scholarly journals The cost of correcting for error during sensorimotor adaptation

2021 ◽  
Author(s):  
Ehsan Sedaghat-Nejad ◽  
Reza Shadmehr

AbstractLearning from error is often a slow process. To accelerate learning, previous motor adaptation studies have focused on explicit factors such as reward or punishment, but the results have been inconsistent. Here, we considered the idea that a movement error carries an implicit cost for the organism because the act of correcting for error consumes time and energy. If this implicit cost could be modulated, it may robustly alter how the brain learns from error. To vary the cost of error, we considered a simple saccade adaptation task but combined it with motion discrimination: movement errors resulted in corrective saccades, but those corrections took time away from acquiring information in the discrimination task. We then modulated error cost using coherence of the discrimination task and found that when error cost was large, pupil diameter increased, and the brain learned more from error. However, when error cost was small, the pupil constricted, and the brain learned less from the same error. Thus, during sensorimotor adaptation, the act of correcting for error carried an implicit cost for the brain. Modulating this cost affects how the brain learns from error.

2021 ◽  
Author(s):  
Ehsan Sedaghat-Nejad ◽  
Reza Shadmehr

Abstract Learning from error is often a slow process. To accelerate learning, previous motor adaptation studies have focused on explicit factors such as reward or punishment, but the results have been inconsistent. Here, we considered the idea that a movement error carries an implicit cost for the organism because the act of correcting for error consumes time and energy. If this implicit cost could be modulated, it may robustly alter how the brain learns from error. To vary the cost of error, we considered a simple saccade adaptation task but combined it with motion discrimination: movement errors resulted in corrective saccades, but those corrections took time away from acquiring information in the discrimination task. We then modulated error cost using coherence of the discrimination task and found that when error cost was large, pupil diameter increased, and the brain learned more from error. However, when error cost was small, the pupil constricted, and the brain learned less from the same error. Thus, during sensorimotor adaptation, the act of correcting for error carried an implicit cost for the brain. Modulating this cost affects how the brain learns from error.


2021 ◽  
Vol 118 (40) ◽  
pp. e2101717118
Author(s):  
Ehsan Sedaghat-Nejad ◽  
Reza Shadmehr

Learning from error is often a slow process. In machine learning, the learning rate depends on a loss function that specifies a cost for error. Here, we hypothesized that during motor learning, error carries an implicit cost for the brain because the act of correcting for error consumes time and energy. Thus, if this implicit cost could be increased, it may robustly alter how the brain learns from error. To vary the implicit cost of error, we designed a task that combined saccade adaptation with motion discrimination: movement errors resulted in corrective saccades, but those corrections took time away from acquiring information in the discrimination task. We then modulated error cost using coherence of the discrimination task and found that when error cost was large, pupil diameter increased and the brain learned more from error. However, when error cost was small, the pupil constricted and the brain learned less from the same error. Thus, during sensorimotor adaptation, the act of correcting for error carries an implicit cost for the brain. Modulating this cost affects how much the brain learns from error.


PEDIATRICS ◽  
1982 ◽  
Vol 70 (6) ◽  
pp. 857-857
Author(s):  
T. E. C.

On November 10, 1880, Dr. Henry H. Smith of Philadelphia read a paper before the Philadelphia County Medical Society in which he condemned the use of the baby carriage as follows: The advocates of the use of baby-carriages contend that they are beneficial by keeping an infant longer in the fresh air than can be done when it is carried by a nurse, who soon becomes fatigued. This is certainly not true in many instances, as a woman who is not strong enough to carry an infant, even if it weighs twenty-five pounds, is physically unfitted for her duty as a nurse. Such an objection is very apt to be raised by the nurses themselves, and should be regarded with suspicion by the mother. Often it is evidence of laziness or a fondness for flirtation or talking, as may be noted at any time in our parks or squares, and especially in Rittenhouse Square, where many nurses of wealthy children can be daily seen amusing themselves by the hour, totally regardless of the infant, who may be likewise seen with its head hanging out over the side of the carriage, so as to compress the veins of the neck and induce a certain degree of congestion of the brain, if it is not found in some equally-improper and injurious attitude likely to result in curvature or caries of the spine, the origin or exciting cause of which it is subsequently difficult to recognize. Another evil liable to ensue from the constant use of the baby-carriage is the jarring and concussion of the delicate brain and spinal cord of the infant, created by bouncing the carriage over gutters or up and down the curbstones of our sidewalks.... The baby-carriage mania has now reached that point in Philadelphia that an infant and a coach appear to be inseparable, and, though the cost of a baby-carriage is quite an item in the expenses of the nursery, "few there are so poor as not to do it reverence." Of course, it is admitted that there may be instances where the use of a baby-carriage occasionally by a child able to walk a little, or where the carriage permits a poor, tired mother to obtain for herself a little relaxation whilst keeping her baby in its carriage in the Park, or in the case of feeble children or those recuperating from an attack of illness, is advantageous: but, as a general rule, the anatomical and physiological facts just alluded to may be deemed as sufficient to induce physicians to give attention to the abuse of a custom that is by no means the result of necessity in the case of infants or those under twelve months of age.


