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History of Research at the SPD Foundation
BY Darci M. Nielsen, PhD
Sarah A. Schoen, PhD, OTR
Sensory Processing Disorder (SPD) was first identified in the mid 1960s by A. Jean Ayres, Ph.D., an occupational therapist and educational psychologist. The condition was not well researched, nor accepted during her lifetime. In 1977, Lucy Jane Miller, PhD, OTR received funding from the U.S. Public Health Service, division of Maternal and Child Health (MCH) to develop the Miller Assessment for Preschoolers (MAP) to evaluate children with developmental disabilities including Sensory Processing Disorder. The success of the MAP led Dr. Miller to establish the SPD Foundation, originally known as the KID Foundation, which 30 years ago received formal IRS designation as a non-profit charitable organization (501(c)3, later upgraded to a public charity with a mission of promoting research, education, and advocacy related to SPD. The following is a historical overview of accomplishments towards establishing a program of research at the Foundation. For the next 15 years the Foundation was geared toward the development and validation of norm-referenced standardized tests that could provide a method of quantifying developmental and behavioral characteristics in children, needed for rigorous research into SPD. Nine nationally standardized tests for young children, school aged children and adolescents are now available for use by professionals.
In 1995, the Wallace Research Foundation began an initiative to increase knowledge about SPD and advance evidence-based treatment options for those with SPD. The Wallace Research Foundation found us at the Foundation and provided pilot funding for the development of our first psychophysiology laboratory, located at the University of Colorado Medical School where the SPD Foundation staff had part time research professor privileges, which provided a unique opportunity to create a paradigm to investigate underlying mechanisms of SPD. Miller and colleagues call the laboratory paradigm the Sensory Challenge Protocol Space Lab. This paradigm is designed to study reactivity to sensory stimuli across 5 sensory domains (auditory, visual, olfactory, tactile and vestibular). The laboratory is decorated to look like a pretend spaceship and the child sits in front of a video monitor watching a "safe" segment of the movie Apollo 13 depicting the astronauts being hooked up to physiological equipment while the experimenter attaches electrodes to the child. Data is collected during an initial 3 minute rest period and following 8 trials of each sensory stimulus. The experiment ends with another 3 minute rest period. Using this paradigm, multiple studies have been conducted to examine the function of the sympathetic branch (i.e. fight or flight reactions) of the autonomic nervous system in children with SPD compared to typically developing children and children with other developmental disorders. Results suggest that children with SPD have increased reactivity to sensory stimuli compared to typically developing children as well as compared to children with Autism Spectrum Disorder (Click here to read an entire article) or Attention Deficit Hyperactivity Disorder (Click here to read an entire article).
Simultaneously, Miller and colleagues received support from the National Institutes of Health (2003-2004) for a randomized controlled pilot study (Click here to read the entire article) of the effectiveness of occupational therapy using a sensory integration approach (OT-SI), conducted in collaboration with The Children‘s Hospital in Denver. In this study OT-SI was provided twice weekly for 10 weeks compared to an active placebo (Alternate Intervention) and to a No Treatment wait-list group. Results indicate that OT-SI may be effective in ameliorating difficulties of children with SPD, Sensory Over-Responsivity. Children in the OT-SI group made significant changes compared to the Alternate Placebo Treatment and the No Treatment groups on several key measures including Goal Attainment Scaling Attention and Cognitive/Social Composite of the Leiter International Performance Measure. In addition, trends occurred toward greater improvement in the OT-SI group on Internalizing (as measured by the Child Behavior Checklist) and the Short Sensory Profile Total Score. Physiologically, even with a very small sample, the OT-SI group showed a greater reduction in reactivity to "sensory stimuli" during the Sensory Challenge Protocol Space Lab compared to the other two groups.
With additional support to Dr. Miller from NIH, psychophysiology laboratories were established across the country by leading Occupational Therapists who were interested in studying Sensory Processing Disorder (SPD) and occupational therapy with a sensory integration approach. The Foundation pulled together a collaborative research group, now called, the Sensory Integration Research Collaborative (Click here to read more about SIRC). The vision of this collaborative is to grow the body of research on evidence-based OT-SI practice so that we will know what aspects of OT-SI treatment are effective and those practices which might not be effective. Specific goals include finding a physiological marker to differentiate children with SPD from children with other disorders such as ADHD and Autism, identifying clusters of signs and symptoms that might constitute subtypes of the disorder and conducting randomized controlled trials of Occupational Therapy using a sensory integration approach.
In 2002, the Sensory Processing Disorder (SPD) Foundation received an award from the Wallace Research Foundation to formalize an interdisciplinary collaboration called the SPD Scientific Work Group(Click here to read more about the SPD SWG). Annual meetings were convened to develop a research agenda for SPD. This interdisciplinary group includes well-established researchers with expertise in genetics, psychophysiology, twin and familial studies, epidemiology, basic science, treatment outcomes research and assessment development. Most SPD Scientific Work Group members added the study of sensory processing to their already funded NIH grants, collaborating with one another where possible, primarily using existing paradigms, but developing new paradigms as needed to explore issues related to SPD.
