Handedness in mental handicap: investigation into populations of Down's syndrome, epilepsy and autism

Left-handedness should not be overrated as a risk factor for postoperative speech impairment in children after posterior fossa tumour surgery: a prospective European multicentre study

PURPOSE

Cerebellar mutism syndrome (CMS) is a severe neurological complication of posterior fossa tumour surgery in children, and postoperative speech impairment (POSI) is the main component. Left-handedness was previously suggested as a strong risk factor for POSI. The aim of this study was to investigate the relationship between handedness and the risk of POSI.

METHODS

We prospectively included children (aged < 18 years) undergoing surgery for posterior fossa tumours in 26 European centres. Handedness was assessed pre-operatively and postoperative speech status was categorised as either POSI (mutism or reduced speech) or habitual speech, based on the postoperative clinical assessment. Logistic regression was used in the risk factor analysis of POSI as a dichotomous outcome.

RESULTS

Of the 500 children included, 37 (7%) were excluded from the present analysis due to enrolment at a reoperation; another 213 (43%) due to missing data about surgery (n = 37) and/or handedness (n = 146) and/or postoperative speech status (n = 53). Out of the remaining 250 (50%) patients, 20 (8%) were left-handed and 230 (92%) were right-handed. POSI was observed equally frequently regardless of handedness (5/20 [25%] in left-handed, 61/230 [27%] in right-handed, OR: 1.08 [95% CI: 0.40-3.44], p = 0.882), also when adjusted for tumour histology, location and age.

CONCLUSION

We found no difference in the risk of POSI associated with handedness. Our data do not support the hypothesis that handedness should be of clinical relevance in the risk assessment of CMS.

An Evaluation of Right-Sided Symptom Onset as a Predictor of Poor Parkinson's Disease Prognosis

Objective

The current study aimed to measure and compare neurological disability in Parkinson’s disease (PD) patients with right-sided symptom onset with that in PD patients with left-sided symptom onset, using the measurements taken at their first and last visits, to determine if right-sided symptom onset was predictive of a poor PD prognosis.

Methods

One hundred and forty-three PD patients were included in the study. The Unified Parkinson’s Disease Rating Scale (UPDRS) and the Hoehn and Yahr Scale were used to measure neurological disability in patients at the first and last visits. The scores for the neurological disability of patients at the first and last visits were compared retrospectively relative to disease onset.

Results

Seventy-six PD patients had right-sided symptom onset (53%), and 67 patients had left-sided symptom onset (47%) (p = < 0.001). The differences between the scores at the first and last visits, measured using the UPDRS and the Hoehn and Yahr Scale, were higher for PD patients with right-sided symptom onset than patients with left-sided symptom onset (p = < 0.001, p = < 0.002, respectively). Similarly, the UPDRS Part II and Part III values, used to evaluate motor function, were higher in PD patients with right-sided symptom onset as compared to those with left-sided symptom onset at the first and last visits (p = < 0.001).

Conclusion

Right-sided symptom onset was predictive of a poor prognosis in PD patients at follow-up.

Triplets, birthweight, and handedness

The mechanisms behind handedness formation in humans are still poorly understood. Very low birthweight is associated with higher odds of left-handedness, but whether this is due to low birthweight itself or premature birth is unknown. Handedness has also been linked to development, but the role of birthweight behind this association is unclear. Knowing that birthweight is lower in multiple births, triplets being about 1.5 kg lighter in comparison with singletons, and that multiples have a higher prevalence of left-handedness than singletons, we studied the association between birthweight and handedness in two large samples consisting exclusively of triplets from Japan (n = 1,305) and the Netherlands (n = 947). In both samples, left-handers had significantly lower birthweight (Japanese mean = 1,599 g [95% confidence interval (CI): 1,526-1,672 g]; Dutch mean = 1,794 g [95% CI: 1,709-1,879 g]) compared with right-handers (Japanese mean = 1,727 g [95% CI: 1,699-1,755 g]; Dutch mean = 1,903 g [95% CI: 1,867-1,938 g]). Within-family and between-family analyses both suggested that left-handedness is associated with lower birthweight, also when fully controlling for gestational age. Left-handers also had significantly delayed motor development and smaller infant head circumference compared with right-handers, but these associations diluted and became nonsignificant when controlling for birthweight. Our study in triplets provides evidence for the link between low birthweight and left-handedness. Our results also suggest that developmental differences between left- and right-handers are due to a shared etiology associated with low birthweight.

