Sensory Integration therapy is a sensory-motor treatment based upon theories developed over the last 30 years by Dr. A. Jean Ayres. Proponents theorize that sensory integration is an innate neurobiological process (Hatch-Rasmussen, 1995), and that children with autism and other developmental delays experience dysfunction in which sensory input is not integrated or organized appropriately by the brain. Fisher and Murray (1991) describe sensory integration as both “a neurological process, and a theory of the relationship between the neurological process and behavior.”
According to Fisher, Murray and Bundy (1991) there are five major assumptions upon which SI theory is based. These are:
“. . .there is plasticity within the central nervous system. Plasticity refers to the ability of the brain structure to change or be modified. . .
. . .the sensory integrative process occurs in a developmental sequence. In normal development, increasingly complex behaviors develop as a result of the circular process, and behaviors present at each stage in the sequence provide, in turn, the basis for the development of more complex behaviors. . .
. . .the brain functions as an integrated whole, but is comprised of systems that are hierarchically organized. . .
. . . evincing an adaptive behavior promotes sensory integration, and, in turn, the ability to produce an adaptive behavior reflects sensory integration. . .
. . .people have an inner drive to develop sensory integration through participation in sensorimotor activities. . .”
(Fisher, Murray & Bundy, 1991)
Sensory integrationists theorize sensory dysfunction is rooted in the central nervous system, and that successful integration of sensory input requires treatment. This treatment is comprised of vestibular, proprioceptive, and/or tactile stimulation.
Ayres (1979) describes sensory integration therapy as sensory stimulation and subsequent adaptive responses which evolve according to the child’s neurological needs. Therapy techniques include vestibular stimulation such as swinging in a hammock, and tactile stimulation achieved by brushing parts of the child’s body (Smith, 1996). SI therapy is viewed as a direct intervention that can improve nervous system function. This is done by providing the child with enhanced levels of sensory information gleaned during physical activities that are meaningful to the child, and that elicit adaptive behaviors (Koomar & Bundy, 1991).
SI theorists also postulate that children with sensory dysfunction are either over- or under-responsive to sensory input. Children with autism may be startled by a slight sound (hypersensitivity), or may totally tune out external stimuli, such as language (under-responsive). SI practitioners further postulate that self-stimulation and stereotypic activities characteristic of many autistic children may be related to sensory dysfunction, and that therefore SI therapy may reduce the rates of self-stimulation and self-injurious behaviors.
According to a critique by Arendt (1988), SI therapy does not seek to teach higher order skills, but rather to rearrange brain functioning (sensory processing capability) as a precursor to learning. Arendt challenges basic SI theory in his critique; he also asserts that even if Ayres’ theories of nervous system hierarchy and neural plasticity are valid, the SI treatment model does not inherently address them. (Arendt, 1988).
It is important to note that while sensory integration may be practiced by occupational and physical therapists, SI does not constitute the full and exclusive range of methods used by OTs and PTs to achieve fine motor, gross motor and adaptive daily living skills. Other methods used in OT and PT include physical prompting, shaping, and modeling, among others.