Differences in social and vocal behavior between left- and right-handed common marmosets (Callithrix jacchus).

Common marmosets (Callithrix jacchus) show either a left- or right-hand preference for reaching to pick up food and they retain the same preference throughout adult life. We compared the behavior of 10 right-handed and 10 left-handed marmosets, matched for age and sex. They were presented with live crickets both when alone and when in their social group. The marmosets captured more crickets and the latency to capture the first cricket was shorter when they were in a group than when they were alone. This effect of social facilitation was significantly greater for right- than left-handed individuals. The number of vocalizations (tsik, crackle, very brief whistle, cough, and phee) produced by the left- and right-handed marmosets differed significantly: right-handed marmosets produced an increased number of all of these calls when the crickets were presented, whereas left-handed marmosets did not show a change from pretesting levels. The right-handed marmosets also produced more tsik (mobbing) calls than left-handed marmosets when they were presented with a fear-inducing stimulus and performed more head cocking and parallax movements than the left-handed marmosets. Hence, hand preference is associated with differences in exploratory and social behavior, the latter including vocal communication. (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)     

Hand preference predicts reactions to novel foods and predators in marmosets (Callithrix geoffroyi).

In chimpanzees (Pan troglodytes) and common marmosets (Callithrix jacchus), left-handed individuals are less likely than right-handed individuals to explore new objects and situations, suggesting a relationship between the hemispheric specialization of emotional states and motor function. To further explore this relationship and to test the hypothesis that fearfulness is related to hand preference, we assessed willingness to approach, sniff, and taste novel foods, and the duration of freeze reactions in response to hawk calls, in 18 Geoffroy's marmosets (Callithrix geoffroyi). In accordance with these hypotheses, left-handed marmosets were slower to explore novel foods and slower to emerge from a freeze response than right-handed marmosets. Hand preference and at least some features of temperament seem to be related in this and other species of primates. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Functional magnetic resonance imaging of motor cortex: hemispheric asymmetry and handedness

A hemispheric asymmetry in the functional activation of the human motor cortex during contralateral (C) and ipsilateral (I) finger movements, especially in right-handed subjects, was documented with nuclear magnetic resonance imaging at high field strength (4 tesla). Whereas the right motor cortex was activated mostly during contralateral finger movements in both right-handed (C/I mean area of activation = 36.8) and left-handed (C/I = 29.9) subjects, the left motor cortex was activated substantially during ipsilateral movements in left-handed subjects (C/I = 5.4) and even more so in right-handed subjects (C/I = 1.3).     

Primary motor cortex asymmetry is correlated with handedness in capuchin monkeys (cebus apella).

Humans exhibit a population-wide tendency toward right-handedness, and structural asymmetries of the primary motor cortex are associated with hand preference. Reported are similar asymmetries correlated with hand preference in a New World monkey (Cebus apella) that does not display population-level handedness. Asymmetry of central sulcus depth is significantly different between left-handed and right-handed individuals as determined by a coordinated bimanual task. Left-handed individuals have a deeper central sulcus in the contralateral hemisphere; right-handed individuals have a more symmetrical central sulcus depth. Cerebral hemispheric specialization for hand preference is not uniquely human and may be more common among primates in general. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intrahemispheric response competition between vocal and unimanual performance in normal adult human males.

Conducted 4 experiments, using a total of 150 right-handed male undergraduates. Ss balanced a dowel rod vertically on the left and right index finger singly and while simultaneously repeating phrases. With right-handed Ss who had no left-handed relatives, concurrent verbalization shortened right- but not left-handed balancing. Increased phonetic difficulty of the phrases produced an increased decrement on right-handed balancing, but left-handed balancing was unchanged; it also produced more verbalization errors on trials with the right hand, but not with the left. Concurrent verbalization shortened balancing duration with both hands of left handers. Right-handers with left-handed relatives produced variable results. Concurrent humming also selectively interfered with right-handed balancing. It is concluded that the results conform to an interpretation based on intrahemispheric interference between incompatible, simultaneously produced sets of responses. (44 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of handedness and type of movement on the contralateral preponderance of mu-rhythm desynchronisation

