The BGaze system uses a child friendly version of the Posner task: the Happy frog task in which the child has to catch tadpoles. The frog’s gaze serves as a cue to inform the child about the location of the upcoming tadpole. In the Happy frog task, the patient’s attention is oriented towards the location of the tadpole while looking at the frog. Such a shift of attention involves top-down control of the brain to separate gaze from attention. Top-down shifting attention represents the activation of a cognitive processing.

 

A Posner Task is a neuropsychological paradigm for studying visual attention. The task, developed by Michael Posner, assesses an individual’s ability to perform an attentional shift and is widely used in scientific research. The task is to detect when a target stimulus is presented and respond as fast as possible. Usually, the target appears either on the left side or the right of the screen, and participants are cued before the target appears. The cue can appear at the same location as the upcoming stimulus (exogenous cue) or at the center, i.e. an arrow pointing to the location of the upcoming target (endogenous cue). After the presentation of an attentional cue, a target requiring a response is shown at either the cued location or a non-cued location. The observers’ performance in detecting a target is typically better when the target is present at the cued location than in trials in which the target appears at the non-cued location.

In a Posner task, attention shifts towards the location of the target without shifting eye gaze. In other words, looking at a center stimulus while paying attention to a peripheral target location. It is important to highlight that this type of shift of attention involves top-down control of the brain to separate gaze from attention. In contrast, when a stimulus attracts the orienting attention (bottom-up attention) an automatic response is shown. Such a shift occurs automatic and is not under voluntary control. Therefore top-down shifting attention, also called covert attention, represents a cognitive processing, whereas bottom-up shifting attention, also called overt attention, represents an automatic response.

We discovered that while orienting attention by top-down, the eyes briefly move inward, that is eye vergence (Solé Puig, Pérez Zapata, Aznar-Casanova, & Supèr, 2013). This small inward eye movement is necessary to shift attention and subsequently detect the target. BGaze uses this method of assessing attention by measuring these small eye movements while the participant performs a Posner task. We designed a child friendly version of the Posner task: the happy frog task in which the child has to catch tadpoles by pressing a button. A central presented frog looks to the left or right side, or straight ahead. The frog’s gaze to the right or left serves as an endogenous cue when to inform the child about the location of the upcoming image of a tadpole or fish. A non-cued situation is considered when the frog looks straight ahead. Anyway, the child needs to keep looking at the frog and when the child catches a tadpole the frog makes a small jump suggesting happiness.

This task is repeated several times (in total 120 trials) to have robust data for classifying he patient and take about 12-15 minutes to complete. The task has been clinically validated as a support tool for the diagnosis of ADHD in children (Varela Casal et al., 2018). A similar task has also been developed for adult ADHD.

References:

  • Solé Puig, M., Pérez Zapata, L., Aznar-Casanova, J. A., & Supèr, H. (2013). A Role of Eye Vergence in Covert Attention. PLoS ONE, 8(1), e52955. https://doi.org/10.1371/journal.pone.0052955
  • Varela Casal, P., Lorena Esposito, F., Morata Martínez, I., Capdevila, A., Solé Puig, M., de la Osa, N., … Cañete, J. (2018). Clinical Validation of Eye Vergence as an Objective Marker for Diagnosis of ADHD in Children. Journal of Attention Disorders. https://doi.org/10.1177/1087054717749931