Grip morphology and hand use in chimpanzees (Pan troglodytes): Evidence of a left hemisphere specialization in motor skill.

Three experiments on grip morphology and hand use were conducted in a sample of chimpanzees. In Experiment 1, grip morphology when grasping food items was recorded, and it was found that subjects who adopted a precision grip were more right-handed than chimpanzees using other grips. In Experiment 2, the effect of food type on grasping was assessed. Smaller food items elicited significantly more precision grips for the right hand. In Experiment 3, error rates in grasping foods were compared between the left and right hands. Significantly more errors were made for the left compared with the right hand. The cumulative results indicate that chimpanzees show a left-hemisphere asymmetry in motor skill that is associated with the use of precision grips. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hand preferences for a coordinated bimanual task in 110 chimpanzees (Pan troglodytes): Cross-sectional analysis.

Hand preference for a coordinated bimanual task was assessed in a sample of 110 chimpanzees (Pan troglodytes). Subjects were presented with opaque tubes, the inside of which was coated with peanut butter. The hand and finger used to extract the peanut butter was recorded in 2 test sessions. A population right-hand bias was found. Juvenile and adolescent subjects were less lateralized than adults. All subjects primarily used their index finger to extract peanut butter. Use of the index finger was higher in adults and adolescents compared with juveniles. The results suggest that coordinated bimanual tasks (a) elicit strong hand preferences at the individual level and (b) elicit population level right-handedness. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sex and handedness effects on corpus callosum morphology in chimpanzees (Pan troglodytes).

Findings suggest that in humans, sex and hand preference may be associated with the size of the corpus callosum (CC). The authors measured CC morphology from MRIs in 67 chimpanzees (Pan troglodytes) to see whether similar effects were present in this species. Hand preference was assessed by performance on 4 tasks, and chimpanzees were classified as left-handed, right-handed, or ambidextrous. In a subsequent analysis, the chimpanzees were reclassified into 2 groups: right-handed and left-handed. The results revealed no sex difference in CC area, but significant effects of hand preference were found for several CC regions (rostrum body, anterior midbody, posterior midbody, isthmus, and splenium) and for overall CC size, with left-handed chimpanzees exhibiting significantly smaller CC measurements than right-handed chimpanzees. The results indicate that lateralized hand use in chimpanzees, as in humans, is associated with variation in CC size. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lateralized scratching in chimpanzees (Pan troglodytes): Evidence of a functional asymmetry during arousal.

This study evaluated laterality in scratching by chimpanzees (n = 89) during socially arousing circumstances. Hand use and the side of the body scratched was recorded during a baseline and experimental condition. In the experimental condition, chimpanzees were shown a video of other conspecifics sharing, fighting over, and consuming a watermelon. Self-touches were categorized as either rubs or scratches. The chimpanzees showed a significant right hand bias for rubbing and also significantly directed the rubs to the right side of the body. For scratching, the chimpanzees showed no hand preference but a significant bias for scratching on the left side of the body. These results support the view that the right hemisphere regulates the autonomic nervous system during arousal. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Gesture laterality in aphasic and apraxic stroke patients

Limb preference during conversational gestures may be a reflection of functional hemispheric asymmetries. In right-handers, speech and praxis are usually mediated by the left hemisphere and in conversation, right-handers gesture more with their right than left hand. However, patients with left hemisphere brain damage, who are aphasic and apraxic but not hemiplegic, may use their right hemisphere to compensate for their left. Therefore, we investigated spontaneous lateralized gesture production during conversation in a group of left hemisphere-damaged stroke patients, who were aphasic and apraxic but not hemiparetic, and compared their performance to a group of matched controls. Whereas the control group had a strong right-hand preference, the nonparetic but apraxic and aphasic stroke patients were as likely to produce gestures with the right, left, or both hands.     

Chimpanzee (Pan troglodytes) handedness: Variability across multiple measures of hand use.

This study examined intertask consistency in handedness across multiple measures of hand use in a sample of 187 chimpanzees (Pan troglodytes). Hand preferences for 2 to 6 measures were collected from the sample, and hand preference scores were derived on the basis of the individual hand preferences for each measure. Seven of 15 possible intratask correlations were significant, with some degree of clustering depending on the motor demands of the tasks. Two overall measures of handedness revealed population-level right-handedness in the chimpanzees, although the degree of bias was reduced for chimpanzees tested on more than 3 measures of hand use. The results are interpreted in the context of several recent studies that proposed theoretical models of handedness in nonhuman primates. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Multiple measures of hand-use lateralization in the ring-tailed lemur (Lemur catta).

