The Effect of Familial Sinistrality and Academic Experience on Cognition in Right-Handed Women.

Research in sex, brain lateralization, and cognition suggests that right-handed women vary in cognitive ability according to handedness inheritance patterns. Right-handed college women with positive familial sinistrality (FS+; i.e., the presence of at least one left-handed biological relative; n = 30) were compared with right-handed women with negative familial sinistrality (FS-; n = 30) by means of visuospatial (the Rey-Osterrieth Complex Figure Test and the Wechsler Adult Intelligence Scale--Revised Block Design subtest), verbal (the California Verbal Learning Test and Animal Naming), and motor performance tests (Finger Tapping and Grooved Pegboard). FS+ women outperformed FS- women on spatial tasks and used more efficient spatial strategies. The FS- group showed no corresponding verbal advantage. Spatial differences were not accounted for by motor skill, intellectual ability, or academic major. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prenatal exposure to diethylstilbestrol (DES) and the development of sexually dimorphic cognitive abilities and cerebral lateralization.

Investigated the possibility that the perinatal hormonal environment is related to the development of cognitive sex differences in humans by comparing 25 women who had been exposed prenatally to DES, a synthetic estrogen, to their unexposed sisters. All Ss completed word fluency and spatial relations tests, the Wonderlic Personnel Test, and a dichotic listening task. The DES-exposed Ss showed a more masculine pattern of lateralization (i.e., a stronger right-ear advantage) than did their sisters on a verbal dichotic task. However, no differences were observed between exposed and unexposed Ss in verbal or visuospatial ability. Although interpretation of these data must be cautious, they provide some support for a relationship between high prenatal estrogen levels and the development of masculine-typical function in humans. Implications for previous studies of biological contributions to cognitive sex differences and possible mechanisms for estrogenic effects on the development of lateralization are discussed. (114 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sex differences in mental abilities, hemispheric lateralization, and rate of physical growth at adolescence.

Tested the hypothesis that sex differences in verbal and spatial abilities are related to sex differences in rates of physical maturation and that this relationship is mediated by variation in the organization of higher cortical functions. 40 males and 40 females, ranging in age from 10-16 yrs, were tested on 3 verbal measures (including the Digit Symbol subtest of the WISC and the Word Fluency subtest of the Primary Mental Abilities Test), 3 spatial measures (including the Block Design subtest of the WISC and a modified version of the Embedded Figures Test), and a dichotic test of phoneme identification. Late-maturing Ss of both sexes performed better than early maturers on tests of spatial ability, but the groups did not differ on tests of verbal ability. Among older Ss, the late maturers of both sexes showed greater hemispheric lateralization than early maturers. Sex differences on the ability measures, although in the predicted direction, did not reach significance. Results are discussed with respect to the relationship between hemispheric organization of function and mental abilities and the relationship between maturational rate and lateralization. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Risk factors for cognitive impairment in epilepsy.

The literature suggests that seizure disorders are associated with an increased likelihood of intellectual problems, prompting researchers to investigate risk factors of cognitive impairment in epileptic patients. This study examined the contribution of certain variables (age of seizure onset, duration, etiology, seizure location and laterality, sex, handedness, and cerebral speech pattern) to cognitive outcome in patients with medically refractory seizures. Seizure location (temporal or extratemporal), age of onset of seizures, and handedness proved to be the best indicators of general intellectual ability. There was a relatively diverse pattern of relationships when neuropsychological tests of language, visuospatial ability, and memory were considered individually. However, a factor analytic approach revealed a simpler pattern in which location of dysfunction, age at seizure onset, hand preference, cerebral speech dominance, and gender were relevant and independent indicators of verbal and nonverbal ability. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Auditory lateralization in monozygotic twins

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

Psychobiological heterogeneity of familial and sporadic schizophrenia

BACKGROUND: Although schizophrenia is presumed to be heterogeneous, there has been limited success distinguishing familial from sporadic cases. We used psychobiological measures to examine heterogeneity, as they may be closer to neurobiology than symptoms. Smooth pursuit eye movement quality (SPEM) and dichotic listening (DL) tests to tones and words were used to assess hemispheric laterality asymmetry. METHODS: Forty-six research unit patients participated in assessments of family history (FH) and physiological measures. FH was categorized by three exclusive groups: FH-1 patients had a chronic schizophrenia-related psychosis in a first-degree relative, FH-2 had it in second-degree relative, and FH-3 had no family member with a reoccurrence. RESULTS: Analysis of variance showed a significant group difference for SPEM and DL tones. SPEM was significantly worse in all three schizophrenia groups than for the normal comparison subjects. Among the schizophrenia groups, the nonfamilial group (FH-3) had the worst SPEM quality, FH-2 had intermediate quality, and FH-1 had the best quality. Conversely, only the nonfamilials (FH-3) had normal right hemispheric lateralization for tones, whereas familials did not, and FH-2 again had intermediate values. The lateralization quotient for DL words did not significantly differ among the groups. CONCLUSIONS: SPEM was affected most in sporadic, not familial schizophrenia, whereas dichotic listening was most affected in familial schizophrenia. This double dissociation supports the utility of the familial/sporadic distinction and suggests that etiological factors in different forms of schizophrenia may impact principally on distinct neurobiological substrates, despite similar patient phenomenology.     

