Neural mechanisms of vibrotactile categorization.

The grouping of sensory stimuli into categories is fundamental to cognition. Previous research in the visual and auditory systems supports a two-stage processing hierarchy that underlies perceptual categorization: (a) a "bottom-up" perceptual stage in sensory cortices where neurons show selectivity for stimulus features and (b) a "top-down" second stage in higher level cortical areas that categorizes the stimulus-selective input from the first stage. In order to test the hypothesis that the two-stage model applies to the somatosensory system, 14 human participants were trained to categorize vibrotactile stimuli presented to their right forearm. Then, during an fMRI scan, participants actively categorized the stimuli. Representational similarity analysis revealed stimulus selectivity in areas including the left precentral and postcentral gyri, the supramarginal gyrus, and the posterior middle temporal gyrus. Crucially, we identified a single category-selective region in the left ventral precentral gyrus. Furthermore, an estimation of directed functional connectivity delivered evidence for robust top-down connectivity from the second to first stage. These results support the validity of the two-stage model of perceptual categorization for the somatosensory system, suggesting common computational principles and a unified theory of perceptual categorization across the visual, auditory, and somatosensory systems.

Genetic characterization of physical activity behaviours in university students enrolled in kinesiology degree programs.

Studies of physical activity behaviours have increasingly shown the importance of heritable factors such as genetic variation. Nonsynonymous polymorphisms of alpha-actinin 3 (ACTN3) and the ß-adrenergic receptors 1 and 3 (ADRB1 and ADRB3) have been previously associated with exercise capacity and cardiometabolic health. We thus hypothesized that these polymorphisms are also related to physical activity behaviours in young adults. To test this hypothesis we examined relationships between ACTN3 (R577X), ARDB1 (Arg389Gly), ADRB3 (Trp64Arg), and physical activity behaviours in university students. We stratified for student enrollment in kinesiology degree programs compared with nonmajors as we previously found this to be a predictor of physical activity. We did not identify novel associations between physical activity and ACTN3. However, the minor alleles of ADRB1 and ADRB3 were significantly underrepresented in kinesiology students compared with nonmajors. Furthermore, carriers of the ADRB1 minor allele reported reduced participation in moderate physical activity and increased afternoon fatigue compared with ancestral allele homozygotes. Together, these findings suggest that the heritability of physical activity behaviours in young adults may be linked to nonsynonymous polymorphisms within ß-adrenergic receptors.

Expanding the phenotypic profile of Kleefstra syndrome: A female with low-average intelligence and childhood apraxia of speech.

Kleefstra syndrome (KS) is a rare neurogenetic disorder most commonly caused by deletion in the 9q34.3 chromosomal region and is associated with intellectual disabilities, severe speech delay, and motor planning deficits. To our knowledge, this is the first patient (PQ, a 6-year-old female) with a 9q34.3 deletion who has near normal intelligence, and developmental dyspraxia with childhood apraxia of speech (CAS). At 6, the Wechsler Preschool and Primary Intelligence testing (WPPSI-III) revealed a Verbal IQ of 81 and Performance IQ of 79. The Beery Buktenica Test of Visual Motor Integration, 5th Edition (VMI) indicated severe visual motor deficits: VMI = 51; Visual Perception = 48; Motor Coordination < 45. On the Receptive One Word Picture Vocabulary Test-R (ROWPVT-R), she had standard scores of 96 and 99 in contrast to an Expressive One Word Picture Vocabulary-R (EOWPVT-R) standard scores of 73 and 82, revealing a discrepancy in vocabulary domains on both evaluations. Preschool Language Scale-4 (PLS-4) on PQ's first evaluation reveals a significant difference between auditory comprehension and expressive communication with standard scores of 78 and 57, respectively, further supporting the presence of CAS. This patient's near normal intelligence expands the phenotypic profile as well as the prognosis associated with KS. The identification of CAS in this patient provides a novel explanation for the previously reported speech delay and expressive language disorder. Further research is warranted on the impact of CAS on intelligence and behavioral outcome in KS. Therapeutic and prognostic implications are discussed.

