Persistence of the Primitive Visual Rooting Reflex in Subjects with Autism Spectrum Disorders and Intellectual Disability

Background: The behavioral abnormalities of the Autism Spectrum Disorders (ASDs) apparently arise from underlying neurobiological mechanisms that are largely genetically determined. Individuals meeting diagnostic criteria for autism appear to form a behaviorally, neurobiologically and genetically heterogeneous group. Examining specific behavioral components or dimensions in ASD individuals might provide a route to understanding the ASDs.  ASD-related phenomena that are not seen at greater than population base rates in family members (such as intellectual disability and seizures) are of particular interest. These "emergenic" phenomena appear to arise from a combination of abnormalities in affected individuals, may have a large influence on behavioral and neurobiological expression, and might be particularly sensitive to early intervention. Among potentially emergenic phenomena are persistent primitive reflexes, including the visual rooting reflex (VRR).

Objectives: We wished to characterize the persistence of the Visual Rooting Reflex (VRR) in a large group of individuals with ASD and Intellectual Disability (ASD+ID) and in a contrast group of subjects with ID only. Specifically, we sought to determine the occurrence (rates) of persistent VRR in the ASD and ID groups, and to examine whether a persistent VRR was associated with severity of domain impairment and with specific behavioral/demographic aspects.

Methods: Presence of a VRR was evaluated in 155 ASD+ID subjects (IQ < 70) and in 65 subjects with ID only. All subjects were ascertained through a population-based epidemiological study on the prevalence of ASD+ID in a Dutch province. Subjects were assessed with the ADI-R, ADOS, Vineland Adaptive Behavior Scales, and standardized intelligence tests. Mean(±SD) ages in the ASD+ID and ID groups were 11.5 yrs±4.0 and 12.3±4.0, respectively; and mean IQs were 39±18 and 45±15, respectively. Presence of the VRR was rated by two trained raters with a kappa of .93 (N=24). Possible associations with age, sex, IQ and behavioral measures were examined. VRR occurrence in autistic disorder (N=95) and PDD-NOS (N=60) subgroups was also examined.

Results: The proportion of subjects with a positive VRR was significantly higher in the ASD+ID group compared to the ID group (52% versus 29%, p=0.002). The occurrence of VRR in the Autistic Disorder+ID subgroup (63%, N=95) was greater than in the PDD-NOS subgroup (44%, N=60; p=0.02). ASD+ID subjects with a positive VRR had significantly lower IQ’s; in both groups, lower IQ was associated with a positive VRR. Severity of impairment in the social interaction domain was significantly greater in ASD+ID subjects with a positive VRR compared to those without. Age and sex did not significantly affect the presence of the VRR.

Conclusions: Persistence of the visual rooting reflex (VRR) was significantly and strongly associated with the presence of ASD, lower cognitive functioning and greater social interaction domain impairment. A persistent VRR offers a potential autism endophenotype. Further characterization of the VRR and other primitive reflexes in ASD is needed to assess their emergenicity and possible utility in assessing early risk to ASD with and without ID. The investigation of possible neurobiological and genetic associations is warranted. Studies that include family members and younger subjects should be particularly informative.