Lateralization of ERPs to speech and handedness in the early development of Autism Spectrum Disorder

BACKGROUND

Language is a highly lateralized function, with typically developing individuals showing left hemispheric specialization. Individuals with autism spectrum disorder (ASD) often show reduced or reversed hemispheric lateralization in response to language. However, it is unclear when this difference emerges and whether or not it can serve as an early ASD biomarker. Additionally, atypical language lateralization is not specific to ASD as it is also seen more frequently in individuals with mixed- and left-handedness. Here, we examined early asymmetry patterns measured through neural responses to speech sounds at 12 months and behavioral observations of handedness at 36 months in children with and without ASD.

METHODS

Three different groups of children participated in the study: low-risk controls (LRC), high risk for ASD (HRA; infants with older sibling with ASD) without ASD, and HRA infants who later receive a diagnosis of ASD (ASD). Event-related potentials (ERPs) to speech sounds were recorded at 12 months. Utilizing a novel observational approach, handedness was measured by hand preference on a variety of behaviors at 36 months.

RESULTS

At 12 months, lateralization patterns of ERPs to speech stimuli differed across the groups with the ASD group showing reversed lateralization compared to the LRC group. At 36 months, factor analysis of behavioral observations of hand preferences indicated a one-factor model with medium to high factor loadings. A composite handedness score was derived; no group differences were observed. There was no association between lateralization to speech at 12 months and handedness at 36 months in the LRC and HRA groups. However, children with ASD did show an association such that infants with lateralization patterns more similar to the LRC group at 12 months were stronger right-handers at 36 months.

CONCLUSIONS

These results highlight early developmental patterns that might be specific to ASD, including a potential early biomarker of reversed lateralization to speech stimuli at 12 months, and a relation between behavioral and neural asymmetries. Future investigations of early asymmetry patterns, especially atypical hemispheric specialization, may be informative in the early identification of ASD.

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.

Visual filtering and covert orienting in persons with Down syndrome

A forced-choice reaction time (RT) task was used to examine the efficiency of visual filtering (the inhibition of processing of irrelevant stimuli) and covert orienting (shifts of visual attention independent of eye movement) components of attention in persons with Down syndrome ( n = 20) and children of average intelligence ( n = 20) matched for mental age (MA) (average MA = approximately 5.4 years). Conditions varied with regard to presence or absence of distractors, and the validity (valid, invalid, or neutral) of location cues. Contrary to expectations, persons with Down syndrome and MA-matched children of average intelligence at approximately age 5 showed similar patterns of performance on a task that required filtering distracting stimuli and searching for relevant information in the visual field. Both groups responded more efficiently to a target preceded by a valid cue as compared to a target preceded by an invalid or neutral cue. In addition, performance was more efficient with a target that was presented without irrelevant information as compared to one that was flanked on either side by extraneous, nontarget information and therefore necessitated filtering for efficient performance. These two findings indicate that: (1) disengaging from the location of an incorrect cue, and then searching for, locating, and responding to a target requires more time and attention than simply locating and responding to a target that has been validly cued; and (2) processing and responding to a target flanked by extraneous information entails filtering, and therefore requires more time and resources than simply responding to a target without distractors. In general, the development of visual reflexive, covert orienting, and filtering are intact in persons with Down syndrome relative to their level of functioning at an MA level of approximately 5 years, a period that is critical in the development of attentional processes.

