Children with specific language impairment show ...

Logopedics Phoniatrics Vocology, 2012; Early Online: 1–9

ORIGINAL ARTICLE

Children with specific language impairment show difficulties in sensory modulation

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MARION N. TAAL1, ANDRÉ B. RIETMAN2, SJOEKE V. D. MEULEN3, MARIA SCHIPPER4 & PHILIPPE H. DEJONCKERE5 1Royal

Auris Group, Rotterdam, The Netherlands, 2Erasmus Medical Centre Rotterdam, The Netherlands, 3Wilhemina Children’s Hospital, Utrecht, The Netherlands, 4University of Utrecht, The Netherlands, and 5University Medical Centre Utrecht, The Netherlands

Abstract The purpose of this study is to investigate whether a group of 116 Dutch children with specific language impairment (SLI) shows differences in sensory processing when compared to a control group of age-matched 4–7-year-old typical peers. The Sensory Profile-NL—a standardized questionnaire of 125 items—was completed by caregivers of children in both groups. Children with SLI differed significantly from the control group on all 14 section scores and 4 quadrant scores of the Sensory Profile-NL. The effect size of the difference in sensory modulation patterns of children with and without SLI on this measure was large (Cohen’s d ⱖ 0.80). Difficulties in sensory modulation can be characterized as frequent co-morbid problems in children with SLI. Key words: Language development, sensory processing, sensory profile, specific language impairment

Introduction Specific language impairment (SLI) is defined as a failure in spoken language development occurring despite average or above average non-verbal intelligence, adequate hearing and vision, absence of neurological, physical, emotional, or social problems, and adequate opportunity to acquire spoken language skills (1,2). Children with SLI are considered a heterogeneous group, varying in severity and in profile of the disorder. The language deficit is proven to be long-lasting, and the prevalence in 5–6-year-olds is around 7% (3). Linguistic impairments co-occur with a number of non-linguistic deficits, impairments in motor skills, cognitive impairments, social problems, behavioral difficulties, literacy deficits, and problems with working memory for verbal material (4,5). This suggests that SLI is not a disorder limited to language. In understanding the etiology of SLI, it has been proposed that in most children the disorder is multifactorial in nature, with several genetic and environmental risk factors interacting with each other (6).

Sensory processing refers to the ability of the nervous system to receive, organize, and interpret sensory input (e.g. auditory, vestibular, visual, proprioceptive, tactile) from one’s own body and from the surrounding world in order to produce an appropriate response and then participate successfully in daily life (7,8). The diagnosis of sensory processing disorder (SPD) is made if sensory processing difficulties impair daily routines or roles. There are three primary subtypes of SPD: sensory modulation disorder (SMD), sensorybased motor disorder, and sensory discrimination disorder (9). This paper will focus on SMD. Sensory modulation refers to the nervous system’s regulation of neural messages about sensory stimuli. Children with SMD have difficulty regulating their responses to sensory input with behavior that is graded or ranked relative to the degree, nature, or intensity of sensory information (9). The subtypes within SMD are sensory overresponsivity, sensory under-responsivity, and sensory seeking/craving. Learning, and particularly language learning, supposes an intact sensory processing system, which

Correspondence: Marion N. Taal, Royal Auris Group, Westblaak 132, 3012 KM Rotterdam, The Netherlands. Fax: ⫹ 31102436717. E-mail: [email protected] (Received 6 June 2011; accepted 2 April 2012 ) ISSN 1401-5439 print/ISSN 1651-2022 online © 2012 Informa UK, Ltd. DOI: 10.3109/14015439.2012.687760


