Sensory integration is defined as the neurological process that organizes sensation from one’s own body and the environment, thus making it possible to use the body effectively within the environment. Specifically, it deals with how the brain processes multiple sensory modality inputs into usable functional outputs. It has been believed for some time that inputs from different sensory organs are processed in different areas in the brain. The communication within and among these specialized areas of the brain is known as functional integration
Newer research has shown that these different regions of the brain may not be solely responsible for only one sensory modality, but could use multiple inputs to perceive what the body senses about its environment. Sensory integration is necessary for almost every activity that we perform because the combination of multiple sensory inputs is essential for us to comprehend our surroundings.
It has been believed for some time that inputs from different sensory organs are processed in different areas in the brain. Using functional neuroimaging, it can be seen that sensory-specific cortices are activated by different inputs. For example, regions in the occipital cortex are tied to vision and those on the superior temporal gyrus are recipients of auditory inputs. There are studies that show that there is new data that suggests that there are deeper multisensory convergences than those just at the sensory-specific cortices listed earlier. This convergence of multiple sensory modalities is known as sensory integration.
Sensory integration deals with how the brain processes sensory input from multiple sensory modalities. These include the five classic senses of vision (sight), audition (hearing), tactile stimulation(touch), olfaction(smell), and gustation(taste). There are other sensory modalities exist, for example the vestibular sense (balance and the sense of movement) and proprioception (the sense of knowing one’s position in space). What is important is that the representations of these different sensory modalities have to coincide. The sensory inputs themselves are in different electrical signals, and in different contexts. Through sensory integration, the brain can relate all of these different sensory modality inputs into coherent outputs that better prepare us to fully comprehend our environment
Unfortunately, in contrast to other areas of brain science, the study of “sensory integration” is in its infancy. There are few neuroscientists, neurologists, neuropsychologists, or neuropsychiatrists who actually consider it to be a condition. Instead, the term “sensory integration” is confined to the field of Occupational Therapy, which is not actually a brain-based field
The theory of Sensory Integration (SI) was developed in the 1960s by Dr. A. Jean Ayres, an occupational therapist who was a pioneer in the field of learning disabilities.
In the 1930s, Dr. Wilder Penfield was conducting a very bizarre operation at the Montreal Neurological Institute. Dr. Penfield “pioneered the incorporation of neurophysiological principles in the practice of neurosurgery. Dr. Penfield was interested in determining a solution to solve the epileptic seizure problems that his patients were having. He used an electrode to stimulate different regions of the brain’s cortex, and would ask his still conscious patient what he or she felt. This process led to the publication of his book, The Cerebral Cortex of Man, in 2007. The “mapping” of the sensations his patients felt led Dr. Penfield to chart out the sensations that were triggered by stimulating different cortical regions. Mrs. H. P. Cantlie was the artist Dr. Penfield hired to illustrate his findings. The result was the conception of the first sensory Homunculus.
The Homonculus is a visual representation of the intensity of sensations derived from different parts of the body. Dr. Wilder Penfield and his colleague Herbert Jasper developed the technique of using an electrode to stimulate different parts of the brain to determine which parts were the cause of the epilepsy. This part could then be surgically removed or altered in order to regain optimal brain performance. While performing these tests, they discovered that the functional maps of the sensorimotor and motor cortices were similar in all patients. Because of their novelty at the time, these Homonculi were hailed as the “E=mc2 of Neuroscience.
She defined SI as the body’s capacity to organize sensory input, information and stimulation a person receives from his/her own body and the environment through the different sensory systems:
- tactile (touch)
- proprioceptive (joint and muscle impulses)
- vestibular (movement, visual, auditory)
- hearing and listening/auditory
This sensory information is then processed by the central nervous system and used to help our body develop spatial awareness, muscle tone, postural stability and self-regulation. SI gives us the awareness of our body and the ability to use it as a tool to interact with others in our world.
For those with Sensory Integration Dysfunction, the brain is not processing organizing the flow of sensory impulses properly. This can impact on a person’s functional, developmental and learning processes.
Examples of sensory integration
One of the earliest sensations is the olfactory sensation. Evolutionary, gustation and olfaction developed together. This sensory integration was necessary for early humans in order to ensure that they were receiving proper nutrition from their food, and also to make sure that they were not consuming poisonous materials. There are several other sensory integrations that developed early on in the human evolutionary time line. The integration between vision and audition was necessary for spatial mapping. Integration between vision and tactile sensations developed along with our finer motor skills including better hand-eye coordination. While humans developed into bipedal organisms, balance became exponentially more essential to survival. The sensory integration between visual inputs, vestibular (balance) inputs, and proprioception inputs played an important role in our development into upright walkers.
Perhaps one of the most studied sensory integrations is the relationship between vision and audition. These two senses perceive the same objects in the world in different ways, and by combining the two, they help us understand this information better. Vision dominates our perception of the world around us. This is because visual spatial information is one of the most reliable sensory modalities. Visual stimuli are recorded directly onto the retina, and there are few, if any, external distortions that provide incorrect information to the brain about the true location of an object. Other spatial information is not as reliable as visual spatial information. For example, consider auditory spatial input. The location of an object can sometimes be determined solely on its sound, but the sensory input can easily be modified or altered, thus giving a less reliable spatial representation of the object. Auditory information therefore is not spatially represented unlike visual stimuli. But once one has the spatial mapping from the visual information, sensory integration helps bring the information from both the visual and auditory stimuli together to make a more robust mapping.
