The Simon effect and attention deficits in Gilles de la Tourette's syndrome and Huntington's disease

Abstract

Tourette's syndrome and Huntington's disease have long been clinically associated with attentional deficits. In this study, we aimed to determine the nature and quantify the extent of such deficits. A technique was devised to ascertain the efficiency with which Tourette's syndrome and Huntington's disease patients could shift and direct attention away from naturally expected stimulus-response (S-R) linkages. This was done by varying the relationships formed between stimulus and response location. Attentional efficiency was indicated by relative speed of responding to relevant (congruent) and irrelevant (incongruent) stimuli, in a paradigm developed from the Simon effect. There were five conditions progressively increasing in complexity. The stimuli consisted of left and right pointing arrows and, in some cases, various conditionality manipulations were also employed, such that in the presence of a certain symbol (i.e. 'x') the nature of the response had to be reversed, whereas in the presence of an alternative symbol (i.e. '='), the response was compatible with the direction of the arrow. As predicted, Tourette's syndrome and Huntington's disease patients, regardless of medication or depression status and unlike controls, were particularly disadvantaged in responding to various conflicting S-R configurations. Tourette's syndrome and Huntington's disease patients may experience difficulties in making attentional shifts, or in inhibiting inappropriate responses; they may also be more susceptible (than controls) to the conflict that can arise when the spatial code formed for the stimulus is irrelevant for selecting the appropriate response. We conclude that our findings support the notion that cognitive deficits in Tourette's syndrome and Huntington's disease may stem from abnormalities of the major pathways interconnecting the basal ganglia and the frontal lobes.

Impaired inhibition of prepotent motor actions in patients with Tourette syndrome

“…Moreover, RT slowing on conflict trials was more pronounced among patients with Tourette syndrome, suggesting greater interference from the activation of a conflicting prepotent response (see Georgiou and colleagues 21 ). Importantly, the DPAS model and distributional analyses provided greater precision in specifying whether patients with Tourette syndrome experienced stronger initial capture by the conflicting prepotent response or had greater difficulties suppressing this response activation due to impaired top-down inhibitory control.…”

“…6,18 The few studies on performance of patients with Tourette syndrome on response conflict tasks have produced mixed findings, showing either the absence or presence of exacerbated interference effects in patients compared with healthy controls. [19][20][21][22] In the present investigation, we used the Simon conflict task and the theoretical framework of the DPAS model to distinguish the effect of Tourette syndrome on the strength of involuntary capture by prepotent motor urges from the proficiency of inhibiting these action urges. Given evidence for dysfunctional frontalbasal ganglia circuitry in individuals with Tourette syndrome, we predicted they would show a reduction in the proficiency of top-down inhibitory control to suppress the response conflict produced by prepotent motor urges.…”

Stimulus-Response Compatibility in Huntington's Disease: A Cognitive-Neurophysiological Analysis

“…Cognitive functions are deteriorated, and tasks measuring attention may allow an adequate assessment of the progression of disease (Lemiere et al 2004). A great deal of evidence indicates that patients with HD show deficits in tasks assessing various processes of spatial and selective visual attention (e.g., Finke et al 2006;Georgiou et al 1995Georgiou et al , 1996GeorgiouKaristianis et al 2002;Jahanshahi et al 1993), and these alterations occur even in presymptomatic HD (pHD) (Lemiere et al 2004).…”

Influence of comorbid obsessive-compulsive symptoms on brain event-related potentials in Gilles de la Tourette syndrome

“…Neuropsychological studies consistently showed attentional disinhibition in both clinical populations (Channon et al, 1992;Georgiou et al, 1995Georgiou et al, , 1996Lavoie et al, 2007;Tata et al, 1996;Tolin et al, 2002). In order to extend findings on neuropsychological variables, several studies have recorded Event-Related Potentials (ERPs), which provide indications about cerebral activation in synchrony with cognitive events such as attention, memory (Linden, 2005) and motor functions (Hackley and Valle-Inclan, 2003).…”