Spatiotemporal processing deficits in female CGG KI mice modeling the fragile X premutation

ArticleinBehavioural brain research 233(1):29-34 · April 2012with18 Reads
DOI: 10.1016/j.bbr.2012.04.029 · Source: PubMed
Abstract
The fragile X premutation is a tandem CGG trinucleotide repeat expansion in the fragile X mental retardation 1 (FMR1) gene between 55 and 200 repeats in length. A CGG knock-in (CGG KI) mouse has been developed that models the neuropathology and cognitive deficits reported in fragile X premutation carriers. It has been suggested that carriers of the premutation demonstrate a spatiotemporal hypergranularity, or reduced resolution of spatial and temporal processing. A temporal ordering of spatial locations task was used to evaluate the ability of CGG KI mice to process temporal and spatial information with either high or low levels of spatial interference. The results indicate that CGG KI mice showed difficulty performing a spatial novelty detection task when there were high levels of spatial interference, but were able to perform the novelty detection task when there was low spatial interference. These data suggest that CGG KI mice show reduced spatial and temporal resolution that are modulated by the dosage of the Fmr1 gene mutation, such that when behavioral tasks require mice to overcome high levels of either spatial or temporal interference, the CGG KI mice perform increasingly poorly as the CGG repeat length increases.
    • "Structural MRI studies indicate white matter involvement in these regions and in parietal projections of the cerebral peduncles [23,24]. Complementing these findings in humans, CGG KI mice exhibit age-dependent decline in performance on a parietal cortex-dependent task [25], which might relate to the ability to overcome spatial interference [26]. "
    [Show abstract] [Hide abstract] ABSTRACT: 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.
    Full-text · Article · Dec 2014
    • "FMR1-KO mice exhibit several phenotypical abnormalities also observed in the human disease such as enlarged testes in males and long, thin dendritic spines [12] . Cognitive deficits have been demonstrated through mildly impaired performance on the Morris water maze and spatial learning tests [13] [14] [15] . To date, the neurological deficits these mice incur have not been studied. "
    [Show abstract] [Hide abstract] ABSTRACT: Fragile X syndrome is the most common form of inherited mental retardation affecting up to 1 in 4000 individuals. The syndrome is induced by a mutation in the FMR1 gene, causing a deficiency in its gene by-product FMRP. Impairment in the normal functioning of FMRP leads to learning and memory deficits and heightened sensitivity to sensory stimuli, including sound (hyperacusis). The molecular basis of fragile X syndrome is thoroughly understood; however, the neural mechanisms underlying hyperacusis have not yet been determined. As the inferior colliculus (IC) is the principal midbrain nucleus of the auditory pathway, the current study addresses the questions underlying the neural mechanism of hyperacusis within the IC of fragile X mice. Acute experiments were performed in which electrophysiological recordings of the IC in FMR1-KO and WT mice were measured. Results showed that Q-values for WT were significantly larger than that of FMR-1 KO mice, indicating that WT mice exhibit sharper tuning curves than FMR1-KO mice. We also found the ratio of the monotonic neurons in the KO mice was much higher than the WT mice. These results suggest that lack of FMRP in the auditory system affects the developmental maturation and function of structures within the auditory pathway, and in this case specifically the IC. The dysfunction observed within the auditory neural pathway and in particular the IC may be related to the increased susceptibility to sound as seen in individuals with fragile X syndrome. Our study may help on understanding the mechanisms of the fragile X syndrome and hyperacusis.
    Article · Jun 2014
    • "Cerebellar error correction may affect executive and motor systems similarly through the general use of temporal information to link stimulus and response. Temporal information processing in a CGG knock-in (KI) mouse model of the premutation is impaired in an age-dependent manner (Borthwell, Hunsaker, Willemsen, & Berman, 2012; Hunsaker, Goodrich-Hunsaker, Willemsen, & Berman, 2010). Thus, inaccurate temporal input to the cerebellum, or dysfunctional processing within the cerebellum, may lead to executive function and motor impairment. "
    [Show abstract] [Hide abstract] ABSTRACT: Objective: 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 (FXTAS) often accompanied by inhibitory control impairments, even in fXPCs without motor symptoms. Inhibitory control impairments might precede, and thus indicate elevated risk for motor impairment associated with FXTAS. We tested whether inhibitory impairments are observable in fXPCs by assessing oculomotor performance. Method: Participants were males aged 18-48 years asymptomatic for FXTAS. FXPCs (n = 21) and healthy age-matched controls (n = 22) performed four oculomotor tasks. In a Fixation task, participants fixated on a central cross and maintained gaze position when a peripheral stimulus appeared. In a Pursuit task, participants maintained gaze on a square moving at constant velocity. In a Prosaccade task, participants fixated on a central cross, then looked at a peripheral stimulus. An Antisaccade task was identical to the Prosaccade task, except participants looked in the direction opposite the stimulus. Inhibitory cost was the difference in saccade latency between the Antisaccade and Prosaccade tasks. Results: Relative to controls, fXPCs had longer saccade latency in the Antisaccade task. In fXPCs, inhibitory cost was positively associated with vermis area in lobules VI-VII. Conclusion: Antisaccades require inhibitory control to inhibit reflexive eye movements. We found that eye movements are sensitive to impaired inhibitory control in fXPCs asymptomatic for FXTAS. Thus, eye movements may be useful in assessing FXTAS risk or disease progression.
    Full-text · Article · Apr 2014
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