"Sensory integration is a neurological process of organising the information we get from our bodies and from the world around us, i.e. it is sensory input processing. When the brain efficiently processes sensory data, appropriate bodily responses are called forth, as well as meaningful perceptions, emotions and thoughts. Sensory integration is a process of turning the sensation into perception; of sorting out, putting into order and unifying all the sensory input of the individual. Its purpose is to have adequate brain reactions" ( Jean Ayres, 1979 ).

According to J.Ayres, information processing comes from different sensory receptors, taking place at the kernels of the brain stem and from there by virtue of reticular formation is resent respectively to the cerebellum, subcortical centres and the centres of the cerebrum cortex. There the reworked sensory data goes through more refined and modulated processing. Impairments of the input transmission or of sensory processing, causes Sensory Integration Dysfunction.

The normal development of a person's sensory system entails the continuous flow of new input being properly received by the sensory system. J. Ayres calls this flow "food for the Nervous System". According to her, new sensory messages begin the creation of (or) develop new neural synapses, which build a wide and complicated network located between the axons. An increase in the quantity of neural impulses, which go through a single synapse, has a positive effect on the ease of conduction of the next impulses - it is a learning process. As J. Ayres traces the evolution of different sensory systems, both of human beings and animals, Ayres creates her theory of the interdependence of these systems, and their hierarchy in terms of importance. Any impairment of sensory integration is due to a dysfunction of some of the hierarchically dependent sensory systems. She distinguishes four levels of sensory information processing. Each level rests on the preceding building blocks.

Listed on the right are the skills necessary for normal social functioning. They are a result of many years' analysis and synthesis in the human brain of the input received.

Listed on the left are the sensory organs. For normal functioning of the sensory organs, the following is required, adequate intake and good conducting of the impulses from the respective sensory receptors to the brain. An impairment in this area will manifested itself as a disability of the brain to adequately rework sensory impulses.

The vertical columns on the table represent the four levels of sensory information reworking. The processes shown do not run at the horizontal level, unevenly or at big intervals, but simultaneously, some of them bringing on the development of others. The vertical columns show the actual reworking of sensory information, showing that many of the processes fuse into one. (For instance, the presentation of the tactile system indicates that touching of skin can have different aims - on one hand it helps the child to suck and to be fed if the touch is near the lips, on the other, it helps to build the relationship between mother and child.)

The first level of sensory integration covers the tactile system. Touching (input to the tactile system) is important for the building of the relationship between a mother and her child. It sets the foundation of the baby's perception of its own bodily dimensions. The skin is the border between the personality and the outer world, which is why reworking of tactile information is a major factor for creating the feeling of security, which the baby needs. Causes for Tactile Dysfunction usually are at the level of the brain stem or in the unconscious areas of the hemispheres. Children with Tactile Dysfunction are either hypersensitive (over-responsive), or hypo sensitive (under-responsive) to tactile stimuli. Sensory input that can be read by the receiver as painful will activate the protection system, and proprioceptive (pressure) input can suppress "painful" input as well as be used to help regulate. It is suspected that impairments of the tactile system are caused by hypoxia during birth, because the kernels of sensory perceptions are very vulnerable during this time period. Impairments of sensory information processing at this level in early childhood may be the cause of emotional problems, communicative difficulties, as well as a shy or apathetic personality.

The second level is connected with normal processing of vestibular and proprioceptive input. If the vestibular and the proprioceptive systems are not well integrated, children have problems with motor planning, causing difficulties in changing body positions from lying on their stomach to lying on their back, and vice versa, as well as creeping or crawling. Performing these activities is an important stage in the process of learning how to stand or walk. Children with impaired proprioceptive and vestibular systems experience problems with maintaining their balance, tiring easily, stiff movements, uneven and slow movements, and low muscular tone. These children have difficulties in orienting themselves in space and moving within it; they have constant fear of falling. All the above makes them unstable personalities, as these problems negatively impact their emotional state. Some of these children become shy and withdrawn, others hyperactive and aggressive. Hyperactivity results from lack of security, and security is present when the three basic sensorial processes - the tactile, the vestibular and the proprioceptive - are functioning properly. Problems at this second level arise when the child's own body scheme is not built sufficiently well. Each part of the body corresponds to a given zone, both in the motor cortex (gyrus praecentralis), and in the sensory cortex (gyrus postcentralis). Body scheme consists of separate body maps, kept in the brain. These maps contain information about every area of the body, the connections between them and all the possible movements each part of the body can make. Building of a person's own body scheme results from all the input coming from the skin, muscles and joints. Visual input is not important for its formation. Therefore, when a child needs to use his visual analyser to perform a given activity, this is a sign of body scheme problems. If the co-ordination between the two halves of the body is not sufficient enough, children have difficulties performing activities which require simultaneous use of both hands and both legs, i.e. dancing, playing drum, etc. These problems concern motor planning (motor stereotypes), i.e. input processing which enable us to adapt to unfamiliar activities, and after some time to automatically perform new movements. Human ability to do that is due to the presence of a well-built body scheme with exact tactile, vestibular and proprioceptive information.

