A cross-sectional analysis of orienting of visuospatial attention in child and adult carriers of the fragile X premutation.
BACKGROUND
Fragile 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.


METHODS
Participants 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.


RESULTS
In 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.


CONCLUSIONS
Because 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.
Davis Medical Center, MIND Institute, University of California, Sacramento, CA 95817 USA ; War Related Illness and Injury Study Center, Veterans Affairs Medical Center, Washington, DC 20422 USA.
Ling M
LM
Wong
Davis Medical Center, MIND Institute, University of California, Sacramento, CA 95817 USA.
Naomi J
NJ
Goodrich-Hunsaker
Davis Medical Center, MIND Institute, University of California, Sacramento, CA 95817 USA.
Yingratana A
YA
McLennan
Davis Medical Center, MIND Institute, University of California, Sacramento, CA 95817 USA ; Department of Biochemistry and Molecular Medicine, University of California, Davis Medical Center, Sacramento, CA 95817 USA.
Flora
F
Tassone
Davis Medical Center, MIND Institute, University of California, Sacramento, CA 95817 USA ; Department of Psychology, University of California, Davis, CA 95616 USA ; Center for Mind and Brain, University of California, Davis, CA 95616 USA.
Susan M
SM
Rivera
Davis Medical Center, MIND Institute, University of California, Sacramento, CA 95817 USA ; Department of Psychiatry and Behavioral Sciences, University of California, Davis Medical Center, Sacramento, CA 95817 USA.
Tony J
TJ
Simon
Cueing; Endogenous; Exogenous; FMR1 gene; FXTAS; Fragile X