Klinefelter's syndrome as a model of anomalous cerebral laterality: testing gene dosage in the X chromosome pseudoautosomal region using a DNA microarray

Consistent handedness and language laterality are two of the most striking behavioral and cognitive asymmetries observed in humans. Alterations in the typical pattern of cerebral laterality, termed "anomalous dominance," is observed in left-handers and some patients with verbal learning disabilities. We undertook the study of a genetically distinct group of subjects, XXY males (Klinefelter's syndrome; KS), who demonstrate anomalous dominance in a variety of testing paradigms in order to begin to elucidate the molecular basis of anomalous dominance in this population. KS subjects manifest specific verbal learning disability, evidence of altered functional laterality for phonologic processing, and an increase in left-handedness when measured by skill. It is proposed that an alteration in gene dosage in the pseudoautosomal region (PAR) of the sex chromosomes is the most likely explanation for anomalous dominance in these patients. This is especially intriguing in light of previously described genetic models of cerebral laterality that suggest a contributing locus in the PAR, or adjacent high homology regions of the X chromosome. We have developed an ordered DNA microarray covering the X chromosome PAR at high resolution for hybridization with two-color fluorescently labeled probes. We demonstrate the ability to detect changes in hybridization signal that will facilitate efficient large-scale screening of this region for alterations in gene dosage associated with features of anomalous dominance and other cognitive or behavioral phenotypes.     

Examining the relationship between degree of handedness and degree of cerebral lateralization for processing facial emotion.

This paper examines the relationship between degree of handedness and degree of cerebral lateralization on a task of processing positive facial emotion in right-handed individuals. Three hundred and thirteen right-handed participants (157 women) were given two behavioral tests of lateralization: a handedness questionnaire and a chimeric faces test. Two further handedness measures were taken: familial lefthandedness and writing posture. Regression analysis showed that both degree of handedness and sex were predictive of degree of lateralization. Individuals who were strongly right-handed were also more strongly lateralized to the right hemisphere for the task. Men were more strongly lateralized than women. Data were reanalyzed for men and women separately. The relationship between handedness and lateralization remained for men only. Neither familial left-handedness nor writing posture were associated with cerebral lateralization for men or women. The results suggest a positive relationship between degree of handedness and degree of cerebral lateralization, and further that there is a sex difference in this relationship. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Changes in perceptual asymmetries with clinical improvement of depression and schizophrenia.

16 depressed patients, 16 schizophrenic patients, and 16 normal controls (20–50 yrs old) were given 2 dichotic listening tests and 2 cognitive tests at intervals ranging from patients' initial hospitalization to recovery. Repeated-measures ANOVA revealed that severely depressed Ss failed to obtain normal ear-superiority in either dichotic test; however, normal superiorities emerged with recovery from depression. Schizophrenic Ss initially failed to show normal right-ear superiority on a dichotic-words test but did obtain the expected left-ear advantage on a dichotic-chords test. Following treatment, schizophrenics shifted from a left-ear to a right-ear advantage in dichotic chords and also increased (although not significantly) their right-ear advantage in dichotic words. Both patient groups showed normal word-fluency but impaired spatial ability, which did not improve with recovery. Results suggest that both depression and schizophrenia are associated with a breakdown in the process of interhemispheric inhibition that mediates perceptual asymmetry. In depression, treatment returned Ss' normal patterns of asymmetry, whereas in schizophrenia, treatment created an abnormal pattern of asymmetry that may have reflected the allocation of both verbal and nonverbal material to the left hemisphere. (42 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Asymmetric effects of ovarian hormones on hemispheric activity: Evidence from dichotic and tachistoscopic tests.

Previous studies have suggested a role of endogenously cycling ovarian hormones in the modulation of perceptual asymmetries. In the present investigation, participants were given perceptual asymmetry tests including verbal and nonverbal tachistoscopic and dichotic listening tasks during the menstrual and midluteal phases of the menstrual cycle. Salivary levels of estrogen and progesterone were also measured. Analyses of performance on the tachistoscopic tests revealed that left visual field, but not right visual field, accuracy was significantly lower for both verbal and nonverbal tasks at the midluteal phase than at the menstrual phase. Right ear performance on the nonverbal dichotic test was significantly reduced at the midluteal phase. Results suggest suppression of right hemisphere processing areas and possible reduction in callosal transfer efficiency at higher levels of ovarian steroids. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Individual differences in cognitive abilities and brain organization: I. Sex and handedness differences in ability.

