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At least 199 records · Page 11Linked to original sources
PubMed1994

Haptic perception of partial-rod lengths with the rod held stationary or wielded.

Three experiments on the haptic perception of partial-rod lengths are reported. The rods were gripped between the two ends and held horizontal. The subjects held the rods stationary; the distribution of mass of the segment in front of the hand was fixed, while the distribution of mass of the segment behind the hand was varied. Perceived forward length was found to be significantly affected by the distribution of mass of the backward segment. Similar results were obtained when the rods were wielded. The results indicated that partial-rod lengths are specified by functions of mechanical perturbations acting on the hand, and not by the breaking up of the first moment of mass or the moment of inertia of the rod by attention as suggested previously by others. The results are also discussed with respect to invariant detection and attention.

Adult↗
PubMedDate not supplied

Weight and weight concerns: are they associated with reported depressive symptoms in adolescents?

INTRODUCTION: The primary purpose of this study was to examine the incidence of obesity, perception of weight, and weight management behaviors in a nationwide sample of adolescents. Further, the relationship between these variables and the adolescents' self-reported depressive symptoms was also explored. METHOD: Cross-sectional data from 16- to 18-year-olds who participated in the 1999 (n=9795) and 2001 (n=8190) Youth Risk Behavioral Surveillance System were used for this secondary analysis. RESULTS: No relationship was found between depressive symptoms and body mass index. However, perception of weight as either underweight or overweight was related to higher depressive symptoms. The risk profile for reporting depressive symptoms includes use of any weight control strategies, female, and perception of weight. DISCUSSION: These findings underscore the importance of addressing adolescents' perceptions of weight in relation to their actual body mass index and psychological well-being.

Adolescent↗
PubMed1977

Effect of weight and sex on perception of line length.

56 obese and 103 normal-weight college students were asked to make line-length estimations of lines on either a light or dark background. Analysis of the results showed significant interactions between weight and contrast and sex and contrast, with the line estimations by women and normal weight individuals being more dependent on the contrast.

Body Weight↗
PubMed2002

[Perception of changes in body weight during pregnancy].

UNLABELLED: ELSPAC (European Longitudinal Study of Pregnancy and Childhood) includes in Czech Republic the set of pregnant women who have their permanent address in Brno and Znojmo district with the term of the delivery between March 1991 and June 1992. OBJECTIVE: Wide and repeated anamnestic and clinical investigations of parents and children making possible prospective analyses pregnancy and development of child. DESIGN: Prospective study. SETTING: Research Institute of Child Health, Brno. METHODS: In the set of 7911 women, the relationship between subjective perception of weight and pregnancy in the first and second trimester was investigated. The data were obtained from two questionnaires filled by pregnant woman and obstetricians. RESULTS: In the whole set, 12% of women are concerned with their weight intensively and perception of their weight is rather negative. 5.8% of women show negative relationship to pregnancy at the beginning, in the second trimester it is only the small fragment of all women. The reason for the negative perception of the weight is influenced by somatic, psychic and social aspects. The most important issue is emotional stability. The most common increase in weight was between 8-15 kg, in average 11.34 kg. The increase in weight in pregnancy is, among other reason, mediated by nutrition, smoking and job. CONCLUSION: Physical and psychical changes occur during the pregnancy. One of very evident changes is also increase in weight. The ability to accept this chance depends especially on emotional stability, food, smoking and job of pregnant women.

Attitude↗
PubMed2004

Estimation of lifted weight and produced effort through perception of point-light display.

It has been shown that human observers can estimate the weight of a box from the observation of a point-light display of a lifting motion. We asked observers to report the weight of the box and the effort produced by five lifters ranging in size and strength to determine if observers can perceive lifter size. In experiment 1, five or six weights from each of five lifters were shown to fourteen observers in a random order. Observers showed less error in estimating the amount of effort each lifter produced than in estimating the actual weight of the box. In experiment 2, the lifters were presented individually to forty observers to remove any effect observing a previous lift might have had on estimating the subsequent lift by a different lifter. The results showed an improvement in estimated weight but not in estimated effort. In experiment 3, the actual size of the lifters was given to thirty-four observers, and the estimations of both weight and effort improved. In experiment 4, observers did not improve when observing practice trials and estimating either only weight or only effort. The results from the four experiments suggest that observers are more sensitive to lifter's effort than to the weight lifted, and that observers tend to use changes in the velocity profile of the lift when making their estimates.

Adult↗
PubMed2004

Inferring false beliefs from the actions of oneself and others: an fMRI study.