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is related to cortical maturation. Learning the symbolic code system of language is preceded by the learning of non-verbal communication via facial and bodily expressions. This process starts just after birth by means of imitation in the child’s developing sensorimotor system. Language learning is influenced and enhanced by social learning and learning of others’ intentions (10,11). Difficulty in sensory processing in young children may affect the development of their social and emotional well-being and the acquisition of cognition, language, and sensorimotor skills (12,13). Information about the nature and extent of sensory processing difficulties in children with SLI may shed light on the relationship between sensory processing and language learning. Research into the nature of SLI has shown that these children often have auditory processing deficits (14). Therefore, many studies that focused on sensory processing deficits among children with SLI only investigated isolated sensory systems, particularly the auditory system (14,15). More recently, a growing number of studies published on multisensory processing in children with SLI have been concerned with auditorytactile, auditory-visual, or motor-auditory-visual integration (16,17) and have emphasized the multisensory integration needed for communication. Norrix et al. compared 28 children with SLI to 28 children with normal language development in a study examining auditory visual integration. They demonstrated that difficulties with speech perception in children with SLI are also influenced by auditoryvisual processing in comparison to auditory processing only (16). In a study exploring body posture and hand movement imitation in 40 children with SLI and 40 age-matched peers, it was shown that children with SLI performed more poorly on the imitation tasks than the children with typical language development and that they showed qualitative differences in their groups’ performances (17). These studies emphasize two or three separate sensory systems. In our study we include all senses. Other studies have concluded that processing sensory information is fundamentally a multisensory phenomenon (8,18). In our study, the Sensory Profile-NL (the Dutch version of the Sensory Profile; SP-NL), the Sensory Profile Supplement, and Dunn’s Model of Sensory Processing are used to investigate and interpret the relationship between language development and sensory processing in children with SLI (19,20). To date, studies with the Sensory Profile and Sensory Profile-NL have yet to examine this relationship. In order to interpret the sensory processing patterns derived from the Sensory Profile, Dunn proposes a Model of Sensory Processing. This clinical

analytical model describes relationships between behavioral responses or self-regulation and neurological thresholds (7,19,20). The present study evaluates the effect of sensory processing on functional performance in the daily lives of children with SLI and a matched population of typical children. The study’s primary aim is to identify domains in sensory processing that are significantly different in children with SLI compared with typical children, as rated by parents in a daily situation using the Sensory Profile-NL. The secondary aim is to characterize sensory processing difficulties in the Sensory Profile-NL profiles in children with SLI. Method and materials Research design A prospective cross-sectional, non-experimental design was used to identify possible differences in sensory processing between children with SLI (the SLI group) and typically developing children (the control group) on the Sensory Profile-NL. We used a convenience sample of children between the ages of 4 and 7 for the SLI group. Data were collected in the period between January and May 2007. Participants SLI group. All SLI group participants were diagnosed with SLI by a multidisciplinary team of specialists that included a physician, a psychologist, special educators, and a certified speech-language pathologist. A child was diagnosed with SLI if he or she had a severe language impairment that was not the result of global intellectual, sensory, motor, emotional, or physical impairments. In the Netherlands, children with SLI are referred to a school for special education when the language impairment and teaching restrictions meet a certain level of severity according to criteria established by the Law of Expertise Centers. These three criteria are: Firstly, there is a speech-language disorder, defined by general speech-language tests with determined arrears of more than two standard deviations compared to the mean; the disorder is not due to the level of cognitive functioning. Secondly, speech therapy for at least six months has yielded insufficient progress. Thirdly, there is a limitation in participation in education, and help and guidance in mainstream schools or health care are inadequate. SLI subjects in this study were recruited from special education schools of the Koninklijke Auris Groep (Royal Auris Group) for children with severe speech and language impairments. Children with SLI between the ages of 4;4 and 7;0 were included. Children of non-Dutch-speaking parents were excluded.


