Use Of Left Hand Research Articles

Infant hand-use preferences for grasping objects contributes to the development of a hand-use preference for manipulating objects.

Twenty-five infants, divided into three approximately equal groups according to their hand-use preference for reaching for and grasping objects (right, left, or no-preference), were videotaped at 7 and 11 months while involved in a semiplay activity in which they were presented with 26 toys (20-40 s for each presentation). Unimanual manipulation activity was coded, and the increase or decrease in preferred hand use across the two ages was analyzed. Infants with a right preference for reaching showed an increase in right-hand use for unimanual manipulatory actions from 7 to 11 months. Infants with a left preference for reaching showed an increase in left-hand use whereas infants with no preference for reaching showed a modest increase in the use of the right hand. These results support a modified progressive lateralization theory, which posits that a hand-use preference for reaching for and grasping objects will concatenate during development into a hand-use preference for manipulating objects.

Left-handedness is Correlated with CSF Monoamine Metabolite and Plasma Cortisol Concentrations, and with Impaired Sociality, in Free-ranging Adult Male Rhesus Macaques (Macaca mulatta)

In this research we examined biological and behavioural correlates of handedness in free-ranging adult male rhesus macaques (Macaca mulatta). Specifically, we examined relationships between handedness and cerebrospinal fluid (CSF) concentrations of the monoamine metabolites 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid (HVA), and 3-methoxy-4-hydroxyphenylglycol (MHPG), plasma concentrations of the hormones cortisol and adrenocorticotropin (ACTH), and multiple indices of social behaviour, including occurrences of proximity to other animals, grooming, submission, and aggression. We determined handedness through systematic observation of animals reaching for food in their unrestricted home environment. The frequency of right- versus left-hand use was significantly positively correlated with CSF 5-HIAA, CSF MHPG, and plasma cortisol concentrations, and with social proximity and the frequency and duration of bouts in which animals received grooming. The frequency of right- versus left-hand use was significantly negatively correlated with the frequency of submissive behaviour, and with the frequency and intensity of bouts in which animals received aggression. We conclude that handedness is associated with an array of biological and behavioural processes in free-ranging adult male rhesus macaques and that left-handedness may be used to identify individuals at increased risk for impaired functioning of the serotonin, norepinephrine, and hypothalamic-pituitary-adrenal systems, and for social isolation and susceptibility to violent attack.

FLOW-CYTOMETRIC ANALYSIS OF T-LYMPHOCYTE SUBSETS IN SINISTRAL AND DEXTRAL PATIENTS WITH GINGIVITIS

The aim of this study was to determine whether there was any change in T-lymphocyte subsets in sinistral and dextral patients with gingivitis. The study was carried out on 36 patients (16 males and 20 females) with gingivitis. The age of the patients ranged from 16 to 25 (mean age = 18.50 + 3.85). Patients were divided into two equal groups according to their right or left hand use. Being right- or left-handed was determined with Edinburgh Handedness Inventory (Oldfield). At the beginning of the study, gingival index (GI-Löe-Silness) and plaque index (PI-Silness-Löe) scores were recorded in order to assess the gingival tissue health in patients. At the same time, the biopsy samples were taken from the gingival pocket wall tissues at sites of gingivitis. Then, CD4+ and CD8+ lymphocyte and CD4/CD8 ratio values were determined using flow-cytometry in the biopsy samples. The two groups were compared by using Student s t-test. The normal value in peripheral blood of CD4+ lymphocyte and that of CD8+ lymphocyte are 25-29% and 19-48%, respectively. According to flow cytometry findings, in both sinistrality and dexterity with gingivitis, CD+ and CD8+ lymphocyte values were under the normal value while the CD4/CD8 rate was within normal distribution interval. CD4+ lymphocyte values observed in the sinistral patients were found to be lower than those in the dextral patients. The difference between the CD8+ lymphocyte values in left-handed patients and that obtained in right-handed patients was not found to be statistically significant while the difference between the CD4+ lymphocyte values in left-handed patients and that obtained in right-handed patients was found to be statistically significant (p <. 05). In addition, the difference between the CD4/CD8 rate obtained in left-handed patients and that obtained in right-handed patients was found to be statistically very significant (p <. 001). Consequently, these findings suggested CD4+ lymphocyte value and CD4/CD8 rate was lower in sinistrality. Sinistrality and dexterity may play an important role in local immune response.

