scholarly journals Frequency-Dependent Effects on Coordination and Prefrontal Hemodynamics During Finger Force Production Tasks

2021 ◽  
Vol 15 ◽  
Author(s):  
Dayuan Xu ◽  
Narae Shin ◽  
Sungjun Lee ◽  
Jaebum Park
Keyword(s):  
Time Series ◽  
Prefrontal Cortex ◽  
Functional Connectivity ◽  
High Frequency ◽  
Neuronal Response ◽  
Statistical Parametric Mapping ◽  
Force Production ◽  
Uncontrolled Manifold ◽  
Finger Force ◽  
Finger Forces

Behavioral stability partially depends on the variability of net outcomes by means of the co-varied adjustment of individual elements such as multi-finger forces. The properties of cyclic actions affect stability and variability of the performance as well as the activation of the prefrontal cortex that is an origin of subcortical structure for the coordinative actions. Little research has been done on the issue of the relationship between stability and neuronal response. The purpose of the study was to investigate the changes in the neural response, particularly at the prefrontal cortex, to the frequencies of isometric cyclic finger force production. The main experimental task was to produce finger forces while matching the produced force to sine-wave templates as accurately as possible. Also, the hemodynamics responses of the prefrontal cortex, including oxy-hemoglobin concentration (ΔHbO) and the functional connectivity, were measured using functional near-infrared spectroscopy. The frequency conditions comprised 0.1, 1, and 2 Hz. The uncontrolled manifold (UCM) approach was applied to compute synergy indices in time-series. The relative phase (RP), the coefficient of variation (CV) of the peak and trough force values were computed as the indices of performance accuracy. The statistical parametric mapping (SPM) was implemented to compare the synergy indices of three frequency conditions in time-series. A less accurate performance in the high-frequency condition was caused not by the RP, but mainly by the inconsistent peak force values (CV; p < 0.01, ηp2 = 0.90). The SPM analysis revealed that the synergy indices were larger in the low-frequency than in high-frequency conditions. Further, the ΔHbO remained unchanged under all frequency conditions, while the functional connectivity decreased with an increase in the frequency of cyclic force production. The current results suggested that the concurrent activation of the prefrontal region mainly depends on the frequency of cyclic force production, which was associated with the strength of stability indices and performance errors. The current study is the first work to uncover the effect of frequency on the multi-finger synergies as to the hemodynamic response in the prefrontal cortex, which possibly provides a clue of the neural mechanism of synergy formation and its changes.

scholarly journals Mechanisms of transcranial magnetic stimulation in the treatment of anorexia nervosa

BJPsych Open ◽  
2021 ◽  
Vol 7 (S1) ◽  
pp. S49-S50
Author(s):  
Lydia Shackshaft
Keyword(s):  
Anorexia Nervosa ◽  
Prefrontal Cortex ◽  
Functional Connectivity ◽  
Resting State ◽  
High Frequency ◽  
Magnetic Stimulation ◽  
Dorsolateral Prefrontal Cortex ◽  
Resting State Functional Connectivity ◽  
Dorsolateral Prefrontal ◽  
Neurophysiological Mechanisms