Handedness in Children With Autism Spectrum Disorder

The left hemisphere is usually predominant in manual skills and language, suggesting a link between hand dominance and language. Studies of autism spectrum disorder show atypical handedness; however, few have examined language-handedness associations. Handedness, assessed by task performance, and standardized receptive and expressive language tests were completed in 110 autism spectrum disorder children (96 boys; M age = 8.3 years, SD = 3.8) and 45 typically developing children (37 boys; M age = 8.6 years, SD = 4.3), 3 to 17 years of age. The autism spectrum disorder group had a lower handedness score (was less strongly lateralized) than the control group. In the autism spectrum disorder group, there was a small effect of handedness on language; right-handers had better language than non-right-handers. Results suggest poorer language prognosis may be associated with left- or mixed-handedness in autism spectrum disorder.

Paraphilic Interests: An Examination of Sex Differences in a Nonclinical Sample

Little research has been conducted to examine paraphilic sexual interests in nonclinical samples. The little that exists suggests that atypical sexual interests are more common in men than in women, but the reasons for this difference are unknown. In this study, we explored the prevalence of paraphilic interests in a nonclinical sample of men and women. We expected that men would report greater arousal (or less repulsion) toward various paraphilic acts than women. We also examined putative correlates of paraphilias in an attempt to explain the sex difference. In all, 305 men and 710 women completed an online survey assessing sexual experiences, sexual interests, as well as indicators of neurodevelopmental stress, sex drive, mating effort, impulsivity, masculinity/femininity, and socially desirable responding. As expected, significant sex differences were found, with men reporting significantly less repulsion (or more arousal) to the majority of paraphilic acts than women. Using mediation analysis, sex drive was the only correlate to significantly and fully mediate the sex difference in paraphilic interests. In other words, sex drive fully accounted for the sex difference in paraphilic interests. The implications of these findings for understanding the etiology of atypical sexual interests are discussed.

Atypically rightward cerebral asymmetry in male adults with autism stratifies individuals with and without language delay

In humans, both language and fine motor skills are associated with left‐hemisphere specialization, whereas visuospatial skills are associated with right‐hemisphere specialization. Individuals with autism spectrum conditions (ASC) show a profile of deficits and strengths that involves these lateralized cognitive functions. Here we test the hypothesis that regions implicated in these functions are atypically rightward lateralized in individuals with ASC and, that such atypicality is associated with functional performance. Participants included 67 male, right‐handed adults with ASC and 69 age‐ and IQ‐matched neurotypical males. We assessed group differences in structural asymmetries in cortical regions of interest with voxel‐based analysis of grey matter volumes, followed by correlational analyses with measures of language, motor and visuospatial skills. We found stronger rightward lateralization within the inferior parietal lobule and reduced leftward lateralization extending along the auditory cortex comprising the planum temporale, Heschl's gyrus, posterior supramarginal gyrus, and parietal operculum, which was more pronounced in ASC individuals with delayed language onset compared to those without. Planned correlational analyses showed that for individuals with ASC, reduced leftward asymmetry in the auditory region was associated with more childhood social reciprocity difficulties. We conclude that atypical cerebral structural asymmetry is a potential candidate neurophenotype of ASC. Hum Brain Mapp 37:230–253, 2016. © 2015 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.

Patterns of hand preference in Italian adolescent high-school students

The Annett Hand Preference Questionnaire (AHPQ) is amongst the most widely used self-report measures of handedness. The psychometric properties of the AHPQ have been rarely evaluated outside the Anglo-Saxon culture where the majority of the studies on the AHPQ were done. In this study, 1,023 students (males=49.5%) from four large high schools operating in the district of Cagliari (Italy) were invited to fill in the Italian version of the AHPQ. The AHPQ was proved to measure a unidimensional latent trait, and the questionnaire was good at assessing deviation from right-handedness with high discrimination between subjects. Some items were more informative than others, and in particular the non-equivalence between the primary and the non-primary actions was confirmed by both the confirmatory factor and the item response theory analysis. The use of the rule of thumb that classifies subjects on the basis of the primary actions was supported for the distinction between consistent right- and left-handed. However, the mixed-handed group identified on the basis of the rule of thumb was not entirely consistent with the mixed-handed class predicted by the latent class analysis. Males were about twice as likely as females to be in the mixed-handed class.

