Study On Audiovisual Integration In Young And Elderly Adults By EEG Complex Network Algorithm

Informations from the different senses(e.g.visual information,auditory information,tactile information and olfactory information)were often efficiently merged to form a unified and robust percept,rather than being perceived as incoherent ones.This is known as multisensory integration which plays an important role in the accurate perception of the external world.Ninety-seven of the information people received comes from vision and hearing.So audiovisual integration occurs frequently and has been shown to exhibit age-related differences via behaviour experiments or time-frequency analyses.However,the underlying neuronal mechanisms are still not fully understood.Recent research has shown that functional interactions between brain areas are crucial for effective cognitive functioning,a concept referred to as “functional connectivity”.We sought to investigate the age-related functional connectivity in different oscillatory frequency bands during audiovisual integration.This research is of great significance in the fields of basic neuroscience,brain computing and artificial bionic science.Twelve young individuals(22–28 years,mean age ± SD,23.9 ± 1.73)and twelve old individuals(60–78 years,mean age ± SD,68.6 ± 4.74)participated in this study.Visual,auditory,and audiovisual stimuli were randomly presented peripherally;during this time,participants were asked to respond promptly to the target stimulus.Meanwhile electroencephalography(EEG)recordings captured visual,auditory,and audiovisual processing.For the target stimulus,hit rates and response times of targets were computed separately.A race model was used to analyze the audiovisual integration.For non-target stimuli,we focused on alpha(8-13 Hz),beta(13-30 Hz),and gamma(30-50 Hz)bands.The modified Phase Lag Index(PLI)was used to study the dynamics of functional connectivity.Then,the network topology parameters,which included the clustering coefficient,path length,small-worldness global efficiency,local efficiency and degree,were calculated for each condition.Then,a Pearson correlation was used to test the relationship between each network topology parameters and response time.The results of race model showed that the time window of behavioral facilitation in older adults was longer and more delayed than that in the younger adults.Lager PLI means old adults activated stronger connections during audiovisual processing in the beta band.The relationship between network topology parameters and the performance of audiovisual integration was detected only in old adults.Thus,we concluded that old adults who have a higher load during audiovisual integration need more cognitive resources.Furthermore,increased beta band functional connectivity influences the performance of audiovisual integration during normal aging.