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1. Introduction
Intellectual and developmental disability comorbid with considerable problems both in intellectual functions and adaptive behaviors that originate before the age of 18 [1, 2]. People with Down Syndrome (DS) are the largest group with intellectual and developmental disabilities. Down syndrome is a genetic disorder, determined with physical features, moderate to severe intellectual disability, and deficits in academic achievement and language. The prevalence of this syndrome is about 1 per 1000 births [3]. 
About 95% of Down syndrome cases, also called trisomy 21, are due to the presence of an extra copy of 21st chromosome. In this type, a baby is born with three #21 chromosomes, rather than the usual pair. These cases of Down syndrome are not inherited and is caused by nondisjunction. In other words, it is a fraction of chromosome 21 in moment meiosis stage. Mother transfers 2 chromosomes instead of 1 in many cases of trisomy 21. Also, some cases of paternal nondisjunction have been reported [4]. Limitation in attention and motor skills are usual features in students with intellectual disabilities like Down syndrome. Intellectual disability is a condition of increased deficiency in brain cells, which negatively affect attention and motor skills [5, 6]. 
Attention is the first stage in information processing. It collects part of the environmental information for later processing. In fact, attention is an important component in learning and education. Children with Down syndrome have attention problems [7]. Motor skill development includes gross and fine motor skills and bilateral coordination [8]. Delay in motor development is common in children with moderate to profound intellectual disabilities. These children usually have deficit or delay in motor skills that can lead to compelled immobility. This delay occurs in locomotion, balance, dexterity and practical skills such as working, playing games, and doing daily living activities [9]. Furthermore, Down syndrome children have frequent problems in attention, motor activities, and sensory integration [10], constantly reported by parents and professionals [11, 12]. 
The sensory integration theory describes the relation between deficit in the interpretation of environmental sensory stimulus and body sensations and problems with motor skills learning [13]. The principles of this theory were derived from contemporary neuroscience, occupational therapy, and developmental psychology. Sensory integration is defined as the interpretation and organization of sensation information from the body and environment to make meaningful responses [14]. Sensory therapy is used in the management of students with intellectual and developmental disabilities. This therapy engages skills which are thought to manage the sensory system with providing proprioceptive, auditory, tactile, and vestibular inputs [8].
Studies showed that the motor activities of students with intellectual disability are either poor or considerably delayed [4]. A research regarding the effect of Spark motor program on the improvement of gross motor skills in children with intellectual disability reported that Spark motor program improves gross motor skills in this group [15]. Another research investigated the effectiveness of teaching basic motor skills to 6-year-old boys and girls. The results stated that motor therapy led to the improvement of fine and gross motor activities of intellectually disabled children [16]. A study examined the effectiveness of sensory motor intervention on attention span of students with learning disabilities. Results indicate that sensory motor intervention increases the attention span of these students [17].
Another study investigated the effectiveness of creative movements on attention span of students with autism spectrum disorders. Their results present significant improvement in the attention span in the experimental group [18]. Another research investigated the effectiveness of gross motor activities on attention process of students with Down syndrome. Their results indicate that gross motor activities increases the attention process of these students [19]. Amel and Amira investigated the effect of sensory integration plan on motor skills of children with autism spectrum disorders and reported a significant difference in gross and fine motor skills at post treatment [8]. Also, Sadati Firoozabadi et al. reported that sensory-motor integration had a positive and significant effect on motor skills in students with learning disabilities [20]. 
According to prior research, students with Down syndrome showed attention problems and delay in motor skills development [6, 21-23]. Studies revealed which levels of cognitive functioning and motor skills are related in students with intellectual disability [6, 23]. Children with Down syndrome have problems in attention span and motor skills which negatively affect gross and fine motor skills. Also, research studies show that Down syndrome children have weak levels of attention span and motor skills in comparison with the normal children. Sensory integration training seems necessary for them. Children with Down syndrome participated in sensory integration program, which improved their attention span, motor skills, daily activities, and quality of life. Also, although children with Down syndrome process similar steps of motor development in the same order as normal students, stages may be obtained delayed and some activities and skills may not be developed the same as normal student, and may rather be achieved later or may not develop. Therefore, this study aimed to investigate sensory integration training on attention span and motor skills of children with Down syndrome.