Brief Note: EFFECT OF LEFT- OR RIGHT-HANDEDNESS ON NURSING PRACTICE

The aim of the present study was to evaluate the association of hand preference of nursing and the success of the nursing practice. The study included 24 students, all of whom attend different classes in the School of Nursing. The status of left- or right-handedness of the students included in the research was determined using Oldfield (Edinburgh Handed­ness Inventory) Index. The students were divided into two equal groups according to their right or left hand use. Then the students were categorized in four groups (Very good: 81-100, Average: 61-80, Pass: 50-60, and Fail: <50) according to the scores they received from the practice and theory tests of the lesson "Fundamentals of Nursing" the lesson requiring hand skills most. The test for the difference between two population proportions was used for statistical analysis. Left-handed nurses were found to be more successful than right-handed nurses in nursing practice. The difference between them was found significant (p <. 01). It was concluded that left-handed nurses should never be forced to convert into right-handedness; instead they should be supported both verbally and in terms of equipment, and they should be motivated, because the data obtained proved that left-handedness means success.­­

Learned movements in a left-handed pianist: an f-MRI evaluation

The spatial arrangement of neuronal sources for digit movement is non somatotopic, and is structured as extensively arranged through different regional cortex. We have functionally examined the cerebro-cortical activation during simple and complex motor sequences, before and after learning sessions, in healthy volunteers, both considering left- and right-dominant hand use, and left non dominant hand use, skilfulness and educational level. We discuss the results with a review on the topic.

A kinematic analysis of hand selection in a reaching task

A group of left- and right-handers was tested on a task requiring them to reach out and pick up an object with either the left or the right hand. We varied the eccentricity of the target object (a small glass) and the required accuracy level, by filling the glass with liquid. We recorded (a) frequency of left or right hand use, (b) hand preference using a handedness questionnaire, and (c) the trajectories of the reaches using a movement registration system. It was found that the stronger the hand preference, the further in contralateral space the shift occurred between left and right hand use. Not only did the transition point corresponding to the shift between the two hands correlate with the point where their deceleration times were equal, but these locations closely coincided. These findings suggest that people are highly skilled perceivers of their own action capabilities, and that they are able to select the action mode that is most suited to perform a given task. We argue that laterality should be understood in terms of asymmetries in action modes.

Left handedness: Facts and Figures across Cultures

Approximately 10% of human beings are left handed, although the incidence rate dif fers as a function of sex, age, and culturelgeographical locations. Studies reveal that (a) the incidence of left handedness is more common in Euro-American than in Orien tal ( India, Japan, China) cultures, (b) the prevalence of left handedness throughout the historical era is best explained by genetic models, (c) left handedness is associated more with immune and psychopathological disorders, and (d) sanctions against left hand use are rooted to the belief system and social construction in a given culture. These obser vations were made in this article to ascertain the issues related to left handedness, espe cially in socio-cultural contexts.

Stress correlates of hand preference in rhesus macaques.

In this research we examined stress-related correlates of hand preference in monkeys. Specifically, we tested the hypothesis that stress reactivity and plasma levels of the stress hormone cortisol are developmentally related to handedness in rhesus macaques (Macaca mulatta). We found a significant positive correlation between cortisol levels sampled in juveniles and the frequency of right- versus left-hand use sampled in these same animals during adulthood. Right-hand preference was negatively correlated with stress reactivity. These data are consistent with the view that stress functioning and reactivity are associated with the development of hemispheric specialization in primates.

