Laterality and language experience

A meta-analysis was conducted on studies that examined hemispheric functional asymmetry for language in brain-intact monolingual and bilingual adults. Data from 23 laterality studies that directly compared bilingual and monolingual speakers on the same language were analysed (n?=?1234). Variables examined were language experience (monolingual, bilingual), experimental paradigm (dichotic listening, visual hemifield presentation, and dual task) and, among bilinguals, the influence of second language proficiency (proficient vs nonproficient) and onset of bilingualism (early, or before age 6; and late, or after age 6). Overall, monolinguals and late bilinguals showed reliable left hemisphere dominance, while early bilinguals showed reliable bilateral hemispheric involvement. Within bilinguals, there was no reliable effect of language proficiency when age of L2 acquisition was controlled. The findings indicate that early learning of one vs. two languages predicts divergent patterns of cerebral language lateralisation in adulthood.     

Laterality and language experience

A meta-analysis was conducted on studies that examined hemispheric functional asymmetry for language in brain-intact monolingual and bilingual adults. Data from 23 laterality studies that directly compared bilingual and monolingual speakers on the same language were analysed (n = 1234). Variables examined were language experience (monolingual, bilingual), experimental paradigm (dichotic listening, visual hemifield presentation, and dual task) and, among bilinguals, the influence of second language proficiency (proficient vs nonproficient) and onset of bilingualism (early, or before age 6; and late, or after age 6). Overall, monolinguals and late bilinguals showed reliable left hemisphere dominance, while early bilinguals showed reliable bilateral hemispheric involvement. Within bilinguals, there was no reliable effect of language proficiency when age of L2 acquisition was controlled. The findings indicate that early learning of one vs. two languages predicts divergent patterns of cerebral language lateralisation in adulthood.     

Laterality and reading proficiency

Lateral asymmetry in tachistoscopic perception of words was investigated in good and poor readers between 7:6 and 8:7 years old. Five-letter words were presented unilaterally to left or right of a fixation point. Good readers showed greater right over left field superiority than poor readers. Several possible causal factors are discussed. It is concluded that good and poor readers of the same age differ in the degree of lateralization in terms of cerebral hemispheric specialization of language functions. In addition, poor readers were superior to good readers on left hemifield presentations. This possibly suggests superior linguistic function in the right cerebral hemisphere of less lateralized individuals. Boys showed greater asymmetry than girls.     

Laterality and reading attainment

This investigation was concerned with measures of laterality and their usefulness as predictors of reading attainment. Previous research has suggested that retarded reading is the result of abnormal development of cerebral dominance, and that this may be indicated by left-handedness or by inconsistencies in lateral preference. A group of schoolboys carried out tests of lateral preference, reading, spelling, and experimental tasks involving dichotic listening and tachistoscopic recognition. There was no evidence that left-handedness, right cerebral dominance, or inconsistencies in laterality were correlated with reading retardation.     

Laterality in schizophrenia

Summary A laterality study in schizophrenia was carried out by measuring reaction time (RT) in a baseline condition and while subjects were engaged in a concurrent task. In the baseline condition, a clinical measure of psychoticism was associated with differential slowing with the right hand in schizophrenic dextrals but not in a control group of affective dextrals. The concurrent task suppressed the effect of psychoticism on RT performance. The results suggest that left-hemisphere deficits in schizophrenia are state dependent, and so not necessarily due to cortical dysfunction.From a doctoral thesis completed at the New School for Social Research     

Laterality and Types of Dyslexia

ANNETT, M. Laterality and types of dyslexia. NEUROSCI BIOBEHAV REV 20(4) 631–636, 1996.—The right shift theory of handedness and cerebral specialization suggests that there is an underlying substrate of random lateral asymmetries in all higher animals and a specific factor in humans which increases the probability of left hemisphere advantage. The specific factor displaces the random distribution along a continuum of asymmetry in favour of the left hemisphere and the right hand. The distribution of handedness in families can be explained if the shift to dextrality depends on a single gene, rs +, when the frequency of the gene is estimated from the proportion of dysphasics with unilateral lesions of the left versus the right hemisphere. The genotype proportions suggested a genetic balanced polymorphism with heterozygote advantage for laterality and ability.

Application of the model to developmental dyslexia led to the hypothesis that both homozygotes (rs −− and rs ++ genotypes) are at risk for reading. The critical question was whether the type of cognitive problem differs as expected, speech based processing for the rs −− and non-speech based for the rs ++. The former should include more left and mixed handers, while the latter should be more strongly dextral than controls. Evidence for this double dissociation between type of cognitive disability and type of handedness has been found in poor readers and in other samples. Copyright © 1996 Elsevier Science Ltd.     

Affective disorders,personality and personality disorders

OBJECTIVE: The article deals with the complex conceptual history and current concepts on the relationship between personality, personality disorders and affective disorders. It is discussed whether these concepts represent distinct clinical entities or whether they lie on a continuum. METHOD: We reviewed the classical literature from the 19th and the first half of the 20th centuries as well as analysed recent empirical data in order to summarize the current knowledge on this topic with respect to its historical origin. As a particular example, the position of the depressive personality disorder is evaluated. RESULTS: Considerable heterogeneity can be seen, both theoretically and empirically. The two major concepts are based either on a continuum model or favour distinct clinical entities, corresponding to a more dimensional or category-orientated recording method. CONCLUSION: The relationship between personality disorders and affective disorders is still unclear and is a highly debated issue. There is as yet no consensus, but a certain shift to dimensional models can be recognized.     

