Disassociation between brain activation and executive function in fragile X premutation females

The role of the prefrontal cortex in modulating aggression in humans and rodents

Accumulating evidence suggests that the prefrontal cortex (PFC) plays an important role in aggression. However, the findings regarding the key neural mechanisms and molecular pathways underlying the modulation of aggression by the PFC are relatively scattered, with many inconsistencies and areas that would benefit from exploration. Here, we highlight the relationship between the PFC and aggression in humans and rodents and describe the anatomy and function of the human PFC, along with homologous regions in rodents. At the molecular level, we detail how the major neuromodulators of the PFC impact aggression. At the circuit level, this review provides an overview of known and potential subcortical projections that regulate aggression in rodents. Finally, at the disease level, we review the correlation between PFC alterations and heightened aggression in specific human psychiatric disorders. Our review provides a framework for PFC modulation of aggression, resolves several intriguing paradoxes from previous studies, and illuminates new avenues for further study.

FMR1 CGG Repeats and Stress Influence Self-Reported Cognitive Functioning in Mothers

Variation in the FMR1 gene may affect aspects of cognition, such as executive function and memory. Environmental factors, such as stress, may also negatively impact cognitive functioning. Participants included 1,053 mothers of children with and without developmental disabilities. Participants completed self-report measures of executive function, memory, and stress (i.e., life events, parenting status), and provided DNA to determine CGG repeat length (ranging from 7 to 192 CGGs). Stress exposure significantly predicted greater self-reported difficulties in executive function and the likelihood of memory problems. Cubic CGG effects independently predicted executive function and memory difficulties, suggesting effects of both genetic variation and environmental stress exposure on cognitive functioning.

Verbal inhibition declines among older women with high FMR1 premutation expansions: A prospective study

The FMR1 premutation has been associated with difficulties in executive functioning, including verbal inhibition. However, little is known about the longitudinal profiles of verbal inhibition among FMR1 premutation carriers, particularly in women, and how individual factors such as aging and CGG repeat length may contribute to changes in verbal inhibition over time. The present study examined verbal inhibition performance (i.e., inhibition errors) on the Hayling Sentence Completion Task in a cohort of 92 women with the FMR1 premutation across two timepoints approximately three years apart. We examined the effects of age, CGG repeat length, and their interactions on verbal inhibition over time. We also evaluated whether response latency affected verbal inhibition errors. We found no significant change in verbal inhibition in the full cohort during the three-year study period. However, a subset of FMR1 premutation carriers, namely older participants with higher CGG repeats, evidenced greater declines in verbal inhibition over time. Longer response latencies did not compensate for verbal inhibition errors. The findings suggest that a subset of women with the FMR1 premutation may be at earlier, increased risk for changes in executive functioning, which if confirmed, should be considered as part of the clinical profile associated with the premutation.

The Phenotypic Profile Associated With the FMR1 Premutation in Women: An Investigation of Clinical-Behavioral, Social-Cognitive, and Executive Abilities

The FMR1 gene in its premutation (PM) state has been linked to a range of clinical and subclinical phenotypes among FMR1 PM carriers, including some subclinical traits associated with autism spectrum disorder (ASD). This study attempted to further characterize the phenotypic profile associated with the FMR1 PM by studying a battery of assessments examining clinical-behavioral traits, social-cognitive, and executive abilities in women carrying the FMR1 PM, and associations with FMR1-related variability. Participants included 152 female FMR1 PM carriers and 75 female controls who were similar in age and IQ, and screened for neuromotor impairments or signs of fragile X-associated tremor/ataxia syndrome. The phenotypic battery included assessments of ASD-related personality and language (i.e., pragmatic) traits, symptoms of anxiety and depression, four different social-cognitive tasks that tapped the ability to read internal states and emotions based on different cues (e.g., facial expressions, biological motion, and complex social scenes), and a measure of executive function. Results revealed a complex phenotypic profile among the PM carrier group, where subtle differences were observed in pragmatic language, executive function, and social-cognitive tasks that involved evaluating basic emotions and trustworthiness. The PM carrier group also showed elevated rates of ASD-related personality traits. In contrast, PM carriers performed similarly to controls on social-cognitive tasks that involved reliance on faces and biological motion. The PM group did not differ from controls on self-reported depression or anxiety symptoms. Using latent profile analysis, we observed three distinct subgroups of PM carriers who varied considerably in their performance across tasks. Among PM carriers, CGG repeat length was a significant predictor of pragmatic language violations. Results suggest a nuanced phenotypic profile characterized by subtle differences in select clinical-behavioral, social-cognitive, and executive abilities associated with the FMR1 PM in women.