The Effect of Right or Left-Handedness on Oral Hygiene

It has been shown that there is a strong relation between periodontal diseases and bacterial plaque with clinical and experimental studies. According to scientific data, the best way to protect against the periodontal diseases is to remove bacterial plaque from tooth surface mechanically. To remove bacterial plaque from tooth surface completely, the patient must have good hand skill and motivation in addition to professional treatment.The aim of our study was to examine whether there is a difference between the left-handed who are known as skilful at drawing, geometry, and graphics and the right-handed at oral hygiene check. The study included 28 persons, 12 female and 16 male, ranging in age from 19 to 26. Subjects were divided into two groups according to their right or left hand use. Being right- or left-handed was determined with Edinburgh Handedness Inventory (Oidfield). Both groups were given oral hygiene education with a systematic treatment at the beginning of the study. At the beginning of the study, GI (Silness-Löe) and PI (Quigley-Hein) scores were taken from all subjects. Then, those scores were repeated in the 1st and 3rd month. Received scores were evaluated statistically with Wilcoxon test. While there was no statistical difference between both groups initially p <. 05, there was a statistical difference between them in the 1st and 3rd month in favour of the left-handed p <.05. Consequently, it was found that the left-handed were more successful at oral hygiene check than the right-handed.

História de desenvolvimento e comportamento de crianças nascidas pré-termo e baixo peso (&lt; 1.500 g)

O presente estudo comparou a historia de desenvolvimento, aprendizagem e comportamento de 20 criancas de 8 a 10 anos nascidas pre-termo < 1500g (MBP) emparelhadas a 20 criancas controle nascidas a termo. Foram realizadas entrevistas e foi aplicada a Escala Comportamental de Rutter nas maes e o Raven nas criancas. Verificou-se sinais de atraso na aquisicao de comportamentos psicomotores iniciais e lateralidade manual canhestra no MBP em relacao ao controle. Na fase escolar, a maioria das criancas de ambos os grupos apresentou nivel intelectual medio e estava frequentando escola regular. As criancas MBP apresentaram mais repetencia escolar do que as controles e reuniram uma parcela de 20% de criancas com deficit auditivo. Embora em ambos os grupos tivesse indicacao de problemas comportamentais na Rutter, as criancas MBP apresentaram mais problemas respiratorios, enurese noturna, recusa escolar, agitacao, impaciencia, inquietude e agarramento a mae em comparacao a escolares de Ribeirao Preto.

Stress correlates of hand preference in rhesus macaques

In this research we examined stress-related correlates of hand preference in monkeys. Specifically, we tested the hypothesis that stress reactivity and plasma levels of the stress hormone cortisol are developmentally related to handedness in rhesus macaques (Macaca mulatta). We found a significant positive correlation between cortisol levels sampled in juveniles and the frequency of right- versus left-hand use sampled in these same animals during adulthood. Right-hand preference was negatively correlated with stress reactivity. These data are consistent with the view that stress functioning and reactivity are associated with the development of hemispheric specialization in primates.

ETHOLOGICAL STUDY OF MANUAL LATERALITY IN THE CHIMPANZEES OF THE MAHALE MOUNTAINS, TANZANIA

Laterality of function in hand use by the chimpanzee ( Pan troglodytes ) is unresolved. Ethological studies of groups observed in nature find mostly ambilaterality, while experimental studies of individuals in laboratories and zoos show evidence of rightside bias. These disparate data can be compared systematically using a 5-level scheme, ranging from Level 1, comprehensive ambilaterality, to Level 5, exclusive use of left or right hand across tasks. We sought to clarify this discrepancy with an ethological study of wild chimpanzees in the Mahale Mountains of Tanzania, East Africa. We observed 44 subjects of all ages using focalsubject sampling, showing 35 patterns of manual behaviour (excluding tool use) over 31/2 months. For the 15 most frequent patterns, which included subsistence, social, communicatory, and self-maintenance patterns, we found mostly Level-1 results, whether pooled across subjects or patterns, or analysed individually or pattern-by-pattern. These findings closely replicate earlier findings from another population in Tanzania, Gombe. We hypothesise that chimpanzees in confined settings may show right side preferences due to (inadvertent) human influence; these can be tested empirically.

