Cortical and reticular contributions to human precision and power grip

Tazoe, Toshiki; Pérez, Mónica A.

doi:10.1113/jp273679

Cited by 51 publications

(46 citation statements)

References 42 publications

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“…other tasks. GABAergic-mediated cortical mechanisms play a role in modulating responses in the S1 during paired-pulse SSEP suppression (Höffken et al, 2010;Stude et al, 2016). Then, another possibility is that intracortical circuits within the S1 con-tributed to the pronounced sensory gating during power grip.…”

Section: Mechanisms Of Sensory Gating During Graspingmentioning

confidence: 99%

Gating of Sensory Input at Subcortical and Cortical Levels during Grasping in Humans

2018

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Afferent input from the periphery to the cortex contributes to the control of grasping. How sensory input is gated along the ascending sensory pathway and its functional role during gross and fine grasping in humans remain largely unknown. To address this question, we assessed somatosensory-evoked potential components reflecting activation at subcortical and cortical levels and psychophysical tests at rest, during index finger abduction, precision, and power grip. We found that sensory gating at subcortical level and in the primary somatosensory cortex (S1), as well as intracortical inhibition in the S1, increased during power grip compared with the other tasks. To probe the functional relevance of gating in the S1, we examined somatosensory temporal discrimination threshold by measuring the shortest time interval to perceive a pair of electrical stimuli. Somatosensory temporal discrimination threshold increased during power grip, and higher threshold was associated with increased intracortical inhibition in the S1. These novel findings indicate that humans gate sensory input at subcortical level and in the S1 largely during gross compared with fine grasping. Inhibitory processes in the S1 may increase discrimination threshold to allow better performance during power grip. Most of our daily life actions involve grasping. Here, we demonstrate that gating of afferent input increases at subcortical level and in the primary somatosensory cortex (S1) during gross compared with fine grasping in intact humans. The precise timing of sensory information is critical for human perception and behavior. Notably, we found that the ability to perceive a pair of electrical stimuli, as measured by the somatosensory temporal discrimination threshold, increased during power grip compared with the other tasks. We propose that reduced afferent input to the S1 during gross grasping behaviors diminishes temporal discrimination of sensory processes related, at least in part, to increased inhibitory processes within the S1.

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Section: Mechanisms Of Sensory Gating During Graspingmentioning

confidence: 99%

Gating of Sensory Input at Subcortical and Cortical Levels during Grasping in Humans

2018

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“…Original research in monkeys suggested that corticospinal neurons were more active during a precision task compared to a power task [9], a finding supported by several studies that found greater MEP amplitudes during complex, precision tasks compared to simple, power tasks [4,11,34]. Alternatively, larger MEP amplitudes have been reported during conventional abduction tasks compared to power, pincer, or grasping tasks [5][6][7]. The discrepancy between our findings and previous research may be that other studies have used precision tasks that were visually guided and externally controlled, whereas our writing task is a dynamic, internally generated task that is retrieved and implemented from memory [35,36].…”

Section: Discussionmentioning

confidence: 94%

“…Measures of CSE differ between these grips. For example, FDI MEP amplitude is greater during conventional abduction tasks compared to power, pincer, or grasping tasks [5][6][7], whereas APB MEPs are greater during pincer tasks compared to during power tasks or at rest [8]. More direct measures made in the monkey reveal that corticospinal neurons are more active during a precision grip compared to a power grip, despite increased EMG activity in the latter [9].…”

Section: Introductionmentioning

confidence: 99%

The Task at Hand: Fatigue-Associated Changes in Cortical Excitability During Writing

2019

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Measures of corticospinal excitability (CSE) made via transcranial magnetic stimulation (TMS) depend on the task performed during stimulation. Our purpose was to determine whether fatigue-induced changes in CSE made during a conventional laboratory task (isometric finger abduction) reflect the changes measured during a natural motor task (writing). We assessed single-and paired-pulse motor evoked potentials (MEPs) recorded from the first dorsal interosseous (FDI) of 19 participants before and after a fatigue protocol (submaximal isometric contractions) on two randomized days. The fatigue protocol was identical on the two days, but the tasks used to assess CSE before and after fatigue differed. Specifically, MEPs were evoked during a writing task on one day and during isometric finger abduction to a low-level target that matched muscle activation during writing on the other day. There was greater variability in MEP amplitude (F (1,18) = 13.55, p < 0.01) during writing compared to abduction. When participants were divided into groups according to writing style (printers, n = 8; cursive writers, n = 8), a task x fatigue x style interaction was revealed for intracortical facilitation (F (1,14) = 9.90, p < 0.01), which increased by 28% after fatigue in printers but did not change in cursive writers nor during the abduction task. This study is the first to assess CSE during hand-writing. Our finding that fatigue-induced changes in intracortical facilitation depend on the motor task used during TMS, highlights the need to consider the task-dependent nature of CSE when applying results to movement outside of the laboratory.

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“…To date, there has only been one documented task resistant to startReact–index finger abduction. While some groups have demonstrated that individuated finger movements exhibit startReact [ 17 – 19 ], two independent groups have shown that startReact is absent during index finger abduction [ 15 , 20 ]. These authors have suggested the lack of startReact in index finger abduction is due to different neural mechanisms driving individuated finger movement and larger reaching movements using proximal joints.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, tasks that rely heavily on corticospinal projections, such as isolated index finger abduction, would not generate startReact because those movements do not rely (or rely less) on these structures. However, the neural mechanisms governing startReact are contested [ 3 – 5 , 15 , 19 , 26 – 29 ] and there is growing evidence that startling stimuli evoke a large cortical response [ 17 , 30 – 32 ]. Furthermore, grasping movements of the hand that also use the first dorsal interosseous (FDI) muscle readily evoke startReact and arguably would utilize the same (or similar) neural structures [ 33 ].…”

Section: Introductionmentioning

confidence: 99%

Evidence for startle as a measurable behavioral indicator of motor learning

et al. 2018

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The ability of the classic startle reflex to evoke voluntarily prepared movement involuntarily has captured the attention of neuroscientists for its wide-ranging functional utility and potential uses in patient populations. To date, there is only one documented task resistant to the startReact phenomenon–index finger abduction. Previous reports have suggested the lack of startReact is due to different neural mechanisms driving individuated finger movement and more proximal joint control (e.g. elbow, wrist movement). However, an alternative hypothesis exists. Though not particularly difficult to execute, isolated index finger abduction is rarely performed during activities of daily living and is not a natural correlate to common individuated finger tasks. We propose that startReact can be evoked during individuated finger movements but only during tasks that are highly trained or familiar. The objective of this study was to determine the impact of a 2-week training regimen on the ability to elicit startReact. We found evidence in support of our hypothesis that following training, individuated movements of the hands (specifically index finger abduction) become susceptible to startReact. This is significant not only because it indicates that individuated finger movements are in fact amenable to startReact, but also that startle has differential response characteristics in novel tasks compared to highly trained tasks suggesting that startle is a measurable behavioral indicator of motor learning.

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Cortical and reticular contributions to human precision and power grip

Cited by 51 publications

References 42 publications

Gating of Sensory Input at Subcortical and Cortical Levels during Grasping in Humans

Gating of Sensory Input at Subcortical and Cortical Levels during Grasping in Humans

The Task at Hand: Fatigue-Associated Changes in Cortical Excitability During Writing

Evidence for startle as a measurable behavioral indicator of motor learning

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