The Effect Of Cross-modality Audiovisual Integration On Perceptual Decision-making Of Older Adults

In the study of the effects of aging on cognitive function,perceptual decision-making plays an important role as the basis of higher cognitive functions and core processing.Audiovisual stimulation can provide complementary information,which can reduce the uncertainty of information processing and improve the perception decision-making in the older adults.However,it remains unclear what role audiovisual integration plays in perceptual decisionmaking in older adults,that is whether multisensory information is integrated during the sensory encoding stage or decision-making formation stage.Therefore,this study attempts to explore dynamic processing mechanisms of audiovisual cross-modality perceptual decision-making in older adults,aiming to find out the influence of audiovisual integration on the processing stages of the perception decision-making in the older adults.This study employs a classic audiovisual stimulus classification task.Pictures of faces and cars were used as visual stimuli,and speech and the sound of car horns were used as auditory stimuli.Considering the individual differences in the visual and auditory functions,as well as better simulating the cognitive process of perceptual decision-making,the constant stimulus method was used to measure the visual and auditory functions of the subjects before the formal experiment.Six visual and auditory stimuli with different signal-to-noise ratios were randomly presented to the subjects.Then the stimuli with an accuracy rate of about 70% for each subject were calculated as the materials for this subject’s formal experiment.The audiovisual stimuli in the formal experiment were visual and auditory pairings,that is,face pictures were paired with speech,and car pictures were paired with sirens.In the formal experiment,subjects were randomly presented with visual stimuli,auditory stimuli,or audiovisual stimuli.Subjects were asked to press the left mouse button on pictures of faces and the sound of speech and press the right mouse button on pictures of cars and the sound of horns.The results showed that:(1)For the older and younger adults,the accuracy of the audiovisual stimuli was significantly higher than that of the visual and auditory stimuli,and the response speed of the audiovisual stimuli was significantly faster than that of the visual and auditory stimuli;(2)The drift-diffusion model fitting behavioral findings show that the decision boundaries of audiovisual,visual and auditory stimuli for the older adults are significantly greater than those of younger adults.The drift rate of the older and younger adults for audiovisual stimuli is significantly greater than that for visual and auditory stimuli.The nondecision time of audiovisual stimuli was significantly smaller than that of visual and auditory stimuli;(3)The relative multisensory gain of the response time in older adults was significantly greater than that in younger adults.There was no significant difference in the relative multisensory gain of the drift rate between older and younger adults.The relative multisensory gain of non-decision time in older adults was significantly greater than that in younger adults;(4)In the early stage of sensory encoding during 150~300ms,younger adults showed audiovisual integration in the prefrontal cortex and central area,but older adults did not show the audiovisual integration.In the late stage of decision-making formation during 500~700ms,younger adults showed audiovisual integration in the frontal,parietal,and occipital lobes,older adults showed audiovisual integration in the prefrontal,parietal,and occipital lobes.(5)In the early stage of sensory encoding during 150~300ms,there was no significant difference in the audiovisual integration between younger and older adults.In the late stage of decision-making formation during 500~700ms,the audiovisual integration of the prefrontal cortex was significantly greater in older adults than in younger adults,while the audiovisual integration in the frontal lobe was significantly greater in younger adults than in older adults.There was no significant difference in audiovisual integration of the parietal lobe between older and younger adults.The above results indicated that :(1)the speed of sensory encoding,information accumulation and motor response to audio-visual stimuli of the older and younger adults was faster than that of visual and auditory stimuli,indicating that audiovisual stimuli can promote the subcomponents of the response process;(2)cross-modality audiovisual integration did not promote the formation of the early coding stage in the older adults,but promoted the formation of the late decision-making stage in the older adults,indicating that the cross-modality audiovisual perception decision-making of the older adults conforms to the hypothesis of late integration promotion;(3)in the 500-700 ms time period In the frontal lobe area,cross-modality audiovisual integration has a smaller promotion effect on the perception decision-making of the older adults than younger adults,but in the prefrontal region of the 500-700 ms time period,the promotion effect of cross-modality audiovisual integration on the perception decision-making of the older adults is greater than that of younger adults,indicating that the prefrontal cortex plays an important role in the late decision-making stage of cross-modality audiovisual perception decision-making in the older adults.