ORCID Profile
0000-0001-9513-2660
Current Organisations
Universidade Federal do Paraná
,
University of Iowa
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Publisher: Wiley
Date: 26-06-2009
DOI: 10.1002/MDS.22601
Publisher: American Psychological Association (APA)
Date: 2012
DOI: 10.1037/A0029218
Publisher: Elsevier BV
Date: 2012
Publisher: Elsevier BV
Date: 03-2018
Publisher: Springer Science and Business Media LLC
Date: 2014
Publisher: Cold Spring Harbor Laboratory
Date: 18-02-2021
DOI: 10.1101/2021.02.17.431568
Abstract: To investigate the timeframe prior to symptom onset when cortico-basal ganglia white matter (WM) loss begins in premanifest Huntington’s disease (preHD), and which striatal and thalamic sub-region WM tracts are most vulnerable. We performed fixel-based analysis, which allows resolution of crossing WM fibres at the voxel level, on diffusion tractography derived WM tracts of striatal and thalamic sub-regions in two independent cohorts TrackON-HD, which included 72 preHD (approx. 11 years before disease onset) and 85 controls imaged at three time points over two years and the HD young adult study (HD-YAS), which included 54 preHD (approx. 25 years before disease onset) and 53 controls, imaged at one time point. Group differences in fibre density and cross section (FDC) were investigated. We found no significant group differences in cortico-basal ganglia sub-region FDC in preHD gene carriers 25 years before onset. In gene carriers 11 years before onset, there were reductions in striatal (limbic and caudal motor) and thalamic (premotor, motor and sensory) FDC at baseline, with no significant change over 2 years. Caudal motor-striatal, pre-motor-thalamic, and primary motor-thalamic FDC at baseline, showed significant correlations with the Unified Huntington’s disease rating scale (UHDRS) total motor score (TMS). Limbic cortico-striatal FDC and apathy were also significantly correlated. Our findings suggest that the initiation of disease modifying therapies 25 years before onset could protect these important brain networks from undergoing neurodegeneration and highlight selectively vulnerable sub-regions of the striatum and thalamus that may be important targets for future therapies.
Publisher: Elsevier BV
Date: 2007
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 10-2012
Publisher: Springer Science and Business Media LLC
Date: 25-05-2022
DOI: 10.1007/S00421-022-04969-5
Abstract: Caffeine improves cycling time trial (TT) performance however, it is unknown whether caffeine is ergogenic when competing against other riders. The aim of this study was to investigate whether caffeine improves performance during a 4-km cycling TT when riding against a virtual opponent, and whether it is associated with increased muscle activation and at the expense of greater end-exercise central and peripheral fatigue. Using a randomized, crossover, and double-blind design, eleven well-trained cyclists completed a 4-km cycling TT alone without supplementation (CON), or against a virtual opponent after ingestion of placebo (OP-PLA) or caffeine (5 mg Compared to CON, OP-PLA improved 4-km cycling TT performance (P = 0.018), and OP-CAF further improved performance when compared to OP-PLA (P = 0.050). Muscle activation was higher in OP-PLA and OP-CAF than in CON throughout the trial (P = 0.003). The pre- to post-exercise reductions in voluntary activation and potentiated twitch force were, however, similar between experimental conditions (P > 0.05). Compared to CON, OP-PLA increased the rating of perceived exertion during the first 2 km, but caffeine blunted this increase with no difference between the OP-CAF and CON conditions. Caffeine is ergogenic when riding against a virtual opponent, but this is not due to greater muscle activation or at the expense of greater end-exercise central or peripheral fatigue.
Publisher: Elsevier BV
Date: 12-2015
DOI: 10.1016/J.NEUROPSYCHOLOGIA.2015.10.033
Abstract: The occipital lobe is an important visual processing region of the brain. Following consistent findings of early neural changes in the occipital lobe in Huntington's Disease (HD), we examined cortical thickness across four occipital regions in premanifest (preHD) and early HD groups compared with controls. Associations between cortical thickness in gene positive in iduals and performance on six cognitive tasks, each with a visual component, were examined. In addition, the association between cortical thickness in gene positive participants and one non-visual motor task was also examined for comparison. Cortical thickness was determined using FreeSurfer on T1-weighted 3T MR datasets from controls (N=97), preHD (N=109) and HD (N=69) from the TRACK-HD study. Regression models were fitted to assess between-group differences in cortical thickness, and relationships between performance on the cognitive tasks, the motor task and occipital thickness were examined in a subset of gene-positive participants (N=141). Thickness of the occipital cortex in preHD and early HD participants was reduced compared with controls. Regionally-specific associations between reduced cortical thickness and poorer performance were found for five of the six cognitive tasks, with the strongest associations in lateral occipital and lingual regions. No associations were found with the cuneus. The non-visual motor task was not associated with thickness of any region. The heterogeneous pattern of associations found in the present study suggests that occipital thickness negatively impacts cognition, but only in regions that are linked to relatively advanced visual processing (e.g., lateral occipital, lingual regions), rather than in basic visual processing regions such as the cuneus. Our results show, for the first time, the functional implications of occipital atrophy highlighted in recent studies in HD.
