Right-hand Performance Research Articles

Asymmetry in a verbal-manual task combination: Habitual vs controlled verbal production

Interference between verbal production and left-and right-hand tapping was studied in male right-handed subjects in two experiments. The hypothesis was studied that controlled rather than automatic verbal production causes the interference with right-hand performance. Experiment 1 compared the repeated production of one verbal number response with the production of a random sequence of numbers. Experiment 2 studied one additional condition: counting from one to 20. The results showed that repetition and counting do not selectively interfere with right-hand tapping, while the randomization of numbers does. These results support the controlled-processing hypothesis of interference with right-hand performance.

HEMISPATIAL NEGLECT IN A PATIENT WITH CALLOSAL INFARCTION

Left hemispatial neglect, confined to right-hand and verbal responses, was exhibited by a 56-yr-old right-handed male patient with callosal lesions due to cerebral infarction. Various disconnection signs were also present. His CT and MRI scans disclosed major lesions situated in the posterior half of the genu and the whole trunk of the corpus callosum, as well as in the left medial frontal and temporo-occipital lobes. Left hemispatial neglect was invariably demonstrated in right-hand performance such as copying drawings, line bisection, matching identical figures and copying multiple digit numbers, and in verbal performance such as confrontation naming and reading aloud multiple digit numbers. In contrast, little or no right hemispatial neglect was demonstrated in tasks performed with the left hand. These findings support the hypothesis that the left hemisphere is only concerned with attending to the contralateral hemispace and that the right hemisphere is specialized for attending to both sides of space although the preponderant tendency is for attending to the contralateral hemispace. The neglect symptoms observed in our patient may be a disconnection sign which was attributable to a combination of lesions in the corpus callosum and in the left medial frontal lobe.

Simple reaction time changes after anterior callosotomy

Seven patients treated with anterior callosotomy for drug-resistant atonic seizures were tested to evaluate their simple reaction times (SRTs) to lateralized flashes before surgery (time 0) and then 15 (time I) and 90–100 days (time II) after the operation. The SRTs obtained at the three checkpoints were compared by means of ANOVA for the main effects of time, hand, and visual hemifield, and for their interactions. The mean number of omissions was also analyzed. The results showed increased SRTs at the first check after surgery, with a greater increase for the left hand, followed by a decrease close to the presurgical values. No difference between crossed and uncrossed conditions were observed; no differences in the omission rate were seen at postoperative evaluations. Finally, the left-hand performance showed a trend toward longer SRTs than the right-hand performance at all observations. Our data suggest that SRTs are only transiently affected by anterior callosotomy and that the side effects of surgery are greater in the left hand.

Relation of Hand Performance and Preference in Male and Female Lefthanders to Familial Sinistrality and Writing Hand

The relations of hand performance to the degree of left-hand preference, and left- minus right-hand performance were studied in left-handed male and female subjects considering familial sinistrality and writing hand. Hand performance was assessed by a dot-filling test; hand preference was assessed by the Edinburgh Handedness Inventory. It was established that there were fundamental differences in relationships between performance and preference measures to sex, familial sinistrality, and writing hand, which also created different patterns in the relationships between hand performance and the difference in performance between hands.

A Dual-Task Study of Sex Differences in Language Reception and Production

The notion that females may be less lateralized than males for language reception was tested using a variant of the dual-task technique with 20 normal right-handed subjects. A unimanual tapping task was paired with one language reception task, and two language production tasks (one purely cognitive and the other requiring both cognitive and vocal involvement).Performance was impaired in all treatment conditions, regardless of hand used. Most impairment was, however, found in right-hand performance during the vocal condition. No sex differences were found.

Lateralised Dual-Task Performance: The Effect of Muscular-Repositioning

In two experiments subjects performed tapping tasks requiring different degree of muscular repositioning while concurrently performing a speech task. In all concurrent speech conditions right-hand performance was disrupted more than left-hand performance, but the degree of this differential disruption did not alter as a function of the muscular repositioning requirements of the dual-tasks. It was concluded that rapid muscular repositioning does not appear to be the source of lateralised interference effects observed in concurrent task studies. However, it may be argued that some minimum level of repositioning is required, particularly if the differential effect reflects a lateralisation of “kind” rather than of “degree”. This needs further research. One relevant factor proposed here which may alter the degree of lateralised effects is the degree of muscular effort required to perform each of the dual-tasks.

