Characterization of Hemodynamic Alteration in Parkinson's Disease and Effect on Resting-State Connectivity.

Functional magnetic resonance imaging (fMRI) is a convolution of latent neural activity and the hemodynamic response function (HRF). According to prior studies, the neurodegenerative process in idiopathic Parkinson's Disease (PD) interacts significantly with neuromuscular abnormalities. Although these underlying neuromuscular changes might influence the temporal characteristics of HRF and fMRI signals, relatively few studies have explored this possibility. We hypothesized that such alterations would engender changes in estimated functional connectivity (FC) in fMRI space compared to latent neural space. To test these theories, we calculated voxel-level HRFs by deconvolving resting-state fMRI data from PD patients (n = 61) and healthy controls (HC) (n = 47). Significant group differences in HRF (P < 0.05, Gaussian random field-corrected) were observed in several regions previously associated with PD. Subsequently, we focused on putamen-seed-based FC differences between the PD and HC groups using fMRI and latent neural signals. The results suggested that neglecting HRF variability may cultivate false-positive and false-negative FC group differences. Furthermore, HRF was related to dopamine receptor type 2 (DRD2) gene expression (P < 0.001, t = -7.06, false discover rate-corrected). Taken together, these findings reveal HRF variation and its possible underlying molecular mechanism in PD, and suggest that deconvolution could reduce the impact of HRF variation on FC group differences.

Selected movement and force pattern differences in rail- and rung-climbing of fire apparatus aerial ladders at 52.5° slope.

This study compares human climbing performance, including climbing speed and movement and force patterns, between rail- and rung-climbing styles for a moderate aerial ladder slope (52.5°). Hand and foot movements and forces were recorded for 9 male and 10 female firefighters as they ascended and descended a 3.4-m ladder using elevated handrails (rail-climbing) or rungs (rung-climbing) for hand support. The results indicated that climbers used three or more points of contact 54% of the time for rung-climbing and 100% of the time for rail-climbing. Furthermore, rail-climbing was 10% faster than rung-climbing. In rail-climbing, the lateral hand forces were mostly directed away from the body; while during rung-climbing, they were alternated in lateral and medial directions. Overall, the results suggested that rail-climbing provides better control over body positioning and faster climbing speed. Furthermore, the continuous contact of both hands in rail-climbing may reduce the fall risk by facilitating the recovery from a slip or perturbation.

Effects of aerial ladder rung spacing on firefighter climbing biomechanics.

This study investigated the effects of aerial ladder rung spacing on firefighter climbing biomechanics. Ten female and 9 male firefighters ascended and descended instrumented ladders with rungs spaced at 356 mm (current design) and 305 mm in a laboratory setup. The climbing tests were performed at five ladder slope and handrail conditions: 30° with low (305 mm) and high (914 mm) handrails, 52.5° with and without a low handrail, and 75° without a handrail. Foot and hand forces and body movements were recorded and used to calculate joint moments of the upper and lower body. Reduced rung spacing resulted in reduced foot forces, reduced hand forces, and reduced ankle transverse moment. It was also associated with increased climbing speed for female climbers, and increased ankle vertical overshoot. The results indicate that reduced rung spacing on aerial ladders may lead to lower biomechanical stress; better climbing efficiency and safety; and reduced climbing speed disparity across sexes.