Event-related desynchronisation (ERD) of mu-rhythm was studied in 12 right-handed and 11 left-handed subjects during brisk and slow self-paced index finger movements of dominant and nondominant hand. Electroencephalogram (EEG) was recorded from the sensorimotor hand area of both hemispheres. The contralateral preponderance of mu-rhythm ERD in the pre-movement period showed the following changes: (i) the contrasts between left- and right-finger movements were larger and earlier in the dominant than nondominant hemisphere in both handedness groups; (ii) right-handed subjects showed larger lateralisation of mu-rhythm ERD prior to right-finger as compared to left-finger movements, whereas about equal contralateral preponderance for both sides was found in the left-handed; (iii) the lateralisation of mu-rhythm ERD was lower prior to brisk as compared to slow movements, especially in the left-handed subjects. The results demonstrate that hand dominance, handedness and type of movement influence the proportion of pre-movement mu-rhythm desynchronisation in the left and right peri-rolandic area.     

Frequency-dependent performance and handedness in professional baseball players (Homo sapiens).

I used data on handedness and pitching and hitting performance in annual cohorts of professional baseball players (1957-2005) to test the hypothesis that handedness among pitchers was subject to negative frequency-dependent selection. As predicted by this hypothesis, right-handed pitchers were more successful (i.e., opposing batters hit more poorly against them) when they were relatively rare in the population. Contrary to the predictions of this hypothesis, however, left-handed pitchers were more successful when they were relatively common. Both right- and left-handed batters performed better in years dominated by right-handed pitchers, despite the fact that right-handed batters perform relatively poorly against right-handed pitchers. I suggest that batters form cognitive representations based on pitcher handedness, and that these representations are strengthened by repeated exposure or priming. When the pitcher handedness polymorphism is more balanced (e.g., 67% right-handed, 33% left-handed), these cognitive representations are less effective, which leads to decreased batting averages and improved performance by all pitchers. Furthermore, these cognitive representations are likely to be more critical to the success of right-handed hitters, who have reduced visuomotor skills relative to left-handed hitters. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hemispheric interactions are different in left-handed individuals.

In a previous study, N. Cherbuin and C. Brinkman (2006) showed that in right-handed participants, interhemispheric transfer time (measured with A. T. Poffenberger's, 1912, paradigm) was a significant predictor of the efficiency of hemispheric interactions (measured with a split visual field, letter-matching task). No effect was found for degree of handedness in this study. This was surprising because handedness has been shown to be associated with differences in the morphology and the structure of the corpus callosum, and cerebral anatomical lateralization, as well as functional lateralization both in behavioral and scanning studies. Because these findings were found in a large sample, but one limited to right-handed participants, the aim of the present study was to determine whether a similar relationship was present between interhemispheric transfer time and hemispheric interaction in left-handed participants (using identical measures) and to assess whether the analysis of a larger sample that comprised both left- and right-handed participants might reveal an effect of handedness. Results demonstrate significant handedness effects, suggesting that left-handed individuals tend to have more efficient hemispheric interactions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Handedness, sex, and eyedness as moderating variables in the relation between hypnotic susceptibility and functional brain asymmetry.

The number of eye movements to the right in response to verbal and spatial questions in an E-facing-S situation correlated moderately with measured hypnotic responsiveness for a sample of 30 male and 30 female right-handed undergraduates. This finding confirms earlier indications that hypnotic responsiveness may be a right hemisphere function in right-handed Ss. The correlation was not significant for 19 male and 11 female left-handed Ss. Further breakdowns of the sample produced much higher correlations with hypnotizability, indicating the roles of sex, handedness, and eyedness as moderating variables. Right-handed males yielded a correlation of -.68 and left-handed females a correlation of .58, while the correlations for right-handed females and left-handed males were nonsignificant. Left-handed males, if also left-eyed, showed a correlation of .52. Left-handed males who were right-eyed, however, showed a correlation of -.41. Right-handed females who were left-eyed and right-eyed produced correlations with appropriate opposite signs, but the differences were not significant. (45 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Left-handedness.

