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PubMedDate not supplied

Field dependence, laterality and the EEG: a reanalysis of O'Connor and Shaw (1978).

O'Connor and Shaw (1978) investigated the relationship between field-dependence-independence (taken as a measure of cognitive organization), handedness strength (taken as a measure of functional organization), and resting EEG coherence spectra in the alpha band (taken as a measure of cortical organization). All three variables were found to be significantly interrelated in the right-handed as well as the left-handed subsample. However, some inconsistencies in the original report suggested the need for reanalysis of the data. The results of that reanalysis are presented here. When a mean unsigned error was used as score for the Rod and Frame Test, more field-independent subjects consistently showed lower EEG coherence spectra than more field-dependent subjects. Also, both right-handed and left-handed field-independent individuals tended to show a stronger degree of handedness in the direction of their lateral preference than field-dependent subjects, indicating that a more field-independent approach is associated with greater specialization irrespective of the direction of lateral preference.

Alpha Rhythm↗
PubMedDate not supplied

Cerebral laterality and the study of alcoholism.

This paper suggests that the strategy of studying individuals at high risk to develop alcoholism by comparing, for example, sons of alcoholic fathers with sons of nonalcoholic fathers might not control for handedness or for patterns of cerebral laterality. In our sample of alcoholic men, at least 50% of the men left-handed or having a left-handed first-degree relative had an alcoholic father, versus only 26% of the right-handed men not having a left-handed first-degree relative. If generalized to nonalcoholic individuals, these data suggest that a larger proportion of the sons of alcoholic fathers either would be left-handed or would have a left-handed first-degree relative, and might have an anomalous pattern of cerebral dominance. Furthermore, several findings associated with being at high risk for alcoholism have also been associated with left-handedness or with left-hemisphere dysfunction.

Alcoholism↗
PubMedDate not supplied

Congenital adrenal hyperplasia and cerebral lateralizations.

Handedness, immunologic disorders, language lateralization, reading fluency, and visual-motor achievements were assessed in 25 patients with congenital adrenal hyperplasia and age-matched right- and left-handed normal controls. An increased rate of left-handedness in the congenital adrenal hyperplasia group was evident. The prevalence of immunologic disorders, dichotic listening patterns, and visual-motor/reading achievement ratio were more similar to left-handed and significantly different from right-handed controls. Females appeared to be more affected than males in some of the functions. These results partly support the hypothesis of intrauterine androgenic effects on hemispheric function, but not to the extent of a complete lateralization shift.

Adolescent↗
PubMed1995

Are there neurological and sensory risk factors for schizophrenia?

The association between left-handedness, epilepsy, and hearing impairment with schizophrenia was investigated using data from a cohort of 50,000 male Swedish conscripts linked to the Swedish National Register of Psychiatric Care. Though epilepsy was rare in this cohort, no association with schizophrenia was found. Left-handedness was associated with neither schizophrenia nor other psychoses. The study shows that, when studied from a population base, the apparent increase in neurodevelopmental anomalies in schizophrenia may be an artefact of bias. However, schizophrenia was 1.81 (95% CI 1.2-2.7) times higher amongst those with severe hearing loss, which may be preventable.

Adolescent↗
PubMed1995

P300 differences between sinistrals and dextrals.

The P3(00) event-related potential (ERP) was elicited in 20 left- and 20 normal right-handed young adult male subjects using a simple visual stimulus discrimination task. For left-compared to right-handed subjects, P3 amplitude was larger at anterior electrode sites for the target stimuli and larger overall for the novel visual stimuli; P3 latency was shorter for left-compared to right-handers for the target stimuli. The N1, P2, and N2 components demonstrated similar handedness effects. The relationships of ERP amplitude and handedness to anatomical variables and cognitive factors are discussed.

Adult↗
PubMed2004

Phonological processing of words in right- and left-handers.

