Representation Mechanism Of Attentional Template In Visual Search Task

Visual working memory is a system for processing and storing visual information.Visual attention is a process by which individuals filter and select external information.There is a close relationship between visual working memory and visual attention.In a visual search task,the visual information needs to be stored in the working memory first,and then the information stored in the working memory is compared with the information in the visual search task,and the item that matches the information in the working memory is selected.In the visual search task,the items stored in the working memory and used to match the items in search interface are called attention templates.However,it is still controversial whether the attention template contains the location information of the memory item.Some researchers believe that the attention template contains all the information of the memory item,including location information;while other researchers believe that in the visual search task,it is only necessary to compare the features of the memory item with the features of the search interface item,and the location information is not required,so that the template does not contain location information.In order to study this question,this study adopted a retro-cue paradigm,and used the event-related potential(ERP)indicator of contralateral delayed activity(CDA)and the lateralized alpha power representing spatial attention to evaluate the performance of visual working memory.The position information is tracked by comparing the CDA and lateralization alpha power changes before and after the appearance of the retro-cue,it is explored whether the attention template contains position information.This study includes two experiments.In Experiment 1,the subjects needed to memorize two items presented in the middle of the visual field and on the side of the visual field,and then construct an attention template according to the direction of the retro-cue to perform visual attention tasks.It was found that whether the retro-cue point to items in the middle of the field of view or the items on the side of the field of view,CDA was founded in the occipital lobe before the retro-cue were presented,indicating that the memory contains lateralization representations;and after the retro-cue is presented,CDA was disappeared.Meanwhile,instead of emerge alpha power suppression or CDA,the alpha power be enhanced,indicating that no lateralization spatial attention is produced.This shows that no matter whether the retro-cue point to the center line or the side,after the retro-cue are presented,the attention template no longer contains location information.However,since the two memory items in Experiment 1are cross-feature items,that is,one of them is a color memory item and the other is a shape memory item.In order to avoid memory items with more features contains a large amount of information so that the location information may not be memorized.In the second experiment,the two memory items were changed to the same category,both of which were color memory items,to further prove whether the position information in the attention template is suppressed.The EEG results were the same as in Experiment 1.After the retro-cue was presented,the lateralized alpha power increased,indicating that no lateralized spatial attention was generated.The above results show that in the feature-based visual search task,the attention template formed by memory representation does not contain location information.