2. Methods 
This was a quasi-experimental research with pretest and posttest and a control group design. Participants were male students with Down syndrome from two exceptional schools in Tehran, Iran. The samples were selected by convenience sampling method. Students were randomly divided into the control and experimental groups; each consisting of 14 students by the following formula: 

 

The inclusion criteria consisted of the having diagnosed with intellectual disability caused by Down syndrome, living with parents, being 10-12 years old and being student of fourth to sixth grade. Exclusion criteria consisted of the symptoms of neurodevelopmental disorders or significant health problems, and receiving any concurrent similar training programs. The importance of this study was explained to the mothers of the subjects and the school counselors. The mothers of the subjects provided an informed consent. We randomly assigned the subjects into the control and experimental groups. The experimental group received 10 sensory integration training and the control group participated in the routine program of school. 
The computerized Stroop color-word test was used to assess subject’s attention span. This test was developed 

 

 

by Reedley Stroop. The Persian version of the computerized Stroop color-word test (Ravan Sina Inc, Iran) includes two stages. The first stage is the training phase, and the participant should choose the color of circle shown on the monitor screen in 4 possible colors of red, blue, green and yellow, then press the key that is covered by each colorful label on keyboard. The score of this stage has no influence on the final result. The main part of the test consists of 96 colorful words, 48 colorful congruent words (the meaning of the word complies with the ink color, the word is written with) and 48 colorful incongruent words (the meaning of the word does not comply with the ink color the word is written with) which were displayed in a pseudorandom sequence in the middle of the monitor screen for 2000 ms with 800 ms inter stimulus interval. Subjects answered to ‘identify words color’ regardless of their meanings.
The correct responses, incorrect responses, no responses, reaction time of congruent words and reaction time of incongruent words in the Stroop test were calculated by computer. The Persian version of the Stroop test has an acceptable validity and reliability [24]. The reliability of this test, (based on retest) falls in the range of 0.80 to 0.91 [25].
To evaluate the participants’ motor skills, Bruininks Oseretsky Test of Motor Proficiency-short form (BOT-2) was used. This test is a famous instruments for assessing motor proficiency and was designed to obtain useful information about the motor skills of children aged 4.5 to 14.5 years. BOT-2 includes 14 items and 8 subscales [26]. Three subscales of BOT-2 were used to evaluate fine motor skills in this study: fine motor integration subscale, fine motor precision subscale, and manual dexterity subscale. Four subscales were used to assess gross motor skills: balance, speed and agility, upper limb coordination, and strength. Also, bilateral coordination subscale was used to evaluate both gross motor skills and fine motor skills. Retest coefficient and reliability of BOT-2 was reported as 0.86 [27].
The experimental group participated in 10 intervention sessions (twice a week, each lasting for 40 minutes) and were trained by the sensory integration program, while the control group did not receive these interventions (for an overview of session content, see Table 1). The Stroop color-word test and Bruininks Oseretsky Test of Motor Proficiency were used for measuring the attention span and motor skills in students as the pretest. Then, the experimental group participated in 10 intervention sessions. In the final stage of the research, each group was assessed by the Stroop color-word test and Bruininks Oseretsky Test of Motor Proficiency as the posttest. The obtained data were analyzed with Multivariate Analysis of Covariance (MANCOVA).

3. Results 
The mean age of the experimental and control groups were 11.09 and 11.14 years, and the mean score of IQ were 63.04 and 61.97, respectively. The descriptive indices of attention span and motor skills for the experimental and control groups in the pretest and posttest are reported in Table 2. 

 

 

MANCOVA was used due to the presence of one independent variable and several dependent variables (subscales of attention span and motor skills) as well as the moderate of pretest effect. After checking and approving the normality of research variables, Box’s test approved equality of variance-covariance matrices (P>0.05). Also, the assumption of variance equality was approved using Leven’s test (P>0.05). Therefore, MANCOVA test could have been applied. The overall Wilk’s lambda was significant (F6, 15=5.34, P=0.0001), indicating a significant difference between the experimental and control groups, at least in one variable. In order to determine differences among the scores of attention subscales and motor skills between the control and experimental groups, MANCOVA test was used, and the findings are presented in Table 3.
To analyze the data, pretest variable was moderated because of correlation with posttest. According to Table 3, the type of the group has a significant effect on post

 

 

test scores and there is a significant difference in the scores of attention subscales and motor skills between the control and experimental groups (P<0.0001). As per Table 3, the results of MANCOVA showed that the sensory integration program had a positive and significant effect on correct responses (F=29.41, P<0.0001), incorrect responses (F=31.18, P<0.0001), no responses (F=33.52, P<0.0001), reaction time of congruent words (F=28.03, P<0.0001), reaction time of incongruent words (F=34.86, P<0.0001) and motor skills (F=29.12, P<0.0001). According to Eta-squared (η2), 52%, 57%, 60%, 56%, 58%, and 63% of the variation in variables of correct responses, incorrect responses, no responses, reaction time of congruent words, reaction time of incongruent words and motor skills, could be explained respectively due to the effect of sensory integration training in the experimental group. 