Differential-handed response to verbal and visual spatial stimuli: Evidence of specialized hemispheric processing following callosotomy

Left- and right-hand responses were studied in a patient who had undergone complete corpus callosotomy to examine selective hemispheric processing employing free-field stimuli. Tests of verbal and visual spatial processing were presented, and multiple choice performances were obtained using both left and right hands. A double dissociation emerged, with superior left-handed performance on visual spatial tasks, and better right-handed performance on verbal tasks. In addition, the patient displayed hemispatial dyscalculia in which he solved written arithmetic problems disregarding free-field numerical information presented toward his left. Evidence of multimodality left-sided extinction was also present. Further, despite unilateral callosal apraxia, the left hand displayed superiority during a continuous performance task. These results demonstrate that specialized functions of the cerebral hemispheres may be observed for response output in the absence of restricted hemispheric input, and that components of the neglect syndrome may be seen following corpus callosotomy.

Manual Proficiency in Cattle's Intelligence Test in Left-Handed Male and Female Subjects

The relationship between nonverbal intelligence (spatial reasoning) and manual proficiency was studied in male and female left-handers. Manual proficiency was assessed by measuring the speed and accuracy in performing the dot-filling test. Nonverbal intelligence was assessed by Cattle's Culture Fair Intelligence Test. Females were found to be better than males in left-hand performance, and were more lateralized than males in manual proficiency. No significant sex difference could be established in right-hand performance. The right-hand skill was positively correlated to test intelligence (p less than 0.001). There was a negative correlation between the left- minus right-hand skill difference and the scores for nonverbal intelligence (p less than 0.001). The left-hand skill did not show any correlation with nonverbal IQ. It was concluded that the left-hemisphere is of utmost importance even for nonverbal intelligence; strong cerebral lateralization is disadvantageous for spatial reasoning.

Interhemispheric Transfer of Spatial Tactile Information in Callosal Agenesis and Partial Commissurotomy

The De Renzi Rod Test was used to investigate the transfer of spatial tactile information between hands in acallosals and partial commissurotomy patients. The righthanded performance of young acallosals was impaired, confirming the results of an earlier study by Meerwaldt (1983). The adult acallosals, with one exception, showed no difference between right and left hand performances. Two partial callosotomy patients with sparing of the most caudal parts of the body of the callosum showed no difference between the hands. A third callosotomy patient with little, if any, sparing of the most caudal part of the body of the callosum showed a marked impairment when performing the tactile task withthe right hand. The unimpaired performances of the adult acallosals are attributed to the use of ipsilateral pathways and the development of behavioural strategies. The callosotomy patients' results are consistent with the mapping by Pandya and Seltzer (1986) of the interhemispheric callosal pathways between the cortical parietal areas in non-human primates.

Cerebral organization of verbal and motor functions in left-handed and right-handed adults: effects of concurrent verbal tasks on unimanual tapping performance.

Two experiments were conducted to study the interference effects of different concurrent verbal tasks on unimanual single-finger tapping and unimanual sequential finger tapping. Experiment 1 involved 24 right-handed university students. In the dual-task conditions, right-handers showed a greater right-hand than left-hand performance reduction for single-finger tapping, and an equal right-hand and left-hand reduction for sequential tapping. Experiment 2 involved 60 left-handed university students, divided into four groups according to familial sinistrality and writing hand posture. In the dual-task conditions, left-handers showed a greater left-hand than right-hand performance reduction for single-finger tapping, and an equal left-hand and right-hand reduction for sequential finger tapping. A dichotic listening task revealed a left hemispheric dominance for auditory linguistic functioning in most of the left-handers. Familial sinistrality and hand posture, on the whole, did not influence tapping performances. However, these factors influenced the ear asymmetries on the dichotic listening task. It is speculated that, with single-finger tapping, interference only takes place beyond the point of language motor programming, that is to say, at the motor areas and the supplementary motor areas of the cortex.

Hesitations in continuous tracking induced by a concurrent discrete task.

Subjects performed continuous, visually guided pursuit tracking with the right hand while giving simultaneous discrete left-hand responses, which were signaled by auditory tones appearing at the average rate of one tone per 30 s. This left-hand secondary task was frequently associated with tracking hesitations lasting 333 ms or longer. The rate of occurrence of these hesitations was about the same when the left-hand response involved a choice between competing responses as when the left hand responded in a previously specified direction. Hesitations occurred for three different mechanical tracking manipulanda using different controlling muscles and appeared to be due to active muscular freezing rather than to relaxation. The rate of hesitations declined with practice, and this improvement in right-hand performance was accompanied by an improvement in performance of the concurrent left-hand response.