Proper functioning of a child's brain is conditioned by two factors: ability to concentrate and attention scope. If the child were not able to control the constant flow of perceptions from the outside, then he would not be capable of concentrating on any given activity. He will become easily distracted by auditory and visual input. This is common for children with poor body awareness.

The third level of sensory integration includes visual and auditory perceptions. Visual and auditory systems can develop normally only when there is proper functioning of the three basic systems - vestibular, tactile and proprioceptive. All of these systems, rework the corresponding three main types of sensory data, create the basis of harmonious functioning of the brain and are responsible for the formation of the body scheme as well as all the functions connected with it. They are important for the person's ability to speak and understand speech. Visual perceptions are crucial for the coordination between the eye and hand and are related to the three basic types of sensory data. Proper functioning of systems on this third level is manifested in the child's abilities to eat with a spoon and a fork, to draw, to construct and to dismember different objects.

The fourth level, at the top of the hierarchy, presents the final product of all sensory processing done throughout the previous three levels, and conditions the overall functioning of the brain: learning skills, speech and language development. This is due to the fact that verbal communication is a final product of sensory integration. A well-functioning vestibular system is especially important for understanding speech because it unites all the input that runs through the channels which are used by all the organs of perception. Short Postrotatory Nystagmus (PRN) means the contractions of the eye muscles, caused by a reflex reaction to the input received by a vestibular apparatus. It is proved that children with articulation, speech and language problems have a short PRN. If the Nistagmus has short duration or is lacking, this signals that the vestibular kernels at the brain stem do not receive enough information from the vestibular organs and this information's processing is not efficient. If the PRN's duration is longer than the normal, it means that the vestibular system is oversensitive for lack of repressive power, which normally works within it. A research in Northern America shows that 50% of children with speech and language problems have a short duration of PRN, and those children who have difficulties learning the spelling and the symbolic side of language have a longer PRN.

High Cortical functions are to some extent dependent on the activity of the subcortical centres. Right-handed people's speech centre is in the left hemisphere, the latter being a part of a big network encompassing other parts of the kernel and the subcortical integration centres. Development of speech and language skills requires constant interaction of the High and Low centres, and when the lower centres in the brain do not receive enough information, then the Higher centres have to work more than the norm requires to compensate for this.

It is important to note that not all speech and language impairments are connected with vestibular problems. Sometimes they are due to improper functioning of the speech centre in the left hemisphere - in this case, sensory integration therapy would not be effective.

Age levels for the development of each of the different functions mentioned above cannot be strictly defined. Throughout childhood each level of sensory integration is engaged. At the age of 2 months, for instance, the nervous system works primarily at the1st level, the 2nd level being activated to some extent, and the 3rd level not yet functioning. At the age of 1 year, the most important levels are the 1st and the 2nd, while the 3rd one starts to gain significance. At the age of 3, all the first three levels of the nervous system are active, and inclusion of the 4th gradually begins. At the age of 6, the 1st level is accomplished, the 2nd level is almost completely built, the 3rd level is active and the 4th gains in significance. The child acquires different skills through repeating movement acts over and over again - first the child learns how to crawl, then to walk, then ride a bicycle, etc. The brain works as a united whole, each part of it interacting with the others.

