Memory representations underlying motor commands used during manipulation of common and novel objects

1993 ◽  
Vol 69 (6) ◽  
pp. 1789-1796 ◽  
Author(s):  
A. M. Gordon ◽  
G. Westling ◽  
K. J. Cole ◽  
R. S. Johansson
Keyword(s):  
Isometric Force ◽  
Sensory Information ◽  
Target Object ◽  
Force Output ◽  
Visual Identification ◽  
Force Increase ◽  
Novel Objects ◽  
Memory Representations ◽  
Different Shapes ◽  
Lift Off

1. While subjects lifted a variety of commonly handled objects of different shapes, weights, and densities, the isometric vertical lifting force opposing the object's weight was recorded from an analog weight scale, which was instrumented with high-stiffness strain gauge transducers. 2. The force output was scaled differently for the various objects from the first lift, before sensory information related to the object's weight was available. The force output was successfully specified from information in memory related to the weight of common objects, because only small changes in the force-rate profiles occurred across 10 consecutive lifts. This information was retrieved during a process related to visual identification of the target object. 3. The amount of practice necessary to appropriately scale the vertical lifting and grip (pinch) force was also studied when novel objects (equipped with force transducers at the grip surfaces) of different densities were encountered. The mass of a test object that subjects had not seen previously was adjusted to either 300 or 1,000 g by inserting an appropriate mass in the object's base without altering its appearance. This resulted in either a density that was in the range of most common objects (1.2 kg/l) or a density that was unusually high (4.0 kg/l). 4. Low vertical-lifting and grip-force rates were used initially with the high-density object, as if a lighter object had been expected. However, within the first few trials, the duration of the loading phase (period of isometric force increase before lift-off) was reduced by nearly 50% and the employed force-rate profiles were targeted for the weight of the object.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Spinal Cord Modular Organization and Rhythm Generation: An NMDA Iontophoretic Study in the Frog

1998 ◽  
Vol 80 (5) ◽  
pp. 2323-2339 ◽  
Author(s):  
Philippe Saltiel ◽  
Matthew C. Tresch ◽  
Emilio Bizzi
Keyword(s):  
Spinal Cord ◽  
Isometric Force ◽  
Pattern Generation ◽  
The Body ◽  
Lumbar Spinal Cord ◽  
Modular Organization ◽  
Rhythmic Pattern ◽  
Rhythm Generation ◽  
Force Output ◽  
Electrical Microstimulation

Saltiel, Philippe, Matthew C. Tresch, and Emilio Bizzi. Spinal cord modular organization and rhythm generation: a NMDA iontophoretic study in the frog. J. Neurophysiol. 80: 2323–2339, 1998. Previous work using electrical microstimulation has suggested the existence of modules subserving limb posture in the spinal cord. In this study, the question of modular organization was reinvestigated with the more selective method of chemical microstimulation. N-methyl-d-aspartate (NMDA) iontophoresis was applied to 229 sites of the lumbar spinal cord gray while monitoring the isometric force output of the ipsilateral hindlimb at the ankle. A force response was elicited from 69 sites. At 18 of these sites, tonic forces were generated and rhythmic forces at 44. In the case of tonic forces, their directions clustered along four orientations: lateral extension, rostral flexion, adduction, and caudal extension. For the entire set of forces (tonic and rhythmic), the same clusters of orientations were found with the addition of a cluster directed as a flexion toward the body. This distribution of force orientations was quite comparable to that obtained with electrical stimulation at the same sites. The map of tonic responses revealed a topographic organization; each type of force orientation was elicited from sites that grouped together in zones at distinct rostrocaudal and depth locations. In the case of rhythmic sequences of force orientations, some were distinctly more common, whereas others were rarely elicited by NMDA. Mapping of the most common rhythms showed that each was elicited from two or three regions of the cord. These regions were close in location to the tonic regions that produced those forces that represented components specific to that rhythm. There was an additional caudal region from which the different rhythms also could be elicited. Taken together, these results support the concept of a modular organization of the motor system in the frog's spinal cord and delineate the topography of these modules. They also suggest that these modules are used by the circuitry underlying rhythmic pattern generation by the spinal cord.

scholarly journals Goal-directed and stimulus-driven selection of internal representations

2020 ◽  
Vol 117 (39) ◽  
pp. 24590-24598
Author(s):  
Freek van Ede ◽  
Alexander G. Board ◽  
Anna C. Nobre
Keyword(s):  
Working Memory ◽  
Feature Matching ◽  
Memory Performance ◽  
Sensory Information ◽  
Internal Representations ◽  
Memory Representations ◽  
External Stimuli ◽  
Selection Of ◽  
Do So

