What is sensory processing? |

Sensory processing, sometimes called sensory integration, is the way in which the nervous system receives and organizes stimulation from the senses.

Overview

Sight, hearing, touch, taste, and smell help people respond appropriately to occurrences in the environment. For example, these senses help protect the body from injuries such as burns or insect stings. Other senses include the vestibular system, which regulates balance through fluids in the inner ear, and
proprioception, which provides awareness of the position and movement of the body's limbs and other parts without visual cues. The brain combines and integrates all the input to coordinate perceptions with the position and movement of the body and generate an appropriate response.

In the brain, the information meets another threshold.
Neurons
, nerve cells that carry messages, differ in the amount of stimulation they require to produce a response. Those that respond slowly are said to have a high threshold, while neurons that respond quickly have a low threshold. Neuron systems with high thresholds for sensation require increasingly stronger stimuli to evoke a response.

Sensory acuity, which describes individuals' sensitivity to sensory stimuli, varies from person to person. Those whose sensory acuity is diminished by age or injury are sometimes able to process sensory information through assistive devices. Glasses or hearing aids are common devices that help overcome loss of acuity, which then allows normal sensory processing.

Some people, particularly children, have difficulty integrating information from the senses and may underreact or overreact to stimuli. Symptoms range from difficulty with motor skills to hypersensitivity to loud noises, strong odors, or irritating clothing, which often interferes with normal activities in life. The condition, called sensory processing disorder (SPD), can lead to school difficulties and emotional problems such as depression. Children with
autism spectrum disorder
(ASD) also have difficulty processing or regulating sensory experiences.

Integrating the Senses

Much of what is processed by the brain is provided by more than one of the senses simultaneously. For instance, important connections among the senses of touch, balance, and body position allow people to function easily in the world. Integration allows people to walk, run, and play in a coordinated and spontaneous way.

Other senses, such as vision and hearing, integrate in ways that are both ordinary and surprising. Stimuli from the environment assemble in an area of the brain called the superior colliculus, where they can provide something like a map of an object's position. The brain then prepares the body for an appropriate reaction, such as dodging a moving bicycle or reaching for a ball to be caught. Such integration also can serve as a survival tool, warning of incoming missiles or an enemy behind a tree. For example, if a person walking in the woods hears the crackle of leaves and glimpses movement through peripheral vision, the brain immediately processes the information and causes the body to turn in the direction of the stimuli for more information: Was it a threat such as a bear, or just a robin? An individual whose sensory systems are either overly sensitive or not responsive enough might be fearful of moving, or could experience a desire to push sensory experiences farther, possibly leading to injury.

Sometimes integrated responses can be unexpectedly inaccurate. While researchers know that speech is much more easily understood if the listener can also see the speaker's mouth, a discrepancy can occur between what people hear when they can see the speaker and what they hear when they cannot. In one example, when watching a person say the word "vase," observers heard the word correctly, yet if they listened with eyes closed they heard "base." This is known as the McGurk Effect. Researchers Harry McGurk and John McDonald unexpectedly found that when the sound "ba" was dubbed into a video of a woman saying "ga," they both heard "da." They soon realized they had discovered an unusual phenomenon in human sensory integration.

Sensory Processing Challenges

Some brain abnormalities may lead to learning and behavior problems. Dr. Temple Grandin, an authority on autism spectrum disorders who is also autistic, recognizes the struggles that many children with autism face regarding sensory processing. Grandin believes that the integration problems experienced by individuals with ASD originate in the cerebellum. Research shows that stimulation of that area of the brain in laboratory animals results in dysfunctional processing that can cause tactile and auditory sensitivity. In her work, some based on her own experience, Grandin found that many individuals with autism can be helped through sensory therapy. She recommends deep pressure therapy, such as rolling the child in a mat or providing a weighted vest, which is often calming to children who have trouble processing sensory input. Lightly brushing the skin is soothing to others. Frequent, scheduled breaks from highly stimulating activities and situations are also helpful.

Sensory processing disorder has not been officially recognized as a disease. Symptoms in children generally include hypersensitivity to touch, sound, or light. Researchers have found that children with SPD have abnormalities at the back of the brain, rather than in the front, as is found in children with ASD. Typical SPD behavior includes anxiety or aggression in crowds, extreme sensitivity to clothing textures or tags, and a strong aversion to certain foods. Researchers estimate that up to 16 percent of school-aged children could be affected.

Bibliography

Grandin, Temple. "Calming Effects of Deep Touch Pressure in Patients with Autistic Disorder, College Students, and Animals." Journal of Child and Adolescent Psychopharmacology. Mary Ann Liebert, Inc. 1992. Web. 1 Apr. 2015. http://grandin.com/inc/squeeze.html

Hatch-Rasmussen, Cindy. "Sensory Integration." Autism Research Institute. Autism Research Institute. Web. 1 Apr. 2015. http://www.autism.com/symptoms_sensory_overview

"Introduction to Sensory Processing Concepts." Sensory Processing in Everyday Life. University of Kansas Medical Center. Web. 1 Apr. 2015. http://classes.kumc.edu/sah/resources/sensory_processing/learning_opportunities/concepts/sp_concepts_main.htm#sp

Kapes, Beth A. "Sensory Integration Disorder." The Gale Encyclopedia of Medicine. 3rd ed. Vol. 4. Detroit: Gale, 2006. 3346-3349. Gale Virtual Reference Library. Web. 2 Apr. 2015. http://go.galegroup.com/ps/i.do?id=GALE%7CCX3451601466&v=2.1&u=itsbtrial&it=r&p=GVRL&sw=w&asid=f5fe721204354bf24212aebaa44c9858

King, Andrew J. "Sensory Integration." The Oxford Companion to the Body. Oxford, UK: Oxford University Press, 2001. 605-606. Gale Virtual Reference Library. Web. 1 Apr. 2015. http://go.galegroup.com/ps/i.do?id=GALE%7CCX1548700846&v=2.1&u=itsbtrial&it=r&p=GVRL&sw=w&asid=5a3a8a05e4fefb3ce8d27cad35e6f74d

Rosenblum, Lawrence D. "The McGurk Effect: Hearing Lips and Seeing Voices." Haskins Laboratories. Haskins Laboratories. Web. 2 Apr. 2015. http://www.haskins.yale.edu/featured/heads/mcgurk.html

"Sensory Processing Disorder Checklist: Signs and Symptoms of Dysfunction " Sensory Processing Disorder. Sensory Processing Disorder. Web. 2 Apr. 2015. http://www.sensory-processing-disorder.com/sensory-processing-disorder-checklist.html