The racially diverse affective expression (RADIATE) face stimulus set

Faces are often used in psychological and neuroimaging research to assess perceptual and emotional processes. Most available stimulus sets, however, represent minimal diversity in both race and ethnicity, which may confound understanding of these processes in diverse/racially heterogeneous samples. Having a diverse stimulus set of faces and emotional expressions could mitigate these biases and may also be useful in research that specifically examines the effects of race and ethnicity on perceptual, emotional and social processes. The racially diverse affective expression (RADIATE) face stimulus set is designed to provide an open-access set of 1,721 facial expressions of Black, White, Hispanic and Asian adult models. Moreover, the diversity of this stimulus set reflects census data showing a change in demographics in the United States from a white majority to a nonwhite majority by 2020. Psychometric results are provided describing the initial validity and reliability of the stimuli based on judgments of the emotional expressions.

The direct basal ganglia pathway is hyperfunctional in focal dystonia

See Fujita and Eidelberg (doi:10.1093/brain/awx305) for a scientific commentary on this article. Focal dystonias are the most common type of isolated dystonia. Although their causative pathophysiology remains unclear, it is thought to involve abnormal functioning of the basal ganglia-thalamo-cortical circuitry. We used high-resolution research tomography with the radioligand 11C-NNC-112 to examine striatal dopamine D1 receptor function in two independent groups of patients, writer’s cramp and laryngeal dystonia, compared to healthy controls. We found that availability of dopamine D1 receptors was significantly increased in bilateral putamen by 19.6–22.5% in writer’s cramp and in right putamen and caudate nucleus by 24.6–26.8% in laryngeal dystonia (all P ≤ 0.009). This suggests hyperactivity of the direct basal ganglia pathway in focal dystonia. Our findings paralleled abnormally decreased dopaminergic function via the indirect basal ganglia pathway and decreased symptom-induced phasic striatal dopamine release in writer’s cramp and laryngeal dystonia. When examining topological distribution of dopamine D1 and D2 receptor abnormalities in these forms of dystonia, we found abnormal separation of direct and indirect pathways within the striatum, with negligible, if any, overlap between the two pathways and with the regions of phasic dopamine release. However, despite topological disorganization of dopaminergic function, alterations of dopamine D1 and D2 receptors were somatotopically localized within the striatal hand and larynx representations in writer’s cramp and laryngeal dystonia, respectively. This finding points to their direct relevance to disorder-characteristic clinical features. Increased D1 receptor availability showed significant negative correlations with dystonia duration but not its severity, likely representing a developmental endophenotype of this disorder. In conclusion, a comprehensive pathophysiological mechanism of abnormal basal ganglia function in focal dystonia is built upon upregulated dopamine D1 receptors that abnormally increase excitation of the direct pathway, downregulated dopamine D2 receptors that abnormally decrease inhibition within the indirect pathway, and weakened nigro-striatal phasic dopamine release during symptomatic task performance. Collectively, these aberrations of striatal dopaminergic function underlie imbalance between direct and indirect basal ganglia pathways and lead to abnormal thalamo-motor-cortical hyperexcitability in dystonia.

Neural correlates of abnormal sensory discrimination in laryngeal dystonia

Aberrant sensory processing plays a fundamental role in the pathophysiology of dystonia; however, its underpinning neural mechanisms in relation to dystonia phenotype and genotype remain unclear. We examined temporal and spatial discrimination thresholds in patients with isolated laryngeal form of dystonia (LD), who exhibited different clinical phenotypes (adductor vs. abductor forms) and potentially different genotypes (sporadic vs. familial forms). We correlated our behavioral findings with the brain gray matter volume and functional activity during resting and symptomatic speech production. We found that temporal but not spatial discrimination was significantly altered across all forms of LD, with higher frequency of abnormalities seen in familial than sporadic patients. Common neural correlates of abnormal temporal discrimination across all forms were found with structural and functional changes in the middle frontal and primary somatosensory cortices. In addition, patients with familial LD had greater cerebellar involvement in processing of altered temporal discrimination, whereas sporadic LD patients had greater recruitment of the putamen and sensorimotor cortex. Based on the clinical phenotype, adductor form-specific correlations between abnormal discrimination and brain changes were found in the frontal cortex, whereas abductor form-specific correlations were observed in the cerebellum and putamen. Our behavioral and neuroimaging findings outline the relationship of abnormal sensory discrimination with the phenotype and genotype of isolated LD, suggesting the presence of potentially divergent pathophysiological pathways underlying different manifestations of this disorder.

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Abnormal temporal but not spatial discrimination is an LD mediational endophenotype.

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Penetrance of abnormal TDT is higher in familial than sporadic LD.

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No differences in penetrance between clinical phenotypes of LD

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Distinct neural phenotype/genotype relations of TDT reflect divergent pathophysiology.

GNAL mutation in isolated laryngeal dystonia

BACKGROUND

Up to 12% of patients with laryngeal dystonia report a familial history of dystonia, pointing to involvement of genetic factors. However, its genetic causes remain unknown.

METHOD

Using Sanger sequencing, we screened 57 patients with isolated laryngeal dystonia for mutations in known dystonia genes TOR1A (DYT1), THAP1 (DYT6), TUBB4A (DYT4), and GNAL (DYT25). Using functional MRI, we explored the influence of the identified mutation on brain activation during symptomatic task production.

RESULTS

We identified 1 patient with laryngeal dystonia who was a GNAL mutation carrier. When compared with 26 patients without known mutations, the GNAL carrier had increased activity in the fronto-parietal cortex and decreased activity in the cerebellum.

CONCLUSIONS

Our data show that GNAL mutation may represent one of the rare causative genetic factors of isolated laryngeal dystonia. Exploratory evidence of distinct neural abnormalities in the GNAL carrier may suggest the presence of divergent pathophysiological cascades underlying this disorder. © 2016 International Parkinson and Movement Disorder Society.