Adaptive behavior relies on the selection of relevant sensory information from both the external environment and internal memory representations. In understanding external selection, a classic distinction is made between voluntary (goal-directed) and involuntary (stimulus-driven) guidance of attention. We have developed a task—the anti-retrocue task—to separate and examine voluntary and involuntary guidance of attention to internal representations in visual working memory. We show that both voluntary and involuntary factors influence memory performance but do so in distinct ways. Moreover, by tracking gaze biases linked to attentional focusing in memory, we provide direct evidence for an involuntary “retro-capture” effect whereby external stimuli involuntarily trigger the selection of feature-matching internal representations. We show that stimulus-driven and goal-directed influences compete for selection in memory, and that the balance of this competition—as reflected in oculomotor signatures of internal attention—predicts the quality of ensuing memory-guided behavior. Thus, goal-directed and stimulus-driven factors together determine the fate not only of perception, but also of internal representations in working memory.

Mechanical and metabolic alterations in rat diaphragm during electrical stimulation

1989 ◽  
Vol 67 (1) ◽  
pp. 210-220 ◽  
Author(s):  
P. S. Massarelli ◽  
H. J. Green ◽  
R. L. Hughson ◽  
M. T. Sharratt
Keyword(s):  
Duty Cycle ◽  
Adenine Nucleotide ◽  
Isometric Force ◽  
Low Frequency ◽  
Maximal Velocity ◽  
Force Output ◽  
Experimental Conditions ◽  
Adult Rats ◽  
Male Adult ◽  
Fatigue Development

To investigate the hypothesis that the rate of fatigue development is not influenced by the absolute duration of contraction (train duration) and relaxation (off-phase of duty cycle) at constant duty cycle, strips of the diaphragm from 36 male adult rats (mean +/- SD wt 152 +/- 21 g) were stimulated directly for periods of 180, 250, and 320 ms at a constant duty cycle of 50%. The frequency of stimulation was adjusted to produce 40% of maximal tetanic tension at supramaximal voltages. After 30 min of stimulation, analysis of twitch characteristics between control and experimental groups indicated a prolongation of contraction time of 9% (P less than 0.05), an increase in relaxation time of 75% (P less than 0.05), and a decrease in twitch tension by 78% (P less than 0.05). Similarly, reductions (P less than 0.05) in isometric force output at high stimulation frequency (100 Hz) of 58% and at low frequency (20 Hz) of 67% were also noted. These changes were accompanied by an approximately 60% reduction in the maximal velocity of shortening. No difference was observed for any of the mechanical measures between experimental conditions. After 30-min stimulation, decreases of between 43 and 46% were noted for ATP (P less than 0.05) and increases of between three- and fourfold noted for IMP (P less than 0.05). No changes were found for either ADP or AMP. Total adenine nucleotide concentrations declined (P less than 0.05) an average of 24%. As with the mechanical data, no differences were found between the different stimulation conditions. It is concluded that for the conditions studied, fatigue mechanisms become manifest early in the stimulation period and are only minimally altered by the duration of specific contractions provided the relaxation period is of equal duration.

Contrasting properties of monkey somatosensory and motor cortex neurons activated during the control of force in precision grip

1991 ◽  
Vol 65 (3) ◽  
pp. 572-589 ◽  
Author(s):  
T. M. Wannier ◽  
M. A. Maier ◽  
M. C. Hepp-Reymond
Keyword(s):  
Firing Rate ◽  
Neuronal Activity ◽  
Isometric Force ◽  
Precision Grip ◽  
Cell Activity ◽  
Emg Activity ◽  
Firing Patterns ◽  
Neuronal Populations ◽  
Force Increase ◽  
Discharge Patterns