It is commonly accepted that phonology is the exclusive domain of the left hemisphere. However, this pattern of lateralization, which posits a right visual field advantage, has been questioned by several studies. In fact, certain factors such as characteristics of the stimuli and subjects' handedness can modulate the right visual field advantage. Thus, the goal of this study was to compare the hemispheric dynamics of right-handers and left-handers during a divided visual field presentation of words that varied in terms of their phonological transparency. For non-transparent words, the left hemisphere seems more competent in both handedness groups. With regard to transparent words, the right hemisphere of both groups also appears competent. Surprisingly, left-handers achieved optimal processing with a functionally isolated left hemisphere, whereas right-handers needed the participation of both hemispheres. The pattern of performance cannot be fully explained by either the callosal or the direct access model.

Adult↗
PubMed2006

Cultural and environmental pressure against left-hand preference in urban and semi-urban Malawi.

The study assessed views of teachers, pupils and their guardians on left-hand preference. Seventy-five percent of the responders indicated that the left hand should not be preferred for habitual activities and 87.6% of them indicated that left-handers should be forced to change the hand. Gender had significant effect on the view on left hand preference (df = 1, OR (odds ratio) = 0.465, p = 0.027). Giving a handshake when greeting a person, drawing and writing were the three top target activities against left-hand preference. An assumption that the left hand is less skilled and less powerful than the right one was the most common reason for negative view on left-hand use. Most of volunteers reported that parents and close relatives were the primary group of people who usually discourage left-hand use. Eighty point one percent of the responders indicated that people should stop preferring the left hand as soon as somebody noticed their left-handedness. The results indicated that cultural and environmental pressures might significantly affect visibility of left-handedness in urban Malawian populations.

Adolescent↗
PubMed2005

Which factors affect hand selection in children's grasping in hemispace? Combined effects of task demand and motor dominance.

Sixty-five right- and left-handed preschool and school children were tested on three reach-to-grasp tasks of different levels of complexity, performed in three space locations. Our goal was to evaluate how the effect of attentional information related to object location interacts with task complexity and degree of handedness on children's hand selection. Results revealed a shift to the non-preferred hand in the contralateral hemispace, which was more or less pronounced according to the level of task complexity. The subject's degree of handedness also influenced this shift, since strongly lateralized children exhibited a greater use of their preferred hand than less lateralized ones for actions in the contralateral hemispace. These findings confirm that hand selection is to some extent adaptable to task demand and environmental context.

Analysis of Variance↗
PubMed2005

Analysis of skeletal movements in mandibular distraction osteogenesis.

PURPOSE: The purpose of this study was to use geometric parameters of movement, calculated from 3-dimensional computed tomography (CT) data, to determine the curvilinear distractor dimensions required to correct mandibular deformities in a series of patients. MATERIALS AND METHODS: Preoperative CT scans from 15 patients with symmetric (n = 5) and asymmetric (n = 10) deformities were imported into a CT-based software program (Osteoplan; an open-source visualization application developed by Gering et al at the Surgical Planning Laboratory [SPL, Brigham and Womens Hospital, Boston, MA]). The software was used to reconstruct virtual 3-dimensional models from these scans. Two experienced surgeons, working with a computer scientist, then used Osteoplan to create an ideal treatment plan for each patient. In each case, the 3-dimensional curvilinear movement was quantified using 4 "parameters of movement" (POMs). These parameters were then used to prescribe a distraction device capable of executing the planned skeletal correction. Curvilinear distractor dimensions calculated by Osteoplan included the radius of curvature of the prescribed device, and the distractor elongation, pitch, and handedness. RESULTS: Treatment plans including POMs were developed for each patient. The radii of curvature for the prescribed distractors ranged from 2.3 to 14.1 cm, the distractor elongation dimensions ranged from 0.7 to 3.2 cm, and the pitch (horizontal plane) dimensions ranged from 0.005 to 0.8 cm. Handedness was either a left (n = 12) or right (n = 8) turning helix. CONCLUSION: The results of this study indicate that, using geometric parameters of movement calculated from 3-dimensional CT scans, curvilinear devices could be prescribed for correction of the range of skeletal deformities in this group of patients.