The effect of handedness on grip strength in older adults with intellectual disabilities

Grip strength is an important predictor of several health outcomes in the general older population. Grip strength assessment is feasible and reliable in older adults with intellectual disabilities (ID), which makes it a valuable measurement for application in this population. The purpose of this study was to investigate the effect of handedness on grip strength in the older population with ID. Handedness and grip strength were assessed in a sample of 1050 older adults (≥ 50 years) with borderline to profound ID. Results showed that 26.2% of the study sample was left-handed. In right-handed participants the dominant hand (right) was on average 8.7% stronger than the non-dominant hand (p<0.001). For lefthanded participants there was no significant difference between the dominant hand (left) and nondominant hand. However, more detailed analyses revealed that 34.5% of the participants were stronger with their non-dominant hand, (on average 16.6% stronger for right-handed and 16.3% stronger for left-handed participants). Because of the large strength ratios, distributed in favor of both the dominant as the non-dominant hand, it is recommended to assess both hands to get a valid result of grip strength in older adults with ID.

Clinical and neuroanatomical predictors of cerebellar mutism syndrome

Cerebellar mutism syndrome (CMS) is an important medical challenge in the management of pediatric posterior fossa brain tumors, because it occurs in a subset of children following tumor resection. A definitive clinical profile and neuroanatomical substrate associated with CMS remains unclear. We investigated the relationship between presurgical and clinical variables and the incidence of CMS, along with diffusion tensor imaging, to characterize the integrity of cerebello-thalamo-cerebral white matter pathways. Seventeen children with posterior fossa tumors and CMS, 34 children with posterior fossa tumors without CMS, and 28 healthy children were enrolled in this study. Bilateral cerebello-thalamo-cerebral pathways were delineated and segmented into anatomical regions. Mean integrity measures for each region were compared among children with CMS, children without CMS, and healthy children. Left-handedness, medulloblastoma histology, and larger tumor size distinguished between patients with CMS and patients without CMS (P < .04). Right cerebellar white matter within the cerebello-thalamo-cerebral pathway was compromised in children with CMS relative to children without CMS and healthy children (P < .02). We provide a potential schema for CMS risk among children treated for posterior fossa tumors. Left-handed children treated for medulloblastoma may be the most at risk for CMS, and unilateral, localized damage within the cerebello-thalamo-cerebral pathway at the level of the right cerebellum is implicated in the presentation of CMS. This disruption in communication between the right cerebellum and left frontal cortex may contribute to speech-language problems observed in children with CMS. Our findings may be relevant for surgical planning and speech-language therapy to mitigate symptoms of CMS.

The Effect of Handedness in Vocational Training among Adults with Intellectual Disability

Aim:

The main aim of this study was to describe the relationship between right-handed, left-handed and mixed-handed adults with intellectual disability and their success in vocational training courses.

Method:

A total of 71 research participants in Iran with moderate and severe intellectual disability were chosen and their hand preferences were determined by means of a hand preference test.

Results:

The results showed that the research participants who were right-handers or left-handers were significantly more successful than those participants who were mixed-handers. There was a significant relationship between left or right handedness and success in job training (chi2= 11.490, df = 2, p = 0.003). Left-handers were statistically more successful in job training programmes than their mixed-hander counterparts (chi2= 9.252, df = 1, p = 0.002).A similar difference was found between right-hander and mixed-hander groups (chi2= 9.047, df = 1, p = 0.003). The difference between left and right handers in job training was not statistically significant (chi2= 0.227, df = 1, p = 0.634).

Conclusion:

Hand preference could be an important consideration in the vocational rehabilitation assessment and evaluation of people with intellectual disabilities. Training programmes may need to be tailored to suit an individual according to handedness, particularly with those who are mixed-handers.