CK-MM Polymorphism is Associated With Physical Fitness Test Scores in Military Recruits.

OBJECTIVE: Muscle-specific creatine kinase is thought to play an integral role in maintaining energy homeostasis by providing a supply of creatine phosphate. The genetic variant, rs8111989, contributes to individual differences in physical performance, and thus the purpose of this study was to determine if rs8111989 variant is predictive of Physical Fitness Test (PFT) scores in male, military infantry recruits. METHODS: DNA was extracted from whole blood, and genotyping was performed in 176 Marines. Relationships between PFT measures (run, sit-ups, and pull-ups) and genotype were determined. RESULTS: Participants with 2 copies of the T allele for rs8111989 variant had higher PFT scores for run time, pull-ups, and total PFT score. Specifically, participants with 2 copies of the TT allele (variant) (n = 97) demonstrated an overall higher total PFT score as compared with those with one copy of the C allele (n = 79) (TT: 250 ± 31 vs. CC/CT: 238 ± 31; p = 0.02), run score (TT: 82 ± 10 vs. CC/CT: 78 ± 11; p = 0.04) and pull-up score (TT: 78 ± 11 vs. CC/CT: 65 ± 21; p = 0.04) or those with the CC/CT genotype. CONCLUSION: These results demonstrate an association between physical performance measures and genetic variation in the muscle-specific creatine kinase gene (rs8111989).

Reduced Functional Connectivity of Default Mode and Set-Maintenance Networks in Ornithine Transcarbamylase Deficiency.

BACKGROUND AND PURPOSE: Ornithine transcarbamylase deficiency (OTCD) is an X-chromosome linked urea cycle disorder (UCD) that causes hyperammonemic episodes leading to white matter injury and impairments in executive functioning, working memory, and motor planning. This study aims to investigate differences in functional connectivity of two resting-state networks--default mode and set-maintenance--between OTCD patients and healthy controls. METHODS: Sixteen patients with partial OTCD and twenty-two control participants underwent a resting-state scan using 3T fMRI. Combining independent component analysis (ICA) and region-of-interest (ROI) analyses, we identified the nodes that comprised each network in each group, and assessed internodal connectivity. RESULTS: Group comparisons revealed reduced functional connectivity in the default mode network (DMN) of OTCD patients, particularly between the anterior cingulate cortex/medial prefrontal cortex (ACC/mPFC) node and bilateral inferior parietal lobule (IPL), as well as between the ACC/mPFC node and the posterior cingulate cortex (PCC) node. Patients also showed reduced connectivity in the set-maintenance network, especially between right anterior insula/frontal operculum (aI/fO) node and bilateral superior frontal gyrus (SFG), as well as between the right aI/fO and ACC and between the ACC and right SFG. CONCLUSION: Internodal functional connectivity in the DMN and set-maintenance network is reduced in patients with partial OTCD compared to controls, most likely due to hyperammonemia-related white matter damage. Because several of the affected areas are involved in executive functioning, it is postulated that this reduced connectivity is an underlying cause of the deficits OTCD patients display in this cognitive domain.

Investigating neurological deficits in carriers and affected patients with ornithine transcarbamylase deficiency.