Human neuroelectric patterns predict performance accuracy.

In seven right-handed adults, the brain electrical patterns before accurate performance differed from the patterns before inaccurate performance. Activity overlying the left frontal cortex and the motor and parietal cortices contralateral to the performing hand preceded accurate left- or right-hand performance. Additional strong activity overlying midline motor and premotor cortices preceded left-hand performance. These measurements suggest that brief, spatially distributed neural activity patterns, or "preparatory sets," in distinct cognitive, somesthetic-motor, and integrative motor areas of the human brain may be essential precursors of accurate visuomotor performance.

Lateral brain resources and motor performance.

Speaking interferes with concurrent motor activity, the degree and direction of the interference being related to handedness. Dextrals have a decrement for right-hand performance, while sinisuals have left-hand performance decrements ( 2 ) . This is consistent with a limited resources model of brain function having verbal and spatial abilities localized in leftand right-brain, respectively, in dextrals, and the converse in lefthanders. The model predicts that concommitant tasks requiring similar (same hemisphere) resources compere and produce poorer dual-task performance ( 1 ). The present study was designed to test the model further and evaluated the effect of both verbal and spatial secondary tasks on motor performance. Twenty male subjects aged 18 to 21 yt., classified as strong dextrals o n a handedness questionnaire ( I ) , performed a hand-steadiness task under three task conditions, concurrently with a spatial task, concurrently with a verbal task, and a control condition having no secondary task. Subjects held a standard stylus for 3-min. periods inside a 9-mm. annulus fitted to the center of a rear-projection screen. Secondary task stimuli consisted of 35 common adjectives (verbal task) or 35 monochrome photographs of faces (spatial task) projected individually for 5 sec. duracion and centered above the annulus. Following each block of 35 trials having a secondary task, subjects were asked to identify the 35 faces from a matrix of 50 faces or identify 35 antonyms of the adjectives from a list of 50 words. Verbal and spatial secondary tasks were pretested for equal difficulty. Half of the subjects used the right hand and half the left for the steadiness task; and task condition order was counterbalanced. Mean errors on the secondary tasks in the four-hand/task conditions were almost identical: left/verbal = 21.4, left/spatial = 20.3, right/verbal = 19.4, and right/spatial = 20.1, indicating that secondary task difficulty was not influenced by response hand. Contact time, in sec., for the six hand/task conditions were: left/no task = 4.14 (SD = 2.28), left/verbal = 7.74 ( S D = 3.19). left/spatial = 11.01 ( S D = 6:15) , right/no task = 3.95 (SD = 2.77), right/verbal = 5.91 ( S D = 3.87), and r ~ g h t / spatial = 6.91 ( S D = 4.80). A repeated-measures analysis of variance produced significant effects for task (F2.30 = 23.85, p < .001) and for the response hand/cask interaction (F2 .m = 3.76, p = .032), but not for response hand. Both secondary tasks produced steadiness decrements in each response hand; left/verbal (to = 7.61), left/ spatial (to = 4.32), right/verbal (to = 3.55), and righdspatial ( t ~ = 3.59). The spatial task produced a larger deficit than the verbal task for right-hand performance ( to = 2.30), left-hand performance did not differ significantly between secondary task conditions. Both secondary tasks produced a performance decrement in both hands indicating that the steadiness task may be more sensitive to secondary task loading than the dowel balancing, critical instabiliry task reported elsewhere ( 1 ) . The larger decrement for left-hand performance with the spatial compared to the verbal secondary task is consistent with a lateralized, limited resources model of brain function. Right-hand performance did not support the model. This may be attributed to the absence of a motor component in the word recall versus a speaking secondary task (1). The steadiness task may draw upon both cognitive and manual motor resources in right brain but only motor resources in the left. Further study, using a more direct measure of brain activity, is needed to clarify this issue.

Some observations on the Poggendorff and Müller-Lyer tactual illusions.