Computer Simulation↗
PubMed2004

The hierarchy of chirality.

Twisting is a prevalent feature of long, thin vertical leaves; it has been shown that this twist contributes to the mechanical integrity of the leaf. We address the question as to how this twist comes about, and posit that it is a reflection of twist at a lower structural (geometric) level. The stiffness required for maintaining verticality in leaves is due to turgescent parenchyma cells, sometimes thickened epidermis, cuticle, and is generally most significantly contributed to by vascular bundles and fibers. These contain cellulose in the cell walls. Such cellulose chains spiral upward within the cell wall layers which are of a characteristic handedness. This results in an isolated cell behaving mechanically in a chiral manner; specifically elongation (contraction) of a single cell will result in rotation of the cell about its axis of particular handedness. We propose a mathematical model that shows that when cells are mechanically associated in groups, the chiral behavior of the cell will be expressed at larger scales, albeit to a mitigated degree. Thus cell extension during leaf development may explain the characteristic twist of such leaves.

Cell Wall↗
PubMed2005

Vertebral artery dominance and hand preference: is there a correlation?

The two vertebral arteries are usually unequal in size, the left one being generally larger than the right one. It is not clear why this asymmetry exists. One of the hypotheses is that this asymmetry is related to the vascular requirements of the brain. To support this statement, we investigated the correlation between a dominant left vertebral artery and right-handedness and vice versa. No correlation between differences in vertebral artery diameter and hand dominance was found. Hence, the hypothesis that a dominant left vertebral artery is associated with right-handedness and vice versa cannot be confirmed.

Adult↗
PubMed2005

Association between scalp hair-whorl direction and hemispheric language dominance.

Asymmetry is a common phenomenon in higher organisms. In humans, the cortical representation of language exhibits a high degree of asymmetry with a prevalence of about 90% of left hemispheric dominance, the underlying mechanisms of which are largely unknown. Another sign that exhibits a form of lateralization is the scalp hair-whorl direction, which is either clockwise or anti-clockwise. The scalp hair-whorl develops from the same germ layer as the nervous system, the ectoderm, between the 10th and 16th week in utero and has been shown to be associated with various neurodevelopmental disorders. Here, we use an established fMRI paradigm to examine the association of a solely biological marker of asymmetry, hair-whorl direction and language lateralization. We show that the mechanism that influences hair-whorl direction and handedness [Klar, A.J.S., 2003. Human handedness and scalp hair-whorl direction develop from a common genetic mechanism. Genetics 1651, 269-276.] also affects cerebral language dominance.

Adult↗
PubMed2004

Personality, manual preference and neuroendocrine reactivity in hirsute subjects.

Behavioral and neuroendocrine differences may be postulated in hirsute subjects since central effects of gonadal steroids are well established. We conducted a controlled clinical study with 25 consecutive young hirsute participants compared with 20 consecutive controls. Neuropsychological evaluation included the Minnesota Multiphasic Personality Inventory (MMPI) and the Edinburgh Inventory of Manual Preference (EIMP). Neuroendocrine reactivity was assessed by the adrenocorticotropic hormone (ACTH) and cortisol responses to corticotropin releasing hormone (CRH). Hirsute participants presented a flattened personality profile with lower neurotic triad scores--146 +/- 20 versus 166 +/- 28. Left-hand preference was more common in hirsute participants--4/21 versus 0/20. Decreased ACTH [area under the curve (AUC)--36 +/-2 8 vs. 72 +/- 63 pg/ml h] and cortisol (AUC--18 +/- 4 vs. 25 +/- 10 microg/dl h) responses to CRH were found in the hirsute group. In the hirsute group, higher manual preference scores were associated with lower ACTH responses to CRH, while the opposite association was found in the control group. In the hirsute group, the hyporeactive hypothalamic-pituitary-adrenal (HPA) axis was associated with lower behavior-deviant scores, while in the control group, the hyporeactive HPA axis was associated with more psychopathology. We conclude that personality and HPA axis reactivity are different in hirsute female participants when compared with controls, with a trend for differences regarding handedness. Personality and handedness are differently associated with HPA reactivity. Distinctive features in hirsute participants are probably established very early during ontogenic development.