Evaluated a free-ranging matriline of 13 ring-tailed lemurs (Lemur catta) from videotaped records for lateralized hand use with 2 tasks and 4 measures: food reaching, feeding posture, duration of food holding, and manipulation of food between mouth and hand while eating. Binomial z scores determined 7 lemurs to be left preferent in reaching, 3 right, and 3 ambipreferent. Ideographic analyses suggested possible sex-linked and early experience twin effects. When compared to right and ambipreferent lemurs, left reach preferent lemurs used the left hand more but bimanuals grasped less in food holding and also engaged in less hand-mouth food manipulation. The tendency to manipulate food was not correlated with bimanual holding but was inversely related to left hand holding and directly related to right hand holding. These patterns are discussed as possible precursors of human bimanual manipulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Coexisting psoriatic arthritis, gout, and chondrocalcinosis

BACKGROUND: Constructional impairment following left vs. right hemisphere damage has been extensively studied drawing tasks. A confounding factor in these studies is that right-handed patients with left hemisphere damage (LHD) are often forced by weakness to use their non-dominant (left) hand or hemiparetic dominant hand. Qualitative differences in the drawing characteristics of left and right hand drawings by normal subjects have not previously been characterized. The present study was undertaken to determine the qualitative differences between left and right hand drawings of normal subjects. METHODS: Thirty right-handed, elderly subjects without a history of neurological disease were asked to draw, from memory, seven objects using the right and left hand. Half of the subjects were randomly assigned to draw with the left hand first, and half the right hand first. Right and left hand drawings were compared using a standardized scoring system utilized in several previous studies of drawing in focal and diffuse neurological disease. Each drawing was scored on eighteen criteria. Right and left hand drawing scores were then compared using the t-test for paired samples or the Wilcoxon matched-pairs test. RESULTS: Drawings made using the left hand were found to be significantly simpler, more tremulous and of poorer overall quality than drawings made by the same subjects using the right hand. CONCLUSIONS: The deficits found in left versus right hand drawings of normals are similar to those found in patients with LHD, suggesting that much of the drawing impairment seen following LDH is due to an elementary motor disturbance related to use of the non-dominant hand.     

The use of bouts and frequencies in the evaluation of hand preferences for a coordinated bimanual task in chimpanzees (Pan troglodytes): An empirical study comparing two different indices of laterality.

Hand preferences for a coordinated bimanual task were assessed in 109 chimpanzees (Pan troglodytes). Hand preference was evaluated for 4 test sessions using bouts and frequencies of hand use to compare the sensitivity of each level of analysis in evaluating individual variation in handedness. Overall, significant population-level right-handedness was found using several different measures of hand use. Handedness indices based on bouts and frequencies were highly and significantly correlated. Moreover, hand preferences were consistent across tests despite efforts to situationally bias preference during each test. Taken together, these data do not support the view that bouts are a better level of analysis for evaluating hand preference. The results further suggest that hand preferences for coordinated bimanual actions are not influenced by situational factors and may reflect an inherent specialization of the left hemisphere for motor skill. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Birth order and hand preference in chimpanzees (Pan troglodytes): Implications for pathological models of handedness in humans.

The effect of birth order on hand preference was assessed in a sample of 154 captive-born chimpanzees. Subjects were classified as first, middle, or latter born using 2 classification criteria based on their birth order. Hand preference was measured using a task that elicited coordinated bimanual actions. Significant birth-order effects were found for both classification criteria, with first- and latter-born subjects exhibiting a lesser degree of right-handedness compared with middle-born subjects. These data suggest that biological rather than sociological factors play a greater role in explaining the observed birth-order effects on hand preference in humans. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A lateralized comparison of handedness and object proximity.

This study was motivated by the emerging hypothesis that right-handers are more strongly lateralized and perform better on various aspects of functional asymmetry than do left-handers. 84 Right- and 60 left-handers (undergraduates) were observed for hand selection responses to a unimanual task of reaching for a small cube in positions of right and left hemispace, prompting hemispheric decision-making related to hand dominance and attentional (visuospatial) stimuli. As predicted, left-handers did not respond with their preferred limb as consistently across positions as did right-handers. Additional inspection of the task suggests that being less lateralized may not be a disadvantage in this context, and that environmental influence may play a significant role in hand selection for a particular motor event. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Heritability of hand preference in chimpanzees (Pan troglodytes): Evidence from a partial interspecies cross-fostering study.

