Quantitative Measurement

of Sensory Dysfunction in

Children with Cognitive

Disabilities

Laura J. Meyer, Lucy Jane Miller,

Daniel N. McIntosh, Sally Rogers,

and Randi J. Hagerman

University of Colorado Health Sciences Center

Departments of Rehabilitation Medicine

and Pediatrics

Abstract

Electrodermal responses (EDRs) to sensory stimuli were examined in individuals diagnosed with fragile X syndrome and sensory modulation disorder. Theory and clinical observation suggest that their responses should be larger than that of non-affected people. However, there has been little experimental work on hyperarousal and sensory sensitivity in these groups. We established a laboratory method for examining generalized sensory defensiveness.

Abstract (cont’d.)Individuals with fragile X syndrome showed greater EDR amplitude, more responses per stimulation, EDRs on a greater proportion of trials, and lower rates of habituation than age and gender-matched controls.

Individuals with autism show diverse EDR patterns after sensation. There is a small group of non-responders and a small group of hyper-reactive responders. In addition, about one third of our pilot sample had EDR responses within normal limits.

Participants

Study 1: Males with the fragile X mutation (n = 15) and age matched control males.

Study 2: Ten individuals with Autism and age and gender matched control group (M age = 16[range 5 to 53 years]; 8 male, 2 female).

Sensory Challenge Protocol

To gauge individuals’ responses to stimulation, we created a laboratory paradigm during which experimenters presented sensory stimulation while EDA was recorded continuously. There were ten trials in each of five sensory systems administered in the order below. Each stimulation takes approximately 3 seconds, and they are presented on a pseudo-random schedule 12 or 17 seconds apart. Ten of each type are presented before moving to the next modality.

Sensory Challenge Protocol (cont’d.)

Olfactory: (wintergreen oil in vial 2 waved 2.5cm below nose)

Auditory: (fire engine siren, 90-decibels)Visual: (20 watt strobe light at 10 flashes persecond)Tactile: (a feather is gently run from theparticipant’s right ear canal, along chin lie tobottom of chin, and finally raised to thechild’s left ear)Vestibular: (child’s chair is smoothly andslowly tipped back to a 45 degree angle)

Electrodermal Responses

Electrodermal activity (EDA) assessed extent to which individuals respond to stimuli. EDA changes in the presence of startling or threatening stimuli, aggressive or defensive feelings (Fowles, 1986), and during positive experiences. Measuring skin conductance indirectly assesses SNS activity (Andreassi, 1989). (See Fowles et al., 1981 for methods and Dawson, et al., 1990 for scoring.)

Electrodermal Responses(cont’d.)

Variables were:

amplitude of the main (largest) peak inresponse to each stimulus

number of responses for each stimulus;and

participant’s mean probability ofresponding to all five sensory stimuli ateach trial.

Fragile X Syndrome

Although fragile X syndrome is well known for causing cognitive disabilities or learning disabilities, it also causes behavior problems including hyperarousal, hyperactivity, aggression, anxiety, tantrums and extreme sensitivity to sensations (Hagerman, 1996b). The observed hyperarousal may be partially related to strong reactions to sensory stimuli such as noises, touch, visual and olfactory stimuli (Hagerman and Cronister, 1996). We hypothesize that people with fragile X syndrome will show higher amplitude EDRs, more EDRs, and slower habituation to stimulation than seen in the control group.

Figure 1: EDA profile of a normal control (responses to 10 olfactory stimuli). Amplitude is in micromhos. Note lower amplitudes of EDR, one main peak after stimuli,

and definite habituation.

Figure 2: EDA profile of an individual with Fragile X Syndrome (response to 10 olfactory stimuli). Amplitude

in micromhos. Note large amplitudes, numerous reactions, and a lack of habituation.

Figure 3: Mean amplitude in log10 (micromhos) of responses to each trial, presented separately for Fragile X and Control

participants. {Significant effects: Group; Trials]

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Miller et al., 1999

Figure 4: Mean number of responses to each trial, presented separately for Fragile X and Control participants. [Significant

effects: Group; Trials]

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Miller et al., 1999

Figure 5: Mean proportion of trials during which responses were greater than .05 micromhos, presented separately for

Fragile X and Control participants. [Significant effects: Group; Trials; Group x Trials]

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Miller et al., 1999

AutismPrevious Literature on EDR

Author Date N FindingsBarry & James 1988 Aut = 32 Aut failed to habituate to repeated

stimuliMR = 32 Aut Hyper-reactive

Stevens & 1984 Aut = 20 No significant differences Gruzelier Normal CA =

20MA = 20MR CA = 20MA = 20

van Engeland 1984 Aut = 35 Aut more often non-responsive to firsttrial

Normal = 45MR = 20 When responded had large

amplitudes & fast recoveryChild = 38 Psychiatric

Bernal & Miller 1970 Aut = 20 Aut lower mean response in first blockof 3 trials

Normal = 20 No differences in habituation

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Figure 6: Mean amplitude in log10 (micromhos) of responses to each trial, presented separately for Autistic and Control

participants. [Significant effect of trials]

Miller et al., 2001

Discussion

This study provides psychophysiological evidence that individuals diagnosed with fragile X syndrome and autism show differential responses to sensory stimuli, as indexed by EDR.

Discussion (cont’d.)

1. This pattern of sensory over-reactive is not simply due to cognitive delay or behavioral problems. Individuals show atypical responsiveness, which is different than controls (Martinez-Silva et al., 1995).

Discussion (cont’d.)

2. There appears to be a subgroup of disorders that show this pattern; further work needs to investigate the possible connections among these disorders. Individuals with autism sometimes show hyper-responsive and sometimes hypo-responsive EDA patterns.

Discussion (cont’d.)

3. Our findings support an intrinsic and physiologically based enhancement of reactions to sensations in boys with fragile X syndrome. Because EDA indexes SNS activity, the present data demonstrate that the SNS is affected. This ponts to the need for additional research on the physiological and anatomical underpinnings of abnormal responses to sensory stimulation.

Discussion (cont’d.)

4. Our findings support a physiological underpinning of sensory modulation disorder. As with fragile X syndrome, that EDA is affected in children with autism suggests that the SNS is affected.

Discussion (cont’d.)

5. The role of anxiety needs to be examined. Clinically, increased sensory responsiveness may also be related to the anxiety or aversive responses that occur with direct eye contact, light touch, or loud sounds. Anxiety is intrinsically tied to hyperarousal (Hagerman, 1996b). Further research should explore whether it is actually generalized anxiety or specific anxious reactions to sensory modulation disorder.

Discussion (cont’d.)

6. EDRs could be used in studies of the effectiveness of interventions for disorders showing these EDA profiles (Hagerman, 1996a; Reisman and Gross, 1992).

Acknowledgements

We wish to thank the Wallace Research Foundation for primary support of this research. In addition, support was obtained from Sensory Integration International for psychophysiological equipment, March of Dimes Grant #0492, and MCH Grant #MCJ-08-9413. We also wish to thank the Kids Helping Kids Program of The Children’s Hospital Research Institute. The support of Dr. Dennis Matthews and other staff and faculty at The Children’s Hospital, Department of Rehabilitation in Denver is greatly appreciated.

Acknowledgements (cont’d.)

We value the work of Jan Ingebrittsen in writing the KIDcal program, and of Tara Wass in information management. Finally, the dedication of evaluating occupational therapists and lab experimenters was invaluable: Margaret Frohlich, Patricia Kenyon, Nicki Pine, Robin Seger, Clare Summers, Sharon Trunnell, Molly Turner, Lisa Waterford, and Julie Wilbarger.