Children with SLI show difficulties in sensory modulation Control group. Using age, gender, parental socioeconomic level, and geographic environment as matching criteria, this sample of typical children was selected from a larger sample of 1172 cases taken from the Dutch norm study of the SP-NL (ages ranging from 4;4 to 7;0 years). Children were excluded if they had been diagnosed with any clearly defined developmental disorder, speech-language deficit, or apparent sensory or neurological deficit (e.g. mental retardation or hearing impairment). For this study children were recruited from randomly selected primary schools. Caregivers were requested to complete the SP-NL only if their child had not been diagnosed with one of these impairments. No IQ scores were available for the group of typical children from the Dutch norm study on the Sensory Profile. Instrumentation Language evaluation. Current language measures were gathered from the school files of the children under study. Their language problems were diagnosed by use of the Reynell Test voor Taalbegrip (21) and the Schlichting Test voor Taalproductie (22). The Reynell Test voor Taalbegrip is a Dutch language comprehension test (originally an English one, developed by Reynell) for children from 1;3 to 6;3 years of age. The outcome measure is a receptive language quotient (RLQ). The Schlichting Test voor Taalproductie is a Dutch language production test, developed by Schlichting for children from 3;0 to 6;3 years of age. The outcome measures are a word quotient (WQ) and a sentence quotient (ZQ). For the purpose of this study an expressive language quotient is (ELQ) is established by combining the WQ and ZQ. Intelligence. Intelligence level was measured by means of a non-verbal intelligence test, the Snijders–Oomen Non-verbal intelligence tests – Revised 2½–7 (SON-R 2½–7) (23). The outcome measure was a non-verbal intelligence quotient (IQ). No IQ scores were available for the group of typical children from the Dutch norm study on the Sensory Profile. For this study caregivers were requested to complete the SP-NL only if their child had not been diagnosed with one of these impairments. The Sensory Profile and the Sensory Profile-NL. The Sensory Profile was designed by Dunn (24) in order to create an inventory and a scale to measure the sensory processing abilities of children between 3 and 10 years old. The Sensory Profile is a standardized questionnaire with 125 items or behavioral statements in which caregivers rate their children’s responses to sensory events that occur in daily life (24). The items

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are divided into three main sections: 1) sensory processing, 2) modulation, and 3) behavioral and emotional responses. The questionnaire uses a 5-point Likert scale (i.e. 1 ⫽ always, 100% of the time; 2 ⫽ frequently, 75% of the time; 3 ⫽ occasionally, 50% of the time; 4 ⫽ seldom, 25% of the time; and 5 ⫽ never, 0% of the time). The Sensory Profile-NL, was published in 2006 (19). This version was approved by Dunn as being identical to the Sensory Profile. The Supplement Summary Score Sheet to the Sensory Profile (20) provides four quadrant scores (registration, seeking, sensitivity, and avoiding) that correspond to Dunn’s (7) Model of Sensory Processing. According to the model, ‘registration’ is a pattern in which a child misses sensory input, ‘seeking’ is a pattern in which a child obtains sensory input, ‘sensitivity’ is a pattern in which a child notices sensory input, and ‘avoiding’ is a pattern in which a child is bothered by sensory input. Procedure In this study, demographic data such as age, gender, parental socio-economic level, and geographic environment were gathered. Data from expressive and receptive language scores and intelligence level were obtained from the school files of the children with SLI. Cases in which one or more sections of the questionnaires were missing were excluded. For ethical reasons, the data were anonymized in order to guarantee privacy. Caregivers provided written informed consent. Data analysis Means and standard deviations of the observed variables in both groups were calculated. Due to the normal distribution of the SLI group, as tested with the Kolmogorov–Smirnov test, the paired samples t test was applied to evaluate means for significant difference between the SLI group and the control group over the selected components of the sensory processing data (on the 14 section scores and the 4 quadrant scores). A Bonferroni correction was performed to correct for multiple testing, and a probability of P ⬍ 0.001 was considered significant. Effect size was calculated to establish clinical significance; Cohen’s d was applied as effect size measure (25). The Sensory Profile-NL has not yet been validated for Dutch children. Therefore, new cut-off scores for the control group were determined according to the cut-off score indices of the Sensory Profile Supplement Classification System (20). The SLI group was scored according to the control group’s

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cut-off scores. Performance percentages on the Sensory Profile-NL sections were calculated for the SLI group and for the control group according to the same new cut-off Sensory Profile Supplement Summary Score Sheet (20).

Large effect sizes demonstrate clinical significance for all section scores and quadrant scores as reflected by Cohen’s d values ranging from ⱖ 0.8 to 1.7. Sensory processing performance