Effect of handedness on the Stroop Colour Word Task

Handedness is associated with cerebral organisation, but its relationship with cognition remains unclear. Since the Stroop task is believed to measure aspects of executive control, this study aims to investigate the effect of handedness on Stroop interference. We used the Stroop task with 90 young adults with university education, of whom 47 (23 males) were right-handed and 43 (21 males) were left-handed. Main dependent variables were Stroop baseline (SB), Stroop incongruent (SI), and the proportional derivative Stroop reduction (SR) [SR=(SB - SI)/SB×100%] (Bugg, Delosh, Davalos, & Davis, 2007; Graf, Uttl, &Tuokko, 1995) scores. The analysis revealed that SI is significantly affected by both handedness and the interaction of sex×handedness, whereas SR is only affected by handedness. After controlling for the effect of SB on SI, only the effect of handedness remained statistically significant [F(1, 83) = 6.44, p=.013]. Post-hoc comparisons showed that left-handed females performed significantly better than right-handed females on both SI (p=.003) and SR (p=.007). The data suggest that handedness is associated with cognitive function alterations, which lead to a smaller Stroop interference of left-handers irrespectively of sex, an effect that is more pronounced in the female subpopulation.

Individual Differences in Ambiguous-Figure Perception: Degree of Handedness and Interhemispheric Interaction

Research has shown that persons with strong right-hand preference (ie who report using their dominant hand for all manual activities) display a decreased tendency to update bodily and conceptual representations, possibly arising from decreased interaction between the left and right cerebral hemispheres. Current experiments extend these findings to the domain of perceptual representations. In experiments 1 and 2, strong right-handedness was associated with a decreased ability to update perceptual representations in response to gradually changing perceptual input. In experiment 3, strong right-handedness was associated with lower spontaneous reversal rates during the extended viewing of ambiguous figures, and experiment 4 ruled out an explanation in terms of response bias.

Abnormal EEG lateralization in boys with autism

OBJECTIVE

Functional brain abnormalities associated with autism in 3-8-year-old boys were studied with EEG recorded under controlled experimental condition of sustained visual attention and behavioral stillness.

METHODS

EEG was recorded in two independent samples of boys with autism (BWA) from Moscow (N=21) and Gothenburg (N=23) and a corresponding number of age-matched typically developing boys (TDB). EEG spectral power (SP) and SP interhemispheric asymmetry within delta, theta and alpha bands were analyzed.

RESULTS

BWA comprised a non-homogeneous group in relation to theta and alpha SP. When four outliers were excluded the only between-group difference in absolute SP was a higher amount of prefrontal delta in BWA. BWA of both samples demonstrated atypical leftward broadband EEG asymmetry with a maximum effect over the mid-temporal regions. Concurrently, the normal leftward asymmetry of mu rhythm was absent in BWA.

CONCLUSIONS

The abnormal broadband EEG asymmetry in autism may point to a diminished capacity of right temporal cortex to generate EEG rhythms. The concurrent lack of normal leftward asymmetry of mu rhythm suggests that abnormalities in EEG lateralization in autism may be regionally/functionally specific.

SIGNIFICANCE

The data provide evidence for abnormal functional brain lateralization in autism.

Laterality in Persons with Intellectual Disability. I—Do Patients with Trisomy 21 and Williams–Beuren Syndrome Differ from Typically Developing Persons?

Persons with trisomy 21 (T21) and Williams-Beuren syndrome (WBS) have different brain abnormalities which may affect manual laterality. We assessed 45 persons with T21 and 34 with WBS (mean age 13) and 81 typically developing children (TD). Manual laterality was assessed with a fifteen-item task administered two times, and Bishop's card-reaching task. We found more left-handers in the T21 group compared to the other two groups. Inconsistent laterality was higher in the two groups with genetic diseases than in the TD group. For Bishop's test, both T21 and WBS participants were less right-oriented than the TD group. They displayed different response patterns in midline crossing when reaching for the cards, but did not display more midline crossing inhibition than the TD group. Is atypical handedness linked to specific genetic syndromes and, more specifically for persons with T21, to the trisomy of some of the genes?

