Impaired multiple object tracking in children with chromosome 22q11.2 deletion syndrome

We used a multiple object tracking task to assay capacity and resolution performance of children with 22q11.2DS aged 7 to 14 years versus age-matched typically developing (TD) peers.Children with 22q11.2DS but not TD children demonstrated impaired performance when task demands increased due to an increase in the number of targets presented, but not from an increase in object speed. Task performance in children with 22q11.2DS was also unrelated to intelligence or measures of attention deficit hyperactivity disorder.These findings suggest that children with 22q11.2DS may be particularly susceptible to dynamic crowding of objects with increasing cognitive demands related to monitoring multiple targets reflecting a reduced acuity in spatiotemporal cognitive representation.Chromosome 22q11.2 deletion syndrome (22q11.2DS), also known as DiGeorge [1], velocardiofacial VCFS; [2] and conotruncal anomaly face [3] syndromes among other labels, results from a hemi-zygotic interstitial deletion between 1.5 and 3 Mb on the q11 band of chromosome 22. It is the most common survivable chromosomal micro-deletion with a prevalence of approximately 1:4,000 live births [4-6]. Syndrome presentation is highly variable, but physical dysmorphisms [7], socioemotional difficulties [8] and cognitive impairments in both the verbal and non-verbal domains [9,10] are characteristic of this population.Cognitive deficits commonly reported with 22q11.2DS include difficulties with numerical thinking [11,12] that may arise from decreased representational resolution for both space and time [13-15], which Simon [15] labels 'spatiotemporal hypergranularity' (see also [16]). As a result, children with 22q11.2DS may have greater difficulty attending to multiple objects moving and interacting dynamically in visual space. Reduced acuity in spatiotemporal representation increases apparent crowding between interacting objects, thereby reducing accessibility to individual items [17]. Successful interaction with