Results


Demographics and test scores Caregivers of 155 children (74% boys) in the SLI group received the Sensory Profile-NL. In total, 121 questionnaires were filled out and sent back, resulting in a response rate of 78%. Five questionnaires were excluded due to one or more missing sections; therefore, the SLI group consisted of a convenience sample of 116 children with SLI (mean ⫽ 5;9 years, range 4;4–7;0; 76% boys (n ⫽ 88) and 24% girls (n ⫽ 28)). The matched control group consisted of 116 typically developing children (mean ⫽ 5;9 years, range 4;4–7;0; 76% boys (n ⫽ 88) and 24% girls (n ⫽ 28)). Parental education level was determined as being either lower general education or intermediate higher-vocational education. Not all the data of the expressive and receptive language and non-verbal intelligence of the 116 children with SLI were available in the school files. The data available are mentioned as number of cases (n) of 116: ⫽ x/116. The mean of the ELQ is 77 (SD 11.5; n ⫽ 105/116) and the mean of the RLQ is 82 (SD 14; n ⫽ 114/116). Because the IQs of the SLI group ranged from 70 to 125 (mean 90, SD 12.9; n ⫽ 110/116), we determined the correlation between total IQ and the scores on the Sensory Profile-NL. This Pearson correlation coefficient varied from 0.144 to 0.002. This indicates that IQ could have a small effect on the scale scores of the SP-NL. Since the IQ of the children in the normative sample was not measured, we could not make any comparisons. There was no significant difference in the results of the paired samples t test between the children with an IQ ⱖ 85 (55% of the SLI group; n ⫽ 62) and the children with an IQ ⬍ 85 (45% of the SLI group; n ⫽ 54) or between either group and the total group of 116 participants. Scores on the Sensory Profile-NL, therefore, may be considered as IQ-independent in this study. Differences in sensory processing The results of the paired samples t test are presented in Table I. The statistics measuring the difference between the two groups showed a significant difference on all section scores and quadrant scores compared to the matched control group (P ⬍ 0.001).

To characterize the sensory processing difficulties in the Sensory Profile-NL profiles of children with SLI, we conducted analyses of the Sensory Profile-NL’s subtests in order to establish the actual percentage of children with sensory processing difficulties in the SLI group and the control group. The SLI group scores exceeded the control group scores in all definite difference section scores and quadrant scores (Table II). The control group outnumbered the SLI group consistently in the typical performance range. In the sections containing items related to sensory processing, the highest percentages of cases with scores ⱖ 2 SD in the SLI group were found on auditory processing (41.4%) and multisensory processing (32.8%). Within the modulation section, the highest percentages of cases with scores ⱖ 2 SD in the SLI group were found on modulation of sensory input affecting emotional responses (58.6%) and modulation related to body position and movement (46.6%). The behavior and emotional responses sections showed that the highest percentage of cases with scores ⱖ 2 SD in the SLI group was found on items indicating emotional-social (31.0%). The quadrant scores of the cases with scores ⱖ 2 SD in the SLI group ranged from 34.5% (seeking) to 42.2% (avoiding).

Discussion Our findings suggest that there is evidence that children with SLI have significantly more difficulties in all sections of the Sensory Profile-NL as compared to the control group. The large effect sizes (Cohen’s d values ranged from 0.8 to 1.6) on all sections, and the quadrants of the Sensory Profile-NL suggest that the differences between the SLI group and the control group are meaningful. This is highlighted by the large percentage of children of the SLI group who respond in a deviant way ‘more than others’ (1 SD ⱖ x ⬍ 2 SD) and ‘much more than others’ (ⱖ 2 SD) in all sections and quadrants of the Sensory Profile-NL as compared to the control group participants. Atypical behaviors were most prevalent in the SLI group in auditory processing (63.8%), followed by touch processing (52.6%), vestibular processing (51.7%), oral processing (46.0%), and visual processing (43.1%).

Children with SLI show difficulties in sensory modulation

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Table I. Results of paired samples t test, SLI group (n ⫽ 116) versus control group (n ⫽ 116): Mean scores (Mean), standard deviations (SD), paired t statistic (t), P values, and effect size (Cohen’s d).

Section: Sensory processing A. Auditory processing B. Visual processing C. Vestibular processing D. Touch processing E. Multisensory processing F. Oral processing Modulation G. Sensory processing related to endurance-tone H. Modulation related to body position and movement I. Modulation of movement affecting activity level J. Modulation of sensory input affecting emotional responses K. Modulation of visual input affecting emotional responses and activity level Behavior and emotional responses L. Emotional / social responses M. Behavioral outcomes of sensory processing N. Items indicating thresholds for response Quadrant: 1. Registration 2. Seeking 3. Sensitivity 4. Avoiding

