Antisaccades elicited by visual and acoustic cues – an investigation of children with and without attention deficit hyperactivity disorder

Abstract

Impulsivity and with it deficient inhibition control is one of the core symptoms of attention deficit hyperactivity disorder (ADHD) – one of the most prevalent chronic psychiatric disorders in childhood and adolescence. One possibility to investigate inhibitory mechanisms is the antisaccade task – a task, in which a subject is required to suppress a saccade towards a suddenly appearing cue (prosaccade) and to generate a voluntary saccade of equal size towards the opposite direction instead. Aim of the present thesis was to investigate if children with ADHD are constricted in their inhibition of not only suddenly arising visual but also suddenly arising acoustic cues in order to establish a basis for a better differential diagnostic. Study I – an eye tracker pilot study – investigated control children in a random anti-/prosaccade task and revealed similar inhibition performance in visual and acoustic conditions: more errors in the anti- compared to the prosaccade condition. Additionally, modality dependant differences were found: the “grasp-reflex” was weaker for acoustically elicited saccades and they seemed less prone to be influenced by impulsivity as their latency was longer which in turn resulted in fewer antisaccade errors. During Study II the same paradigm was tested with children with and without ADHD in an Electroencephalography (EEG) experiment. On the behavioural level no group differences were found but in a 23-source-model analysis group differences were observable in acoustically elicited and correct performed antisaccades: children with ADHD showed more activity in the anterior temporal lobe and medio-frontal cortex (structures important for inhibition) to achieve the same behavioural output than children without ADHD. The heightened activation could possibly be seen as a compensatory mechanism. In Study III children with and without ADHD were compared during a blocked saccade task in an EEG experiment. In the visual condition children with ADHD were impaired on the behavioural level (more errors and elongated latency in the antisaccade condition) as well as on the physiological level. The findings suggest a frontal hypoactivation and a parietal-cerebellar compensatory network in ADHD. During the acoustic experiment children with ADHD seemed to have greater difficulties generating saccades but not inhibiting. Finally, it is to assume that children with ADHD are probably impaired quite differently concerning inhibition control. This seems to depend on task complexity and not on cue modality per se.