Hormonal Correlates of Hand Preference in Free-ranging Primates

In this research we examined hormonal correlates of hand preference in free-ranging primates. Specifically, we tested the hypothesis that levels of the stress hormone cortisol and the male sex hormone testosterone are correlated with handedness in male rhesus macaques (Macaca mulatta). We found significant positive relationships between cortisol and testosterone levels sampled during adolescence and the frequency of right- versus left-hand use sampled during adulthood. These data indicate that adolescent measures of cortisol and testosterone are correlated with hemispheric specialization in adult free-ranging primates.

A comparative study of aimed throwing by monkeys and humans

This research examined hand preference and postural characteristics of aimed throwing in capuchin monkeys and humans. We sought to directly compare the throwing performances of these primates, particularly the extent to which target distance influences hand preference, throwing posture, and throwing accuracy. For both species we found positive correlations between target distances for throwing accuracy, direction and strength of hand preference, percentage of bipedal vs tripedal throws, and percentage of overarm vs underarm throws. Throwing accuracy did not vary as a function of right vs left hand use although for monkeys throwing accuracy was positively associated with hand preference strength. We noted a sex difference among humans as males threw more accurately than did females. Between-species analysis indicated that humans exhibited greater right- vs left-hand use, greater hand preference strength, a greater relative percentage of bipedal vs tripedal throws, and a lower relative percentage of overarm vs underarm throws than did monkeys. We believe that the capuchin monkey is an informative nonhuman primate model of aimed throwing in humans and that research examining the throwing behavior of capuchins provides insight into the neurological and behavioral characteristics that underlie coordinated multi-joint movements across the primate order.

Handedness and cortisol in tufted capuchin monkey infants.

In this research, we examined the relationship between handedness and levels of plasma cortisol in infant monkeys (Cebus apella). Specifically, we sought to test the hypothesis that stress functioning is related to hemispheric specialization and is manifested in a positive correlation between cortisol levels and the frequency of right- versus left-hand use. We found a significant relationship between stress cortisol at age 6 months and lateral bias towards greater use of the right versus left hand at ages 6 and 12 months. These data suggest an early developmental influence of stress reactivity on the emergence of hemispheric specialization for manual control in infant monkeys through the 1st year of postnatal life.

Environmental Influences in Hand Preference: An African Point of View

In order to examine further the role of cultural and environmental factors in human manual preference, two surveys were undertaken in students from Ivory Coast and Sudan. In the first study (Abidjan, Ivory Coast) 382 secondary students, ages 12 to 22, answered a 20-item manual preference questionnaire. The observed frequency of left-hand preference was 7.9%, with very low left-hand use among the 18–22 age group (1%) and high among the 12–15 age group (14%). In the second study (Khartoum, Sudan) 759 undergraduates, ages 18 to 33, answered a 25-item questionnaire. The observed frequency of left manual preference was 5%. Subjects were also asked to indicate any pressure to change hand for writing, eating, or other manual activities and, in the second study, any upper limb injury which temporarily rendered the subject unable to use his (her) preferred hand. Report of an upper limb injury in the past was related to mixed (or inconsistent) hand preference. In both studies, the target activity against left-hand use was eating. These results show that cultural and environmental factors could change “natural” hand preference in three ways: (i) by changing the hand used for only one activity (e.g., eating), with no change for other familiar unimanual activities; (ii) by reducing the degree of hand preference; (iii) by changing the overall preferred hand, generally reducing the prevalence of left-handedness. The design of handedness studies should allow these possibilities to be distinguished.

Line bisection with a head-mounted pointing device: An investigation of the role of right hand use and bilateral hemisphere activation in left neglect

Left hand use in left hemispace has been shown to reduce left neglect. Right hand use can theoretically increase neglect by right spatial cueing and left hemisphere activation. The aim of the present study was to investigate the role of right hand use and right hemisphere activation in left neglect by dissociating hemisphere activation from the hemispace in which the motor response is made. Twelve neglect patients performed line bisection by two means: with their right hand and with a lamp mounted centrally on the forehead (‘miner's lamp’). Lamp use induces left and right hemisphere activation without hemispace involvement. Bisection with the lamp and the hand were done with right, left and neutral cues. No difference was found in bisection performance between lamp and right hand use, and no interaction between lamp/hand use and cueing. This indicates that right hand use per se does not influence neglect in line bisection. It is suggested that the apparent lack of right hemisphere activation with lamp use is due to the widespread right-sided lesion of the typical neglect patient.