Reviews the phenomenon of left-handedness from prehistoric man through contemporary studies of lateralization of cerebral function. The following conclusions seem warranted: Handedness is most appropriately regarded as a continuum ranging from strong right-handedness across mixed-handedness to strong left-handedness. Left-handedness, ranging from moderate through strongly left-handed, is found in approximately 10% of the population. Evidence for a genetic basis of handedness remains positive, but with no direct link established. There is remarkably little evidence for any association of left-handedness with deficit. The familial left-handed show greater recovery of functioning following unilateral cerebral insult than do nonfamilial right-handed and nonfamilial left-handed. Both behavioral and clinical lesion studies indicate systematic differences in lateralization of cerebral function between the right- and left-handed and the familial and nonfamilial left-handed. A classification of handedness and lateralization of cerebral function is suggested. The possibilities exist that bilaterality of cerebral functioning either is stable in the human race or is changing at an extremely slow rate. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Letters as spatial-oriented shapes and/or graphemic signs: a developmental study of left- and right-handed girls during the period of learning to read

This study is concerned with the problem of hemispheric specialization and/or cooperation in relation to development and manual laterality. The processing of alphabetic signs and its relationship to interhemispheric transfer and functional hemispheric asymmetries were studied by comparing left- and right-handed girls during acquisition of reading. The children perform matching tasks with letters having different orientations and with meaningless forms having the same orientations as the letters. Each subject performed the matching under three conditions: right/left intermanual transfer, left/right intermanual transfer, and dichaptic exploration. Results indicate: (1) A differentiated development between the two handednesses. (2) The functional lateralization change was different for left- and right-handed girls, a greater effect of the ability to identify the letter on matching tasks was observed for the right-handed children than for the left-handed children. These last results are discussed with regard to inter-hemispheric transfer and functional hemispheric asymmetry changes. We hypothesized a strategy difference between left- and right-handed girls and a difference in their ability to change their cognitive strategy (left-handers continue to favor a spatial coding with letters).     

Motor imagery theory of a contralateral handedness effect in recognition memory: Toward a chiral psychology of cognition.

The assumption that cognitive processes are independent of handedness was questioned. Five experiments with left-handed and right-handed participants centered on investigating recognition memory for the orientation of heads. Their results provided consistent evidence of a general contralateral handedness effect: Left-facing heads are more likely to be remembered correctly by right-handed participants, whereas right-facing heads are more likely to be remembered correctly by left-handed participants. Motor imagery and hemispheric differences explanations were compared. The results supported the hypothesis that the effect is a consequence of differences between handedness groups in terms of specific patterns of underlying motor activation rather than in terms of more general differences in function between cerebral hemispheres. The possibility of a chiral psychology of cognition that takes note of a person's handedness is considered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Appendicular cortical bone loss after age 65: sex-dependent event?

Distal radius photodensitometric and second metacarpal radiogrammetric measurements were obtained from computerized analyses of standard hand X-Ray films of 296 Caucasian subjects (189 women and 107 men). This sample included 134 subjects > or = 65 years old (75 women and 59 men). Distal radius bone density and metacarpal index showed a significant linear decrease with age in both sexes. Rates of bone loss, calculated from the regression curves, were -0.7% per year in women and -0.5% per year in men by distal radial photodensitometry, and -0.49% per year in women and -0.33% per year in men by metacarpal radiogrammetry. In the elderly subgroup, women > or = 65 years of age showed an even faster bone loss, with an annual decrease of -1.4% by distal radial photodensitometry. Conversely, men > or = 65 years of age had no significant bone loss, not even by metacarpal radiogrammetry. In conclusion, these data suggest that appendicular cortical bone loss occurs at a higher rate in elderly females than in the elderly males, both at the distal radial and at the metacarpal site.     

Salivary testosterone concentrations in left-handers: An association with cerebral language lateralization.

The level of testosterone exposure in early brain development may influence the direction or degree of cerebral language lateralization. Possible links between individual differences in testosterone levels and patterns of speech representation were investigated in 180 healthy young adults (97 left handed, 83 right handed) using the Fused Dichotic Words Test (T. Halwes, 1991). Among left-handed participants, significantly higher testosterone concentrations were observed in individuals with a left-ear advantage on dichotic listening than in individuals with a right-ear advantage. Among right-handed participants, the pattern of group differences in testosterone tended to be reversed, resulting in a statistically significant interaction. Results extend prior findings by S. D. Moffat and E. Hampson (see record 1996-03260-006) and raise the possibility that higher testosterone is associated with patterns of brain organization in which speech and praxic functions are lateralized to the same hemisphere. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reversed free osteoarthrocutaneous dorsalis pedis flap for simultaneous reconstruction of the trapeziometacarpal joint and the first metacarpal bone