Laterality of hand, foot, eye, and ear in twins

Information on handedness, footedness, eyedness, and earedness was collected from 33 monozygotic (MZ) twin pairs and 67 dizygotic (DZ) twin pairs. The incidence of nonright-sidedness in the twins is not higher than that reported in the literature for singletons. Similar results are found for the other lateralities. The results of assessing handedness with preference tests do not differ from those carried out with performance tests. There are no differences in incidence of nonright-sidedness between MZ and DZ twins. The concordance of lateralities is similar in MZ and DZ twins. The proportions of Right-Right, Right-Nonright, and Nonright-Nonright pairs in both groups of twins show a binomial distribution. The present results do not confirm a genetic hypothesis of determination of sidedness in humans and are comparable with the results obtained by other twin studies.     

Laterality,sex, and everyday spatial behaviours: an exploratory analysis

ABSTRACT

Exploratory analyses of a 126-item self-report assessment of difficulty of spatial behaviours (revision of the Everyday Spatial Behavioral Questionnaire, ESBQ) were used to examine principal components and the underlying root structure of perceived spatial competencies. We also examined laterality measures (handedness, footedness, and earedness), sex, and age as predictors of spatial behaviour component scores. 12 principal components were identified that represented facets of spatial behaviour and perception. Canonical analysis revealed 2 underlying dimensions of perceived difficulty in performing spatial behaviours: difficulty with spatial relations in the context of movement and difficulty with judging how things relate to each other or to a larger surround. Sex was more closely related to the former dimension; laterality measures and age were more closely related to the latter. With respect to specific components, women tended to report more difficulty with making judgements in relation to earth-fixed axes but less difficulty in judging relations to nearby objects and how objects fit together or within a surround. Right-handedness was associated with more perceived difficulty in judging spatial relations while driving, overlaying surfaces, and moving in relation to other objects in nearby space. Future confirmatory analyses will be needed to establish subscales of the ESBQ and their usefulness for practical applications.     

Handedness,Footedness, and Language Laterality: Evidence from Wada Testing

A total of 37 candidates for temporal lobe resection for epilepsy completed the Lateral Dominance Examination, a self-report instrument that measures hand and foot preference. Questionnaire results were compared with speech dominance, which had been determined by Intracarotid Sodium Amytal Procedure. Footedness was as good as handedness as a predictor of language laterality.     

Intercorrelation of Laterality Indices

Five previously proposed laterality indices were found to correlate very highly with each other in both a verbal dichotic listening task and a word recognition task, despite large individual differences in overall accuracy. In the dichotic listening task, all of the laterality indices were positively correlated with overall accuracy; that is, accuracy increased as the magnitude of the laterality effect increased. In the word recognition task, however, no consistent relationship was found between laterality and accuracy.     

Laterality and performance of agility-trained dogs

Correlations between lateralised behaviour and performance were investigated in 19 agility-trained dogs (Canis familiaris) by scoring paw preference to hold a food object and relating it to performance during typical agility obstacles (jump/A-frame and weave poles). In addition, because recent behavioural studies reported that visual stimuli of emotional valence presented to one visual hemifield at a time affect visually guided motor responses in dogs, the possibility that the position of the owner respectively in the left and in the right canine visual hemifield might be associated with quality of performance during agility was considered. Dogs' temperament was also measured by an owner-rated questionnaire. The most relevant finding was that agility-trained dogs displayed longer latencies to complete the obstacles with the owner located in their left visual hemifield compared to the right. Interestingly, the results showed that this phenomenon was significantly linked to both dogs' trainability and the strength of paw preference.     

Laterality of brain tumors

Tumor laterality was evaluated with respect to presenting symptoms and demographic factors among 489 adults with histologically confirmed glioma (354 high-grade, 135 low-grade), 197 with meningioma, and 96 with acoustic neuroma. The ratio of left-sided to right-sided tumors did not differ significantly from 1.00 for any of the major tumor types. Low-grade glioma and meningioma occurred nonsignificantly more often on the left side, whereas high-grade glioma and acoustic neuroma occurred nonsignificantly more often on the right side. Aphasia or mental status changes were significantly more common among glioma patients with tumors on the left side than among those with tumors on the right side. Associations between tumor laterality and symptoms may influence the probability or timing of diagnosis, possibly differentially by marital status.     

Laterality effects for simple and complex geometrical figures, and nonsense patterns

Three groups of normal, right-handed subjects were trained to give same-different responses to pairs of stimuli presented simultaneously to the right or the left side of a fixation point. The subjects exhibited faster reactions (pressing one of two keys) to stimuli appearing in the right visual field when the stimuli were simple geometrical figures (e.g. triangles and squares) or nonsense patterns. By contrast, the subjects showed a left-visual field advantage when the stimuli were complex geometrical figures (e.g. ten- and eleven-sided regular polygons). These differences in performance for the halves of the visual field are attributed to differential hemispheric specializations. The opposite hemispheric superioritieis found with different classes of stimuli are in turn attributed to the discrimination of single features by the left hemisphere and to the use of a spatial strategy by the right hemisphere.     

Depression, anxiety, and temporal lobe epilepsy. Laterality of focus and symptoms

The association between anxiety, depression, and lateralization of an epileptogenic focus was explored in 18 adult patients with a left temporal lobe focus, 21 with a right focus, 20 with bilateral temporal foci, and 16 individuals with absence seizures. No significant difference in the level of anxiety was found among the groups. However, patients with left-sided temporal lobe epilepsy scored significantly higher than other groups on self-ratings for depression. This could not be accounted for by factors such as duration of epilepsy, employment status, education, age at seizure onset, or medication status. The left temporal lobe epilepsy group had a nonsignificantly larger number of males and left-handed subjects. The possible interactions between gender, handedness, seizure focus, and vulnerability to depression are described.