Publisher: BMJ
Date: 26-03-2012
Publisher: Informa UK Limited
Date: 13-06-2022
DOI: 10.1080/17461391.2022.2072772
Abstract: This study compared central and peripheral fatigue development between the Sprint and Olympic distance triathlon. Fifteen male triathletes performed Sprint and Olympic triathlon simulations in a randomized and counterbalanced order. Central and peripheral fatigue was evaluated from changes in voluntary activation level (VAL) and twitch responses of quadriceps muscle (Q
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 06-2010
Publisher: Wiley
Date: 20-12-2012
DOI: 10.1002/HBM.22214
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 07-2011
Publisher: American Medical Association (AMA)
Date: 06-2006
DOI: 10.1001/ARCHNEUR.63.6.883
Abstract: The optimal design and outcome measures for preventive clinical trials in neurodegenerative diseases are unknown. To examine measures that may be associated with disease in the largest cohort ever recruited of prediagnosed in iduals carrying the gene expansion for Huntington disease (HD). The Predict-HD study is a multicenter observational research study in progress at 17 sites in the United States, 4 in Canada, and 3 in Australia. Genetics and HD outpatient clinics. Five hundred five at-risk in iduals who had previously undergone elective DNA analyses for the CAG expansion in the HD gene (predictive testing) and did not currently have a clinical diagnosis of HD. Basal ganglia volumes on magnetic resonance images, estimated probability of diagnosis (based on CAG repeat length), performances on 21 standardized cognitive tasks, total scores on 3 scales of psychiatric distress, and motor diagnosis based on the Unified Huntington's Disease Rating Scale. Several variables showed progressive decline as the diagnostic ratings advanced toward manifest disease. Estimated probability of diagnosis was associated with Unified Huntington's Disease Rating Scale prediagnostic stages and varied from 15% in persons with no motor abnormalities to nearly 40% in those with abnormalities suggestive of probable disease. Striatal volumes, cognitive performances, and even psychiatric ratings declined significantly with motor manifestations of disease. The documentation of biological and refined clinical markers suggests several clinical end points for preventive clinical trials. Longitudinal study is critical to further validate possible markers for prediagnosed HD.
Publisher: Frontiers Media SA
Date: 25-11-2015
Publisher: MDPI AG
Date: 22-06-2018
Publisher: Wiley
Date: 18-02-2010
DOI: 10.1002/AJMG.B.30992
Publisher: Frontiers Media SA
Date: 04-06-2018
Publisher: Oxford University Press (OUP)
Date: 19-06-2019
DOI: 10.1093/BRAIN/AWZ115
Abstract: The mismatch repair gene MSH3 has been implicated as a genetic modifier of the CAG·CTG repeat expansion disorders Huntington’s disease and myotonic dystrophy type 1. A recent Huntington’s disease genome-wide association study found rs557874766, an imputed single nucleotide polymorphism located within a polymorphic 9 bp tandem repeat in MSH3/DHFR, as the variant most significantly associated with progression in Huntington’s disease. Using Illumina sequencing in Huntington’s disease and myotonic dystrophy type 1 subjects, we show that rs557874766 is an alignment artefact, the minor allele for which corresponds to a three-repeat allele in MSH3 exon 1 that is associated with a reduced rate of somatic CAG·CTG expansion (P = 0.004) and delayed disease onset (P = 0.003) in both Huntington’s disease and myotonic dystrophy type 1, and slower progression (P = 3.86 × 10−7) in Huntington’s disease. RNA-Seq of whole blood in the Huntington’s disease subjects found that repeat variants are associated with MSH3 and DHFR expression. A transcriptome-wide association study in the Huntington’s disease cohort found increased MSH3 and DHFR expression are associated with disease progression. These results suggest that variation in the MSH3 exon 1 repeat region influences somatic expansion and disease phenotype in Huntington’s disease and myotonic dystrophy type 1, and suggests a common DNA repair mechanism operates in both repeat expansion diseases.