Language processing skills linked to FMR1 variation: A study of gaze-language coordination during rapid automatized naming among women with the FMR1 premutation

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.

Functional correlates of cognitive dysfunction in clinically isolated syndromes

Cognitive dysfunction can be identified in patients with clinically isolated syndromes suggestive of multiple sclerosis using ocular motor testing. This study aimed to identify the functional neural correlates of cognitive dysfunction in patients with clinically isolated syndrome using MRI. Eighteen patients with clinically isolated syndrome and 17 healthy controls were recruited. Subjects underwent standard neurological and neuropsychological testing. Subjects also underwent functional MRI (fMRI) during a cognitive ocular motor task, involving pro-saccade (direct gaze towards target) and anti-saccade (direct gaze away from target) trials. Ocular motor performance variables (averaged response time and error rate) were calculated for each subject. Patients showed a trend towards a greater rate of anti-saccade errors (p = 0.09) compared to controls. Compared to controls, patients exhibited increased activation in the right postcentral, right supramarginal gyrus, and the right parietal operculum during the anti-saccade>pro-saccade contrast. This study demonstrated that changes in functional organisation of cognitive brain networks is associated with subtle cognitive changes in patients with clinically isolated syndrome.

Long term verbal memory recall deficits in fragile X premutation females

Carriers of a FMR1 premutation allele (between 55 and 199 CGG repeats) are at risk of developing a wide range of medical, psychiatric and cognitive disorders, including executive dysfunction. These cognitive deficits are often less severe for female premutation carriers compared to male premutation carriers, albeit similar in nature. However, it remains unclear whether female premutation carriers who exhibit executive dysfunction also report verbal learning and memory deficits like those of their male counterparts. Here we employed the CVLT to assess verbal learning and memory function in 19 female premutation carriers, contrasting performance with 19 age- and IQ-matched controls. Group comparisons revealed similar performance during the learning and short delay recall phases of the CVLT. However, after a long delay period, female premutation carriers remembered fewer words for both free and cued recall trials, but not during recognition trials. These findings are consistent with reports for male premutation carriers, and suggest that aspects of long term memory may be adversely affect in a subgroup of premutation carriers with signs of executive dysfunction.

White matter microstructure, cognition, and molecular markers in fragile X premutation females

Objective:

To examine the interrelationships between fragile X mental retardation 1 (FMR1) mRNA and the FMR1 exon 1/intron 1 boundary methylation, white matter microstructure, and executive function, in women with a FMR1 premutation expansion (PM; 55–199 CGG repeats) and controls (CGG < 44).

Methods:

Twenty women with PM without fragile X-associated tremor/ataxia syndrome (FXTAS) and 20 control women between 22 and 54 years of age completed this study. FMR1 mRNA and methylation levels for 9 CpG sites within the FMR1 exon 1/intron 1 boundary from peripheral blood samples were analyzed. To measure white matter microstructure, diffusion-weighted imaging was used, from which fractional anisotropy (FA) and mean diffusivity (MD) values from anatomic regions within the corpus callosum and cerebellar peduncles were extracted. Executive function was assessed across a range of tasks.

Results:

No differences were revealed in white matter microstructure between women with PM and controls. However, we reveal that for women with PM (but not controls), higher FMR1 mRNA correlated with lower MD values within the middle cerebellar peduncle and Paced Auditory Serial Addition Test scores, higher methylation of the FMR1 exon 1/intron 1 boundary correlated with lower MD within the inferior and middle cerebellar peduncles and longer prosaccade latencies, and higher FA values within the corpus callosum and cerebellar peduncle regions corresponded to superior executive function.

Conclusions:

We provide evidence linking white matter microstructure to executive dysfunction and elevated FMR1 mRNA and FMR1 exon 1/intron 1 boundary methylation in women with PM without FXTAS. This suggests that the FXTAS phenotype may not be distinct but may form part of a spectrum of PM involvement.