target.The ERP-fMRI integrative analysis demonstrated that the WM-benefit related N1 component is generated in the bilateral parietal cortex,and the location overlaps with the regions from the fMRI activation maps.For the later stage of target identification,this part of the study included catch trials in which no target but only a matching distracter was presented,and participants were asked to refrain from responding.By calculating the catch vs.valid contrast,and the catch vs.invalid contrast,the left precentral/postcentral gyrus was found to be involved in the search target processing under WM biases;the ventrolateral prefrontal cortex,frontal medial cortex and right parietal cortex were identified to be involved in the response inhibitory under WM biases.It is worth noting that more target processing and response inhibitory related regions were recruited under invalid WM cues.In summary,this paper reveals that working memory can enhance the initial visual perception,early attentional selection,and later identification processing of the search target from the time dimension,and the processing of the latter two stages will be modulated by the resource allocation between the WM maintenance and the search target processing.From the spatial dimension,on the one hand,the paper reveals the causal role of the rDLPFC and the rPPC in modulating the resource allocation between the WM maintenance and the search target processing;on the other hand,the paper reveals the critical role of bilateral parietal cortex in mediating the beneficial WM biases in human visual attention.In addition,it is further revealed that the left precentral/postcentral gyrus was involved in the search target processing under WM biases;the ventrolateral prefrontal cortex,frontal medial cortex and right parietal cortex were involved in the response inhibitory under WM biases.