Reading requires the combination of vision and audition, which builds the connection between grapheme and phoneme. It has been found that developmental dyslexia(DD) exhibits the deficit of attentional shift. Audiovisual attention shift has been related to the integration of phoneme and grapheme. However, only a few studies have examined the deficit of audiovisual attention shift of DD in the context of alphabetic writings. These studies have found that DD show a cross-modal attention shift when the task requires the attention shift from vision to audition. The authors speculated that the deficit may be related to the disability of auditory processing in DD. There are many differences between Chinese and alphabetic writing systems. For example, one Chinese character corresponds to one syllable, and there are no obvious rules for the correspondence of characters and syllables. Do Chinese readers with DD exhibit the similar deficits of audiovisual attention shift with DD in alphabetic writing systems? However, there is no study exploring the ability of attention shift between vision and audition as well as the relationship with the ability of visual and auditory processing in Chinese with DD. In addition, cross-modal attention shift can be divided into exogenous and endogenous attention. Exogenous attention, which is also called involuntary or stimulus-driven attention, can be triggered reflexively by a salient sensory event in the external world. In contrast, endogenous attention is also called voluntary or goal-driven attention and involves a more purposeful and effort intensive orienting process. They have the different cognitive and neural mechanisms. However, previous studies have not divided the exogenous and endogenous attention when exploring the ability of audiovisual attention shift in DD. Therefore, the ability of audiovisual attention shift for DD should be further carried out in exogenous and endogenous aspects.
By using meta-analysis, behavioral experiments and electroencephalogram, this study aimed to explore the audiovisual attention shift in Chinese children with DD from the perspective of exogenous and endogenous aspects. The results show that:
(1) The meta-analysis show that in the context of alphabetic languages, the deficit of auditory attention shift of DD is more obvious than that of visual attention shift. Combined with the previous research on audiovisual attention shift in DD, the deficit of audiovisual attention shift in DD may be related to the disability of auditory attention shift.
(2) Under the exogenous task, behavioral results found that Chinese children with DD performed worse in audiovisual attention shift. They showed a deficit when asked to shift attention from audition to vision. This indicates that there is a cross-modal attention shift deficit from audition to vision in Chinese children with DD. The results of EEG also showed a deficit of audiovisual attention shift. There are significant differences between cross-modal condition and amodal condition in amplitude of N1 in typical children. However, these significant difference disappeared in children with RD. The a oscillation power of RD in the condition of vision to audition is higher than that in auditory condition. Typical children didn't showed the different a oscillation power between cross-modal and amodal condition. In addition, the study found that the audiovisual attention shift deficit of children with DD was related to the visual and auditory attention attention processing.
(3) Under the endogenous task, the behavioral results found that Chinese children with DD did not show the deficit of audiovisual attention shift. The results of EEG showed that there was no significant difference between the amplitude of N1 and P2 component in children with DD and control group. RD showed a higher activity of a oscillation in the visual only condition than that in audition to vision condition. Interestingly, children with DD showed amodal attention processing in endogenous task, which indicated a separate mechanism between endogenous cross-modal attention shift and amodal attention processing.
The above results show that Chinese children with DD showed deficit in exogenous audiovisual attention shift rather than in endogenous aspects, which exhibited deficits from vision to audition and audition to vision. Moreover, the deficit of audiovisual attention shift of DD is related to the deficit of visual and auditory processing. Present study fills the gap of the research about cross-modal attention shift in Chinese children with DD. Besides, the study also provides a new approach for the correction of DD in the future, which could improve their reading ability by training their ability of exogenous audiovisual attention shift.
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