1. Single cell activity was investigated in the precentral motor (MI) and postcentral somatosensory (SI) cortex of the monkey to compare the neuronal activity related to the control of isometric force in the precision grip and to assess the participation of SI in motor control. 2. Three monkeys (Macaca fascicularis) were trained in a visual step-tracking paradigm to generate and precisely maintain force on a transducer held between thumb and index finger. Great care was taken to have the monkeys use only their fingers without moving the wrist or proximal joints. In two monkeys electromyographic (EMG) activity was checked in 23 muscles over several sessions. 3. Five similar classes of task-related firing patterns were found in both SI and MI cortical hand and finger representations, but their relative proportions differed. The majority of the SI neurons were phasically or phasic-tonically active (61%), whereas in MI the neurons that decreased their firing rate with force were most frequent (42%). 4. The timing of activity changes related to the onset of force increase from low to higher levels strongly differed in the two neuronal populations. In SI, only 14% of the task-related neurons increased or decreased their firing rate before the onset of force increase, in contrast to 56% in MI. Only 3% of the SI neurons showed changes before the earliest EMG activation. 5. In both SI and MI neurons with tonic and phasic-tonic, increasing or decreasing discharge patterns disclosed a relationship between neuronal activity and static force. Distinction was made between neurons modulating their activity in a monotonic way and those that were active only at one force level and had a kind of recruitment or deactivation threshold. The latter ones were more frequent in MI than in SI, and in the neuron population with decreasing firing patterns. For the neurons with increases in activity, statistically significant linear correlations between firing rate and force were found more frequently in MI than in SI, where the proportion of nonsignificant correlations was relatively high (35% vs. 15% in MI). In SI the indexes of force sensitivity, calculated from the slopes of the regression lines, covered a wider range than in MI; and their distribution was bimodal, with one mean of 30 Hz/N and the other of 155 Hz/N. In contrast, the mean rate-force slope in MI was 69 Hz/N.(ABSTRACT TRUNCATED AT 400 WORDS)

The length dependency of maximum force development in rat medial gastrocnemius muscle in situ

2008 ◽  
Vol 33 (3) ◽  
pp. 518-526 ◽  
Author(s):  
Cornelis J. de Ruiter ◽  
Tinelies E. Busé-Pot ◽  
Arnold de Haan
Keyword(s):  
Muscle Activation ◽  
Isometric Force ◽  
Force Production ◽  
Time History ◽  
Medial Gastrocnemius ◽  
Force Output ◽  
Force Development ◽  
Activation Times ◽  
Maximal Isometric Force

During many movements (e.g., running, jumping, and kicking) there is little time for skeletal muscles to build up force, thus rapid force development is important. The length dependency of isometric force development was investigated in maximally activated rat medial gastrocnemius muscles in situ with intact blood flow at 35 °C. Depending on time available for muscle activation, the length dependency of force development was expected to differ from that of the maximal isometric force (Fmax) reached much later during the contraction. During isometric force development in intact muscle–tendon preparations, the contractile elements actually shortened. Therefore, similar to previous findings on shortening contractions, it was hypothesized that maximal rate of force development (MRFD) would be obtained at a length below the optimum (Lo) for maximal isometric force production. To measure the effect of the entire time history of activation, force time integrals (FTIs) for different activation times (10–50 ms) were also calculated. The highest MRFD was obtained 1.94 ± 0.42 mm below (p < 0.05) Lo. When expressed relative to Fmax obtained at each individual length, the optimum was found at Lo – 4.4 mm. For FTI 10 ms and FTI 20 ms, optimum length was obtained at ~2 and 1 mm above (p < 0.05) Lo, respectively, whereas the optima for FTI 30, 40, and 50 ms were ~1 mm below (p < 0.05) Lo. In addition, at short lengths (< Lo – 4 mm) and for all activation times FTIs were relatively more decreased than Fmax. In conclusion, length dependency of force output during rapid force development differed from that of maximal isometric force; specifically, MRFD was obtained 2 mm below Lo.

Modeling constraints to redundancy in bimanual force coordination

2011 ◽  
Vol 105 (5) ◽  
pp. 2169-2180 ◽  
Author(s):  
Xiaogang Hu ◽  
Karl M. Newell
Keyword(s):  
Muscle Force ◽  
Coupling Effect ◽  
Isometric Force ◽  
Force Production ◽  
Force Output ◽  
Task Constraints ◽  
Task Goal ◽  
Force Coordination ◽  
Finger Forces ◽  
Coordination Patterns

This study investigated the interactive influence of organismic, environmental, and task constraints on the organization of redundant force coordination patterns and the hypothesis that each of the three categories of constraints is weighted based on their relative influence on coordination patterns and the realization of the task goal. In the bimanual isometric force experiment, the task constraint was manipulated via different coefficients imposed on the finger forces such that the weighted sum of the finger forces matched the target force. We examined three models of task constraints based on the criteria of task variance (minimum variance model) and efficiency of muscle force output (coefficient-independent and coefficient-dependent efficiency models). The environmental constraint was quantified by the perceived performance error, and the organismic constraint was quantified by the bilateral coupling effect (i.e., symmetric force production) between hands. The satisficing approach was used in the models to quantify the constraint weightings that reflect the interactive influence of different categories of constraints on force coordination. The findings showed that the coefficient-dependent efficiency model best predicted the redundant force coordination patterns across trials. However, the within-trial variability structure revealed that there was not a consistent coordination strategy in the online control of the individual trial. The experimental findings and model tests show that the force coordination patterns are adapted based on the principle of minimizing muscle force output that is coefficient dependent rather than on the principle of minimizing signal-dependent variance. Overall, the results support the proposition that redundant force coordination patterns are organized by the interactive influence of different categories of constraints.