Children with SLI

Control group

Mean differences

Mean

SD

Mean

SD

t

P

d

29.2 36.9 46.6 77.0 27.0 50.1

5.7 5.2 4.8 8.3 4.2 8.7

35.0 40.5 51.0 83.6 31.5 56.6

2.9 3.3 3.1 4.4 2.3 4.1

9.8∗∗ 6.4∗∗ 8.8∗∗ 8.5∗∗ 10.3∗∗ 6.8∗∗

0.000 0.000 0.000 0.000 0.000 0.000

1.3 0.8 1.1 1.0 1.3 1.0

38.5

6.5

43.9

2.4

8.5∗∗

0.000 1.1

40.2

5.3

45.0

3.4

9.9∗∗

0.000 1.1

23.4

4.4

27.7

3.6

8.1∗∗

0.000 1.1

15.0

3.1

18.9

1.5

14.8

2.6

17.5

2.1

8.6∗∗

0.000 1.1

64.7

9.6

75.0

6.1

10.4∗∗

0.000 1.3

17.0

3.8

21.7

3.0

10.1∗∗

0.000 1.4

12.6

1.8

14.3

0.9

9.2∗∗

0.000 1.2

61.3 102.0 82.1 112.9

9.3 13.9 8.7 13.6

70.6 115.6 92.8 129.8

3.7 8.2 4.9 8.1

10.1∗∗ 8.9∗∗ 12.2∗∗ 12.0∗∗

12.1∗∗ 0.000 1.6

0.000 0.000 0.000 0.000

1.3 1.2 1.5 1.5

Effect size: small d = 0.20, medium d = 0.50, and large d = 0.80 (25). Section M is calculated with 5 items, as item 118 is deleted. ∗∗P < 0.001. A Bonferroni correction was performed to correct for multiple testing, and a probability of P < 0.001 was considered significant.

The finding of auditory processing deficits is consistent with several previous studies’ conclusions that rapid auditory processing (e.g. the ability efficiently to process brief, rapidly presented, successive auditory stimuli) is critical for accurately analyzing and segmenting the speech stream; such deficits hamper phonetic perception in children with SLI (14,15). Children with SLI have, by definition, normal hearing thresholds. However, the auditory system works closely with the vestibular system, as they together form the inner ear; additionally, there are important connections to the touch and proprioceptive systems (12). Our study’s findings confirm difficulties in all sensory processing domains; for normal development, information from different senses has to be combined to get functional performance in daily life. When a child is affected in one or more sensory systems this can disrupt everyday life and influence language development.

Iverson (26) argued that the developing motor system plays an important role in the development of language and is a key participant in a typically developing child in a typical environment. Children with SLI show difficulties in sensory processing sections related to endurance, tone, body position, movement, and activity level. These problems can interfere with motor development, which normally supports language acquisition. To our knowledge, there has been only one study conducted on children with severe childhood apraxia of speech in which the Sensory Profile was used. Newmeyer et al. (27) found that comparing section scores revealed statistically significant differences in 7 out of the 14 sections. In contrast, we found significant differences on all 14 sections. In Newmeyer’s study, 4 out of 6 sections from the main section, sensory processing (A–F), were significantly different,

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Table II. Percentages of cases in the SLI group (SLI, n ⫽ 116) and the control group (Con, n ⫽ 116) according to the Sensory Profile Supplement Classification System (20).

Section: Sensory processing A. Auditory processing B. Visual processing C. Vestibular processing D. Touch processing E. Multisensory processing F. Oral processing Modulation G. Sensory processing related to endurance-tone H. Modulation related to body position and movement I. Modulation of movement affecting activity level J. Modulation of sensory input affecting emotional responses K. Modulation of visual input affecting emotional responses and activity level Behavior and emotional responses L. Emotional / social responses M. Behavioral outcomes of sensory processing N. Items indicating thresholds for response Quadrant: 1. Registration 2. Seeking 3. Sensitivity 4. Avoiding

