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Biomedical subjects

J I Todor

Publications and source records attributed to J I Todor.

11 recordsLinked to original sources
PubMed1991

The role of attention in the regulation of associated movement in children.

The effect of attentional processes in regulating associated movement was studied in 10 male children in each of five age-groups from six to 16 years. They were asked to squeeze their index finger and thumb to 75 per cent of their own maximal volitional force under three conditions: a spontaneous baseline condition, a sensory feedback condition and a post-training condition without sensory feedback. Children of all ages were able to reduce the magnitude of associated movements during the sensory feedback condition. In the post-training condition some of the ability to inhibit was lost, particularly for the six-year-olds. This supports the view that the integration of higher order processes, such as attention, with lower-level neuromotor inhibitory mechanism, plays a role in the reduction of associated movement with increasing age. Implications for therapy with clinical populations are discussed.

Adolescent↗
PubMed1987

Age differences in the magnitude of associated movement.

Using a quantitative measure of unintended mirror-movements in the contralateral limb during a unimanual task, the magnitude of associated movement across the ages from six to 16 years was determined. Male children in five age-groups (means 6.5, 8.5, 10.4, 12.4 and 16.5 years) were asked to squeeze their index finger and thumb together to various percentages of their own maximal volitional force. Results indicate that the 6.5-year-old group differ from all other age-groups, exhibiting significantly greater associated movements at all levels of force. The results are discussed in terms of the development of inhibitory control over innate neuromotor synergies.

Adolescent↗
PubMed1986

Exertion level and the intensity of associated movements.

Associated movements in the contralateral limbs were measured quantitatively for 42 seven- to eight-year-old children who wrote with the right hand. Associated movements of the contralateral homologous muscles systematically increased as a function of the intensity of contraction of the active hand. The associated movements were more intense when the left hand was active. The order of hand use markedly affected the lateral asymmetry, indicating that the right and left hands were affected differentially by previous activity. Associated movements of the contralateral antagonist muscles were also observed, and their frequency varied as a function of active hand and exertion level.

Child↗
PubMed1985

Accommodation to increased accuracy demands by the right and left hands.

This study was designed to identify the phase of rapid aimed movements responsible for hand differences in motor skill, and to evaluate potential differences between the hands in accommodating to greater accuracy demands. In both experiments, an accelerometer mounted on a stylus allowed key changes in acceleration to be used to partition the movement into phases. In Experiment 1, slower left hand movement times were attributable primarily to a terminal homing-in phase, especially as target size decreased. Since error rates varied as a function of hand and target size, speed-accuracy trade-offs may have occurred. Experiment 2 rigidly controlled error rate and confirmed the major hand difference to occur in the latter phase of the movement where error correction is presumed. Although less pronounced, adjustments were made in the earlier movement phases as well. Accommodation to greater accuracy demands involved moving the stylus closer to the target before decelerating to engage in error correction. This adjustment to gain enhanced precision was more pronounced in the left hand.

Journal Article↗
PubMed1982

Lateral asymmetries in arm, wrist and finger movements.

On the assumption of contralateral control, lateral asymmetries in motor performance are often associated with the functional specialization of the cerebral hemispheres. However, anatomical as well as previous behavioral studies, indicate this assumption may not be valid for all joints of the limbs. To test this assumption, right-handed male subjects performed a rapid tapping task using movements of the index finger, the wrist, or the shoulder. The hand used and order of conditions were counterbalanced across subjects. The rate and variability data were submitted to a 2 x 3 (hand x joint) Analysis of Variance with repeated measures on both factors. For both rate and variability significant (all p less than .01) main effects were evident for hand and joint with no significant interactions. It is argued that the variability of tapping reflects the processing mode of the contralateral hemisphere and thus leads to the conclusion that crossed pathways are the principal mechanism for controlling rapid movements of all limb joints. It is tentatively concluded that where either crossed or ipsilateral pathways are available, the type of movement control required will dictate which pathway is used.

Adolescent↗
PubMed1980

Hand differences in the rate and variability of rapid tapping.

Hand differences in the rate and variability of rapid tapping were evaluated for the intertap interval and its constituents-the key depression and key release phases of each tap. To accentuate potential hand differences, only subjects with a clear manual superiority in one hand were included. Relative manual proficiency on Fitts' reciprocal tapping task was used to exclude individuals with less-defined hand superiority or dominance, and to categorize subjects as having a dominant left (n=13) or right (n=11) hand. Analysis of variance indicated the dominant hand to have a shorter average intertap interval and thus a faster tapping rate. This hand difference in rate was found to be significant for the key-depression phase, but not the key-release.phase, of the tap. In each handedness group the dominant hand exhibited less variability in the intertap interval and both constituents. Potential associations of these findings with hemispheric asymmetries in sequential ability are discussed.

Journal Article↗
PubMed1978

Handedness and hemispheric asymmetry in the control of movements.

This study investigated the influence of hemispheric specialization of function on the motor performance of the hands. Right-handed (n=7), ambidextral (n=21), and ambisinistral (n=12) subjects performed Fitts' (1954) reciprocal tapping task under two conditions with each hand. Conditions had the same index of difficulty but differed in movement precision. The left hand of right-handers was superior in the condition requiring the greatest amount of preprogramming. Conversely, the right hand was not superior in the condition having the greatest demand for feedback control. For ambidextrals, left-hand superiority in the relatively preprogrammed condition was also revealed. Ambisinistrals showed no significant difference between conditions with either hand. The results partially support the hypothesis that the motor performance of the hands mirrors the dominant processing mode of their contralateral hemisphere. Failure to find supportive evidence in ambisinistrals is consistent with the contention that they lack hemispheric specialization of function.

Journal Article↗
PubMed1977

Handedness classification: preference versus proficiency.

Relative hand preferences as indicated by questionnaire were compared with asymmetries in manual proficiency at three levels of task difficulty (N equal to 63 adults). Correlations between odd/even trial relative hand proficiency scores were .887 and .879 attesting to their stability. Test-retest (6-wk. interval) reliabilities for relative hand proficiency ranged from .831 to .893. Spearman rbos between the questionnaire responses and relative hand proficiency were .733, .689, and .619. These relatively low relationships, especially at the highest level of task difficulty (r2 = 38%), indicate that hand preference does not reflect relative hand proficiency at moderate to high levels of task difficulty.

Female↗
PubMed1975

Age differences in integration of components of a motor task.

To study effects of practice on the ability of 6-, 11-, and 18-yr.-old Ss to integrate the components of the Rho task 3 groups of 50 boys performed 30 consecutive trials. (a) With practice all age groups improved in total movement time; (b) 11-yr.-old Ss attained the 18-yr.-olds' level of performance in both components, initial differences existing only the linear component; (c) relative to the 18-yr.-old Ss, the 6-yr.-olds achieved proportionally less improvement in the linear component; (d) unlike 11- and 18-yr.-old Ss, the 6-yr.-olds evidenced increasing specificity of task components across trials. Unlike the two older age groups, the 6-yr.-old Ss were unable to achieve a high degree of integration of task components. The findings were discussed in light of Pascual-Leone's neo-Piagetian model of learning and development.

Adolescent↗