[2][3] Sensory processing disorder has been characterized as the source of significant problems in organizing sensation coming from the body and the environment and is manifested by difficulties in the performance in one or more of the main areas of life: productivity, leisure and play[4] or activities of daily living.

[citation needed] While many people can present one or two symptoms, sensory processing disorder has to have a clear functional impact on the person's life: Signs of over-responsivity,[12] including, for example, dislike of textures such as those found in fabrics, foods, grooming products or other materials found in daily living, to which most people would not react, and serious discomfort, sickness or threat induced by normal sounds, lights, ambient temperature, movements, smells, tastes, or even inner sensations such as heartbeat.

[23] After sensory information passes through these centers, it is then routed to brain regions responsible for emotions, memory, and higher level cognitive functions.

Electroencephalography (EEG),[24] measuring event-related potential (ERP), and magnetoencephalography (MEG) are traditionally used to explore the causes behind the behaviors observed in SPD.

[25] Differences in auditory latency (the time between the input is received and when reaction is observed in the brain), hypersensitivity to vibration in the Pacinian corpuscles receptor pathways, and other alterations in unimodal and multisensory processing have been detected in autism populations.

[29] People with sensory over-responsivity might have increased D2 receptor in the striatum, related to aversion to tactile stimuli, and reduced habituation.

[1] The SDD subtypes are:[48] Typically offered as part of occupational therapy, ASI that places a child in a room specifically designed to stimulate and challenge all of the senses to elicit functional adaptive responses.

[49] Although Ayres initially developed her assessment tools and intervention methods to support children with sensory integration and processing challenges, the theory is relevant beyond childhood.

[58][59] This therapy retains all of the above-mentioned four principles and adds:[60] While occupational therapists using a sensory integration frame of reference work on increasing a child's ability to adequately process sensory input, other OTs may focus on environmental accommodations that parents and school staff can use to enhance the child's function at home, school, and in the community.

[61][62] These may include selecting soft, tag-free clothing, avoiding fluorescent lighting, and providing ear plugs for "emergency" use (such as for fire drills).

"[68] It has been estimated by proponents that up to 16.5% of elementary school aged children present elevated SOR behaviors in the tactile or auditory modalities.

The AOTA provides several resources pertaining to sensory integration therapy, some of which includes a fact sheet, new research, and continuing education opportunities.

The American Academy of Pediatrics (AAP) in 2012 stated that there is no universally accepted framework for diagnosis and recommends caution against using any "sensory" type therapies unless as a part of a comprehensive treatment plan.

[76][77] Critics have noted that what proponents claim are symptoms of SPD are both broad and, in some cases, represent very common, and not necessarily abnormal or atypical, childhood characteristics.

[79][78] Sensory processing disorder as a specific form of atypical functioning was first described by occupational therapist Anna Jean Ayres (1920–1989).

"[1] The sensory processing model's nosology divides SPD in three subtypes: modulation, motor based and discrimination problems.