关键词: 发展性阅读障碍, 视听时间整合, 视听时间再校准, 动态加工, Bayesian理论

Abstract:

Developmental dyslexia is a neurological disorder characterized by a specific deficit in reading, despite adequate intelligence and socioeconomic opportunity. The nature of deficits of developmental dyslexia has been under debate for a long time. A large number of studies have revealed that dyslexics suffer from impaired audiovisual temporal integration. Behavioral studies have found that developmental dyslexics have an abnormally wide audiovisual temporal binding window, making it difficult for them to separate temporally asynchronous stimuli. At the neural level, dyslexics showed no significant difference between mismatched negative (MMN) waves evoked by audiovisual asynchronous stimuli and those evoked by audio-visual synchronous or unimodal stimuli. Such audiovisual temporal integration deficits in developmental dyslexia are consistent across language, age and stimulus types. However, previous studies generally used the mean of all test results under different experimental conditions as the dependent variable, which only reflected the overall (i.e., average level) performance of audiovisual temporal integration processing and neglected to explore its dynamic process over time. Therefore, the audiovisual temporal integration deficits in developmental dyslexia are not fully exposed. The study of audiovisual temporal recalibration may make up for this deficiency. Temporal recalibration reflects the dynamic process of individuals adapting to different asynchronous times, that is, to re-establish stable prior knowledge of temporal relationships, which affects subsequent multisensory integration. Previous studies have shown that difficulties in recalibrating differences between internal temporal representations and sensory inputs can lead to impaired multisensory integration. Bayesian-based priori attenuation theory suggests that attenuated prior knowledge makes individuals without sufficient sensory reference to compare current inputs, thus increasing the difficult to recalibrate differences between internal representations and sensory inputs, resulting in impaired multisensory integration processing. Behavioral studies have found that developmental dyslexics have phonological recalibration deficits and they are unable to integrate audiovisual temporal information across sensory modals in accordance with optimal Bayesian statistical principles. At the neural level, developmental dyslexics have weaker neural adaptations than normal readers. The ability to adapt to temporal asynchrony requires temporal recalibrations. Furthermore, behind the normal overall performance of audiovisual temporal integration, there will also be rapid audiovisual temporal recalibration deficits that represent an abnormal integration process. Thus, impaired audiovisual temporal recalibration may underlie audiovisual temporal integration deficits in developmental dyslexia.
At present, to the best of our knowledge, no studies have directly explored the audiovisual temporal recalibration ability in developmental dyslexics. Future research can be carried out in the following areas: 1) The performance of audiovisual temporal recalibration ability of developmental dyslexia at different time scales; 2) The changes of audiovisual temporal integration window and audiovisual temporal recalibration effect over time in individuals with developmental dyslexia; 3) The neural basis of the audiovisual temporal recalibration deficits in developmental dyslexia; and 4) The correlations between audiovisual temporal recalibration ability and reading in developmental dyslexia; 5) The causal relationship between developmental dyslexia and audiovisual temporal recalibration deficits.

Key words: developmental dyslexia, audiovisual temporal integration, audiovisual temporal recalibration, dynamic processing, Bayesian theory