Abstract
The FMR1 premutation (PM) is relatively common in the general population. Evidence suggests that PM carriers may exhibit subtle differences in specific cognitive and language abilities. This study examined potential mechanisms underlying such differences through the study of gaze and language coordination during a language processing task (rapid automatized naming; RAN) among female carriers of the FMR1 PM. RAN taps a complex set of underlying neuropsychological mechanisms, with breakdowns implicating processing disruptions in fundamental skills that support higher order language and executive functions, making RAN (and analysis of gaze/language coordination during RAN) a potentially powerful paradigm for revealing the phenotypic expression of the FMR1 PM. Forty-eight PM carriers and 56 controls completed RAN on an eye tracker, where they serially named arrays of numbers, letters, colors, and objects. Findings revealed a pattern of inefficient language processing in the PM group, including a greater number of eye fixations (namely, visual regressions) and reduced eye-voice span (i.e., the eyes’ lead over the voice) relative to controls. Differences were driven by performance in the latter half of the RAN arrays, when working memory and processing load are the greatest, implicating executive skills. RAN deficits were associated with broader social-communicative difficulties among PM carriers, and with FMR1-related molecular genetic variation (higher CGG repeat length, lower activation ratio, and increased levels of the fragile X mental retardation protein; FMRP). Findings contribute to an understanding of the neurocognitive profile of PM carriers and indicate specific gene-behavior associations that implicate the role of the FMR1 gene in language-related processes.
Highlights
The fragile X mental retardation 1 gene (FMR1) is associated with a constellation of cognitivebehavioral phenotypes
In its premutation (PM) state (55–200 CGG repeats), FMR1 has been linked to clinical and sub-clinical phenotypes ranging from subtle differences in executive functioning to more severe age-related cognitive and motor decline that occur in fragile X associated tremor/ataxia syndrome (FXTAS) [2,3,4]
In those with a full mutation, methylation of the FMR1 gene shuts down production of the fragile X mental retardation protein (FMRP), which plays a critical role in brain development and function [5,6,7,8,9]
Summary
The fragile X mental retardation 1 gene (FMR1) is associated with a constellation of cognitivebehavioral phenotypes. Amtmann et al [82] reported that individuals who were overall slower namers during RAN tended to show progressively longer naming times with each subsequent row, whereas individuals who were generally faster namers demonstrated a more stable naming pattern across rows This suggests that examining patterns of naming over the course of trials, when coupled with analysis of eye movement patterns, might reveal important performance differences in the nature of RAN difficulties, implicating component executive skills that have been reported to be impacted in the PM [37,38,39,40,41,42]. Associations between RAN and FMR1-related variation (i.e., FMRP expression, CGG repeat length) were examined
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