Neural correlates of abnormal sensory discrimination in laryngeal dystonia

AbstractAberrant 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

Race Information Influences Cognitive Processes in Brain and Behavior in Black and White Individuals

Race is a prevailing social category in the United States, and physical cues that indicate race are often used as a heuristic to distinguish in- and out-group members. The salience of race can influence our cognitive processes and contribute to racially-biased behavior. The present dissertation examines the contexts in which race information biases behavior and investigates the underlying cognitive and neurobiological processes that contribute to racially-biased behavior. Furthermore, the present dissertation studies illustrate the importance of implementing diversity in participant samples and experimental stimuli in psychological research. Chapter 1 reviews the importance of race as a social group in the United States, how it can uniquely impact cognitive processes, and highlights gaps in the literature due limited representation in experimental paradigms. Chapter 2 examines how task-irrelevant race information impacts cognitive control and illustrates how representative samples can nuance our understanding of cognitive and neurobiological processes underlying biased behavior. Chapter 3 builds upon the previous chapter by investigating the effects of perceived threat on impulse control to task-irrelevant race information and the representation of race information in the brain. Chapter 4 leverages a large open-access dataset to demonstrate the importance of diverse racial representation in experimental samples and stimuli by demonstrating the effects of race information on a series of cognitive processes in youth. Together, these studies examine the contexts in which race information influences cognition and elucidates the neurobiological processes that contribute to racially-biased behavior. Lastly, Chapter 5 highlights the implications of the current work and discusses the opportunity and responsibility researchers have to improve future psychological research work by implementing diverse and representative experimental designs

Neural correlates of dystonic tremor: a multimodal study of voice tremor in spasmodic dysphonia

Tremor, affecting a dystonic body part, is a frequent feature of adult-onset dystonia. However, our understanding of dystonic tremor pathophysiology remains ambiguous as its interplay with the main co-occurring disorder, dystonia, is largely unknown. We used a combination of functional MRI, voxel-based morphometry and diffusion-weighted imaging to investigate similar and distinct patterns of brain functional and structural alterations in patients with dystonic tremor of voice (DTv) and isolated spasmodic dysphonia (SD). We found that, compared to controls, SD patients with and without DTv showed similarly increased activation in the sensorimotor cortex, inferior frontal (IFG) and superior temporal gyri, putamen and ventral thalamus, as well as deficient activation in the inferior parietal cortex and middle frontal gyrus (MFG). Common structural alterations were observed in the IFG and putamen, which were further coupled with functional abnormalities in both patient groups. Abnormal activation in left putamen was correlated with SD onset; SD/DTv onset was associated with right putaminal volumetric changes. DTv severity established a significant relationship with abnormal volume of the left IFG. Direct patient group comparisons showed that SD/DTv patients had additional abnormalities in MFG and cerebellar function and white matter integrity in the posterior limb of the internal capsule. Our findings suggest that dystonia and dystonic tremor, at least in the case of SD and SD/DTv, are heterogeneous disorders at different ends of the same pathophysiological spectrum, with each disorder carrying a characteristic neural signature, which may potentially help development of differential markers for these two conditions