Abstract
BackgroundFragile X premutation carriers (fXPCs) have an expansion of 55–200 CGG repeats in the FMR1 gene. Male fXPCs are at risk for developing a neurodegenerative motor disorder (fragile X-associated tremor/ataxia syndrome (FXTAS)) often accompanied by cognitive decline. Several broad domains are implicated as core systems of dysfunction in fXPCs, including perceptual processing of spatial information, orienting of attention to space, and inhibiting attention to irrelevant distractors. We tested whether orienting of spatial attention is impaired in fXPCs.MethodsParticipants were fXPCs or healthy controls (HCs) asymptomatic for FXTAS. In experiment 1, they were male and female children and adults (aged 7–45 years). They oriented attention in response to volitional (endogenous) and reflexive (exogenous) cues. In experiment 2, the participants were men (aged 18–48 years). They oriented attention in an endogenous cueing task that manipulated the amount of information in the cue.ResultsIn women, fXPCs exhibited slower reaction times than HCs in both the endogenous and exogenous conditions. In men, fXPCs exhibited slower reaction times than HCs in the exogenous condition and in the challenging endogenous cueing task with probabilistic cues. In children, fXPCs did not differ from HCs.ConclusionsBecause adult fXPCs were slower even when controlling for psychomotor speed, results support the interpretation that a core dysfunction in fXPCs is the allocation of spatial attention, while perceptual processing and attention orienting are intact. These findings indicate the importance of considering age and sex when interpreting and generalizing studies of fXPCs.
Highlights
Fragile X premutation carriers have an expansion of 55–200 CGG repeats in the fragile X mental retardation 1 (FMR1) gene
By using complementary cueing tasks, we determined whether different aspects of orienting ability were affected in Fragile X premutation carriers (fXPCs) asymptomatic for fragile X-associated tremor/ataxia syndrome (FXTAS)
In summary, because we controlled for psychomotor speed by dividing task reaction times (RTs) by psychomotor RT, our results suggest that male fXPCs have slower cognitive processing speed required to perceptually process stimuli, allocate attention, and generate a response
Summary
Fragile X premutation carriers (fXPCs) have an expansion of 55–200 CGG repeats in the FMR1 gene. Experiment 1 examined the ability to volitionally and reflexively orient attention We tested these abilities with a classic cueing paradigm using endogenous and exogenous cues, respectively. Experiment 2 examined the ability to use probabilistic cues to volitionally orient attention We tested this ability by replicating a paradigm used by Hahn et al [42], which was a modification of a classic Posner cueing task. Because these cues have more or less information about where the upcoming target will appear, successful use of the cues to orient attention results in faster NRT when fewer locations are cued This task utilizes high- and low-saliency targets, which allows us to examine the effect of bottom-up perceptual processing. Compared to experiment 1, this task allows for a more detailed assessment of volitional orienting, while still allowing for an assessment of perceptual processing
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