Adrenocorticotropic Hormone↗
PubMed2005

Fluctuating asymmetry, second to fourth finger length ratios and human sexual orientation.

Sexual orientation in humans may be influenced by levels of prenatal sex steroids which canalise neurodevelopment along sex-typical (heterosexual) or sex-atypical (homosexual) lines. Some evidence for sexual-orientation-related differences in putative somatic markers of prenatal sex hormones supports this view. A competing theory asserts that human homosexuality is due to developmental instability (DI) because it represents a shift from the species-typical pattern of heterosexual orientation. Evidence for elevated rates of non-right handedness among homosexuals provides limited support for this account. The current study tested both theories by examining nine bilateral somatic traits in 120 healthy heterosexual and homosexual men and women in order to compute second to fourth finger length ratios (2D:4D), a measure ascribed to levels of prenatal sex steroids, and fluctuating asymmetry (FA), a measure of DI. Homosexual men and women had significantly lower right hand 2D:4D ratios (even after controlling for handedness, height and weight differences) in comparison to heterosexuals, but sexual orientation did not relate to composite FA scores. The findings constrain the number of possible neurodevelopmental pathways responsible for sexual orientation in humans.

Adult↗
PubMed2005

Childhood laterality and adult schizophrenia spectrum disorders: a prospective investigation.

Left or mixed-handedness, footedness, and eye dominance are thought to indicate abnormalities in lateralization related to schizophrenia. Increased left or mixed-dominance in schizophrenia suggests possible hemispheric abnormalities associated with the disorder. A related body of research suggests that some indications of lateralization abnormalities may be evident prior to the onset of schizophrenia, suggesting that disruptions in lateralization are inherent to the developmental course of the disorder. We attempted to replicate and extend upon findings indicating differences in lateralization between children who later developed a schizophrenia spectrum disorder (n = 26) and those who did not develop a schizophrenia spectrum disorder (n = 216), among a high-risk and control, longitudinal sample. The rate of left or mixed-footedness, eye dominance, and any anomalous lateralization, but not handedness, discriminated between those who developed schizophrenia spectrum disorders and those who did not. Left or mixed-laterality appears to signal neurological disruption relevant to the development of schizophrenia spectrum disorders.

Adolescent↗
PubMed2006

Diagnostic specificity and predictors of neurological soft signs in schizophrenia, bipolar disorder and other psychoses over the first 4 years of illness.

BACKGROUND: Neurological soft signs (NSS) are well described among patients with schizophrenia, the neurology of other psychoses is relatively unexplored and few comparative studies have prospectively examined these signs in first-episode patients. METHODS: We assessed neurological functioning in 242 patients presenting with a first episode of psychosis (in accordance with DSM-IV diagnosis) using the Condensed Neurological Examination (CNE). We sought to determine whether NSS were specific to patients with schizophrenia, bipolar affective disorder and other forms of psychosis. We also examined the factors associated with and predictive of neurodysfunction at first presentation and at 4 year follow-up. RESULTS: NSS were not specific to any diagnostic group. Neurological functioning was closely associated with psychopathology and mixed-handedness at first presentation. At follow-up there was a statistically significant improvement in neurological functioning. Persistent neurodysfunction at this stage was related to enduring negative symptoms and associated with poorer outcome. DISCUSSION: Schizophrenia and bipolar disorder are indistinguishable in terms of neurodysfunction at presentation. At presentation and 4 years NSS closely parallel psychopathology and mixed-handedness indicating that NSS may be a function of these factors or possibly an independent factor operates equally upon both symptoms and neurological function.

Adolescent↗
PubMed2006

Schneider's first rank symptoms and continuous performance disturbance as indices of dysconnectivity of left- and right-hemispheric components of language in schizophrenia.