Lateral preferences in children with intellectual deficiency of idiopathic origin

The goal of this study was to evaluate lateral preferences in a population of children with intellectual deficiency of idiopathic origin, compared with those of typically developing (TD) children. Two groups of children with mild or moderate intellectual deficiency were observed. Handedness (using a 10-item test and Bishop's card-reaching task), eyedness and footedness were studied. The younger group consisted of sixteen 10- to 11-year olds; the older group comprised fourteen 12- to 14-year olds. A control group of fifteen TD children was matched for age with the younger group of intellectually deficient (ID) children. The results show that the occurrence of left-handedness is not higher in children with ID of unknown origin than in age-matched TD children. However, we observed a marginally reduced tendency toward right-handedness in ID than in TD children: more mixed-handers among ID than TD children; test-retest consistency of hand preference significantly lower in the 10- to 11-year-old ID children than in the age-matched TD children; greater tendency of ID children to use their nonpreferred left hand when the card was presented to the left, as compared with TD children. Left-eyedness and crossed hand-eye preference were also more frequent in ID than in age-matched TD children. No age-related difference in laterality was found in ID children. These results partially support other studies indicating that less rightward asymmetry is associated with intellectual deficiency in children.

Increased prevalences of left-handedness and left-eye sighting dominance in individuals with Williams-Beuren syndrome

Handedness and eye sighting dominance were assessed in a sample of 50 individuals (25 male, 25 female; aged 5-38 years) with Williams-Beuren syndrome (WBS). The prevalences of left-handedness and left-eyedness were compared to the normative prevalences in the general population. We found significantly higher prevalences of left-handedness and left-eyedness in the WBS sample. The higher prevalences were more salient in younger than in older individuals and in male than in female individuals. We suggest that the increased prevalence of left-handedness in WBS is a consequence of a slower maturation rate, which allows deviation from a predetermined laterality pattern.

Functional analysis of genes implicated in Down syndrome: 2. Laterality and corpus callosum size in mice transpolygenic for Down syndrome chromosomal region -1 (DCR-1)

The association between atypical laterality and mental retardation has been reported several times, particularly in Down syndrome (DS). We investigated common genetic correlates of these components of the syndrome, examining direction (number of right paw entries in the Collins test) and degree (absolute difference between the number of right paw entries and the number of left paw entries) in mice that had incorporated extra-contiguous HSA21 fragments covering DCR-1 (Down Chromosomal Region-1). As corpus callosum size is substantially reduced in DS, and as the structure has been suspected of playing a role in atypical laterality, we also measured the corpus callosum in these mice. Extra copies of two regions (F7 and E6) have been associated with an atypical degree of laterality (strongly reduced degree). Extra copies of E8, G6 and E6 are also linked to the reduced size of the corpus callosum, indicating that the abnormal number of fibers linking the two hemispheres is not associated with atypical laterality in DS. Together, these results indicate that some of the genes involved in atypical laterality and in the reduced size of the corpus callosum in DS are present on DCR-1. An extra copy of F7 and, to a lesser extent, an extra copy of E6, are also associated with cognitive impairment. These results support the hypothesis of common genetic correlates in atypical laterality and mental retardation in DS.

Laterality biases to chimeric faces in Asperger syndrome: what is 'right' about face-processing?

People show a left visual field (LVF) bias for faces, i.e., involving the right hemisphere of the brain. Lesion and neuroimaging studies confirm the importance of the right-hemisphere and suggest separable neural pathways for processing facial identity vs. emotions. We investigated the hemispheric processing of faces in adults with and without Asperger syndrome (AS) using facial emotion and identity chimeric tasks. Controls showed an LVF bias in both tasks, but no perceptual bias in a non-social control task. The AS group showed an LVF bias during both tasks, however the bias was reduced in the identity condition. Further, the AS group showed an LVF bias in the non-social condition. These results show a differential pattern of hemispheric processing of faces in AS.