Neuropsychological outcome at age 5 following unilateral neonatal brain lesion. 1728

Retrospective studies of neonates who sustain unilateral brain lesions demonstrate small but persistent deficits contralateral to lesion side. Prospective studies have generally been constrained by small sample size, variability in age of lesion onset, and wide range of ages when outcome has been assessed. We report neuropsychological outcome at age five for 24 children who were ascertained in the neonatal period to have unilateral brain lesions (LL=12; RL=12). The sample is part of a cohort of 152 critically ill term neonates (> 2kg) who received routine neonatal neuroimaging (US/CT) following ECMO treatment for cardiorespiratory failure and were available for comprehensive neuropsychological evaluation at age 5. The lesion groups were comparable in terms of birthweight, GA, Apgar scores, neuroimaging severity score, ethnicity, maternal education, and age at test. One child (RL) had post-neonatal seizures. We compared performance on neuropsychological measures presumed subserved by the right hemisphere (e.g. visual/spatial, left-hand use) and left hemisphere (e.g. language, right-hand use). Data were converted to z-scores. The RL group showed a visual/spatial deficit relative to language, and the LL group showed the corresponding language deficit relative to visual/spatial skills. Verbal and visual memory scores were equivalent. One child in each group was left-hand dominant. Visual/motor tasks were poorer for the LL group, given the dominant hand was contralateral to the side of lesion. Overall, the effect was predictable for lesion side, although the effect size was small. Our data suggest residual effects at age five within the general pattern of recovery following lateralized neonatal brain injury. [Funded by NIH/NINDS]

Haptic discrimination in capuchin monkeys (Cebus apella): Evidence of manual specialization

Two experiments investigated the effects of haptic and visual discrimination on hand preference in 22 brown capuchin monkeys (Cebus apella). The percentage of left-handed subjects in Experiment 1 were 63.6%, 45.5%, and 18.2% for haptic, bipedal, and quadrupedal reaching, respectively. In Experiment 2, the haptic demands of the task were manipulated by using additional food types and another tactile medium. Left-hand preferences were further strengthened when reaching into water compared to pine-shavings in Experiment 1. Reaching with no tactile interference resulted in equal numbers of lateralized and nonlateralized subjects. These results show that when reaching demands the use of haptic cues, as opposed to visual ones, monkeys shift towards greater left hand use. This is consistent with what is known about right hemisphere superiority for haptic discrimination in humans.

A study of correlates of hand preferences in squirrel monkeys (Saimiri sciureus)

The purpose of this study was to test the influence of sex, age, social rank, matriline membership, posture, and visual and tactual motor control on manual preferences inSaimiri sciureus. A well-established social group of 12 squirrel monkeys, aged 2 to 14 yrs and consisting of two matrilines with social rank known for each animal, was presented with four different food-reaching tasks and assessed for hand preferences with a minimum of 100 reaches per animal. Frequency of occurrence of hand preferences at the group level and degree of hand preferences at the individual level depended on posture and on whether the reaching act took place under visual or tactual guidance. Sex, age, social rank, and matriline membership were not found to determine frequency of occurrence, direction or degree of hand preferences with the exception of one task in which a significant negative correlation between the degree of hand preference and age was found. Nine out of 12 monkeys showed task-dependent changes in the hand they used preferentially while only three animals preferred the same hand in all four tasks. Significant preferences for the use of right or left hand on a given task were distributed almost equally between individuals. Thus, the results of this study suggest task-specific demands like posture and/or whether reaching was visually or tactually guided to be the major correlates of hand preferences in food-reaching tasks in squirrel monkeys.