BACKGROUND: Here we investigate pathophysiological dimensions (language disturbance, negative symptoms, lateralisation and the continuous performance test) in relation to ICD-10 and DSM-IV concepts of diagnosis. METHODS: A total of 32 consecutive psychotic patients with at least one Schneider's first rank symptom (SFRS), 15 depressed patients without SFRS and 17 normal volunteers were assessed with the Clinical Language Disorder Rating Scale (CLANG), SFRS, "pure defect" Huber's basic symptoms (HBS), handedness (Annett's pegboard task), and the A-X Continuous Performance Test (AX-CPT). RESULTS: CLANG total score (an index of severity of language disorder) was correlated with the severity of SFRS, a higher leftward shift of handedness, and poorer performance on AX-CPT. Receiver operating characteristic (ROC) analysis showed that only CLANG and AX-CPT variables had adequate predictive validity in separating cases of ICD-10 schizophrenia from other diagnoses. The logistic regression model predicting the presence of ICD-10 schizophrenia was statistically significant using CLANG and AX-CPT variables, but not SFRS or other variables. HBS did not correlate with other variables and did not predict ICD-10 diagnosis. CONCLUSIONS: A cross-sectional diagnosis based on language disturbance and CPT performance yields a diagnostic construct largely overlapping with the ICD-10 definition of schizophrenia. We suggest that Schneider's first rank symptoms (that play a large role in the DSM-IV concept) can be considered an index of left hemisphere dysconnectivity for language whereas CPT dysfunction reflects dysconnectivity of the right hemisphere for those remoter ("spatial") associations that are closer to Bleuler's core defect and to the chronicity implicit in the ICD definition. Thus the dimensions of language disturbance in psychosis can be traced to specific cortico-cortical dysconnectivities.

Adult↗
PubMed2005

Race/ethnicity: a predictor of temporal lobe epilepsy surgery outcome?

PURPOSE: The success of epilepsy surgery in temporal lobe epilepsy reaches a 64% rate of seizure freedom, based on a randomized control trial. Observational studies from epilepsy centers worldwide indicate seizure freedom rates up to 93% when the etiology is unilateral hippocampal sclerosis. Several risk factors are attributed to the recurrence of seizures following the surgical procedure. Nonetheless, whether race influences the outcome of temporal lobe surgery is unknown. The purpose of this study was to evaluate if race plays a role in outcome following surgery. METHODS: Data were obtained from the discharge database of the University of Alabama at Birmingham video/EEG monitoring unit, between 1998 and 2003, as well as the clinical charts. Seizure recurrence was evaluated 1 year following surgery. The sample consisted of all patients with a primary diagnosis of mesial temporal sclerosis (MTS) who underwent anterior temporal lobectomy. Multiple logistic regression analysis was used to model the presence of seizure recurrence after anterior temporal lobectomy for MTS. Two sets of logistic regression models were estimated to generate odds ratios (ORs) for seizure recurrence after an anterior temporal lobectomy for African-Americans or other possible ethnic/racial group present relative to non-Hispanic Caucasians. The first model incorporated only ethnicity as the independent variable and generated unadjusted ORs for seizure recurrence following the surgical procedure. The second set included the independent variables: duration of epilepsy, history of febrile seizures, lateralization of epileptogenic focus, handedness, and age. RESULTS: Seventy patients underwent surgical treatment and all of them had pathologic confirmation of MTS. Follow-up information for six was not available. Analysis of the remaining 64 patients revealed that African-Americans were more likely than non-Hispanic Caucasians to have seizure recurrence after surgery (OR=2.1, 95% CI=0.6-8.0). After potential confounders (duration of epilepsy, history of febrile seizures, lateralization of epileptogenic focus, handedness, and age) were controlled, this finding did not change (OR=1.7, 95% CI=0.3-10.7). CONCLUSION: Our data suggest that race may be an important factor related to seizure outcome following temporal lobectomy.

Adult↗