Publisher: Wiley
Date: 16-01-2017
DOI: 10.1002/ACN3.384
Publisher: Cambridge University Press (CUP)
Date: 2015
DOI: 10.1017/S1355617714001076
Abstract: The current study sought to examine the utility of intra-in idual variability (IIV) in distinguishing participants with prodromal Huntington disease (HD) from nongene-expanded controls. IIV across 15 neuropsychological tasks and within-task IIV using a self-paced timing task were compared as a single measure of processing speed (Symbol Digit Modalities Test [SDMT]) in 693 gene-expanded and 191 nongene-expanded participants from the PREDICT-HD study. After adjusting for depressive symptoms and motor functioning, in iduals estimated to be closest to HD diagnosis displayed higher levels of across- and within-task variability when compared to controls and those prodromal HD participants far from disease onset ( F ICV (3,877) =11.25 p .0001 F PacedTiming (3,877) =22.89 p .0001). When prodromal HD participants closest to HD diagnosis were compared to controls, Cohen’s d effect sizes were larger in magnitude for the within-task variability measure, paced timing (−1.01), and the SDMT (−0.79) and paced tapping coefficient of variation (CV) (−0.79) compared to the measures of across-task variability [CV (0.55) intra-in idual standard deviation (0.26)]. Across-task variability may be a sensitive marker of cognitive decline in in iduals with prodromal HD approaching disease onset. However, in idual neuropsychological tasks, including a measure of within-task variability, produced larger effect sizes than an index of across-task IIV in this s le. ( JINS , 2015, 21 , 8–21)
Publisher: Elsevier BV
Date: 2011
Publisher: Frontiers Media SA
Date: 22-04-2014
Publisher: Wiley
Date: 18-11-2011
DOI: 10.1002/HBM.21449
Publisher: American Psychological Association (APA)
Date: 11-2015
DOI: 10.1037/NEU0000199
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 10-11-2010
Publisher: Wiley
Date: 14-07-2015
DOI: 10.1002/HBM.22835
Publisher: Oxford University Press (OUP)
Date: 29-05-2007
DOI: 10.1093/BRAIN/AWM107
Abstract: Previous studies of emotion recognition suggest that detection of disgust relies on processing within the basal ganglia and insula. Research involving in iduals with symptomatic and pre-diagnostic Huntington's disease (HD), a disease with known basal ganglia atrophy, has generally indicated a relative impairment in recognizing disgust. However, some data have suggested that recognition of other emotions (particularly fear and anger) may also be affected in HD, and a recent study found fear recognition deficits in the absence of other emotion-recognition impairments, including disgust. To further examine emotion recognition in HD, we administered a computerized facial emotion recognition task to 475 in iduals with the HD CAG expansion and 57 in iduals without. Logistic regression was used to examine associations of emotion recognition performance with estimated proximity to clinical diagnosis (based on CAG repeat length and current age) and striatal volumes. Recognition of anger, disgust, fear, sadness and surprise (but not happiness) was associated with estimated years to clinical diagnosis performance was unrelated to striatal volumes. Compared to a CAG-normal control group, the CAG-expanded group demonstrated significantly less accurate recognition of all negative emotions (anger, disgust, fear, sadness). Additionally, participants with more pronounced motor signs of HD were significantly less accurate at recognizing negative emotions than were in iduals with fewer motor signs. Findings indicate that recognition of all negative emotions declines early in the disease process, and poorer performance is associated with closer proximity to clinical diagnosis. In contrast to previous results, we found no evidence of relative impairments in recognizing disgust or fear, and no evidence to support a link between the striatum and disgust recognition.
Publisher: Wiley
Date: 14-03-2020
DOI: 10.1002/ANA.25709
Publisher: Elsevier BV
Date: 12-2007
DOI: 10.1016/J.BIOPSYCH.2006.11.034
Abstract: Psychiatric disturbances are relatively common in manifest Huntington's disease (HD), but less is known about these symptoms in the earliest phase of the illness. This study examined self-reported psychiatric symptoms in a large s le (N = 681) of prediagnosed in iduals who show the gene expansion for HD ("expansion-positive") compared with a s le of in iduals who do not show the gene expansion but are at risk for HD ("expansion-negative"). Using baseline Symptom Checklist 90-Revised (SCL-90-R) data from the Predict-HD study, expansion-positive in iduals reported significantly more psychiatric symptoms (e.g., depression, anxiety, obsessive-compulsiveness) than expansion-negative in iduals. Within the expansion-positive group, in iduals with more motor signs had higher levels of psychiatric symptoms. The SCL-90-R scores had stronger relationships with reported abilities to perform activities of daily living than other markers of HD. Finally, when companions of the expansion-positive in iduals also completed the SCL-90-R on the participants, there was considerable consistency in the ratings of psychiatric symptoms. Subtle, subclinical psychiatric symptoms are present in this prediagnosed HD s le, even though most are estimated to be more than 10 years from HD diagnosis. As suggested by other research, these subtle symptoms might be the earliest markers of the disease however, longitudinal data are needed.
Publisher: Wiley
Date: 04-09-2015
DOI: 10.1002/MDS.26364
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 12-2012
Publisher: Informa UK Limited
Date: 08-05-2023
Publisher: Elsevier BV
Date: 07-2013
Publisher: Elsevier BV
Date: 10-2015
Publisher: Informa UK Limited
Date: 08-01-2016
Location: Brazil
No related grants have been discovered for Hans Johnson.