Heritability of hand preference was tested in a sample of 188 chimpanzees (Pan troglodytes). Hand preference was measured by coordinated bimanual actions, and concordance percentages were compared between parents and offspring and siblings. Among siblings, concordance percentages were compared for dyads in which both individuals were raised by chimpanzees, both were raised by humans, or 1 was raised in each environment. The results indicated population-level right hand preferences for coordinated bimanual actions. There were no significant associations in hand preference between parents and offspring. In full and maternal half siblings, concordance in hand preference was significantly greater than chance in mother and human-reared individuals but not in cross-fostered dyads. The cumulative results suggest that the direction of hand preference is heritable in chimpanzees but the mechanism of transmission is not genetic. Several environmental explanations are proposed to explain the findings, including the potential role of maternal cradling bias and in utero fetal position. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Assessment of shoulder dimensions and angles of porcelain bonded to metal crown preparations

This research examined hand preference for a bimanual task in 45 tufted capuchin (Cebus apella) and 55 rhesus macaque (Macaca mulatta) monkeys. Investigators presented subjects with plastic tubes lined with food and noted which hand the animals used to hold the tubes and which hand the animals used to remove the food. Several significant findings emerged from this investigation. First, rhesus macaques, but not tufted capuchins, exhibited a population-level bias toward use of the right hand (although the difference in direction of hand preference between species was not significant). Second, capuchins exhibited greater hand preference strength than did macaques. Third, among capuchins, but not among macaques, hand preference strength was greater for adults than for immatures. Finally, both species used their index digit to remove food most frequently when compared with other digits. Findings of hand preference direction and strength in this study were compared with other findings noted for chimpanzees which performed a bimanual tube task in a previous study. The authors conclude that using the same procedure to compare hand preference across species represents a powerful research tool that can lead to a more complete understanding of the evolution and ontogenesis of primate handedness.     

Lateral bias in infant chimpanzees (Pan troglodytes).

This study documents the presence, strength, and direction of lateralization in chimpanzees (Pan troglodytes) over the first 3 months of life. Nursery-reared chimpanzees (7 males and 5 females) were repeatedly assessed on a behavioral scale. Lateral bias was measured for 4 behaviors: hand-to-mouth, hand-to-hand, defensive grasp, and first step. Hand-to-mouth was significantly lateralized for the sample. Eight of the 10 chimpanzees that showed hand-to-mouth used the right hand. Lateral bias for defensive grasp was positively related to lateral bias both of first step and of hand-to-mouth. Lateral bias in hand-to-mouth was inversely related to lateral bias in hand-to-hand. Strength of lateralization increased as chimpanzees matured. These laterality effects in infant chimpanzees were expressed under conditions of emotional arousal. Moreover, degree of laterality may be a predictor of responsivity to stress. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hand preferences for simple reaching in juvenile chimpanzees (Pan troglodytes): Continuity in development.

Hand preferences were assessed in 51 chimpanzees (Pan troglodytes; 28 male and 23 female) ranging from 2 to 5 years of age. Simple reaching served as the measure of lateral bias in hand preference during 2 assessments separated by 1 year. A significant sex by hand preference interaction was found with a greater prevalence of right-handed males than females. No significant differences were found between age and either strength or direction of hand preference. A significant interaction was found between rearing and strength of hand preference. Mother-reared chimpanzees showed significantly greater strength in hand preference than nursery-reared chimpanzees. Finally, a significant positive correlation was found between tests of hand preference conducted over a 1-year interval. These data suggest that in chimpanzees hand preferences are established by 2 years of age and are stable throughout the juvenile developmental period. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Speech-induced changes in corticospinal excitability

The aim of the experiments was to investigate the effects of speech on the excitability of corticospinal pathways to human hand muscles. Single transcranial magnetic stimuli were given randomly over the hand area of either the left or right motor cortex of 10 right-handed and 3 left-handed normal volunteers. Electromyographic responses were recorded in the relaxed first dorsal interosseous muscle while the subjects (a) read aloud a piece of text, (b) read silently, (c) spoke spontaneously, or (d) made sounds without speaking. The only consistent effect across subjects occurred during task a, which significantly increased the size of responses evoked in the dominant hand of all subjects, but had either no effect (8 subjects) or a smaller effect in the nondominant hand. Tasks b and d had no reliable effect, whereas task c tended to increase response size in both hands. Control measurements suggest that the effects in task a were caused by changes in cortical rather than spinal excitability. This is the first demonstration of lateralized speech effects on the excitability of cortical arm areas. The results provide a useful adjunct to other tests of cerebral dominance, using only single- rather than repetitive-pulse cortical stimulation.     