Much less than others

Less than others

Similar to others

More than others

Much more than others

Definite difference ⱕ –2 SD

Probable difference –2 SD ⬍ x ⱕ –1 SD

Typical performance –1 SD ⬍ x ⬍ 1 SD

Probable difference 1 SD ⱖ x ⬍ 2 SD

Definite difference ⱖ 2 SD

SLI

Con

SLI

Con

SLI

Con

SLI

Con

SLI

Con

– – – – – –

– – – – – –

1.7 6.9 3.4 4.3 – –

11.2 13.8 12.1 9.5 11.2 –

34.5 50.0 44.9 43.1 26.7 44.0

73.3 73.3 75.0 75.0 73.3 83.6

22.4 19.8 27.6 26.7 40.5 33.6

13.8 11.2 11.2 13.8 14.7 14.7

41.4 23.3 24.1 25.9 32.8 22.4

1.7 1.7 1.7 1.7 0.9 1.7

–

–

–

–

36.2

83.6

31.9

15.5

31.9

0.9

–

–

2.6

15.5

31.0

70.7

19.8

12.1

46.6

1.7

–

–

4.3

16.4

31.9

65.5

32.8

16.4

31.0

1.7

–

–

–

–

26.7

84.5

14.7

13.8

58.6

1.7

–

–

–

–

38.9

79.3

44.8

19.8

17.2

0.9

– –

– –

0.9 2.6

16.4 18.1

34.4 39.6

67.2 72.4

33.6 35.4

14.7 7.8

31.0 22.4

1.7 1.7

–

–

–

–

33.6

82.8

42.3

17.2

24.1

0.0

– 0.9 – –

– 1.7 – 1.7

3.4 3.4 0.9 1.7

18.1 13.8 13.8 13.8

31.9 35.4 25.0 23.3

70.7 68.1 70.7 68.1

23.3 25.8 37.0 32.7

9.5 14.7 13.8 14.7

41.4 34.5 37.1 42.2

1.7 1.7 1.7 1.7

namely auditory, visual, tactile, and multisensory processing. These limitations in sensory processing can interfere with speech motor development and language acquisition. The sections for vestibular and oral sensory processing were not significantly different in the study of Newmeyer et al. In our study, oral sensory processing was significantly different in children with SLI, but with a smaller difference than in other sections. This could be due to the questions asked, as they mainly concerned food, taste, and smell. In analyzing the quadrant scores, consistent with our study, Newmeyer found significant differences between the study groups in all four quadrants. Differences between our study and that of Newmeyer et al. (27) may be due to population differences. Newmeyer et al. only studied children with severe apraxia of speech. Our population consists of predominantly children with SLI. Furthermore, there were sample differences in age and in number of participants

between the studies, which could account for such differences. Studies investigating other developmental disabilities than SLI, such as Autism Spectrum Disorder (ASD), Asperger syndrome, and Attention Deficit Hyperactivity Disorder (ADHD), also show difficulties in sensory processing. Our findings are in line with studies investigating differences in sensory processing between children with and without these disabilities using the Sensory Profile (28,29). One could hypothesize that developmental disabilities in general influence sensory modulation by means of an intermediate variable, such as stress, fear, or feelings of insecurity. Considering the results of the Sensory Profile-NL, one must take into account that the Sensory Profile-NL addresses not only sensory processing but also behaviors that refer to areas like attention and social-emotional functioning. It can be hypothesized


Children with SLI show difficulties in sensory modulation that arousal and attention play an important role in the information processing of children with SLI because the sections auditory processing and multisensory processing both contain several questions that can also refer to (auditory) attention (e.g. item 4: ‘Is distracted or has trouble functioning if there is a lot of noise around’ and item 48: ‘Has difficulty paying attention’). Future studies that investigate the relationship between sensory processing, attention, and language learning may clarify the roles of arousal and attention. The term SLI applies to a very heterogeneous group of children (2). Studies that investigate genetic influences on language impairment show that SLI is a disorder with multiple genetic and environmental risk factors, in which environmental modification at an early stage can have an effect on the course of the disorder (1). It is often assumed that language itself is the problem but processing limitations may considerably influence the ability of the child to access the input that is necessary for language development (30). All input is of a sensory nature to start with. If information is not perceived well, processing this information will result in incorrect conclusions concerning this input. Quadrant scores express how a child in general behaves in reaction to stimuli from different modalities. Analysis of the quadrant scores indicated that children in the SLI group can have high and/or low neurological thresholds. This can interfere with sensory modulation of auditory, visual, tactile, and/or vestibular information. As stated by Dunn, children with low scores on the quadrants ‘registration’ and ‘seeking’ have higher neurological thresholds (24). Low scores on the quadrants ‘sensitivity’ and ‘avoiding’ are associated with lower neurological thresholds (24). Indirectly, this can interfere with non-linguistic abilities such as eye contact, joint attention, gesturing, and body posture needed both to sustain attention and to provide a base for pattern recognition in the developing language system. These non-linguistic processing factors are considered a prerequisite for language learning (10,31). The results of our study could imply dysfunctions in sensory modulation in a population of children with SLI. Bishop (32) suggests that children with specific language impairment fail to learn at a normal rate, so it is important to pay attention to mechanisms of learning instead of focusing on perceptual or linguistic impairments as causal factors. Problems in sensory modulation could be one of the processing problems that interfere with normal learning in general and language learning in particular (12,13). Speech-language pathologists must understand the effects of sensory processing on speech-language development. Enhanced sensory modulation can be

