Neural Mechanism And Modulation Of Multimodal Working Memory

Working memory is widely used in daily life and is associated with many cognitive abilities.There is little consensus on which neural regions are necessary and sufficient for working memory across modal and which neural oscillatory dynamics best describe its capacity.In different studies on neural modulation of working memory,there are problems such as disarray of effects and increased variability of effects due to different cognitive strategies adopted by individuals during tasks.More importantly,there is a lack of strong evidence to combine cognitive behavioral changes with neural responses.Here,using neural decoding techniques,this study investigates the cognitive neural mechanisms in different working memory modalities and mixed-modality working memory,as well as the brain network dynamics mechanisms on the cognitive modulation of working memory.The main study components and findings are as follows.Firstly,single modal stimuli(visual language,auditory language,and visuospatial)were used to study the cognitive neural mechanisms in different modalities and processing mode of working memory.The modal and load differences in visual language and auditory language working memory,and the processing mode and load differences in visual language and visuospatial working memory were analyzed by calculating the rhythm oscillations and brain network changes under the three-type stimuli.The results showed that load effects were associated with frontal theta rhythm,frontotemporal alpha rhythm and frontoparietal beta rhythm oscillatory activity.Modal effects were associated with frontal theta rhythm,temporoparietal alpha rhythm and parietal beta rhythm oscillatory activity.Processing modality effects were associated with frontal-occipital theta rhythm,temporoparietal alpha and parietal beta rhythm oscillatory activity.These results suggested that theta rhythm oscillatory activity may be prevalent in different modal working memory tasks and operated in the deployment of working memory resources.Attentional processes to different modal stimuli during working memory may be associated with temporoparietal alpha rhythm oscillatory activity,whereas beta rhythm oscillations may be related to successful maintenance in different modal working memory.Secondly,electroencephalogram(EEG)oscillatory properties and brain network information interaction patterns in a bimodal task were investigated using an audiovisual bimodal n-back experiment.Behavioral results showed that subjects performed better in the auditory modality than in the visual modality in a simultaneous bimodal n-back task,suggesting that auditory signals were more dominant than visual signals when visual and auditory inputs were updated and maintained simultaneously in working memory.Further from the neural signal decoding,it was found that theta rhythmic oscillatory activity was predominantly in the prefrontal lobe and increased with greater load,while alpha and beta rhythmic oscillatory activity was predominantly in the temporoparietal lobe.These results suggested that the frontal lobe theta rhythm played an executive control role in the integration of multichannel sensory input in bimodal working memory,that increased parietal alpha rhythm activity played a role in multimodal object representation and attentional control in mixed-modal working memory,and that beta rhythm oscillatory activity was associated with transfer effects in the mixed-modality n-back task.Thirdly,using visual graphic working memory 2-back task,we investigated the specific promotion effect of cognitive strategy combined with high-definition transcranial direct current stimulation(HD-t DCS)on working memory and the neural response mechanism of working memory.The results were as follows: first,in the absence of strategy and with electrical stimulation,different electrical stimulation methods can improve the executive ability of working memory,but there was no significant difference in the improvement effect of different methods.The results of brain network showed that the subjects mainly used the visuospatial sketchpad at this time;second,effective cognitive strategies can significantly improve the executive performance of working memory when there was no electrical stimulation.The results of brain network showed that the strategy group participants switched to using phonological loop;finally,when the specific cognitive strategy was matched with the corresponding neural control,the executive ability of working memory was significantly improved,and the neural response was consistent with the executive ability of behavior.