scholarly journals Aging, Visual Intermittency, and Variability in Isometric Force Output

2006 ◽  
Vol 61 (2) ◽  
pp. P117-P124 ◽  
Author(s):  
J. J. Sosnoff ◽  
K. M. Newell
Keyword(s):  
Isometric Force ◽  
Force Output

Mathematical Model for Yarn Unwinding Part ΙΙ: Conic Packages

2011 ◽  
Vol 403-408 ◽  
pp. 5136-5141
Author(s):  
Stanislav Praček ◽  
Franci Sluga ◽  
Klemen Možina
Keyword(s):  
Mathematical Modeling ◽  
Mathematical Model ◽  
Angular Velocity ◽  
Effective Radius ◽  
Apex Angle ◽  
Average Radius ◽  
Different Shapes ◽  
Lift Off ◽  
Winding Angle

Mathematical modeling can be used to simulate the unwinding of yarn from packages of different shapes. This method can be applied to design packages that can sustain high unwinding velocities at low and steady tension in the yarn. In the case of conic packages the angular velocity of unwinding depends not only on the winding angle as is the case for cylindric packages, but also on the apex angle. We will show that the dimensionless angular velocity depends very little on the apex angle. The apex angle, however, also determines the effective radius of the package at the lift-off point, therefore the angular velocity can be proportionally higher. We will compare unwinding from a cylindrical and a conic package with equal smallest radius and show that unwinding from the conic package is faster due to higher average radius of the package at the lift-off point.

scholarly journals Categorical judgments do not modify sensory information in working memory

2020 ◽  
Author(s):  
Long Luu ◽  
Alan A. Stocker
Keyword(s):  
Working Memory ◽  
Model Comparison ◽  
Human Subjects ◽  
Sensory Information ◽  
Memory Recall ◽  
Stimulus Feature ◽  
Inference Process ◽  
Categorical Judgment ◽  
Memory Representations ◽  
Stimulus Features

AbstractCategorical judgments can systematically bias the perceptual interpretation of stimulus features. However, it remained unclear whether categorical judgments directly modify working memory representations or, alternatively, generate these biases via an inference process down-stream from working memory. To address this question we ran two novel psychophysical experiments in which human subjects had to revert their categorical judgments about a stimulus feature, if incorrect based on feedback, before providing an estimate of the feature. If categorical judgments indeed directly altered sensory representations in working memory, subjects’ estimates should reflect some aspects of their initial (incorrect) categorical judgment in those trials.We found no traces of the initial categorical judgment. Rather, subjects seem to be able to flexibly switch their categorical judgment if needed and use the correct corresponding categorical prior to properly perform feature inference. A cross-validated model comparison also revealed that feedback may lead to selective memory recall such that only memory samples that are consistent with the categorical judgment are accepted for the inference process. Our results suggest that categorical judgments do not modify sensory information in working memory but rather act as top-down expectation in the subsequent sensory recall and inference process down-stream from working memory.

scholarly journals Different theta frameworks coexist in the rat hippocampus and are coordinated during memory-guided and novelty tasks

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Víctor J López-Madrona ◽  
Elena Pérez-Montoyo ◽  
Efrén Álvarez-Salvado ◽  
David Moratal ◽  
Oscar Herreras ◽  
...  
Keyword(s):  
Sensory Information ◽  
Gamma Oscillations ◽  
Theta Activity ◽  
Coherent Oscillation ◽  
Phase Coupling ◽  
Internal Memory ◽  
Complex Interactions ◽  
Theta Frequency ◽  
Memory Representations ◽  
Hippocampal Theta

Hippocampal firing is organized in theta sequences controlled by internal memory processes and by external sensory cues, but how these computations are coordinated is not fully understood. Although theta activity is commonly studied as a unique coherent oscillation, it is the result of complex interactions between different rhythm generators. Here, by separating hippocampal theta activity in three different current generators, we found epochs with variable theta frequency and phase coupling, suggesting flexible interactions between theta generators. We found that epochs of highly synchronized theta rhythmicity preferentially occurred during behavioral tasks requiring coordination between internal memory representations and incoming sensory information. In addition, we found that gamma oscillations were associated with specific theta generators and the strength of theta-gamma coupling predicted the synchronization between theta generators. We propose a mechanism for segregating or integrating hippocampal computations based on the flexible coordination of different theta frameworks to accommodate the cognitive needs.

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