Biology subjects

Reschechtko, S.

Publications and source records attributed to Reschechtko, S..

7 recordsLinked to original sources

bioRxiv2026

Unintentional finger force drifts are minimally influenced by temporal evolution of surface friction

Humans consistently decrease the amount of force they produce during isometric finger pressing in the absence of visual feedback, a phenomenon often called "force drift." This decrease in force production has been attributed to limitations in working memory and/or adaptive neural control processes that minimize energy consumption. In this study, we investigated a potential peripheral reason for such force drifts: increases in the coefficient of friction between the fingertip and the surface it contacts due to changes in fingertip contact area as the fingertip hydrates under prolonged pressure. We investigated this possibility by eliciting force drifts from participants performing isometric pressing tasks against smooth glass, which shows the phenomenon of increasing contact area during prolonged contact, and a polymer which does not exhibit this phenomenon. We confirmed that the coefficient of friction only increased on the glass plate, however we did not observe a difference in force drifts between these two surfaces, although we found some evidence that force drift could be associated with coefficient of friction. Our findings suggest that factors other than peripheral changes in coefficient of friction are the primary drivers of force drifts.

neuroscience↗

bioRxiv2024

Single-shot detection of microscale tactile features

Tactile detection of very small features requires relative motion between the fingertip and a surface. The specific movement strategies that people use may be critical to maximize detection ability but little is known about the movement strategies people employ to support such detection. Here, human participants actively scanned a fingertip across a pair of silica wafers to detect which of the two contained a microscale feature (2, 6, and 10 m height and 525 m diameter). We constrained fingertip movement to ensure that participants would always contact the feature and would only contact the feature once. These procedures encouraged participants to use strategies that optimized detection rather than search and thus allowed us to more directly link movement strategies to detection. We also investigated the effects of fingertip movement direction and the finger used on detection. We found that participants were able to consistently detect microscale features as small as 2 m on the basis of a single contact event. The contact forces that participants used were substantially higher than those observed in previous studies focused on tactile search or geometric feature extraction. Scanning speeds were slower than those found during tactile search but faster than those reported during geometric feature extraction. Taken in conjunction with the associations between detection and finger used as well as scan direction, our results suggest that control and consistency of fingertip movement may be a primary consideration for movement strategies that optimize tactile detection.

neuroscience↗

bioRxiv2023

Interaction of multiple future movement plans in sequential reaching

Real world actions often comprise of a series of movements that cannot be entirely planned before initiation. When these actions are executed rapidly, the planning of multiple future movements needs to occur simultaneously with the ongoing action. How the brain solves this task remains unknown. Here we address this question with a new sequential arm reaching paradigm that manipulates how many future reaches are available for planning while controlling execution of the ongoing reach. We show that participants plan at least two future reaches simultaneously with an ongoing reach. Further, the planning processes of the two future reaches are not independent of one another. Evidence that the planning processes interact is two-fold. First, correcting for a visual perturbation of the ongoing reach target is slower when more future reaches are planned. Second, the curvature of the current reach is modified based on the next reach only when their planning processes temporally overlap. These interactions between future planning processes may enable smooth production of sequential actions by linking individual segments of a long sequence at the level of motor planning.

neuroscience↗

bioRxiv2022

Reach corrections toward moving targets are faster than reach corrections toward jumping targets

Visually guided reaching is a common motor behavior that engages subcortical circuits to mediate rapid corrections. These circuits help us successfully grasp objects we see, even if those objects move during the reach. Although these neural mechanisms have evolved for interaction with the physical world, they are almost always studied in the context of reaching toward virtual targets displayed on a computer or projection screen. Virtual targets are unrealistic both because they cannot be physically grasped and because they generally move by "jumping" from one place to another instantaneously. Recent work has indicated that various aspects of "real" visual stimuli, including proximity and graspability, elicit distinct neural activity. In this study, we instructed participants to perform rapid reaches to physical objects. On some trials, these objects either moved realistically (continuously from one position to another) or unrealistically (jumping instantaneously to an equivalent position). Participants were consistently faster in correcting their reach trajectories when the object moved continuously.

neuroscience↗

bioRxiv2022

Standing balance is not affected by estrogen fluctuations during the menstrual cycle

When people stand still, they exhibit a phenomenon called postural sway, or spontaneous movement of the bodys center of pressure, which is related to balance control. In general females show less sway than males, but this difference only begins to appear around puberty, pointing to different levels of sex hormones as one potential mechanism for sway sex differences. In this study, we followed one group of young females using oral contraceptives (n = 32) and one group not using oral contraceptives (n = 19), to investigate associations between estrogen availability and postural sway, both over the course of the menstrual cycle (in the group not using oral contraceptives) and long-term (between the two groups). All participants visited the lab four times over the putative 28-day menstrual cycle. At each visit, we performed blood draws to measure plasma estrogen (estradiol) levels, and tests of postural sway using a force plate. Due to the hormone-stabilizing effects of oral contraceptives, estradiol levels were higher in participants not using oral contraceptives (690.45 pmol/L versus 464.50 pmol/L), reflecting higher estradiol concentrations during the late follicular and luteal phase. Postural sway was similar on average for participants not using oral contraceptives (21.47 cm versus 23.56 cm). Overall, we found no significant effects of the estimated menstrual cycle phase - or absolute levels of estradiol - on postural sway.

physiology↗

bioRxiv2020

Voluntary modification of rapid tactile-motor responses during reaching differs from its visuo-motor counterpart

People commonly hold and manipulate a variety of objects in everyday life, and these objects have different physical properties. In order to successfully control this wide range of objects, people must associate new patterns of tactile stimuli with appropriate motor outputs. We performed a series of experiments investigating the extent to which people can voluntarily modify tactile-motor associations in the context of a rapid tactile-motor response guiding the hand to a moving target (previously described in Pruszynski et al. 2016) by using an anti-reach paradigm in which participants were instructed to move their hands in the opposite direction of a target jump. We compared performance to that observed when people make visually guided reaches to a moving target (cf. Day & Lyon 2000, Pisella et al. 2000). When participants had visual feedback, motor responses during the anti-reach task showed early automatic responses toward the moving target before voluntary modification to move in the instructed direction. When the same participants had only tactile feedback, however, they were able to suppress this early phase of the motor response, which occurs less than 100 ms after the target jump. Our results indicate that, while the tactile motor and visual motor systems both support rapid responses that appear similar under some conditions, these responses show sharp distinctions in terms of their malleability.

neuroscience↗

bioRxiv2019

Maintaining arm control during self-triggered and unpredictable unloading perturbations.

We often perform actions where we must break through some resistive force, but want to remain in control during this unpredictable transition; for example, when an object we are pushing on transitions from static to dynamic friction and begins to move. We designed a laboratory task to replicate this situation in which participants actively pushed against a robotic manipulandum until they exceeded an unpredictable threshold, at which point the manipulandum moved freely. Human participants were instructed to either stop the movement of the handle following this unloading perturbation, or to continue pushing. We found that participants were able to modulate their reflexes in response to this unpredictable and self-triggered unloading perturbation according to the instruction they were following, and that this reflex modulation could not be explained by pre-perturbation muscle state. However, in a second task, where participants reactively produced force during the pre-unloading phase in response to the robotic manipulandum to maintain a set hand position, they were unable to modulate their reflexes in the same task-dependent way. This occurred even though the forces they produced were matched to the first task and they had more time to prepare for the unloading event. We suggest this disparity occurs because of different neural circuits involved in posture and movement, meaning that participants in the first task did not require additional time to switch from postural to movement control.

neuroscience↗