Inspection time and attention-deficit/hyperactivity disorder symptoms in children with cerebral palsy.

Cerebral palsy (CP) is a group of permanent disorders of movement and posture attributed to nonprogressive disturbances in brain development that occurred in the developing fetal or infant brain (Rosenbaum et al., 2007). While the location of lesions in CP may vary, damage to periventricular white matter tracts is a common presentation (White & Christ, 2005). World-wide prevalence of CP is greater than two per thousand live births. In the United States, approximately 10,000 children a year are diagnosed with CP (Blair & Watson, 2006; Odding, Roebroeck, & Stam, 2006). There is significant heterogeneity in the nature and severity of the motor abnormalities associated with CP. There also is significant heterogeneity in the comorbidities associated with the condition, which often include disturbances of sensation, perception, cognition, communication, and behavior, as well as seizures and secondary musculoskeletal problems (Rosenbaum et al., 2007). Individuals with CP appear to be at increased risk for a variety of cognitive impairments including attention and executive functions such as inhibitory control (Pirila, van der Meer, Korhonen, Nieminen, & Korpela, 2004; White & Christ, 2005). Studies have shown that the impairment in inhibitory control is apparent regardless of response modality (i.e., oral, manual, or ocular). There are also risks for impairments in selective visual attention (Craft, White, Park, & Figiel, 1994, Schatz, Craft, White, Park, & Figiel, 2001). At the more molar level, strategic planning difficulties have been demonstrated in children with CP (Pirila et al., 2004). Attention-Deficit / Hyperactivity Disorder (ADHD) is reported to be more common in children with CP than in the general population, with reported prevalence rates varying by study. Recent estimates of overall prevalence of ADHD have been reported at 19% in children with CP (Schenker, Coster & Parush, 2005). Earlier population based research suggested that 25.5% of children with CP displayed hyperactive behaviors (McDermott, et al., 1996). Some studies have suggested that 40% of children with CP demonstrate severe difficulties with emotional regulation, behavior, and concentration (Parkes et al., 2008). Goodman (1998) reported a 31 percent prevalence rate of hyperactivity in a CP sample. Among school-age children with CP, symptoms of restlessness and inattentiveness were also strong predictors of persisting emotional or behavioral problems at four-year follow-up. Despite high prevalence rates, there is a limited understanding about the nature of ADHD symptoms in children with CP. While the prominent diagnostic symptoms of ADHD are inattention and/or hyperactivity/impulsivity, it has been well-demonstrated that individuals with diagnoses of ADHD also have a higher incidence of co-occurring slowed processing speed (PS) than their typically developing peers (Chhabildas, Pennington, & Willcutt, 2001; Lahey et al., 1998; Mayes, Calhoun, Chase, Mink, & Stagg, 2009; Mayes & Calhoun, 2007; Nigg, Blaskey, Huang-Pollock, & Rappley, 2002; Wassenberg et al., 2008). Similar to those with ADHD who are not affected by CP, individuals with CP diagnoses may be at risk for sluggish cognitive tempo in association with ADHD; though examination of this process is confounded by the speeded motor demands of most neuropsychological measures of PS. In a study of children with CP, Christ, White, Brunstrom, & Abrams (2003) found that slowed PS initially appeared to drive inhibitory control deficits; however, after statistically controlling for PS, children with CP continued to show inhibitory control deficits. Christ et al. (2003) noted a primary difficulty in assessing PS, given the confound of motor speed for most measures of cognitive PS. To date, there have been no studies of cognitive PS in CP that have fully addressed this motor speed confound. In order to investigate PS in children with CP who, by definition, have motor abnormalities, this study utilized a visual inspection time (IT) task that required a dichotomous discrimination choice regarding a perceived quality of a simple visual stimulus without a speeded response demand. Stimuli were presented with gradually reduced on-screen durations until the critical stimulus onset asynchrony, or shortest duration at which a participant can be successful, was obtained; this is the participant’s IT threshold (Burns & Nettlebeck 2005; Fox, Roring, & Mitchum, 2009). Success is indicated by a reliable correct response at a given stimulus presentation speed, rather than response speed as utilized in traditional PS tasks (Edmonds et al., 2008). Thus, IT methodology significantly reduces or eliminates the confound of speeded motor responding. Processing speed is not a unidimensional construct and factor analyses of PS measures suggest a four-factor solution defined as perceptual speed, visualization speed, decision time, and movement time. IT performance is significantly associated with general processing speed (Gs), but most closely associated with the visualization speed factor (O’Connor & Burns, 2003). In the Cattell-Horn-Carol factor analytically derived model of intelligence, IT is found to load on PS and general intellect (Burns & Nettlebeck, 2003) and appears to be related to both PS and attentional control (Fox, Roring, & Mitchum (2009). Children with CP are at risk for impairments in attention and executive functions as well as ADHD symptoms. Evidence also suggests that CP entails risk for slowed PS, which in turn has been associated with higher level cognitive difficulties and ADHD. This study utilized an IT task with untimed limited motor response demands, to examine the associations between aspects of PS and parent/guardian reports of ADHD symptoms in children with CP and unaffected control peers. It was hypothesized that children with CP and Control peers would show positive correlations between IT duration thresholds and parent/guardian ratings of ADHD symptom severity.