An independent race model involving an abort and re‐plan strategy explains reach redirecting movements during planning and execution

Venkataramani, PrasannaVenkhatesh; Gopal, Atul; Murthy, Aditya

doi:10.1111/ejn.13821

Cited by 6 publications

(17 citation statements)

References 55 publications

(110 reference statements)

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“…[FS Weibull fit parameters: range (␥ Ϫ ␦): min ϭ 0.91, max ϭ 1, median ϭ 0.9579; slope (␤): min ϭ 1.9, max ϭ 5.07, median ϭ 3.3; SF Weibull fit parameters: range (␥ Ϫ ␦): min ϭ 0.902, max ϭ 1, median ϭ 0.94402; slope (␤): min ϭ 1.92, max ϭ 3.77, median ϭ 2.44]. In general, subjects were able to do the task well, and the behavior conformed to the performance curves seen in the standard redirect task (Venkataramani et al 2018).…”

Section: Speed Redirect Taskmentioning

confidence: 67%

“…The experimental setup and the recording procedures were same as described in previously published papers from our laboratory (Gopal and Murthy 2015;Jana et al 2017;Venkataramani et al 2018). Briefly, visual stimuli were displayed and behavioral parameters were stored with TEMPO/VIDEOSYNC software (Reflective Computing, St. Louis, MO).…”

Section: Methodsmentioning

confidence: 99%

“…This could be a consequence of using movement duration rather than speed as an online criterion to reward subjects. Although the absence of a strictly monotonic relationship raises the question of whether the duration rather than the speed is a parameter that is explicitly planned and controlled, the monotonically increasing compensation function seen in both SF and FS for movement duration suggests that some aspect of the kinematics is part of the evolving motor plan and justified our use of a race model framework that has explained performance in previous versions of the redirect task in both eye and hand movements (Kapoor and Murthy 2008;Ramakrishnan et al 2012;Venkataramani et al 2018).…”

Section: Performance Of Subjects In a Novel Speed Redirect Taskmentioning

confidence: 98%

“…The model implementation is described in detail elsewhere in previously published work (Gopal and Murthy 2016;Ramakrishnan et al 2012;Venkataramani et al 2018). Briefly, the parameters that characterize the GO processes ( GO , GO ) were estimated with a Monte Carlo method.…”

Section: Model Implementationmentioning

confidence: 99%

“…To the best of our knowledge, no study has formally tested such a corollary hypothesis. Using a modification of a reach redirect task in which subjects were instructed to change the speed of their movement plan, we assessed the applicability of different race model architectures to explain performance, analogous to the classic redirect task that involves a change in the location of the target (Venkataramani et al 2018).…”

Section: Introductionmentioning

confidence: 99%

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Distinct mechanisms explain the control of reach speed planning: evidence from a race model framework

Venkataratamani

Murthy

2018

Journal of Neurophysiology

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Previous studies have investigated the computational architecture underlying the voluntary control of reach movements that demands a change in position or direction of movement planning. Here we used a novel task in which subjects had to either increase or decrease the movement speed according to a change in target color that occurred randomly during a trial. The applicability of different race models to such a speed redirect task was assessed. We found that the predictions of an independent race model that instantiated an abort-and-replan strategy was consistent with all aspects of performance in the fast-to-slow speed condition. The results from modeling indicated a peculiar asymmetry, in that although the fast-to-slow speed change required inhibition, none of the standard race models was able to explain how movements changed from slow to fast speeds. Interestingly, a weighted averaging model that simulated the gradual merging of two kinematic plans explained behavior in the slow-to-fast speed task. In summary, our work shows how a race model framework can provide an understanding of how the brain controls different aspects of reach movement planning and help distinguish between an abort-and-replan strategy and merging of plans. NEW & NOTEWORTHY For the first time, a race model framework was used to understand how reach speeds are modified. We provide evidence that a fast-to-slow speed change required aborting the current plan and a complete respecification of a new plan, while none of the race models was able to explain an instructed increase of hand movement speed, which was instead accomplished by a merging of a new kinematic plan with the existing kinematic plan.

