Feedback Gains modulate with Motor Memory Uncertainty

Franklin, Sae; Franklin, David W.

doi:10.51628/001c.22336

Cited by 9 publications

(3 citation statements)

References 74 publications

(150 reference statements)

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“…The stiffness or compliance of the body has long been acknowledged as an important factor in motor control (Franklin & Wolpert, 2011; Hogan, 1984; McIntyre et al, 1995; Wolpert & Flanagan, 2010), but most reaching studies examine changes due to co-contraction (Franklin et al, 2007; Franklin & Franklin, 2021; Osu et al, 2002) or changing posture (Franklin et al, 2013; Lametti & Ostry, 2010; Trumbower et al, 2009). However, reflexes also contribute significantly to the stiffness of the muscles and limbs (Akazawa et al, 1983; Crago et al, 1976; Hoffer & Andreasse,n 1981; Kearney et al, 1997; Nichols & Houk, 1976).…”

Section: Discussionmentioning

confidence: 99%

Assistive loading promotes goal-directed tuning of stretch reflex gains

Torell

Franklin

et al. 2022

Preprint

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Voluntary movements are prepared before they are executed. Preparatory activity has been observed across the CNS and recently documented in first order neurons of the human PNS i.e., in muscle spindles. The changes seen in these sensory organs suggest that the independent modulation of stretch reflex gains may represent an important component of movement preparation. The aim of the current study was to further investigate the preparatory modulation of short- and long-latency stretch reflex responses ('SLR' and 'LLR') of the dominant upper limb. Specifically, we investigated how different target parameters (target distance and direction) affect the preparatory tuning of stretch reflex gains in the context of goal-directed reaching, and whether any such tuning depends on preparation duration and the direction of background loads. We found that target distance produced only small variations in reflex gains. In contrast, both SLR and LLR gains were strongly modulated as a function of target direction, in a manner that facilitated the upcoming voluntary movement. This goal-directed tuning of SLR and LLR gains was present or enhanced when the preparatory delay was sufficiently long (>250 ms) and the homonymous muscle was unloaded i.e., when a background load was first applied in the direction of homonymous muscle action (assistive loading). The results extend further support for a relatively slow-evolving process in reach preparation that functions to modulate reflexive muscle stiffness, likely via the independent control of fusimotor neurons. Such control can augment voluntary goal-directed movement and is triggered or enhanced when the homonymous muscle is unloaded.

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Section: Discussionmentioning

confidence: 99%

Assistive loading promotes goal-directed tuning of stretch reflex gains

Torell

Franklin

et al. 2022

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“…This measurement was used to estimate predictive feedforward adaptation, both during learning and in determining generalization to different temporal relations between the two hands. This method offers greater accuracy than relying solely on a reduction in kinematic error, as it avoids the effect of limb impedance due to muscle co-contraction [69][70][71][72] .…”

Section: Discussionmentioning

confidence: 99%

Kernels of Motor Memory Formation: Temporal Generalization in Bimanual Adaptation

Howard,

Franklin,

Franklin

2024

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In daily life, we coordinate simultaneous and sequential bimanual movements to manipulate objects. Despite the complexity, people adapt rapidly, suggesting neural mechanisms optimized for efficient adaptation. Here we extract the temporal kernel that underlies motor memory formation, by testing the contextual effects of past, simultaneous, and future contralateral arm movements and measuring their temporal generalization in three novel bimanual interference tasks. The actions of one arm can serve as a contextual cue for the other arm for all three timing contexts, facilitating dual adaptation. More importantly, the timing of the learned contextual action plays a pivotal role in the temporal generalization. While motor memories trained with past contextual movements generalize broadly, motor memories trained with future movements exhibit limited generalization, and motor memories trained with simultaneous movements do not generalize to past or future timings. This highlights temporal tuning in sensorimotor plasticity: different training conditions yield substantially different temporal generalization.

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“…We present feedback on the kinematic measure of each trial rather than only for force compensation on the channel trials, as these are most frequently encountered by participants and allow the presentation of reward feedback as often as possible. It is important to note that participants can reduce the kinematic error to increase reward through predictive compensation to the force field, through increased co-contraction, limb stiffness and feedback gains, or through combinations of all of these [64, 65]. Five ranges of ± 0.75 cm error were defined to provide the different rewards (Fig 1B).…”

Section: Methodsmentioning

confidence: 99%

Reward actively engages both implicit and explicit components in dual force field adaptation

Forano¹,

Franklin

2023

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Motor learning occurs through multiple mechanisms, including unsupervised, supervised (error-based) and reinforcement (reward-based) learning. Although studies have shown that reward leads to an overall better motor adaptation, the specific processes by which reward influences adaptation are still unclear. Here, we examine how the presence of reward affects dual-adaptation to novel dynamics, and distinguish its influence on implicit and explicit learning. Participants adapted to two opposing force fields in an adaptation/de-adaptation/error-clamp paradigm, where five levels of reward (a score and a digital face) were provided as participants reduced their lateral error. Both reward and control (no reward provided) groups simultaneously adapted to both opposing force fields, exhibiting a similar final level of adaptation, which was primarily implicit. Triple-rate models fit to the adaptation process found higher learning rates in the fast and slow processes, and a slightly increased fast retention rate for the reward group. While differences in the slow learning rate were only driven by implicit learning, the large difference in the fast learning rate was mainly explicit. Overall, we confirm previous work showing that reward increases learning rates, extending this to dual-adaptation experiments, and demonstrating that reward influences both implicit and explicit adaptation. Specifically, we show that reward acts primarily explicitly on the fast learning rate and implicitly on the slow learning rates.

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Feedback Gains modulate with Motor Memory Uncertainty

Cited by 9 publications

References 74 publications

Assistive loading promotes goal-directed tuning of stretch reflex gains

Assistive loading promotes goal-directed tuning of stretch reflex gains

Kernels of Motor Memory Formation: Temporal Generalization in Bimanual Adaptation

Reward actively engages both implicit and explicit components in dual force field adaptation

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