Two experiments were conducted in which illusory and nonillusory figures were presented in the right and left tactual fields. Experiment 1 used 24 men (aged 18–24 years) and the Poggendorff (P) illusion and an alignment (Al) task; Experiment 2 used another 24 men and the Müller-Lyer (ML) illusion and a line-match (Lm) task. Standard and mirror-image presentations of the figure were used in each case. Nested designs of analysis of variance and analysis of covariance were adopted for comparing left- and right-hand performance under each experimental condition. Covariance analysis on distortion scores of P and ML was performed separately with discrepancy measures on Al and Lm tasks as covariates. An investigation was also made into whether the direction of tactually perceived distortions was the same as or opposite to that reported for the visual illusions. The results show large P and ML tactual distortions. For ML, the tactual effects found were similar to those predictable from visual illusions, whereas for P, a high value of inversion emerged. Differences between hands were significant for P under the standard presentation, exploration with the right hand inducing a higher value of inversion. The latter results are discussed with reference to differences between the functions of human hemispheres which some authors have suggested for perceptual distortions.

Sex differences in dual-task interference between speaking and a manual force-production task.

12 male and 12 female right-handed adults performed a unimanual force-production task alone and while sound-shadowing high frequency words. The secondary speech task disrupted right-hand performance by men and left-hand performance by women. The implications of these findings for intrahemisphere-interference models of dual-task performance are discussed.

The effect of visual guidance and hemispace on lateralized vocal-manual interference

When right-handers speak while performing manually, their right-hand performance declines disproportionately to their left. The present study shows that this: (i) is true for a sequentially homogeneous activity—repetitive single finger tapping; (ii) does not depend on the hemispace location of the performing hand; (iii) is not abolished by viewing the performing hand; and (iv) is not an artifact of trade-off with rate of concurrent speech production. These findings contradict some suggested models for such effects.

Performance difference between hands in children on the motor accuracy test-revised.

This study was designed to determine the developmental trends in the difference between right-hand and left-hand skill development in children ages 4 to 9 as measured by the Motor Accuracy Test-Revised (MAC-R). There were 120 right handers (60 males, 60 females), with 20 subjects at each age interval, and 68 left handers (36 males, 32 females), with no less than 8 and no more than 20 subjects at each age interval. Performance was analyzed by sex, age, and handedness for the difference scores between the two hands, and the preferred and nonpreferred hand adjusted scores. The difference scores were obtained by subtracting the nonpreferred hand scores from the preferred hand scores. Results showed the mean difference between hands for all children to be 6.7 points with a standard deviation of 4.8. This data suggests that a normative range of difference between right-hand and left-hand skill performance on the MAC-R may be from 2 to 11 points. Left-handed children performed very similarly to right-handed children, supporting the use of right-handed norms for left-handed subjects. No significant differences in sex or handedness were found in the adjusted or difference scores. Comparison of the means and standard deviations of MAC-R normative data with these data showed no consistent significant differences.

Visuospatial performance in left-handed patients with unilateral brain lesions

A test of visuospatial judgment was given to left-handed patients with lesions of either the right or left hemisphere. In right-handed patients impaired performance on the test has been found to be almost exclusively associated with right hemisphere disease, the performance of patients with left hemisphere disease being comparable to that of controls. The left-handed patients in this study showed the same performance pattern: a high proportion of patients with right hemisphere lesions performed defectively while all the patients with left hemisphere lesions performed on a normal level. Thus the findings are in accord with the conclusion that hemispheric cerebral organisation with respect to the mediation of visuospatial performance do not differ in right-handers and left-handers.

Speech lateralization assessed by concurrent task performance

A sequential button pressing task using either the left or the right hand while concurrently performing a speech task was investigated. Subjects with left-hemisphere speech representation, determined by a dichotic monitoring task showed a lateralized practice effect: left-hand performance improved with practice during the speech task, but right-hand performance did not. Subjects with right-hemisphere speech representation showed disruption of either hand with concurrent speech, and no lateralized practice effect. The results from this study suggest the mechanisms mediating speech perception and speech production may not always be concordantly lateralized. A discriminant analysis of the data showed that 93% of subjects could be correctly classified according to side of representation of speech perception given the performance measures on the concurrent tasks.

Sex differences in dichaptic processing.

The failure to control for variables known to relate to cerebral asymmetries accounts, in part, for inconsistencies in research reporting sex differences in tactuospatial processing. In the present study, a dichaptic task procedure which attempted to minimize response bias was given to 20 males and 20 females at Grades 1, 6, and undergraduate while controlling for handedness, familial sinistrality, verbal ability, and visuospatial performance. Under these controlled conditions, there was a sex difference in tactuospatial functioning. Males performed more accurately than females with the left hand at all grade levels while there was no difference between right-hand performances. Older males performed more accurately over-all than older females. These results support the hypothesis that the males' right hemisphere is more specialized for spatial processing.