The ability to make judgments about mental states is critical to social interactions. Simulation theory suggests that the observer covertly mimics the activity of the observed person, leading to shared states of mind between the observer and the person observed. We tested this hypothesis by investigating the neural networks activated while subjects watched videos of themselves and of others lifting a box, and judged the beliefs of the actors about the weight of the box. A parietal premotor circuit was recruited during action perception, and the activity started earlier when making judgments about one's own actions as opposed to those of others. This earlier activity in action-related structures can be explained by simulation theory on the basis that when one observes one's own actions, there is a closer match between the simulated and perceived action than there is when one observes the actions of others. When the observers judged the actions to reflect a false belief, there was activation in the superior temporal sulcus, orbitofrontal, paracingulate cortex and cerebellum. We suggest that this reflects a mismatch between the perceived action and the predicted action's outcomes derived from simulation.

Brain Mapping↗
PubMed2002

Predictors of maternal control over children's eating behaviour.

The aim of the study was to investigate the determinants of the level of control mothers exert over the food intake and eating behaviour of their young children. Questionnaires assessing maternal perception of child's weight status, control over food intake, body dissatisfaction and dietary restraint were completed by 89 mothers of 5-8-year-old children (40 boys, 49 girls). It was found that there was little difference between the control of boys' and girls' eating, but that the pattern of correlations was different. In particular, mothers' dietary restraint predicted the degree of monitoring of daughters', but not sons', eating behaviour, even when actual and perceived weight of the child were taken into account. It was concluded that the degree of control over child-feeding might provide a behavioural mechanism for the inter-generational transmission of eating attitudes and beliefs within families.

Adult↗
PubMed1994

Formation and lateralization of internal representations underlying motor commands during precision grip.

The capability to store and retrieve weight-related information from a lift to scale the force output during a subsequent lift was examined in 10 healthy adults and 50 children (age 2-10 years), as well as a 22-year-old patient with corpus callosum agenesis. Subjects lifted a test object between the thumb and index finger while the isometric fingertip forces were measured. The results suggest that both healthy children and adults can transfer weight-related information between the right and left hand, although a lateralization was found. Also, the storage and retrieval of weight-related information appears to be a dynamic process dependent on both previous sensory information and knowledge of future movements. Late maturation of interhemispheric connections and asymmetric loss of some information during the transfer between hemispheres suggest a lateralization of the internal representation. The patient with a corpus callosum agenesis supported this hypothesis.

Adolescent↗
PubMed2006

Physiological and psychophysical responses in handling maximum acceptable weights under different footwear--floor friction conditions.

A study on combined manual materials-handling tasks performed on floors under three friction levels was conducted. Eight male subjects participated in the study. The maximum acceptable weight of handling, including lifting, carrying for 3m, lowering, and walking 3m back at twice per minute was determined. The subject then performed the same tasks for 10 min. Heart rate, Vo2, energy efficiency, perceived sense of slip, and rating of perceived exertion for whole body strain were measured. The results showed that the effects of friction level on the maximum acceptable weights of handling, perceived sense of slip, Vo2, and energy efficiency were statistically significant (p<or=0.0006). As the friction level increased from low to high, the maximum acceptable weights of handling increased from 8.15 to 9.34 kg. The energy efficiency on the low friction condition (12.58 kg/L/min) was significantly lower than those of the medium (15.73 kg/L/min) and high (15.38 kg/L/min) friction conditions. The perceived sense of slip was the highest (5.44) on the low-friction condition, followed by the medium-friction condition (3.58), and last the high-friction condition (1.84). The implication of this study was that friction level should be regarded as one of the major environmental factors in designing MMH tasks as it affected both physiological and psychophysical responses of the subjects. Low-friction footwear-floor interface should be avoided as it resulted in not only high scores of perceived sense of slip but also in low-energy efficiency utilized in the body.

Adult↗
PubMed2004

Deficits of anticipatory grip force control after damage to peripheral and central sensorimotor systems.

Healthy subjects adjust their grip force economically to the weight of a hand-held object. In addition, inertial loads, which arise from arm movements with the grasped object, are anticipated by parallel grip force modulations. Internal forward models have been proposed to predict the consequences of voluntary movements. Anesthesia of the fingers impairs grip force economy but the feedforward character of the grip force/load coupling is preserved. To further analyze the role of sensory input for internal forward models and to characterize the consequences of central nervous system damage for anticipatory grip force control, we measured grip force behavior in neurological patients. We tested a group of stroke patients with varying degrees of impaired fine motor control and sensory loss, a single patient with complete and permanent differentation from all tactile and proprioceptive input, and a group of patients with amyotrophic lateral sclerosis (ALS) that exclusively impairs the motor system without affecting sensory modalities. Increased grip forces were a common finding in all patients. Sensory deficits were a strong but not the only predictor of impaired grip force economy. The feedforward mode of grip force control was typically preserved in the stroke patients despite their central sensory deficits, but was severely disturbed in the patient with peripheral sensory deafferentation and in a minority of stroke patients. Moderate deficits of feedforward control were also obvious in ALS patients. Thus, the function of the internal forward model and the precision of grip force production may depend on a complex anatomical and functional network of sensory and motor structures and their interaction in time and space.