AimsSevere and Enduring Anorexia Nervosa (SE-AN) is a challenging condition to treat, with limited therapeutic options, high morbidity, and the highest mortality rates of any psychiatric illness. Repetitive Transcranial Magnetic Stimulation (rTMS) is an emerging treatment option, as evidence demonstrates promising efficacy in improving mood and reducing core Anorexia Nervosa symptoms, as well as safety and tolerability to patients. We aimed to investigate the neurophysiological mechanisms of rTMS use in SE-AN patients by assessing changes in resting state functional connectivity, in the first functional neuroimaging analysis investigating rTMS effects in Anorexia Nervosa patients.Method26 females with a current diagnosis of SE-AN received 20 sessions of sham or real high frequency rTMS (10 hertz) to the left dorsolateral prefrontal cortex in a randomised double-blind trial. Resting-state functional magnetic resonance imaging was performed before and after rTMS. Neural correlates of rTMS treatment were identified using a seed-based functional connectivity analysis with the left dorsolateral prefrontal cortex and bilateral amygdalae as regions of interest. Functional connectivity differences were analysed using t-contrasts in a mixed ANOVA (flexible factorial analysis) to assess interactions between treatment group (real rTMS vs sham) and time-point (pre or post TMS).ResultNo statistically significant changes in resting-state functional connectivity were observed post-rTMS compared to baseline in participants receiving active rTMS compared to sham. Increased functional connectivity between the left amygdala and left pre-supplementary motor area was observed to reach cluster-wise significance (PFWE < 0.05). However, after Bonferroni correction for multiple comparisons (3 seed regions), this did not reach the significance threshold PFWE <0.017.ConclusionThis study highlights the need for further investigation of neurophysiological mechanisms, including resting-state functional connectivity modulation, resulting from rTMS to the dorsolateral prefrontal cortex in SE-AN patients. This requires higher powered studies to account for heterogeneity in treatment response. We have provided some indication that high frequency rTMS may have therapeutic benefit in SE-AN by modification of functional connectivity between prefrontal and limbic brain regions, resulting in improved top-down cognitive control over emotional processing and ability to enact goal-directed behaviours, enabling secondary reductions in eating disorder behaviours.

scholarly journals Equifinality and its violations in a redundant system: multifinger accurate force production

2013 ◽  
Vol 110 (8) ◽  
pp. 1965-1973 ◽  
Author(s):  
Luke Wilhelm ◽  
Vladimir M. Zatsiorsky ◽  
Mark L. Latash
Keyword(s):  
Force Production ◽  
Uncontrolled Manifold ◽  
Total Force ◽  
Redundant System ◽  
Uncontrolled Manifold Hypothesis ◽  
Final State ◽  
Performance Variables ◽  
Force Mode ◽  
Finger Forces ◽  
The Individual

We explored a hypothesis that transient perturbations applied to a redundant system result in equifinality in the space of task-related performance variables but not in the space of elemental variables. The subjects pressed with four fingers and produced an accurate constant total force level. The “inverse piano” device was used to lift and lower one of the fingers smoothly. The subjects were instructed “not to intervene voluntarily” with possible force changes. Analysis was performed in spaces of finger forces and finger modes (hypothetical neural commands to fingers) as elemental variables. Lifting a finger led to an increase in its force and a decrease in the forces of the other three fingers; the total force increased. Lowering the finger back led to a drop in the force of the perturbed finger. At the final state, the sum of the variances of finger forces/modes computed across repetitive trials was significantly higher than the variance of the total force/mode. Most variance of the individual finger force/mode changes between the preperturbation and postperturbation states was compatible with constant total force. We conclude that a transient perturbation applied to a redundant system leads to relatively small variance in the task-related performance variable (equifinality), whereas in the space of elemental variables much more variance occurs that does not lead to total force changes. We interpret the results within a general theoretical scheme that incorporates the ideas of hierarchically organized control, control with referent configurations, synergic control, and the uncontrolled manifold hypothesis.

Interaction between Finger Force and Neural Command in Multi-Finger Force Production

2006 ◽  
Vol 326-328 ◽  
pp. 751-754
Author(s):  
Yoon Hyuk Kim
Keyword(s):  
Mathematical Model ◽  
Force Production ◽  
Voluntary Contraction ◽  
Finger Force ◽  
Healthy Male ◽  
Hand Biomechanics ◽  
Single Finger ◽  
Finger Forces ◽  
The Relationship ◽  
Male Subjects