There have been studies done that show that a dynamic neural mechanism exists for matching the auditory and visual inputs from an event that stimulates multiple senses. One example of this that has been observed is how the brain compensates for target distance. When you are speaking with someone or watching something happen, auditory and visual signals are not being processed concurrently, but they are perceived as being simultaneous. This kind of integration can lead to slight misperceptions in the visual-auditory system in the form of the ventriloquist effect. An example of the ventriloquism effect is when a person on the television appears to have his voice coming from his mouth, rather than the television’s speakers. This occurs because of a pre-existing spatial representation within the brain which is programmed to think that voices come from another human’s mouth. This then makes it so the visual response to the audio input is spatially misrepresented, and therefore misaligned.
Hand eye coordination is one example of sensory integration. In this case, we require a tight integration of what we visually perceive about an object, and what we tactilely perceive about that same object. If these two senses were not combined within the brain, then one would have less ability to manipulate an object. Hand-eye coordination is the tactile sensation in the context of the visual system. The visual system is very static, in that it doesn’t move around much, but the hands and other parts used in tactile sensory collection can freely move around. This movement of the hands must be included in the mapping of both the tactile and visual sensations, otherwise one would not be able to comprehend where they were moving their hands, and what they were touching and looking at. An example of this happening is looking at an infant. The infant picks up objects and puts them in his mouth, or touches them to his feet or face. All of these actions are culminating to the formation of spatial maps in the brain and the realization that “Hey, that thing that’s moving this object is actually a part of me.” Seeing the same thing that they are feeling is a major step in the mapping that is required for infants to begin to realize that they can move their arms and interact with an object. This is the earliest and most explicit way of experiencing sensory integration.
Problems with sensory integration
Sometimes there can be a problem with the encoding of the sensory information. This disorder is known as sensory integration dysfunction, or SID. This disorder can be further classified into three main types. Type 1 is when the patient exhibits a sensory modulation disorder, where he/she seek sensory stimulation due to an over or under response to sensory stimuli. Type 2 is when the patient exhibits a sensory based motor disorder. Patients who have this type of SID have incorrect processing of motor information that leads to poor motor skills. Type 3 sensory integration dysfunction occurs when the patient has a sensory discrimination disorder, which is characterized by postural control problems, lack of attentiveness, and disorganization. There are several therapies used to treat SID. Dr. A. Jean Ayres claimed that a child needs a healthy “sensory diet,” which is all of the activities that a child performs that gives him/her the necessary sensory inputs that he/she needs to get the brain into better performing sensory integration.
Signs of Sensory Integration Dysfunction include:
- Overly sensitive to touch, movement, sights or sounds
- Easily distracted
- Decreased awareness of surroundings
- Activity level that is unusually high or unusually low
- Impulsive, lacking in self-control
- Inability to unwind or calm self
- Poor self-concept
- Social and/or emotional problems
- Physical clumsiness or apparent carelessness
- Difficulty making transitions from one situation to another
- Delays in speech, language, or motor skills
- Delays in academic achievement
- Slow reaction to touch, movements, sights, or sounds
A Typical SI/OT Session
Providing the right kinds of sensory stimulation helps normalization of the sensory systems – tactile, vestibular, proprioceptive, auditory, and visual – to provide the optimal state of alertness and attention. In addition, it helps to develop an adaptive response for daily functioning.
A typical session includes:
- tactile and proprioceptive input using a technique such as ‘brushing’ & deep pressure stimulation
- vibratory input
- movement play (i.e. swings, balance beam, rock wall climbing, scooters, obstacle courses) for body awareness
- postural activities designed to increase strength, postural control, stability, coordination and motor planning
- visual motor/perceptual activities (puzzles, manipulatives, three-dimensional block designs, figure-ground activities, etc.)
- oral motor activities (blow toys, whistles, etc.) fine motor activities (Handwriting Without Tears)
A complete evaluation takes 3-4 hours and consists of a variety of assessment tools that measure key issues, including sensory processing, postural skills/strength, and motor planning. The most common standardized test used is the Sensory Integration and Praxis Texts (SIPT) for children between the ages of 4 to 8 years, 11 months; other tests include the Test of Sensory Integration (3-5 years), Bruininks Osteretsky Test of Motor Proficiency (5-15 years), and the PEERAMID (6-14 years).
An evaluation includes a formal report with assessment scores, a sensory motor history and clinical observations. Recommendations and long term goals and objectives are also included in this comprehensive report.
Clients may choose a screening if they have had a previous and adequate evaluation and are looking to begin the therapeutic process, to make sure our approach fits yours, to get an overview and general verbal feedback when a full evaluation is not required. A screening is 2 hours and includes clinical observations of developmental and sensory-motor based issues. This is an overview and not meant to be a comprehensive evaluation.
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