Handedness in twins: a meta-analysis

In the largest meta-analysis of twins and singletons conducted to date we have found a higher incidence of left-handedness in twins compared to singletons. Our analysis revealed no difference in the frequency of left-handedness among monozygotic versus dizygotic twins. However, identical twins were more likely to be concordant for hand preference than non-identical twins, which is consistent with a genetic model of handedness. Prior analyses have not revealed these findings consistently, and this has led to a number of conflicting models of handedness.

Evaluation of empirical methods and methodological foundations of human left-handedness

The methodological and empirical foundations underlying the theories on human left-handedness are examined, including the definition and classification of left-handedness, its relation to pathology, and the results on family, adoption, and twin research. It is argued that major research findings on left-handedness are based on inadequate empirical methods, and the concrete definitions and assessment procedures do not meet validity and reliability criteria. This also casts doubt on the relationship between left-handedness and pathology reported in the literature. Furthermore, findings from family, adoption, and twin studies do not allow interpretation of possible direct genetic contributions to explaining left-handedness. It is concluded that the methodological limitations of a causal explanation should encourage an examination of the epistemological and methodological premises of theory formulation. The functional method and a theoretical framework based on early childhood experiences and the neural plasticity of the brain may be more appropriate for the selection of empirical methods in research of human left-handedness.

Intelligence, Memory, and Handedness in Pedophilia

A sample of 473 male patients with pedophilia (assessed by the patients' sexual history and penile response in the laboratory to standardized, erotic stimuli) or other problematic sexual interests or behaviors received brief neuropsychological assessments. Neuropsychological measures included a short form of the Wechsler Adult Intelligence Scale--Revised (D. Wechsler, 1981), the Hopkins Verbal Learning Test--Revised (R. H. B. Benedict, D. Schretlen. L. Groninger. & J. Brandt, 1998), the Brief Visuospatial Memory Test--Revised (R. H. B. Benedict, 1997), and the Edinburgh Handedness Inventory (S. M. Williams, 1986). Pedophilia showed significant negative correlations with IQ and immediate and delayed recall memory. Pedophilia was also related to non-right-handedness even after covarying age and IQ. These results suggest that pedophilia is linked to early neurodevelopmental perturbations.

Academic achievement and learning abilities in left-handers: guilt or gift?

The main purpose of this cross-sectional study was to compare the acceptance rate (AR) of left-handers (LHs) with that of right-handers (RHs) in the college entrance examination (CEE) for the national universities in Iran. During 5 successive years, fifty thousand participants in this exam were randomly sampled. We evaluated the relationships between AR and hand preference, sex, college admission (CA), entrance exam score (EES) and study areas: Mathematics, Natural Sciences, Humanities and Art. The acceptance rate of the LHs over the entire study period was significantly higher than that of the RHs (27.3% versus 24.3%, p < 0.0001). The mean score attained on examination by LHs was significantly higher than that of RHs in all study areas (p < 0.002). The acceptance rate of LHs in all study areas was higher but the difference reached statistical significance in the Art area only (p < 0.01). It is concluded that left-handers may be regarded as a heterogeneous large group consisting of different subgroups. Those who are able to compete for the college entrance examination score are even more successful than right-handers in terms of average EES and the rate of CA.

Cognitive status in Down syndrome individuals with sleep disordered breathing deficits (SDB)

Twelve subjects with Down syndrome underwent polysomnographic studies during night sleep and performed the Mini-Mental state test and the Raven Progressive Matrices (RPM), sets A, B, and B(1). Sleep-disordered breathing (SDB) deficits were observed in Down syndrome individuals and their Mini-Mental and RPM scores were extremely low. Regression analysis of the results revealed that the number of apneas per hour was related with the results of the RPM, set A, which were also related with the orientation of Mini-Mental test, indicating that the more apneas an individual has the more difficulties he has in the kind of visuoperceptual skills, including orientation, associated with normal right hemisphere functioning, which are tested by set A of the RPM.