In this study, we investigated the relationship between the finger force and the neural command in multi-finger force production tasks in order to characterize the neural enslaving effect and the force-deficit effect among fingers. Seven healthy male subjects were instructed to press one, two, three and four fingers on the finger sensors as hard as possible acting in parallel in all possible combinations. Then, the finger forces in each task were recorded and analyzed to represent the neural enslaving effect and the force-deficit effect. The results confirmed that individual finger forces were smaller in multi-finger maximal voluntary contraction tasks than in single-finger tasks. The force deficit effect increased with the number of fingers involved. A mathematical model proposed in this paper based on the experimental results could explicitly describe the two effects of finger interaction by representing the relationship between the neural commands and finger forces. The present results could be useful information to understand the basic neuro-muscular mechanism in hand biomechanics and the fundamentals of intelligent hand robots.

scholarly journals Age-related changes in the control of finger force vectors

2010 ◽  
Vol 109 (6) ◽  
pp. 1827-1841 ◽  
Author(s):  
Shweta Kapur ◽  
Vladimir M. Zatsiorsky ◽  
Mark L. Latash
Keyword(s):  
Neural Control ◽  
Healthy Aging ◽  
Force Production ◽  
Uncontrolled Manifold ◽  
Total Force ◽  
Finger Force ◽  
Healthy Elderly ◽  
Age Related ◽  
Young Subjects ◽  
Force Vectors

We explored changes in finger interaction in the process of healthy aging as a window into neural control strategies of natural movements. In particular, we quantified the amount of force produced by noninstructed fingers in different directions, the amount of force produced by the instructed finger orthogonally to the task direction, and the strength of multifinger synergies stabilizing the total force magnitude and direction during accurate force production. Healthy elderly participants performed accurate isometric force production tasks in five directions by individual fingers and by all four fingers acting together. Their data were compared with a dataset obtained in a similar earlier study of young subjects. Finger force vectors were measured using six-component force/torque sensors. Multifinger synergies were quantified using the framework of the uncontrolled manifold hypothesis. The elderly participants produced lower force magnitudes by noninstructed fingers and higher force magnitudes by instructed fingers in nontask directions. They showed strong synergies stabilizing the magnitude and direction of the total force vector. However, the synergy indexes were significantly lower than those observed in the earlier study of young subjects. The results are consistent with an earlier hypothesis of preferential weakening of intrinsic hand muscles with age. We interpret the findings as a shift in motor control from synergic to element-based, which may be causally linked to the documented progressive neuronal death at different levels of the neural axis.

scholarly journals Preliminary findings of finger independency and visual force control in children with DCD

2015 ◽  
Vol 9 (2) ◽  
Author(s):  
Marcio Alves de Oliveira
Keyword(s):  
Force Control ◽  
Degrees Of Freedom ◽  
Motor Task ◽  
Force Production ◽  
Typically Developing ◽  
Finger Force ◽  
Force Sharing ◽  
Finger Forces ◽  
Sharing Patterns ◽  
Maximum Voluntary Force

<p>Finger independency and visual force control were studied in children with DCD. Five children, 9 to10 years of age, diagnosed with DCD and five age-matched typically developing children were asked to perform two isometric tasks, maximum voluntary force production (MVF) and visual force control (VFC), in seven different finger conditions [Index (I), Middle (M), Ring (R), Little (L) IM, IMR, and IMRL]. For the VFC tasks, the participants were asked to continuously control their finger forces at 20% of the MVF. To examine finger force independency, maximum voluntary force (MVF), force enslaving (FE) and force sharing (FS) values were computed. To analyze the ability of children with DCD to visually control their finger forces, the following performance measures were calculated: rate of force change, initial overshoot, coefficient of variation (CV), root mean square error (RMSe), and inter-trial variability. The results from the MVF task showed that children with DCD as compared with TD children (a) produced similar levels of maximum finger force; (b) demonstrated less finger independency; (c) had similar finger-force sharing patterns. In addition, from the VFC task we found (d) larger performance errors in children with DCD; (e) and lower inter-trial consistency as compared to their TD peers. Our preliminary findings suggest that the impairments in manipulative skills often observed in children with DCD during everyday activities may be related to deficits in finger independency. Additionally we found that children with DCD do not have difficulties in reducing the number of joint/muscle-level degrees of freedom in order to achieve a common motor task.</p>

scholarly journals Stability of hand force production. I. Hand level control variables and multifinger synergies

