Purpose:

As reported in the previous behavioral research¹, the working memory development of deaf children was retarded. This issue was significantly related to their poor academic performance, impulsivity, self-control defects and other behavioral problems, as well as various psychological barriers such as inferiority and polarization². Working memory, including the temporary storage and processing of information in the cognitive tasks, constitutes the core of high-level cognitive activities such as learning, memory, decision-making and cognitive control. Previous studies found that working memory has specific neural basis and the neuroplasticity can be improved through training³. Increased evidence suggests that proper physical exercise can improve the working memory of normal children⁴. In this study a combined aerobic exercise program was used on deaf children aged 9-13 years for eleven weeks to investigate the working memory function, in order to explore the brain mechanism of deaf children influenced by aerobic exercise.

Materials and Methods:

Subjects：Twenty eight deaf children aged from 9 to 13 years were recruited. They were randomly and evenly divided into an experimental group and a control group (Table 1). The experimental group was offered an 11-week aerobic exercise program consisting of martial arts, rope skipping and 8-figure running at moderate intensity for 30 minutes with four times per week. In comparison, the control group was not given any intervention. MRI Experiment:Both groups were scanned using a GE-750W 3.0-Tesla MRI scanner during performing a working memory task before and after the intervention. In this task, the classic 2-back task was used to evaluate working memory. It included two task states: 0-back and 2-back, adopting the block design, including six 0-back blocks and five 2-back blocks. In 0-back blocks, the subjects were required to make odd-even judgment with each stimulation for 2s (the stimulus presentation time=1500ms and the interval between two stimuli=500 ms). In 2-back block, the screen may appear 1-4 four numbers and asked participants to judge whether the displayed numbers were consistent before and after. Each block contained 12 exciting with each stimulation for 2s.T1-weighted anatomical images were acquired with the scan parameters of TR/TE=1900/2.52ms, TI=900ms, slice thickness=1.0mm, flip angle=9degrees, acquisition matrix=256*256, and FOV=250*250mm. For task functional MRI (fMRI) measurement, the scan parameters were TR/TE=2000/30ms; thickness=3.0mm, spacing=1mm, flip angle =90degrees, acquisition matrix =64*64 and FOV=200*200mm. Data analysisFor each subject, task images were corrected for slice timing, head motion and normalization. Two data from the control group were excluded by the criteria of ±2mm head translation and ±2°rotation. After preprocessing, the activation regions of working memory task were achieved through 2-back > 0-back by using a general linear model in SPM8 software. Repeated-measures-analysis-of-variance was applied to evaluate the intervening effect of 11-week aerobic exercise on 2-back performance. Flexible factorial-design was applied to explore the intervening effect of aerobic exercise in brain activation patterns.

Results:

The comparison of behavioral performance of deaf children after 11-week exercise intervention included: 1) 2-back reaction time analysis: group main effects [F(1,24)=5.25;P=0.03]; time-induced effects [F(1,24)=21.73;P<0.01]; interaction effects between time and group [F(1,24)=15.8;P<0.01]; 2-back accurate rate analysis: group main effects [F(1,24)=4.85;P=0.03]; time-induced effects [F(1,24)=18.48;P<0.01]; interaction effects between time and group [F(1,24)=2.25;P=0.15]; difference of two group post-experiment accurate rate [t(1,24)=3.16;P=0.004]( Table 2). The brain activation alternation of working memory was also shown for deaf children after 11 week exercise intervention (Fig.1&Table3). The interaction effects between time and group were significant difference in right precuneus and temporal pole (p<0.005,corrected). In addition, significantly decreased functional activation was found in left middle temporal gyrus of patients after aerobic exercise (p<0.005,corrected).

Discussion and Conclusion:

Compared to the control group, the experimental group showed a significant improvement in the 2-back task performance after the intervention. The interaction effects of time and group indicated that the intervention has a prominent effect on the behavior in the 2-back task. The fMRI results revealed the regions of interaction effects between time and group and decreased functional activity of left middle temporal gyrus after the intervention. Temporal lobe is responsible for encoding information in working memory, and precuneus is involved with episodic memory and visuospatial processing. The alternation in these regions indicated a functional or interconnections improvement, which optimized the brain activation patterns of integration in deaf children. The evidence from our study showed that the exercise intervention can improve cognitive function which may associate with the expression of synaptic plasticity of brain. As being consistent with the assumption, it may help to reveal the underlying mechanism. To summarize, aerobic exercise intervention could optimize the deaf children’s working memory performance and alter activation regions of working memory task in fMRI.

Acknowledgements

We confirm that the manuscript has been read and approved by all named authors and there areno known conflicts of interest associated with this publication.All protocols of this study were approved by the ethics committee of the Yangzhou University, Yangzhou, China.