Biology subjects

Brinkerhoff, S. A.

Publications and source records attributed to Brinkerhoff, S. A..

3 recordsLinked to original sources

bioRxiv2024

A Method for Electrical Stimulus Artifact Removal Exploiting Neural Refractoriness: Validation by Contrasting Cathodic and Anodic Stimulation

ObjectiveTo present a novel method for removing stimulus transient that exploits the absolute refractory period of electrically excitable neural tissues. BackgroundElectrical stimulation often generates significant signal artifacts that can obscure important physiological signals. Removal of the artifact and understanding latent information from these signals could provide objective measures of circuit engagement, potentially driving advancements in neuromodulation research and therapies. MethodsWe conducted intracranial physiology studies on five consecutive patients with Parkinsons disease who underwent deep brain stimulation (DBS) surgery as part of their routine care. Monopolar stimuli (either cathodic or anodic) were delivered in pairs through the DBS electrode across a range of inter-stimulus intervals. Recordings from adjacent unused electrode contacts used broadband sampling and precise synchronization to generate a robust template for the stimulus transient during the absolute refractory period. These templates of stimulus transient were then subtracted from recordings at different intervals to extract and analyze the residual neural potentials. ResultsAfter artifact removal, the residual signals exhibited absolute and relative refractory periods with timing indicative of neural activity. Cathodic and anodic DBS pulses generated distinct patterns of local tissue activation, showing phase independence from the prior stimulus. The earliest detectable neural responses occurred at short peak latencies (ranging from 0.19 to 0.38 ms post-stimulus) and were completely or partially obscured by the stimulus artifact prior to removal. Cathodic stimuli produced stronger local tissue responses than anodic stimuli, aligning with clinical observations of lower activation thresholds for cathodic stimulation. However, cathodic and anodic pulses induced artifact patterns that were equivalent but opposite. InterpretationThe proposed artifact removal technique enhances prior approaches by allowing direct measurement of local tissue responses without requirements for stimulus polarity reversal, template scaling, or specialized filters. This approach could be integrated into future neuromodulation systems to visualize stimulus-evoked neural potentials that would otherwise be obscured by stimulus artifacts.

bioengineering↗

bioRxiv2023

Walking (and talking) the plank: Dual-task performance costs in a virtual balance-threatening environment

We evaluated the effects of engaging in extemporaneous speech while walking in virtual environments meant to elicit low or high levels of mobility-related anxiety. We expected that mobility-related anxiety imposed by a simulated balance threat (i.e. virtual high elevation) would impair walking behavior and lead to greater dual-task costs. Altogether, 15 adults (age = 25.6 {+/-} 4.7 yrs, 7 women) walked at their self-selected speed within low (ground) and high elevation (15 meters) VR settings while speaking extemporaneously (dual-task) or not speaking (single-task). Likert-scale ratings of cognitive and somatic anxiety, confidence, and mental effort were evaluated after experiencing each condition, and gait speed, step length, and step width, and the variability of each, was calculated for each trial using the position of trackers attached to participants ankles. Silent speech pauses (>150ms) were determined from audio recordings to infer the cognitive costs of extemporaneous speech planning at low and high virtual elevation. The presence of a balance threat and the inclusion of a concurrent speech task both perturbed gait kinematics, but only the virtual height illusion increased anxiety and mental effort while decreasing confidence. Extemporaneous speech pauses were longer on average when walking, but no effects of virtual elevation were reported. Trends toward interaction effects arose in self-reported responses, participants reported more comfort walking at virtual heights if they engaged in extemporaneous speech. Walking at virtual elevation and walking while talking have independent and significant effects on gait; both effects were robust and did not support an interaction when combined (i.e., walking and talking at virtual heights). Rather than additive cognitive-motor demands, the nature of extemporaneous speech may have distracted participants from the detrimental effects of walking in anxiety-inducing settings.

bioengineering↗

bioRxiv2022

Habitual weekly exercise affects gait adaptation in healthy young adults

Changing movement patterns in response to environmental perturbations is a critical aspect of gait and is related to reducing the energetic cost of the movement. Exercise improves energetic capacity for submaximal exercise and may affect how people adapt movement to reach an energetic minimum. The purpose of this study was to determine whether self-reported exercise behavior influences gait adaptation in young adults. Young adults who met the optimal volume of exercise according to the Physical Activity Guidelines for Americans (MOVE; n=19) and young adults who did not meet the optimal volume of exercise (notMOVE; n=13) walked on a split-belt treadmill with one belt moving twice the speed of the other belt for 10 minutes. Step length asymmetry (SLA) and mechanical work done by each leg were measured. Nonlinear mixed effects models compared the time course of adaptation between MOVE and notMOVE, and t-tests compared net work at the end of adaptation between MOVE and notMOVE. Compared to notMOVE, MOVE had a faster initial response to the split belt treadmill, and continued to adapt over the duration of split-belt treadmill walking. Young adults who engage in sufficient amounts of exercise responded more quickly to the onset of a perturbation, and throughout the perturbation they continued to explore movement strategies, which might be related to reduction of energetic cost. Our findings provide insights into the multisystem positive effects of exercise, including walking adaptation.

neuroscience↗