Therapy for Sensory Integrative Dysfunction consists of stimulation of the senses in order to call forth a bodily reaction; this includes tactile and vestibular stimulation. This therapy is considered to be direct intervention, which can improve functioning of the nervous system. Individual programmes are designed according to each child's specific needs: working with physical therapist, psychologist, Special Education teacher, Speech &Language Pathologist.

For a diagnosis of Sensory Integration Dysfunction, an assessment is used, which researches the integration of input, the child's motor planning abilities, coordination between the eye and hand, vestibular and postural reactions, eye muscles' reactions, lateralization (the process of establishing priority of one side of the body). Vestibular stimulation is of great importance for the reworking of sensory and motor processes, taking place in the brain stem. Auditory and visual deficits, which effect the data processing in the brain stem, determines how this data becomes reworked in the brain at the Cortical level. Reacting to vestibular stimulation early on in childhood helps to create motor models and will become the basis for developing complex reactions in later childhood. These motor models can compensate considerably for sensory dysfunction.

Games are very important for children and must be incorporated into their play. However, these games should not be aimless and without the adult's structure, as young children cannot not yet compensate for their sensory deficit problems. Children with special needs are capable of playing, but their games must be directed towards improving their sensory integration deficits, perceptions and sensory organs. These children need an environment that is specially designed to help address their needs. This environment requires special equipment, and this cannot be provided at school or at home. In such an environment they would be instructed, and their guidance will be strategically planned; at the same time they would be given freedom to choose their activities. This treatment will have positive effect on their nervous system and on organisation of their needs.

In the course of the therapy session the child usually chooses his own activities, but often a choice of activities have been predetermined by the therapist. The doctor then would introduce the child into the specific activities, like brushing of skin, for instance because this activity creates strong tactile perceptions, which are registered in many areas of the brain. Sensory stimulation can have a conductive or a suppressing effect in respect to which parts of the body are treated, and whether rubbing is mild, or pressure is exerted (the latter has effect on the deep sensitivity). The stimulation of the tactile and the proprioceptive systems through the use of deep pressure in children who have severe sensory defensiveness (hyperactive, or withdrawn children, or those who get distracted easily) enables them to better organise their actions. Sensations of deep pressure can be provoked by exercises of the "sandwich" type, by massages with a brush or towels of different texture, as well as through the use of different exercises consisting of stretching the limbs, etc. A good way to stimulate sensory receptors, especially those located in the bones, is vibration - when exercised on costal level, it sends input to the vestibular organs. Such exercises must be carefully selected though, because they have impact on the growth of the bones themselves. Another form of stimulation is to excite the olfactory analyser. Strong smells influence reticular formation and this has an impact on all sensory organs. Different activities can be useful for the vestibular system - some of them look very simple but their influence on the processing of perceptions at the brain kernels is considerable. This is important for acquiring speech, language and learning skills, as well as fine motor skills, such as manipulation with tools. Such activities include riding on a scooter board while lying on his stomach, seesawing, swinging in a hammock, and different variations of these types of activities. The child's reactions towards sensory stimulation are the most precise indicator for assessment of the degree to which the brain is capable to perceive the input. Sometimes the effect of the exercise doesn't come immediately but is manifested a half an hour, hours later, or even during night. Therefore parents must be prepared for delayed results. It is important that the exercises be repeated several times each, because gaining sensory experience is a specific process during which the motor skills are formed. In this process, traits in the memory are left, and later these memory traits the child has accumulated will enable him to learn step by step how to conduct its own bodily sensations.

Children with damaged nervous systems often react negatively to overloading and hyperstimulation. Therefore only qualified therapists must serve these children and they must approach them carefully.

The therapist must carefully dose the input, especially when working with the vestibular and proprioceptive systems, so that the child develops a spontaneous and adaptive reaction to input. This reaction must lead to integration of the separate components of the nervous system. The therapy will have a much greater effect if the child chooses on his own type of stimulation and the ways in which to exert it. The therapist's task is to follow the child's leading and direct them when necessary. Children with more severe impairments will need more assistance and their activities must be precisely structured.

Integration of sensory perceptions helps in the development of separate components of the nervous system and the organisation of motor, speech and language skills, thinking abilities and emotional reactions. As a result, the child's self-esteem and social functioning improves.

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The site is created in 2001. Last update - 20.06.2008