Afferent Pathways↗
PubMed2005

Force level independent representations of predictive grip force-load force coupling: a PET activation study.

The existence of forward internal models is a fundamental principle in theories of predictive motor control. There are indications that internal models are represented in the cerebellum. So far, no conclusive data exist on automated procedures involving predictive motor behavior. In particular, it is unknown whether single or multiple task-specific internal models handle the broad range of behavioral situations in which they occur. Using H2(15)O PET in eight subjects, we examined predictive motor control in an automated grip force-load force coupling task at three differing load force levels. In the experimental condition, subjects pulled a grasped object against an isometric resistance while simultaneously producing anticipatory grip forces. There were three control conditions (pull force isolated; grip force isolated; motor rest). A 2 x 2 factorial design was chosen to reveal the interaction effect of grip force-pull force coupling. The factors were pull force (with/without) and grip force (with/without). Grip and load forces were well matched between experimental and control conditions. Conjunction inference and interaction analyses identified force coupling related activity in the ipsilateral posterior cerebellum that was independent of force levels. Interaction effects were also identified in the anterior cingulate and frontal association regions, the right caudate nucleus, and the left lingual gyrus. These data demonstrate the existence of modular representations for predictive force coupling, with the ipsilateral cerebellum playing a major role. Moreover, the data implicate that the representations for predictive force control are applicable to a range of different environmental affordances.

Brain↗
PubMed2006

Dexterity in cerebellar agenesis.

Given the well established role of the cerebellum in motor control, deficient motor performance during life time appears to be common in cerebellar agenesis. However, behavioural data on motor performance in living subjects with cerebellar agenesis are scarce. Dexterity during object manipulation was comparatively investigated in a 63-year old female with cerebellar agenesis and three healthy age- and gender-matched control subjects. Participants performed a transport task with an instrumented object and caught a weight that was dropped into a hand-held receptacle either expectedly from the opposite hand or unexpectedly from the experimenter's hand. Compared to healthy subjects, the subject with cerebellar agenesis generated greater grasping forces. For the transport task the patient showed a clear impairment of the predictive adjustment of grasping forces to the differential loading requirements of movement direction. For the weight-catching task, the patient established an accurate reactive mode of control when the weight was dropped unexpectedly. In case the weight was dropped expectedly from the opposite hand, predictive control mechanisms were severely disturbed in the subject with cerebellar agenesis. These data highlight the role of the cerebellum for predictive force control and are interpreted within the concept of internal models reflecting the causal relationship between actions and their consequences.

Aged↗
PubMed2001

Underestimation of object mass in lifting does not increase the load on the low back.

Sudden, unexpected loading on the low back is associated with a high incidence of low back pain. Experiments in which sudden loading was applied during standing revealed increased compression forces on the spine and increased trunk angle, which may cause injury to the spine and hence explain this association. During a more dynamic daily activity, i.e. lifting, this could not be demonstrated, which may be due to experimental constraints. We therefore reinvestigated the loading of the low back when subjects were lifting an unexpectedly heavy object. Ten males lifted boxes, weighing 1.6 or 6.6 kg, at a self-selected lifting velocity. In some trials the mass of these boxes was unexpectedly increased by 10 kg. The ground reaction forces, body movements and trunk muscle activity were measured and from these, the L5/S1 torques and compression forces were estimated. Underestimation of the mass did not lead to an increase in low back loading. This finding was independent of the mass the subjects were expecting to lift. In conclusion, no evidence was found to support inference regarding causality of the association between sudden loading and low back pain during whole body lifting movements.

Adult↗
PubMed1994

Role of the inertia tensor in haptically perceiving where an object is grasped.

When an object is held and wielded, a time-invariant quantity of the wielding dynamics is the inertia tensor Iij. Examination of Iij as a function of different locations at which a cylindrical object is grasped revealed that the off-diagonal components of Iij--the products of inertia--related most systematically to grip position. In 3 experiments, Ss wielded an occluded rod held at an intermediate point along its length and reproduced, with the other hand, the felt grip position on a visible rod. In Experiment 1, the wielded rods were homogeneous; in Experiments 2 and 3, weights were added on either side of the grasp, with different manners of grasp contrasted in Experiment 3. In all 3 experiments, perceived hand position was predicted by Iij. Discussion was focused on the role of Iij's eigenvalues in perceiving the magnitudes of objects and Iij's eigenvectors in perceiving hand-object relations (e.g., position of grasp).

Adult↗