Current estimates indicate that accompanying sensory processing problems are reported in more than 80% children with autism. Hyper or hypo reactivity to sensory inputs is now a diagnostic criterion for Autism Spectrum Disorders in the Diagnostic and Statistical Manual of Mental Disorders-Fifth Edition [11, 12]. A. Jean Ayres, an occupational therapist, developed the sensory Integration theory . Theory is based on neuroscience, developmental psychology, occupational therapy and education sciences. Sensory integration therapy is a common method used in paediatric occupational therapy. Results of a survey made on occupational therapists working with children with autism report that 99% of therapists stated that they were referring to sensory integration therapy . According to this theory; 1.sensorymotor development is important for learning 2. Individual’s interaction with environments shapes brain development 3. Neurological system has plasticity capability. 4. Meaningful sensory-motor activity is a strong mediator of plasticity . Sensory integration is a process of organizing sensory information in brain in order to create an adaptive response. The aim of sensory integration therapy is to provide controlled and meaningful sensory experiences so that the child can spontaneously and appropriately form responses that require integration of those sensations .
2.1. The importance of sensation
According to the theoretical basis of sensory integration vestibular, proprioceptive, tactile, auditory and visual systems as well as olfaction (sense of smell) and gestation (sense of taste) have a significant importance. The tactile/proprioceptive and vestibular/proprioceptive systems interact routinely with the auditory and visual systems to supply the multimodal sensory information needed to make a meaningful motor response. It’s reported that sensory integration is a dynamic process that sustains during development and sensory information can be organized as a result of interaction with environment .
2.1.1. Tactile system
Skin has numerous receptors that perceive touching, pressure, texture, heat, pain and movement. A signal is transmitted to the related parts of the brain when tactile receptors are stimulated with touch, heat or vibration. Tactile system is a sensory system that affects behaviour both physically and mentally. Sense of touch is quite important for neural organization and praxis development [16, 18].
2.1.2. Vestibular system
Vestibular receptors related with balance and gravity, and located in inner ear consist of semi-circular canals, utricle and saccule. Semi-circular canals are responsible for detection of angular, fast, short bursts of motion, and result in phasic limb movements and momentary head righting. Vestibular system is a system that affects balance, eye movements, posture, muscle tonus and attention [16, 19].
2.1.3. Proprioseptive system
This system is related with position and movement. Pushing and pulling activities related with muscles and joints are activities that provide maximum stimulation for this system. Proprioceptive system provides information on postural and oculomotor control, position in space and balance together with vestibular and visual system. In terms of the problems reported in vestibular and proprioceptive system, difficulties in good body scheme and laterality development, poor balance, poor postural control and difficulties in coordinated movements are observed in children with autism [2, 16-18].
Children who are hypo responsive against proprioceptive stimulation have weak proprioceptive discrimination and awareness and fail to use proprioceptive input correctly. Therefore they tend to break their toys easily and have low postural tonus. Bites, pushes, hits, scratches, bumps, hurls, hangs and aggressive behaviours as well as self-stimulatory and hyperactive behaviours such as banging head, biting hands are observed in children seeking for proprioceptive inputs .
2.1.4. Auditory system
The sound information from each ear goes to auditory cortex of opposite hemisphere. The relation between the auditory system and valgus nerve is important in sensory modulation .
2.1.5. Visual system
The light received stimulates retina in order to send sensory input to the processing centre in the brain. Integration of visual inputs with different senses provides our awareness about our environments. Visual and vestibular systems work together for perceptual motor integration and visual perception [16, 18].
2.1.6. Gustatory sense
Different senses of tastes ensure that we like the food we eat and distinguish those that may be harmful .
2.1.7. Olfactory sense
Smell is directly processed via limbic system and creates memories and associations that influence some of our choices and preferences .
It’s reported that sensory processing problems observed in individuals with autism are associated with behavioural and/or functional performance problems and specifically stereotypical or repetitive are associated with self-calm or sensory seeking . The studies show that repetitive behaviours, behaviours such as climbing, turning and twirling may indicate existence of sensory processing behaviours .
Sensory registration, modulation, discrimination and praxis defined as motor behaviour planning capability are performance components, which are important for sensory integration. Sensory registration is receiving different stimulus from body or environment . Sensory registration process is important for the individual to perform effective function by paying attention. Children with autism who have sensory registration problems fail in creating appropriate adaptive responses against pain, touch, movement, taste, smell, light and sound . Sensory modulation is defined as “capacity to regulate and organize the degree, intensity, and the nature of responses to sensory input in a graded and adaptive manner” . Sensory discrimination is important for development of motor functions, postural tonus and postural adjustment. Different sensory modulation problems such as hyporesponsivity, hyperresponsivity, sensory avoiding or sensory seeking are reported in children with autism. Hypersensitivity is the most common auditory and tactile defensiveness. High pain tolerance is the most significant indicator of hypo responsiveness in children with autism .