1993 ◽  
Vol 70 (5) ◽  
pp. 1741-1758 ◽  
Author(s):  
F. R. Robinson ◽  
A. Straube ◽  
A. F. Fuchs

1. We studied the effect of temporarily inhibiting neurons in the caudal fastigial nucleus in two rhesus macaques trained to make saccades to jumping targets. We placed injections of the gamma-aminobutyric acid (GABA) agonist muscimol unilaterally or bilaterally at sites in the caudal fastigial nucleus where we had recorded saccade-related neurons a few minutes earlier. 2. Unilateral injections (n = 9) made horizontal saccades to the injected side hypermetric and those to the other side hypometric (mean gain of 1.37 and 0.61, respectively, for 10 degrees target steps, and 1.26 and 0.81 for 20 degrees target steps; normal saccade gain was 0.96). Saccades to vertical targets showed a small but significant hypermetria and curved strongly toward the side of the injection. The trajectories and end points of all targeted saccades were more variable than normal. 3. After unilateral injections, centripetal saccades were slightly larger than centrifugal saccades (mean gains for ipsilateral saccades were 1.42 and 1.31, respectively, for 10 degrees target steps, and 1.37 and 1.15 for 20 degrees target steps). 4. Unilateral injections increased the average acceleration of ipsilateral saccades and decreased the acceleration of contralateral saccades. Injections decreased both the acceleration and deceleration of vertical saccades. 5. After dysmetric saccades, monkeys acquired the target with an abnormally high number of hypometric corrective saccades. Injection increased the average number of corrective saccades from 0.6 to 2.1 after 10 degrees horizontal target steps and from 0.8 to 2.1 after 20 degrees steps. The size of each successive corrective saccade in a series decreased, and the latency from the previous corrective saccade increased. 6. Bilateral injections (n = 2) of muscimol, in which we injected first into the left caudal fastigial nucleus and then, within 30 min, into the right, made all saccades hypermetric (mean gain for 10 degrees right, left, up, and down saccades was 1.18, 1.49, 1.43, and 1.10, respectively). Paradoxically, bilateral injection decreased both saccade acceleration and deceleration. Saccade trajectories and end points were more variable than normal. 7. To account for the effects of our injections, we propose that the activity of caudal fastigial neurons on one side normally helps to decelerate ipsilateral saccades and helps to accelerate contralateral saccades by influencing the feedback loop of the saccade burst generator in the brain stem. Without caudal fastigial activity the brain stem burst generator produces hypermetric, variable saccades. We therefore also propose that the influence of caudal fastigial neurons on the burst generator makes saccades more consistent and accurate.(ABSTRACT TRUNCATED AT 400 WORDS)


Author(s):  
Anne-Claire Kopp ◽  
Robert H. Sturges

Abstract Recent concern for the environment has caused growing attention to recycling, both using recycled materials to make products and recycling products after use. Although environmentalists may be eager to buy recycled/recyclable products, other consumers may not be so easily convinced. It may also be difficult to convince manufacturers that it is beneficial to develop green products. This paper supports a joint project between engineering and marketing disciplines to determine the cost and value of an environmentally designed product. Specifically, this paper evaluates the resources spent to manufacture a green videocassette in comparison with a standard videocassette by performing a resource analysis. This analysis estimates the cost, time and energy necessary to produce both videocassettes. This paper also compares the value of the videocassettes in terms of performance and physical attributes.


Author(s):  
Robin I.M. Dunbar

The brain consumes about 20 per cent of the total energy intake in human adults. Primates, and especially humans, have unusually large brains for body size compared with other vertebrates, and fuelling these is a significant drain on both time and energy. Larger-brained primates generally eat fruit-intense diets, but human brains are so large that a reduction in gut size is needed to free up sufficient resources to allow a larger brain to be evolved, placing further pressure on foraging. The early invention of cooking increased nutrient absorption by around 30 per cent over raw food. Increasing digestibility in this way perhaps inevitably leads to risk of obesity when food is super-abundant, as it is in post-industrial societies. However, obesity has clearly been around for a long time, as suggested by the late Palaeolithic Venus figures of Europe, so it is not a novel problem.


2003 ◽  
Vol 90 (6) ◽  
pp. 4016-4021 ◽  
Author(s):  
Thrishantha Nanayakkara ◽  
Reza Shadmehr

The delays in sensorimotor pathways pose a formidable challenge to the implementation of stable error feedback control, and yet the intact brain has little trouble maintaining limb stability. How is this achieved? One idea is that feedback control depends not only on delayed proprioceptive feedback but also on internal models of limb dynamics. In theory, an internal model allows the brain to predict limb position. Earlier we had found that during reaching, the brain estimates hand position in real-time in a coordinate system that can be used for generating saccades. Here we tested the idea that the estimate of hand position, as expressed through saccades, depends on an internal model that adapts to dynamics of the arm. We focused on the behavior of the eyes as perturbations were applied to the unseen hand. We found that when the hand was perturbed from stable posture with a 100-ms force pulse of random direction and magnitude, a saccade was generated on average at 182 ms postpulse onset to a position that was an unbiased estimate of real-time hand position. To test whether planning of saccades depended on an internal model of arm dynamics, arm dynamics were altered either predictably or unpredictably during the postpulse period. When arm dynamics were predictable, saccade amplitudes changed to reflect the change in the arm's behavior. We suggest that proprioceptive feedback from the arm is integrated into an adaptable internal model that computes an estimate of current hand position in eye-centered coordinates.