Hand, space and attentional asymmetries in goal-directed manual aiming

Two experiments were conducted to explore the interaction of the two cerebral hemispheres in motor control, by examining hand, space and attentional asymmetries in goal-directed aiming. In Experiment 1, right-handed subjects moved to targets more quickly with their right hand than their left hand. In addition, each hand was faster when moving in its own hemispace. Although in a control condition, movements were initiated more quickly with the left hand, visual distractors disrupted left hand performance more than right hand performance. For contralateral aiming, ipsilateral distractors caused the greatest interference. In Experiment 2, when targets and distractors were all presented at the midline, a right hand advantage was found for movement time along with a left hand advantage for reaction time, independent of target and distractor location. Our findings are discussed in terms of a right hemisphere role in movement preparation and the allocation of attention in space, and greater left hemisphere involvement in movement execution.     

Hemifield-specific visual recognition memory impairments in patients with unilateral temporal lobe removals

Recent evidence on visual neglect suggests that each hemisphere maintains a retinotopically organized representation of the visual world contralateral to the current fixation point and that this representation is based not only on analysis of the current retinal input but, equally importantly, on information retrieved from memory. This idea predicts that unilateral damage to memory systems should produce a lateralized impairment of memory for the retinotopically contralateral visual world. To test this prediction we examined visual recognition memory performance in the left and right visual hemifields of patients who had undergone partial unilateral temporal lobe removals for the relief of epilepsy, either in the left hemisphere (n = 5) or the right (n = 5). The patients were given complex artificial scenes to remember, constructed of independent left and right halves, and were then tested for recognition of the left and the right halves separately. Stimuli were exposed tachistoscopically throughout and fixation was maintained on a central position. Patients made significantly more errors with half-scenes in the hemifield contralateral to their removal than in the ipsilateral hemifield, an increase of 50% in the error rate on average. The effect was seen equally in patients with left and right removals. This finding supports the idea that visual memory retrieval is retinotopically organized.     

Influence of concurrent auditory input on tactual processing in very young children: Developmental changes.

Investigated right-hemispheric specialization for tactual processing in 96 2–5 yr old right-handed children. Cross-modal transfer from touch to vision was assessed under conditions where Ss palpated shapes with either their left or right hand while music was simultaneously played to the left ear, right ear, or neither ear. This task pitted music against palpation such that both tasks involved the same or different cerebral hemispheres (if music and haptic perception are both lateralized in the right hemisphere as is thought). Results show that in the absence of music, Ss at each age showed a left-hand (right-hemisphere) advantage. The adultlike patterns of ipsilateral interference from music were evident among 4- and 5-yr-olds, in that music to the left ear selectively disrupted left-hand performance. The adultlike pattern was absent at ages 2 and 3 yrs, and music to the right ear disrupted left-hand performance at these ages. Music had an overall, nonselective interference on right-hand performance at all ages. The early appearing left-hand advantage and the lateralized nature of the interference observed among older Ss support the idea of a right-hemispheric specialization for tactual processing of form in young children. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Bipedal posture and hand preference in humans and other primates.

Hand preference for quadrupedal and bipedal reaching in humans and rhesus macaques (Macaca mulatta) was examined, and the data were compared with postural reaching data that have been reported for 8 other primate species. Population-level biases were found toward use of the right hand for quadrupedal and bipedal reaching in humans and use of the left hand for quadrupedal reaching in rhesus macaques. Rhesus macaques showed a significant shift toward greater use of the right hand for bipedal vs. quadrupedal reaching. Comparisons with other species showed significant variance in the direction and strength of hand preference across reaching postures. The study noted right-hand biases for bipedal reaching in humans, great apes, and tufted capuchins and shifts toward greater use of the right hand for bipedal vs. quadrupedal reaching in great apes, tufted capuchins, and rhesus macaques. These results suggest that posture alters both the direction and strength of primate hand preference and that bipedalism may have facilitated species-typical right-handedness in humans. (PsycINFO Database Record (c) 2010 APA, all rights reserved)