Difficulty in starting and sustaining a social interaction and relation, delays in speaking or communication disorders such as echolalia, repetitive stereotypical plays, visually focusing on any object, cognitive deficits and confusions in impacts and results of behaviours are common sensory integrative – related behaviours in children with autism spectrum disorder. Poor sensory processing affects the child with autism in successful involvement in daily life activities such as playing and participating in social activities with peers, tooth brushing, eating, self-care etc. .
2.2. Sensory integration assessment and intervention
“The Occupational Therapy Practice Framework: Domain and Process (AOTA, 2002)” which is a comprehensive guideline of assessment and intervention is used in the assessment of individuals with autism and in occupational therapy interventions. Accordingly, occupational profile should be initially defined, occupational performance should be assessed, intervention plan should be designed, objectives and goals should be identified and documented, intervention should be implemented, and results of intervention should be assessed and documented .
It is important to identify sensory responsiveness (over, under or labile) and sensory preferences (likes and dislikes) praxis and sensory processing problems that affect involvement in daily life activities in the assessment of sensory integration in children with autism .
Numerous tests like given below are used for assessment of sensory integration in occupational therapy.
Sensory Integration and Praxis Test (SIPT): It is developed to identify sensory integration problems. Test is standardized for use in children 4 –8 : 11 years of age. SIPT assesses sensory and neurological process, which leads to behavioural, learning, language and praxis problems. It consists of 17 subtests, which assess tactile, vestibular proprioceptive processing; form and space perception, visual-motor coordination, praxis, bilateral integration and sequencing, and it takes nearly 90 minutes to complete the test.
Sensory Profile: The Sensory Profile is a caregiver questionnaire, which measures children’s responses to sensory events in everyday life for children 3-10 years of age. 5-point Likert scale (nearly never, seldom, occasionally, frequently, almost always) is used for assessment.
Evaluation of sensory processing: This questionnaire is intended to identify behaviours thought to be indicative of sensory processing problems .
Besides standardized assessments, many occupational therapists refer to clinical observations for assessment of sensory and praxis functions. Clinical observation of postural control, behaviour organization and vestibular functions offer significant information in addition to sensory tests. It’s important to observe playing skills, social interaction and other relevant behaviours of the child in child’s natural settings . Clinical Observations of Motor and Postural Skills is a screen tool for motor deficits and assessment of cerebellar function, postural control and motor coordination . It’s reported that Goal Attainment Scale (GAS) can used in measurement of results in sensory integration studies .
It’s reported that sensory integration therapy should be individually implemented with the consideration of the “inner drive” of the child, based on the sensory experience, challenge and interest and in a structured environments with active participation of the child [16, 22]. More effective feed-forward mechanism required for optimum adaptive response are created with child-directed actions. In responding children with autism, it is important to use controlled and meaningful sensory stimulus to create organized behaviour and to make environmental adaptations when needed. Due to the problems in body awareness, a child with autism fails in receiving sufficient tactile, proprioceptive and vestibular inputs from his/her body. Therefore, environmental arrangements should be adjusted according to motor planning and body awareness required for praxis. It’s important to refer to sensory experiences that motivate and please the child with complex motor planning, social interaction and language skills. Therapist should integrate activities that contain sensory experiences required by the child into daily routine in cooperation with the family, caregivers and teachers . Validity of the results in sensory integration studies are reported to be influenced by different practices in the intervention process and it’s further reported that “Ayres Sensory Integration Fidelity Measure” which is a reliable and applicable verification measure for studies on sensory integration disorders should be used [36, 37].
Fidelity measure consists of 10 essential elements is used in clinic based sensory integration treatment. These essential elements are as follows: a) ensuring safety b) presenting a range of sensory opportunities (specifically tactile, proprioceptive, and vestibular) c) Using activity and arranging the environment to help the child maintain self-regulation and alertness d) challenging postural, ocular, oral, or bilateral motor control e) is challenging praxis and organisation of behaviour f) collaborating with the child on activity choices g) tailoring activities to present the “ just –right challenge”, h) ensuring that activities are successful, i) supporting the child’s intrinsic motivation to play, and j) establishing a therapeutic alliance with the child .