2019 ◽  
Vol 122 (1) ◽  
pp. 378-388 ◽  
Author(s):  
F. Javier Domínguez-Zamora ◽  
Daniel S. Marigold

Frequent gait modifications are often required to navigate our world. These can involve long or wide steps or changes in direction. People generally prefer to minimize the motor cost (or effort) of a movement, although with changes in gait this is not always possible. The decision of when and where to shift gaze is critical for controlling motor actions, since vision informs the brain about the available choices for movement—in this case, where to step. Here we asked how motor cost influences the allocation of gaze. To address this, we had participants walk and step to the center of sequential targets on the ground. We manipulated the motor cost associated with controlling foot placement by varying the location of one target in the lateral direction on a trial-to-trial basis within environments with different numbers of targets. Costlier steps caused a switch from a gaze strategy of planning future steps to one favoring visual feedback of the current foot placement when participants had to negotiate another target immediately after. Specifically, costlier steps delayed gaze shifts away from the manipulated target. We show that this relates to the cost of moving the leg and redirecting the body’s center of mass from target to target. Overall, our results suggest that temporal gaze decisions are affected by motor costs associated with step-to-step demands of the environment. Moreover, they provide insight into what affects the coordination between the eyes and feet for the control of stable and accurate foot placement while walking. NEW & NOTEWORTHY Changes in gait allow us to navigate our world. For instance, one may step long or wide to avoid a spilled drink. The brain can direct gaze to gather relevant information for making these types of motor decisions; however, the factors affecting gaze allocation in natural behaviors are poorly understood. We show how the motor cost associated with a step influences the decision of when to redirect gaze to ensure accurate foot placement while walking.


2008 ◽  
Vol 99 (1) ◽  
pp. 220-230 ◽  
Author(s):  
Yoshiko Kojima ◽  
Yoshiki Iwamoto ◽  
Farrel R. Robinson ◽  
Christopher T. Noto ◽  
Kaoru Yoshida

Cerebellar output changes during motor learning. How these changes cause alterations of motoneuron activity and movement remains an unresolved question for voluntary movements. To answer this question, we examined premotor neurons for saccadic eye movement. Previous studies indicate that cells in the fastigial oculomotor region (FOR) within the cerebellar nuclei on one side exhibit a gradual increase in their saccade-related discharge as the amplitude of ipsiversive saccades adaptively decreases. This change in FOR activity could cause the adaptive change in saccade amplitude because neurons in the FOR project directly to the brain stem region containing premotor burst neurons (BNs). To test this possibility, we recorded the activity of saccade-related burst neurons in the area that houses premotor inhibitory burst neurons (IBNs) and examined their discharge during amplitude-reducing adaptation elicited by intrasaccadic target steps. We specifically analyzed their activity for off-direction (contraversive) saccades, in which the IBN activity would increase to reduce saccade size. Before adaptation, 29 of 42 BNs examined discharged, at least occasionally, for contraversive saccades. As the amplitude of contraversive saccades decreased adaptively, half of BNs with off-direction spike activity showed an increase in the number of spikes (14/29) or an earlier occurrence of spikes (7/14). BNs that were silent during off-direction saccades before adaptation remained silent after adaptation. These results indicate that the changes in the off-direction activity of BNs are closely related to adaptive changes in saccade size and are appropriate to cause these changes.


2002 ◽  
Vol 34 (4) ◽  
pp. 433-461 ◽  
Author(s):  
PAUL SILLITOE

What is the cost of living in the Papua New Guinea highlands? An answer is sought using a time and energy accounting approach. The subsistence regime of Wola-speaking highlanders, the subjects of this investigation, comprises three components. The principal one is horticulture: people clearing gardens from forest and grassland, with tuberous crops predominating, notably sweet potato. The second component comprises animal rearing, notably of domestic pigs. The third, and least important, is hunting and gathering for food in the forest. The calculated returns on investments in these subsistence domains vary considerably. Gardens return in their crops between ten and fifteen times the energy expended in cultivation. Pigs may also give a good return, of four to five times the energy invested in rearing them, if slaughtered when adult, but people regularly keep animals for years and may incur negative energy returns on their labour investments. This relates to the high cultural premium put on pigs. Foraging for food is also energetically costly, the Wola expending four times more energy on these activities than they gain in return from the food they secure. This analysis of energy gains and losses challenges the relative notion of affluence as applied to foragers, by reviewing it in the comparative context of subsistence horticulture.


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