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Section: Speed Redirect Taskmentioning

confidence: 67%

Section: Methodsmentioning

confidence: 99%

Section: Performance Of Subjects In a Novel Speed Redirect Taskmentioning

confidence: 98%

Section: Model Implementationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Distinct mechanisms explain the control of reach speed planning: evidence from a race model framework

Venkataratamani

Murthy

2018

Journal of Neurophysiology

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Preparatory activity links frontal eye field activity with small amplitude motor unit recruitment of neck muscles during gaze planning

Rungta¹,

Basu

Sendhilnathan

et al. 2021

Preprint

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A hallmark of intelligent behavior is that we can separate intention from action. To understand the mechanism that gates the flow of information between motor planning and execution, we compared the activity of frontal eye field neurons with motor unit activity from neck muscles in the presence of an intervening delay period in which spatial information regarding the target was available to plan a response. Whereas we could infer spatially-specific delayed period activity from the activity of frontal eye field neurons, neck motor unit activity during the delay period could not be used to infer the direction of an upcoming movement, Nonetheless, motor unit activity was correlated with the time it took to initiate saccades. Interestingly, we observed a heterogeneity of responses amongst motor units, such that only units with smaller amplitudes showed a clear modulation during the delay period. These small amplitude motor units also had higher spontaneous activity compared to the units which showed modulation only during the movement epoch. Taken together, our results suggest that the temporal information is visible in the periphery amongst smaller motor units during eye movement planning and explains how the delay period primes muscle activity leading to faster reaction times.

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Task context determines whether common or separate inhibitory signals underlie the control of eye-hand movements

Jana

Murthy

2018

Journal of Neurophysiology

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Whereas inhibitory control of single effector movements has been widely studied, the control of coordinated eye-hand movements has received less attention. Nevertheless, previous studies have contradictorily suggested that either a common or separate signal/s is/are responsible for inhibition of coordinated eye-hand movements. In continuation of our previous study, we varied behavioral contexts and used a stochastic accumulation-to-threshold model, which predicts a scaling of the mean reaction time distribution with its variance, to study the inhibitory control of eye-hand movements. Participants performed eye-hand movements in different task conditions, and in each condition they had to redirect movements in a fraction of trials. Task contexts where the behavior could be best explained by a common initiation signal had similar error responses for eye and hand, despite having different mean reaction times, indicating a common inhibitory signal. In contrast, behavior that could be best explained by separate initiation signals had dissimilar error responses for eye and hand indicating separate inhibitory signals. These behavioral responses were further validated using electromyography and computational models having either a common or separate inhibitory control signal/s. Interestingly, in a particular context, whereas in majority trials a common initiation and inhibitory signal could explain the behavior, in a subset of trials separate initiation and inhibitory signals predicted the behavior better. This highlights the flexibility that exists in the brain and in effect reconciles the heterogeneous results reported by previous studies. NEW & NOTEWORTHY Prior studies have contradictorily suggested either a single or separate inhibitory signal/s underlying inhibition of coordinated eye-hand movements. With the use of different tasks, we observed that when eye-hand movements were initiated by a common signal, they were controlled by a common inhibitory signal. However, when the two effectors were initiated by separate signals, they were controlled by separate inhibitory signals. This highlights the flexible control of eye-hand movements and reconciles the heterogeneous results previously reported in the literature.

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An independent race model involving an abort and re‐plan strategy explains reach redirecting movements during planning and execution

Cited by 6 publications

References 55 publications

Distinct mechanisms explain the control of reach speed planning: evidence from a race model framework

Distinct mechanisms explain the control of reach speed planning: evidence from a race model framework

Preparatory activity links frontal eye field activity with small amplitude motor unit recruitment of neck muscles during gaze planning

Task context determines whether common or separate inhibitory signals underlie the control of eye-hand movements

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