Biology subjects

Browner, N.

Publications and source records attributed to Browner, N..

3 recordsLinked to original sources

bioRxiv2019

Altered hypothalamic diffusivity in Parkinsonian autonomic dysfunction

The pathophysiological basis of autonomic symptoms in Parkinsons disease remains incompletely understood. The hypothalamus plays a key regulatory role in autonomic function and has been shown to be affected in Parkinsons disease. Here, using diffusion magnetic resonance imaging, we investigated whether microstructural properties of the hypothalamus differ in Parkinsons disease patients with high compared to low autonomic symptom burden.\n\nParkinsons disease patients with low (n=25) and high (n=25) autonomic symptom burden were identified from a larger pool, based on scores from a questionnaire assessing autonomic symptoms in Parkinsons disease (SCOPA-AUT). In each patient, we first segmented the hypothalamus manually, based on anatomical landmarks. Diffusivity measures were then extracted from the hypothalamus. Diffusivity measures calculated in the brainstem and the putamen were used to assess the specificity of the results.\n\nRelative to patients with low autonomic symptom burden, patients with high burden showed increased mean, axial, and radial diffusivity in the hypothalamus. In contrast, we did not find significant group differences in any of these measures extracted from the brainstem or the putamen.\n\nThese results reveal consistent differences in the microstructural properties of the hypothalamus between patients with low and high autonomic symptom burden. Hypothalamic diffusivity properties can thus potentially be used as an imaging marker to assist in the identification of therapeutic targets for autonomic dysfunction in Parkinsons disease.

neuroscience↗

bioRxiv2019

Integrative Functional Network Interactions Underlie the Association between Physical Activity and Cognition in Neurodegenerative Diseases

Physical activity (PA) has preventive and possibly restorative effects in aging-related cognitive decline, which relate to intrinsic functional interactions (functional connectivity, FC) in large-scale brain networks. Preventive and ameliorative effects of PA on cognitive decline have also been documented in neurodegenerative diseases, such as Parkinson's disease (PD). However, the neural substrates that mediate the association between PA and cognitive performance under such neurological conditions remain unknown. Here we set out to examine if the association between PA and cognitive performance in PD is mediated by FC in large-scale sensorimotor and association brain networks. Data from 51 PD patients were analyzed. Connectome-level analysis based on a whole-brain parcellation showed that self-reported levels of PA were associated with increased FC between, but not within the default mode (DMN) and salience networks (SAL) (p < .05, false discovery rate corrected). Additionally, multiple parallel mediation analysis further demonstrated that FC between left lateral parietal nodes in the DMN and rostral prefrontal nodes in the SAL mediated the association between PA and executive function performance. These findings are in line with previous studies linking FC in large-scale association networks with the effects of PA on cognition in healthy aging. Our results extend these previous results by demonstrating that the association between PA and cognitive performance in neurodegenerative diseases such as PD is mediated by integrative functional interactions in large-scale association networks.

neuroscience↗

bioRxiv2017

Alterations in striato-pallidal intrinsic functional connectivity as a prodrome of Parkinson’s disease

Although the diagnosis of Parkinsons disease (PD) remains anchored around the cardinal motor symptoms of bradykinesia, rest tremor, rigidity and postural instability, it is becoming increasingly clear that the clinical phase of the disease is preceded by a long period of neurodegeneration, which is not readily evident in terms of motor dysfunction. The neurobiological mechanisms that underpin this prodromal phase of PD remain poorly understood. Based on converging evidence of basal ganglia (BG) dysfunction in early PD, we set out to establish whether the prodromal phase of the disease is characterized by alterations in functional communication within the input and output structures of the BG. We analyzed resting-state functional MRI data collected from patients with REM sleep behavior disorder (RBD) and/or hyposmia, two of the strongest markers of prodromal PD, in comparison to age-matched controls. Relative to controls, subjects in the prodromal group showed reduced intra- and interhemispheric functional connectivity in a striato-thalamo-pallidal network. Functional connectivity alterations were restricted to the BG and did not extend to functional connections with the cortex. The data suggest that local interactions between input and output BG structures may be disrupted already in the prodromal phase of PD.

neuroscience↗