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designed to facilitate and support language development by using multiple sensory modalities (8,12). To summarize, children with developmental disorders like SLI exhibit problems in all sections of the Sensory Profile-NL. These deficits in sensory modulation can be regarded as co-morbid problems in children with SLI, suggesting that children with SLI process their sensory information differently from typical children. Disorganized processing of sensory input can affect development in general and language learning in particular. Limitations and future directions This study had several potential limitations. First, information was obtained via a caregiver questionnaire and not through direct observation or testing of the subject, which can cause observer bias. Conversely, parents are the most likely source for obtaining a precise picture of a child’s behavior and performance in response to sensory events in daily life. Second, we used a convenience sample of children with SLI and selected a comparison group from the standardization data of the Sensory Profile-NL. To reach the current sample size, children from different schools were recruited. Therefore different investigators diagnosed children of the SLI group. None of these investigators were involved in assessing the control group. No IQ tests were taken from the children of the control group. A multicenter trial could validate the findings of this initial study about sensory processing abilities in children with SLI. Third, there were no scores of intelligence level of the control group available. To strengthen the outcomes of future studies, it is recommended to include these data. Based on the study’s findings, we recommend future research into using the Sensory Profile as an instrument for studying behavior of children with SLI. The Sensory Profile or the Short Sensory Profile (19,24) can also be used in evidence-based efficacy studies on the treatment of children with SLI, applying a sensory integration frame of reference in the remediation of language processing. Additionally, longitudinal research on sensory processing abilities in younger children is desirable in detecting the influence of early non-linguistic processing limitations on language development. When scores on the Sensory Profile suggest difficulties in sensory processing, therapists are advised to evaluate the sensory processing abilities of a child more directly, using standardized testing to gain a better understanding of the role of sensory processing in the child’s speech-language development. Intervention for children with language impairment should be broader when non-linguistic/non-verbal


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abilities are poor, as Leonard et al. (30) suggest. In this study, one assumes that language treatment may be very beneficial but that these children’s overall developmental functioning might be better aided with a more general approach to intervention. The results of the Sensory Profile-NL suggest directions for broader based language treatment, such as teambased approaches in which speech-language pathologists and occupational therapists provide co-therapy to promote maximum improvement in all areas of development alongside traditional speech and language therapy (33). Because systems for sensory processing are involved in language acquisition, disturbed modulation of sensory input could negatively influence language processing. Sensory processing disorders can be a co-morbid problem in children with SLI. When language disorders and sensory processing disorders co-occur in one child, both should be addressed in treatment. Further research is needed to investigate the relationship between sensory processing patterns and SLI in children.

Acknowledgements We are grateful to the parents of the SLI group for taking part in this study, as well as to the speechlanguage pathologists of the schools of the Royal Auris Group for data collection. We gratefully acknowledge Harcourt Test Publishers/Pearson in the Netherlands for their permission to use their data to extract a matched control group. We would like to thank Miriam Hufen, Eelke van Haeften, Onno Helder, Kino Jansonius-Schultheiss, and Janine Pijls for support and comments on the manuscript. This paper was presented on November 20, 2008 at the American Speech-Language-Hearing Association Conference in Chicago and at several conferences in the Netherlands.

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6. 7.

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11. 12. 13.

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18. 19. 20. 21.

Declaration of interest: The authors report no conflict of interest. The authors alone are responsible for the content and writing of the paper.

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