OTs are trying to better understand the neurophysiological basis of sensory processing disorders. Several sites are conducting research using the Sensory Challenge Protocol . Preliminary studies (McIntosh, Miller, Shyu, & Hagerman, 1999) support the presence of a physiological basis of sensory modulation disorder (SMD), finding that electrodermal responses were larger in children with SMD, excepting those who were non-responders. Additionally, Schaaf, Miller, Sewell, & O'Keefe (2003) found that cardiac vagal tone index was significantly decreased for children who had identified sensory processing difficulties. These studies provide preliminary evidence that there is a physiological basis for SMD.
Another method of researching the nature of sensory processing is to look at sensory processing in people with known neurophysiological problems. Lesion studies are a classic method for understanding function and dysfunction of the human nervous system. Of course precautions must be taken when using lesion study methods: the presence of a lesion in a location may not represent the primary site of a nervous system function, despite the fact that actual function could be severely impacted at that lesion site. Circuit redundancy and multipath parallel processing can make lesion studies a little muddy.
Complex regional pain syndrome (CRPS) is a disorder characterized by chronic pain that is disproportionate to the trauma that caused the pain (NINDS, 2003). Sensory modulation disorders are identified as altered neurological thresholds to sensory information that impact on daily life functioning (Dunn, 1997). Although the exaggerated state of sympathetic arousal in people who have CRPS is not clinically identical to hyperarousal in people who have SMD, these two conditions may constitute a continuum of pathology that is reflective of sympathetic nervous system dysfunction. A more thorough understanding of these conditions, including their apparent similarities and the impact that they have on function, will provide information that can be useful when developing therapeutic interventions.
ABC Therapeutics is finishing up a small scale study that is looking at the Adolescent/Adult Sensory Profile test scores of adults with CRPS. This study will explore the sensory processing abilities and occupational performance of adults who have CRPS.
On another front, we are also completing some preliminary literature review on "Type T" personalities. We hope to use a similar design (as above) using the Adolescent Adult Sensory Profile to explore if there are measurable differences in test scores in adolescents who have this profile or those behavioral characteristics. Another interesting twist is to see if we can find a tool that has been used to measure what I am calling 'inverted-T' personalities. I am interested to see if we can find a tool that will behaviorally identify these people and then see how they self-rate on the Adolescelt Adult Sensory Profile.
Please feel free to contact me if anyone is interested in learning more about the work we are doing here on this topic.
Dunn, W. (1997). The impact of sensory processing abilities on the daily lives of young children and their families: A conceptual model. Infants and Young Children, 9, 23-35.
Farley, F. (1991). The Type T personality. Chapter in L.P. Lipsett & L.L Mitnick (eds), Self-regulatory behavior and risk taking: Causes and consequences. Norwood, NJ: Ablex Publishers.
McIntosh, D.N., Miller, L.J., Shyu, V., Hagerman, R.J. (1999). Sensory-modulation disruption, electrodermal responses, and functional behaviors. Developmental Medicine and Child Neurology, 41, 608-15.
National Institute for Neurological Disorders and Stroke (2003). Complex Regional Pain Syndrome (also called Reflex Sympathetic Dystrophy Syndrome) Fact Sheet. Retrieved May 14, 2004 from http://www.ninds.nih.gov/health_and_medical/pubs/rsds_fact_sheet.htm
Schaaf, R.C., Miller, L.J., Sewell, D., & O'Keefe, S. (2003). Children with disturbances in sensory processing: A pilot study examining the role of the parasympathetic nervous system. American Journal of Occupational Therapy, 57, 442-449.