The Study Of Age-related Multisensory Integration Based On Time-frequency Analysis

Information from the different senses(e.g. visual information, auditory information, olfactory information and tactile information) is seamlessly integrated by the brain in order to modify our behaviors and enrich our perceptions. These informations were often efficiently merged to form a unified and robust percept, rather than being perceived as incoherent ones. A number of studies have demonstrated that multisensory integration has a facilitative effect on behavioral performance, which plays an important role in our perception, learning and memory. Considering of the age-related cognitive deterioration and the alterations in the anatomy and physiology of the brain, it is not surprising that multisensory integration also changes with age.Although there are some reseachers have explored how cognitive aging affects multisensory integration. The conclusion is inconsistent and the neural mechanism remains unclear. Studying multisensory integration during healthy aging can not only explore brain mechanisms of multisensory integration, but also provide theoretical and scientific basis for the diagnosis and treatment of elder brain diseases.In this paper, we designed a classical audiovisual integration EEG experiment. Unisensory auditory stimuli, unisensory visual stimuli and multisensory audiovisual stimuli were presented to the subjects. Using a 32-channel EEG acquisition system, we collected 24 subjects’(12 healthy old subjects and 12 healthy young subjects) EEG signals. After the pre-processing of denoise, segmentation and correction, EEG signals were analyzed on the time-frequency domain from the angel of ERP and oscillatory activity. With behavioural results, we discussed the differences between old peopole and young people during audiovisual integration.Based on the above research, we draw the following conclusions: 1. In the process of simple audiovisual integration, the differences between old people and young people mainly reflect in the reaction times on the level of behavioural performance. Old people can benefit more from the audiovisual integration. 2. Several brain regions participant in the process of audiovisual integration, including primary visual cortex, auditory cortex and other functional cortex, and there are interaction among them. 3. Integration effects were discovered in relatively early stage of audiovisual integration, old people’s integration effects differ in time windown, strength and brain area compared with young people, which represent two different processing mechanisms. 4. Spatio-temporally distinct integration effects were observed in all frequency bands(delta, theta, alpha and beta). These were most pronounced and sustained in the theta and alpha frequency bands in fronto-centro-parietal sites. And the spectral power of integration components in alpha frequency band was the most pronounced between young people and old people.