4. Discussion 
The present research was conducted to investigate the effect of sensory integration training on attention span of students with Down syndrome. Also, this research evaluated the effect of sensory integration training on motor skills in 2 groups (experimental and control) before and after the intervention. 
Findings showed that the sensory integration training program increased the attention span components (correct responses, incorrect responses, no responses, reaction time of congruent words or reaction time of incongruent words in the Stroop test) among students with Down syndrome in the experimental group. These findings are in line with the results of many studies [17-19].
Children with Down syndrome have problem in attention span. The attention problems in children with Down syndrome are reflected in their low academic achievement [3]. Attention deficits are often linked to impairment in their cognitive ability for learning. Moreover, attention is the first stage in information processing that is based on formed concentration, awareness and perception. It initiates learning in children [7]. The sensory integration training program included reinforcement in attention skills; increase in attention span; eye and hand coordination; reinforcement of tactile sensory, body awareness, orientation and selective attention. Therefore, the sensory integration training program could promote attention in children with Down syndrome. 
The results support the effectiveness of sensory integration training on attention span and motor skills in students with Down syndrome. The result was similar to the findings of Sadati Firoozabadi et al. [20] regarding the effect of sensory integration training program on the motor skills in students with learning disorders. This study was consistent with the results of Amel and Amira [8]who investigated the effect of sensory integration training program on motor skills among students with autism spectrum disorders and reported a statistically significant difference between the control and experimental groups after the intervention, on gross and fine motor skills. Our results were in line with the study by Shahbazi et al. representing the effectiveness of sensory motor integration program on reaction time and balance in students with developmental coordination disorder [28]. 
Results of the current research were consistent with the study of Top who investigated the effects of swimming exercise program on the motor development levels in teenagers with intellectual disability and reported a statistically significant difference between the control and experimental groups in fine motor integration, fine motor precision, and bilateral coordination parameters [6]. Also, Top concluded that there are no difference in the experimental and control groups in gross motor skills and total motor skills at pretest and posttest [6]. This result was not in line with the present study. Moreover, the present research was consistent with the study of Parhoon et al. who investigated the effect of sensory motor program on gross motor skills of 5-7 years old students with Down syndrome, and reported a statistically significant difference between the control and experimental groups in gross motor skills, after the intervention [29]. 
The findings of this research was similar to the study of Westendorp, et al. who founded that, the scores of the gross motor skills of the experimental group in sports were significantly higher than the scores of the control group in individuals with mild intellectual disability [30]. Furthermore, the present study was consistent with the results of Vuijk et al. that concluded motor performance in students with borderline intellectual functioning and mild intellectual disability increased after receiving the intervention [23]. Our result was in line with the study of Surtchi et al. reported the effectiveness of sensory integration program on fine and gross motor skills, for 5-7 years old children with Down syndrome [31]. Moreover, this result was similar to the study of Bouffard that reported a significant difference in motor skills of individuals with educable intellectual disability after intervention [26].

In fact, the attention and movements depend on input from sensory channel, at birth. When child grows up and his/her interaction improves with the environment, the visual and auditory system become very important and are accompanied by other sensory systems. Hands and eyes coordination are required to process sensory inputs and direct movements towards the intended targets. When baby’s hand makes contact with the intended object, he/she integrates tactile information regarding the object’s texture via visual proprioceptive about the size, color and shape. 
More object handwork assembles information feedback from the hand movement of baby in response to the object, which may help explain data regarding the shape and size of the object [14]. Also, appropriate operative tasks are used for students with sensory processing problems to help them decrease defensiveness, change of arousal, and attention improvement. Improved fine and gross motor skills in students allows them perform considerable operative activities [8]. In addition, sensory integration training plays a crucial role in attention and motor skills of students with Down syndrome. 
The present study investigated the effects of sensory integration training on attention and motor skills of children with Down syndrome. Although a few children with Down syndrome obtain appropriate motor activities with observing and imitating their classmates and other children in the community, engagement of parents and teachers of these children is also important in direct and indirect acquisition of attention and motor skills. According to the results, sensory integration training can have significant and positive effects [4]. Sensory integration training increase the neuroplasticity of nervous system in children, leading to improvements in desirable skills and behaviors and enhanced attention and motor skills [8].
Several limitations of this study should be noted. The rate of learning differs in the students with Down syndrome. It is difficult to ascertain these students’ achievements in attention and motor skills. Moreover, the socioeconomic status of the students’ parents were disregarded. Therefore, caution should be used when applying statistical generalization of our results to other populations. Also, the sample size in both experimental and control groups were small. It is difficult to relate these findings to other children with special needs, because each group only consisted of 14 children. Moreover, there was no opportunity for a follow-up assessment due to the time limitation [32]. 

5. Conclusion
It is expected that sensory integration training improves attention and motor skills of students with Down syndrome. Thus, paying attention to the sensory integration training plays a crucial role in enhancing attention and motor skills of children with Down syndrome. Ultimately, the present research demonstrated a significant improvement in the attention and motor skills of children with Down syndrome after receiving sensory integration training.

Ethical Considerations
Compliance with ethical guidelines
This research was approved by the Human Ethics Research Committee of Isfahan University and the Exceptional Education Organization of Iran.

Funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Conflict of interest
The authors certify that they have no affiliation with or involvement in any organization or entity with any financial, or non-financial interest in the subject matter or materials dismissed in this manuscript.

Acknowledgements 
We would like to acknowledge the support of the Special Educational Needs Organization and the staff of exceptional schools in Tehran for their sincere cooperation and support that made conducting this research possible. 


References