The SPD Scientific Work Group formulated a research plan for validating SPD as a new syndrome using Pennington‘s model of syndrome validation (Pennington, 1991; 2002) as a blueprint for study development.
The model of syndrome validation adopted describes the following essential components:
- Define and describe the disorder and subtypes (signs and symptoms)
- Investigate the underlying mechanisms or neuropathology
- Evaluate the etiology (or etiologies) of the disorder
- Conduct population-based epidemiologic studies to evaluate prevalence and overlap with existing disorders.
- Examine the developmental course of the disorder
- Evaluate the treatment effectiveness, especially as it relates to hypothesized disordered processes
- Research the rate of comorbidity between the new disorder and existing disorders
Investigators agreed that initial efforts should be devoted to understanding one subtype of SPD, Sensory Over-Responsivity. Following the first five years of research the SPD Scientific Work Group decided to expand the study of SPD to include both Sensory Over-Responsivity and Sensory Under-Responsivity.
With guidance from the SPD Scientific Work Group, two primary streams of research evolved at the SPD Foundation: a study of multisensory integration at the cortical level and the development of an examiner administered performance assessment of Sensory Over-Responsivity, Sensory Under-Responsivity and Sensory Seeking/Craving.
Research on multisensory integration (Click here to read the entire article) in children uses EEG (event related potentials (ERPs) to investigate Dr. A. Jean Ayres‘ original hypothesis that individuals with Sensory Processing Disorder (SPD) have impaired multisensory integration. Therefore, an EEG/ERP paradigm was developed to study auditory and tactile integration at the cortical level in children with Sensory Processing Disorder (SPD). Our work builds on multi-sensory integration research in the field of neuroscience using animal and adult human models. Our first step was to determine if multisensory integration could be reliably measured in typically developing children. Results indicated that typically developing children have patterns of auditory-tactile multisensory interactions similar to adults. Consistent with previous adult research, our study also demonstrated that multisensory integration in typically developing children reflects enhanced processing of multisensory compared to single sensory stimulation, e.g., the amplitude of multisensory responses in typically developing children is larger than responses to a single sensory stimulus, either auditory alone or tactile alone. The first study of multisensory integration in children with Sensory Processing Disorder is soon to be published. Twenty children with the sensory over-responsive subtype of SPD participated in this study of auditory-tactile unisensory vs. multisensory interactions. These preliminary results suggest that multisensory integration is less organized in children with Sensory Over-Responsivity as compared to typically developing children. Children with SOR appear to process multisensory stimuli differently than typically developing children, particularly over fronto-central scalp regions. Even the processing of a single domain stimulus e.g., auditory stimulus or a tactile alone appears different in children with Sensory Over-Responsivity.
The development of a reliable and valid scale for identifying subtypes of sensory processing disorder is proceeding. The Sensory Processing (SP) Scales (Click here to read the entire article), sensory over-responsivity, sensory under-responsivity and sensory seeking/craving, are measured by a performance assessment as well as a parent/caregiver report inventory. The SP Scales are theoretically linked to the current diagnostic classification system proposed by Miller and colleagues and are designed to identify the specific subtype of SPD that a child has for clarity in moving forward with treatment as well as for identifying homogenous samples for clinical research.
The first subtype on the scale was the Sensory Over-Responsivity (SOR) Scale which consists of a self or caregiver rating form (Inventory) and an objective measure of direct assessment by a therapist (Assessment). Both measures reflect sensory activities or components of daily life activities that bother individuals in each of the sensory domains. The assessment attempts to capture typical behaviors that are seen in a child‘s life in the specific test items administered while the inventory, similar to other parent/caregiver report measures, requires the respondent to indicate which of many specific sensory experiences bother their child. The pilot and research editions of the SOR scale had moderately strong internal reliability, demonstrating that the items and subtests were measuring the same construct. In addition, the assessment had moderately strong inter-rater reliability. Both measures discriminated between groups with and without sensory over-responsivity. We are now expanding the scale in order to include items that measure both sensory under-responsivity and sensory seeking/craving. Data on over 185 children with SPD and 102 typically developing children have been collected and we are currently directing our efforts towards refinement of the measures through examination of reliability and validity of the items.
The culmination of research efforts at the SPD Foundation, the Sensory Integration Research Collaborative and the SPD Scientific Work Group were summarized for the recent submission in 2007, 2008, and 2009 of reports to the DSM (Click here to read the latest on our DSM-V initiative) committee and an application to consider SPD as a unique diagnostic category. Over the 30 years of research, many questions have been addressed; but with each study more questions emerge than are answered by the study. The field has expanded dramatically in terms of the number of researchers studying SPD and the disciplines of the researchers involved. Collaboration is the key to answering the many questions remaining about SPD.
We predict that in the next thirty years, the solid groundwork that we and our colleagues have laid will expand exponentially and in time researchers will discover the genetic underpinning of and effective treatments for children with SPD. The secret is persistence and taking rigorous baby steps that build upon each other. The program of research begun at the Foundation will spread to scientists in many fields before final answers to the many questions about SPD can be answered. As we like to say at the Foundation, "it takes a village to do a research project."
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