2017 ◽  
Vol 118 (6) ◽  
pp. 3152-3164 ◽  
Author(s):  
Sasha Reschechtko ◽  
Mark L. Latash
Keyword(s):  
Visual Feedback ◽  
Neural Control ◽  
Control Variable ◽  
Force Production ◽  
Uncontrolled Manifold ◽  
Total Force ◽  
Level Control ◽  
Control Variables ◽  
Finger Forces ◽  
Hand Action

We combined the theory of neural control of movement with referent coordinates and the uncontrolled manifold hypothesis to explore synergies stabilizing the hand action in accurate four-finger pressing tasks. In particular, we tested a hypothesis on two classes of synergies, those among the four fingers and those within a pair of control variables, stabilizing hand action under visual feedback and disappearing without visual feedback. Subjects performed four-finger total force and moment production tasks under visual feedback; the feedback was later partially or completely removed. The “inverse piano” device was used to lift and lower the fingers smoothly at the beginning and at the end of each trial. These data were used to compute pairs of hypothetical control variables. Intertrial analysis of variance within the finger force space was used to quantify multifinger synergies stabilizing both force and moment. A data permutation method was used to quantify synergies among control variables. Under visual feedback, synergies in the spaces of finger forces and hypothetical control variables were found to stabilize total force. Without visual feedback, the subjects showed a force drift to lower magnitudes and a moment drift toward pronation. This was accompanied by disappearance of the four-finger synergies and strong attenuation of the control variable synergies. The indexes of the two types of synergies correlated with each other. The findings are interpreted within the scheme with multiple levels of abundant variables. NEW & NOTEWORTHY We extended the idea of hierarchical control with referent spatial coordinates for the effectors and explored two types of synergies stabilizing multifinger force production tasks. We observed synergies among finger forces and synergies between hypothetical control variables that stabilized performance under visual feedback but failed to stabilize it after visual feedback had been removed. Indexes of two types of synergies correlated with each other. The data suggest the existence of multiple mechanisms stabilizing motor actions.

Analysis of a Network for Finger Interaction during Two-Hand Multi-Finger Force Production Tasks

2003 ◽  
Vol 19 (4) ◽  
pp. 295-309 ◽  
Author(s):  
Simon R. Goodman ◽  
Mark L. Latash ◽  
Sheng Li ◽  
Vladimir M. Zatsiorsky
Keyword(s):  
Experimental Data ◽  
Force Production ◽  
Optimization Procedure ◽  
Mirror Image ◽  
Average Error ◽  
Finger Force ◽  
Single Finger ◽  
Neurophysiological Data ◽  
Finger Forces ◽  
Different Origins

This study involved an optimization, numerical analysis of a network for two-hand multi-finger force production, analogous in its structure to the double-representation mirror image (DoReMi) network suggested earlier based on neurophysiological data on cortical finger representations. The network accounts for phenomena of enslaving (unintended finger force production), force deficit (smaller force produced by a finger in multi-finger tasks as compared to its single-finger task), and bilateral deficit (smaller forces produced in two-hand tasks as compared to one-hand tasks). Matrices of connection weights were computed, and the results of optimization were compared to the experimental data on finger forces during one- and two-hand maximal force production (MVC) tasks. The network was able to reproduce the experimental data in two-hand experiments with high accuracy (average error was 1.2 N); it was also able to reproduce findings in one-hand multi-finger MVC tasks, which were not used during the optimization procedure, although with a somewhat higher error (2.8 N). Our analysis supports the feasibility of the DoReMi network. It suggests that within-a-hand force deficit and bilateral force deficit are phenomena of different origins whose effects add up. Is also supports a hypothesis that force deficit and enslaving have different neural origins.

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