Brain imaging data describe differences in the ASD brain, including amygdala overgrowth (Amaral, Schumann, & Nordahl, 2008), neural interconnectivity (Casanova, 2007), and a three-phase model of neuroanatomical changes from early post-natal development, through late adolescence (Courchesne, Campbell, & Solso, 2011). The pupil reflex test (PRT), a noninvasive measure of brain function, may help improve early diagnosis and elucidate underlying brain function in expression of ASD endophenotype. The PRT is used clinically to identify increased cerebrospinal fluid pressure, a characteristic of ASD observed to be atypical on MRI (Shen, et al., 2013). PRT holds promise for identifying biomarkers. Commonly observed characteristics of ASD include normal visual acuity but difficulty with eye gaze and photosensitivity, suggesting deficient neuromodulation of cranial nerves, or oculomotor palsy. Aims of this study were to confirm sensitivity of the PRT for identifying adolescents with ASD, determine if a phenotype for a subtype of ASD marked by pupil response is present in adolescence, and to determine whether differences could be observed on a neurologic exam testing cranial nerves II and III (CNII; CNIII). Using eye-tracking, latency of pupil constriction in response to the PRT was measured, serving as a proxy for recording neuromodulation of cranial nerves underlying the pupillary reflex. The swinging flashlight method, used to perform the PRT for measuring pupil latency, discriminated ASD participants from typically developing adolescents on 68.9% of trials. Results further confirmed this measure’s sensitivity within a subtype of ASD in later stages of development, recording neural activity via the locus-coeruleus norepinephrine (LC-NE) system. A brainstem model of ASD is examined in relation to modulation of cranial nerves and atypical arousal levels subserving the atypical pupillary reflex.
I pupil reflex, autism, phenotype, locus-coeruleus, visual pathway
|Advisor:||Dyck, Dennis G., Panksepp, Jaak|
|Commitee:||McPherson, Sterling M., Potter, Nancy L., Roll, John M.|
|School:||Washington State University|
|School Location:||United States -- Washington|
|Source:||DAI-B 78/02(E), Dissertation Abstracts International|
|Subjects:||Neurosciences, Nursing, Developmental psychology|
|Keywords:||Autism, Locus-coeruleus, Phenotype, Pupil reflex, Visual pathway|
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