Eye-Tracking Techniques Useful in Quantifying Social Impairment, Study Says

Angelman syndrome (AS) patients have a lower preference for social stimuli than typically developing individuals, a new study shows. Also, AS patients do not show increased pupil dilation in response to social scenarios that is seen in healthy subjects.

The study resulted from a collaboration between several U.S. institutions: Cincinnati Children’s Hospital Medical Center, the University of Cincinnati College of Medicine, and the Indiana University School of Medicine.

Findings were published in the journal Research in Developmental Disabilities, under the title “Eye gaze and pupillary response in Angelman syndrome.”

People with AS normally experience severe developmental delay, movement and seizure disorders, trouble communicating, and a distinctive behavioral profile. The latter includes a happy attitude, frequent laughter, excitability, love of water, and difficulty concentrating.

Eye tracking measures, like analysis of eye movement and pupil size, can help obtain behavioral data, in a non-invasive manner, in individuals with impaired communication.

In fact, “studies have reported that preference for geometric patterns over social scenes, as measured by eye-tracking paradigms, can predict diagnosis of autism spectrum disorder (ASD) in infants, toddlers, and adolescents,” researchers noted.

With that in mind, the team wanted to determine if AS diagnosis was in accordance with the social scene eye-tracking and pupil measures. The researchers also sought to compare the performance of AS participants to individuals with ASD and typically developing subjects.

Seventeen AS patients we recruited. Only eight of them, along with age- and gender- matched controls (ASD plus typically developing individuals selected from two other studies from the same investigators), completed a social eye-tracking paradigm.

The 60-second test consisted of side-by-side silent video clips of social interaction scenes (SS) and animated geometric scenes (GS). Every 20 seconds the pair SS-GS changed. Participants were instructed to watch the paradigm and their eye movements and pupil size were recorded.

Compared to “normal people” AS subjects demonstrated significantly less preference for social scenes than geometric shapes. AS subjects also showed less pupil dilation when observing the social scenario. Pupil dilation is considered a measure of something that the “looking subject” finds pleasurable.

Interestingly, no statistically significant difference was found between AS and ASD subjects in either eye movement or pupil size, which could relate to AS being an ASD; however, the scientific community lacks consensus.

If the use of eye tracking and pupil size can predict AS remains to be clarified. Nonetheless, both non-invasive measures may be useful in quantifying AS-associated impairments.