Simultaneous reconstruction of a traumatic defect of the trapeziometacarpal joint and the first metacarpal with a composite dorsalis pedis flap is described. The transplant, consisting of the second metatarsal and the second metatarsophalangeal joint, was reversed at the defect site for the metatarsophalangeal joint to become a new trapeziometacarpal joint. A long vascular pedicle was necessary for direct micro-vascular anastomoses to the radial vessels at the wrist. This transfer can be expected to be effective in reconstructing composite hand defects involving the trapeziometacarpal joint and the entire first metacarpal bone.     

Auditory lateralization in monozygotic twins

In an attempt to investigate whether auditory lateralization has a heritable component, 20 monozygotic (MZ) twin pairs were examined with four different dichotic listening tests known to produce reliable right-ear advantages (REAs) in right-handers. Ten twin pairs were concordantly right-handed (MZ-RR), and ten twin pairs were discordant for handedness (MZ-RL). Intraclass correlations for MZ twin pairs were weak or nonexistent for ear advantage, but relatively strong for overall correct scores and mean reaction times, measures unrelated to laterality scores. These results support the hypothesis that auditory lateralization, as measured with dichotic tests, is nongenetic in origin. A comparison of MZ twins and right-handed siblings (n = 20) showed that right-handed siblings exhibited strong REAs, whereas left-handed siblings (n = 20) and MZ twins showed weak or absent REAs, indicating that twins may be atypically lateralized with respect to auditory lateralization.     

Anatomic observation of the dorsal metacarpal arteries

Anastomosis between the first to the fourth dorsal metacarpal arteries was observed in 43 hands of adult corpses. It was found that 86% of the first dorsal metacarpal artery arises from the radial artery, 14% is replaced by the main artery of thumb or superficial branches of the radial arteries; eighty-six percent of the second dorsal metacarpal artery originates from the dorsal carpal artery. Sixty-seven percent of the third and the fourth dorsal metacarpal arteries is formed by anastomosis of the dorsal carpal artery and its deep palmar arch. The first to the fourth dorsal metacarpal arteries have 4 to 8 cutaneous branches and proximal and distal anastomoses. It is concluded that the dorsal metacarpal arteries are characterized with multiple sources and abundant anastomoses around the metacarpophalangeal joints, which can be used with advantage in the repair of soft tissue defects of the area.     

The second dorsal metacarpal flap with vascular pedicle composed of the second dorsal metacarpal artery and the dorsal carpal branch of radial artery

A pedicle second dorsal metacarpal flap, comprising the second dorsal metacarpal artery, the partial carpal arterial arch of the dorsal hand, and the dorsal carpal branch of radial artery, was designed. The flap may be rotated through two axes of rotation, one at the entry of carpal branch of radial artery into the first dorsal interosseous muscle and one at the entry of the recurrent cutaneous branch arising from the second dorsal metacarpal artery into the skin. The method introduced can increase as much as possible the length of the vascular pedicle of the second dorsal metacarpal flap. Thus, it can cover a small defect at a more distant area. If the width of this flap is not more than 3 cm, the donor site can be closed directly. The flap had been used in five cases with no necrosis of the flap or complication of the donor site. In further investigation of the postoperative patients, no stiffness and tightness have been observed through a short period of rehabilitation of the hand. The results are satisfactory. The anatomy, the operative technique, and three selective cases are described here.     

Individual variation in hemispheric asymmetry: Multitask study of effects related to handedness and sex.

Functional hemispheric asymmetries were examined for right- or left-handed men and women. Tasks involved (1) auditory processing of verbal material, (2) processing of emotions shown on faces, (3) processing of visual categorical and coordinate spatial relations, and (4) visual processing of verbal material. Similar performance asymmetries were found for the right-handed and left-handed groups, but the average asymmetries tended to be smaller for the left-handed group. For the most part, measures of performance asymmetry obtained from the different tasks did not correlate with each other, suggesting that individual Ss cannot be simply characterized as strongly or weakly lateralized. However, ear differences obtained in Task 1 did correlate significantly with certain visual field differences obtained in Task 4, suggesting that both tasks are sensitive to hemispheric asymmetry in similar phonetic or language-related processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)