Asperger's disorder in the emergency psychiatric setting

Asperger's syndrome (AS) is a pervasive developmental disorder that may be unrecognized, especially if signs of other psychiatric disorders coexist. The objectives of this paper are: 1) to ascertain the prevalence of AS in the emergency psychiatric setting; and 2) to describe features of AS which may help to differentiate these patients from patients with psychotic disorders. Among 2500 patients admitted to a psychiatric intensive care unit, 5 (0.2%) received a diagnosis of AS, for the first time. Besides impairment of social interaction, common features were the following: male gender, left handedness, obsessive-compulsive symptoms, cognitive hyper-abilities, violent behavior, sense of humor, low WAIS total score, high WAIS verbal/performance score ratio, unusual, restricted interest and clumsiness. Comorbid schizophrenia is difficult to rule out in these patients. Psychotic symptoms should not be overvalued in making the diagnosis when specific features of AS are present.

Cerebral dominance and schizophrenia-spectrum disorders in adults with intellectual disability

Studies of the general population without intellectual disability have suggested an association between atypical handedness and schizophrenia-spectrum disorders (SSDs). Mixed handedness is taken as an index of diminished cerebral dominance or laterality. The present study addressed the question of whether such findings extend to the neurodevelopmentally 'at risk' population of adults with intellectual disability and SSDs compared with appropriate controls. Fourteen patients with a dual diagnosis of intellectual disability and SSD were compared with 14 controls with intellectual disability alone. Assessments of self-reported hand preference and relative hand skill were completed. Self-report of hand preference revealed highly significantly greater mixed-handedness in the SSD group. Furthermore, relative hand skill performance was significantly diminished for the dominant hand. The discrepancy between dominant and non-dominant hand functioning was lower in the SSD group and this association was highly significant. The results of the present study support the usefulness of such detailed laterality assessment in this population. Mixed laterality, over and above that of the population with general intellectual disability and developmental disorder, was associated with SSD. These results are consistent with the neurodevelopmental hypothesis of schizophrenia and its cognitive neuropsychiatric/neuropsychological sequelae.

A descriptive survey of long-term residents with epilepsy and intellectual disability at the Chalfont Centre: is there a relationship between maladaptive behaviour and magnetic resonance imaging findings?

The advent of high-resolution magnetic resonance imaging (MRI) has facilitated the identification of subtle, aetiologically relevant structural brain abnormalities in a significant proportion of patients with epilepsy and negative standard neuro-imaging. In the present study of people with intellectual disability (ID), the authors show that a high frequency of cerebral structural abnormalities (72.4%) can be demonstrated by high-resolution MRI in patients with epilepsy and ID. Malformations of cortical development (MCD) were found in 8.7% of people without profound ID. An earlier age of onset of habitual seizures was associated with more severe ID and more severe seizures in adulthood. There was no obvious association between this finding and maladaptive behaviour, but a past history of febrile convulsions was associated with increased irritability and agitation. Since there was no obvious association between a history of febrile convulsions and MRI abnormalities, the reason for the above finding remains unclear. Inevitably, any residential epilepsy centre population is subject to selection biases. The population studied was highly skewed, with only one-third of the sample being female and 80% having mild ID. Thus, the findings of the present study cannot necessarily be generalized to all people with ID.

A developmental study of handedness in Down syndrome pupils

Assessed hand preference in 7- to 9-yr.-old and 13- to 15-yr.-old pupils with Down syndrome (n = 41) was compared with control schoolchildren (n = 50) of the same ages. A significant increase in left-handedness and mixed-handedness was noted in Down syndrome groups compared with the normal population. Younger Down syndrome pupils were less consistent in their hand preference than the older pupils and the normal controls.

Laterality and handedness in mentally retarded subjects

In a study of 69 adults with mental retardation, atypical laterality measured on 12 tasks was only partially noted. Distribution of over-all laterality scores was different from that of handedness with more left-handed than left lateralized and more right manual preference among the 43 women.