| 其他摘要 | Developmental dyslexia is characterized as a specific disability in learning to read fluently despite normal intelligence, adequate instruction and appropriate socio-cultural opportunities, and in the absence of sensory deficiencies in vision or hearing. The nature of deficits in developmental dyslexia has been under debate for a long time. A large number of studies have revealed that the individuals with dyslexia suffer from impaired audiovisual temporal integration. However, these studies only examined the overall performance of individuals with developmental dyslexia in the audiovisual temporal integration, i.e., their mean-level performance, without delving into the dynamic changes of the integration process. Rapid audiovisual temporal recalibration reflects the dynamic process of audiovisual temporal integration. Difficulties in recalibrating the differences between an individual's internal temporal representations and sensory inputs can lead to impaired multisensory integration, and individuals with developmental dyslexia exhibit deficits in recalibration-related abilities. Hence, deficits in rapid audiovisual temporal recalibration may represent the fundamental cause of impaired audiovisual temporal integration in individuals with developmental dyslexia.
The present study aims to systematically investigate the cognitive mechanisms and neural mechanisms of rapid audiovisual time recalibration in individuals with developmental dyslexia through three studies, including differences between individuals with developmental dyslexia and typically developing readers in these aspects and also investigating the relationship between rapid audiovisual temporal recalibration deficits and impaired reading abilities. Furthermore, preliminary exploration will be conducted into the role of rapid audiovisual temporal recalibration training in enhancing the reading abilities of individuals with developmental dyslexia, thereby establishing a causal link between rapid audiovisual temporal recalibration deficits and developmental dyslexia.
Study 1 consisted of two experiments, employing behavioral measurements to investigate the cognitive mechanisms of the rapid audiovisual temporal recalibration ability in individuals with developmental dyslexia. Experiment 1 and Experiment 2 used audiovisual simultaneity judgment tasks to examine the behavioral performances of individuals with developmental dyslexia in their rapid audiovisual temporal recalibration abilities for both speech and non-speech stimuli, and the differences compared to typically developing readers. The results revealed that individuals with developmental dyslexia exhibited an abnormally widened audiovisual temporal integration window at the overall (average) level when processing asynchronous audiovisual stimuli. This abnormal widening was primarily attributed to deficits in adjustment and adaptation within the integration processing rather than to an overall increase in the width of the audiovisual temporal integration window. Specifically, the simultaneity judgment of asynchronously presented audiovisual stimuli in individuals with developmental dyslexia was difficult to be influenced by the order of the sensory channel presented by the previous trial stimuli, indicating a rapid audiovisual temporal recalibration deficit. This impairment was existed not only in the processing of speech stimuli but also extended to non-speech stimuli, suggested a domain-general deficit. Furthermore, the atypical behavioral manifestations of rapid audiovisual temporal recalibration could directly damage reading abilities, or indirectly damage reading abilities by weakening reading related cognitive skills, such as phonological awareness and rapid automatized naming.
Study 2 consisted of two experiments, employing electrophysiological measurements to investigate the electrophysiological mechanisms of the rapid audiovisual temporal recalibration ability in individuals with developmental dyslexia. Experiment 3 and Experiment 4 used passive audiovisual simultaneity judgment tasks to examine the electrophysiological performances of individuals with developmental dyslexia in their rapid audiovisual temporal recalibration abilities for both speech and non-speech stimuli, and the differences compared to typically developing readers. The results revealed that the order of the sensory channel presented by audiovisual stimuli in the previous trial had a less effect on the amplitude of event-related potentials evoked by individuals with developmental dyslexia in the current trial. This phenomenon was accompanied by atypical neural oscillations between different current trial types before or after the first stimulus was presented. These atypical oscillations included abnormal neural oscillatory power differences in the α,β，and γ frequency bands, abnormally reduced differences in y frequency band connectivity strength, and an abnormal positive shift in the preferred coupling phase of rapid neural oscillations along the slow oscillatory cycle in the visual and auditory cortices. Furthermore, the atypical electrophysiological indices of rapid audiovisual temporal recalibration could directly damage reading abilities, or indirectly damage reading abilities by weakening reading related cognitive skills, such as short-term working memory.
Study 3 consisted of one experiment, employing behavioral training to investigate the causal relationship between rapid audiovisual temporal recalibration deficits and developmental dyslexia. In Experiment 5, two groups of children with developmental dyslexia were recruited, and rapid audiovisual temporal recalibration training and audiovisual discrimination training were implemented, respectively. Another group of typically developing chronological-age-matched children, who only participated in daily school activities, was recruited as a control group. After a total of 10 sessions of training in 5 weeks, children with developmental dyslexia who participated in rapid audiovisual temporal recalibration training demonstrated significant improvements in their rapid audiovisual temporal recalibration, reading fluency, phonological awareness, rapid picture naming, and orthographic awareness. This result provided evidence that a deficit in rapid audiovisual temporal recalibration is one of the contributing factors leading to developmental dyslexia.
The present study, for the first time, reveals the underlying mechanisms behind audiovisual temporal integration deficits in developmental dyslexia from the perspective of dynamic processing一rapid audiovisual temporal recalibration deficits. Furthermore, the present study elucidates how the deficit in rapid audiovisual temporal recalibration contributes to impaired reading abilities, and the causal relationship between the rapid audiovisual temporal recalibration deficits and developmental dyslexia. The following conclusions are drawn from this study:
(1) The underlying cognitive neural mechanism behind the impairment of audiovisual temporal integration in developmental dyslexia is the domain-general deficit in rapid audiovisual temporal recalibration.
(2) Rapid audiovisual temporal recalibration deficits can both directly damage reading abilities and indirectly damage reading abilities by weakening reading-related cognitive skills.
(3) Rapid audiovisual temporal recalibration deficits are one of the causes of developmental dyslexia, and individuals' reading abilities can be improved by training their rapid audiovisual temporal recalibration abilities.
At the theoretical level, the results of the present study strengthen our understanding of developmental dyslexia, and enrich and develop the general sensory deficit theory of developmental dyslexia. At the application level, the present study provides novel indicators for the early screening and diagnosis of developmental dyslexia, and provides new insights for clinical intervention and remediation of developmental dyslexia through simple sensory training, such as rapid audiovisual temporal recalibration training. |
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