BACKGROUND: Urea cycle disorders are caused by dysfunction in any of the six enzymes and two transport proteins involved in urea biosynthesis. Our study focuses on ornithine transcarbamylase deficiency (OTCD), an X-linked disorder that results in a dysfunctional mitochondrial enzyme, which prevents the synthesis of citrulline from carbamoyl phosphate and ornithine. This enzyme deficiency can lead to hyperammonemic episodes and severe cerebral edema. The objective of this study was to use a cognitive battery to expose the cognitive deficits in asymptomatic carriers of OTCD. MATERIALS AND METHODS: In total, 81 participants were recruited as part of a larger urea cycle disorder imaging consortium study. There were 25 symptomatic participants (18 female, 7 male, 25.6 year s ± 12.72 years), 20 asymptomatic participants (20 female, 0 male, 37.6 years ± 15.19 years), and 36 healthy control participants (21 female, 15 male, 29.8 years ± 13.39 years). All participants gave informed consent to participate and were then given neurocognitive batteries with standard scores and T scores recorded. RESULTS: When stratified by symptomatic participant, asymptomatic carrier, and control, the results showed significant differences in measures of executive function (e.g. CTMT and Stroop) and motor ability (Purdue Assembly) between all groups tested. Simple attention, academic measures, language and non-verbal motor abilities showed no significant differences between asymptomatic carriers and control participants, however, there were significant differences between symptomatic and control participant performance in these measures. CONCLUSIONS: In our study, asymptomatic carriers of OTCD showed no significant differences in cognitive function compared to control participants until they were cognitively challenged with fine motor tasks, measures of executive function, and measures of cognitive flexibility. This suggests that cognitive dysfunction is best measurable in asymptomatic carriers after they are cognitively challenged.

SLC30A8 nonsynonymous variant is associated with recovery following exercise and skeletal muscle size and strength.

Genome-wide association studies have identified thousands of variants that are associated with numerous phenotypes. One such variant, rs13266634, a nonsynonymous single nucleotide polymorphism in the solute carrier family 30 (zinc transporter) member eight gene, is associated with a 53% increase in the risk of developing type 2 diabetes (T2D). We hypothesized that individuals with the protective allele against T2D would show a positive response to short-term and long-term resistance exercise. Two cohorts of young adults-the Eccentric Muscle Damage (EMD; n = 156) cohort and the Functional Single Nucleotide Polymorphisms Associated with Muscle Size and Strength Study (FAMuSS; n = 874)-were tested for association of the rs13266634 variant with measures of skeletal muscle response to resistance exercise. Our results were sexually dimorphic in both cohorts. Men in the EMD study with two copies of the protective allele showed less post-exercise bout strength loss, less soreness, and lower creatine kinase values. In addition, men in the FAMuSS, homozygous for the protective allele, showed higher pre-exercise strength and larger arm skeletal muscle volume, but did not show a significant difference in skeletal muscle hypertrophy or strength with resistance training.

Musculoskeletal anomalies in a large cohort of boys with 49, XXXXY.

49, XXXXY is a rare aneuploidy and variant of Klinefelter syndrome, occurring in 1 per 80,000-100,000 live births. We present a cohort of 40 affected males, focusing on musculoskeletal problems. Subjects were participants in an annual 49er family support group meeting. Children were examined in a multidisciplinary clinic by a pediatric neurologist and geneticist, a pediatric orthopedist, a neurodevelopmentalist, and two physical therapists. The patient data were collected from this clinic from 2004 to 2012. All patients were required to have karyotypes that confirmed the presence of XXXXY. There was a high prevalence of musculoskeletal disorders, particularly hypotonia (34 patients [85%]), radioulnar synostosis (30 [75%]), pes planus (26 [65%]), asymmetric hip rotation (27 [67.5%]), and clinodactyly (24 [60%]). Other, less common lower-extremity disorders, included, 5 patients (12.5%) with unilateral club foot, 5 boys (12.5%) with pes cavus, 10 patients (25%) genu valgum and 2 children with genu varus (5%). To our knowledge, this is the first large cohort of boys with 49, XXXXY that focuses on musculoskeletal disorders. There was an increased incidence of hypotonia, clubfoot, avascular necrosis of the femoral head, radioulnar synostosis, and pes planus compared to the normative population. Boys with 49, XXXXY would benefit from multidisciplinary evaluations, particularly from pediatric orthopedists, physical therapists, neurologists, and geneticists for appropriate medical care.