Analyzed data on cognitive abilities from 3 samples of normal Ss: (1) 195 undergraduates, (2) 215 18–30 yr old newly married couples, and (3) 122 pairs of monozygotic and dizygotic twins (aged 12–38 yrs). Findings reveal a common Sex by Handedness by Reasoning-Ability interaction: For Ss with above-median reasoning ability, spatial scores of left-handed males were reduced but those of left-handed females were raised, relative to their right-handed counterparts; the opposite pattern was found for Ss with below-median reasoning ability. The dependence of handedness effects on reasoning ability level appears to explain some of the inconsistent findings in the literature. Verbal fluency, perceptual speed, and visual memory also showed sex and handedness effects, which often interacted with level of reasoning ability or other cognitive variables. Results strongly suggest that sex and handedness differences in cognitive ability are partly neurological in origin. Variations in the effects of handedness across levels of reasoning ability (or other abilities) may indicate that different trade-offs among structural, and thus cognitive, characteristics will be found in different subsamples: There may be many kinds of normal brain organization. (French abstract) (98 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cognitive abilities and hemispheric lateralization in females following idiopathic precocious puberty.

Compared 12 right-handed adolescent females with a history of idiopathic precocious puberty (IPP) to 12 closely pair-matched normal controls of similar maturational status. All Ss were aged 13–20 yrs. Cognitive abilities were assessed by subtests of the WISC and Primary Mental Abilities Test, and by combination scales derived from these subtests. Brain hemispheric lateralization was measured by 2 dichotic listening tests. Results show that IPP Ss and controls did not differ in verbal abilities or in dichotic consonant–vowel discrimination. IPP was associated with lower spatial ability. It is concluded that pubertal maturation is associated with spatial but not verbal ability. Left-hemisphere functioning does not seem to constitute a mediating mechanism for this association but a slight weakness of right-hemisphere functioning is suggested by poor left-ear performance on the staggered spondaic word test. (47 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A Laterality Index of cognitive impairment after hemispheric damage: A measure derived from a principal-components analysis of the Wechsler Adult Intelligence Scale.

Attempts to use the WAIS to measure verbal and nonverbal cognitive impairments of the type believed to be associated with unilateral brain damage have been vitiated by the fact that neither the Verbal nor the Performance subtests of the WAIS calls upon purely verbal or nonverbal ability. Advantage may, however, be taken of the factorial composition of these tests so as to devise a laterality index using the Factor-2 score coefficients from a principal-components solution in combination with the individual's age-scaled subtest scores. This index may be used to determine the significance of verbal–nonverbal discrepancies in the single case, as well as differences between groups of patients. Analysis of data from 80 patients with unilateral stroke (20 male left, 20 male right, 20 female left, and 20 female right) who had completed 10 of the 11 WAIS subtests confirmed that the sex of the patients tested influenced the cognitive effects of unilateral brain damage. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Activating effects of androgens on cognitive performance: causal evidence in a group of female-to-male transsexuals

It is still unclear whether sex differences in cognitive functioning are mainly due to perinatal organizing effects of sex hormones on the brain, or to activating effects in adulthood. In a group of 22 female-to-male transsexuals a battery of visuospatial and verbal ability tests was administered twice: shortly before and 3 months after the start of androgen treatment. The administering of androgens was clearly associated with an increase in spatial ability performance. In contrast, it had a deteriorating effect on verbal fluency tasks. This study offers preliminary evidence that androgens directly and quickly affect cognitive performance in females.     

Experimental toxoplasmosis in calves

Two hundred schizophrenics were compared to 200 normal controls on a measure of laterality that included handedness, footedness, and eye dominance scales. Schizophrenics showed more left-sidedness on the laterality score. The established relationship between motoric and cognitive aspects of functional brain asymmetry, found in neurological and normal populations, suggests that the leftward tendency of schizophrenics may be manifested in cognitive and conative functions as well. These results seem to corroborate previous findings indicating that schizophrenia might be related to left hemisphere dysfunction. No relationship was found between handedness and eye dominance either in the schizophrenic or the normal groups. This finding questions the assumption that eyedness-handedness nonconcordance is a pathological sign.     

Modification of glassy carbon surfaces with synthetic laminin-derived peptides for nerve cell attachment and neurite growth

Working memory and its contribution to performance on strategic memory tests in schizophrenia were studied. Patients (n = 18) and control participants (n = 15), all men, received tests of immediate memory (forward digit span), working memory (listening, computation, and backward digit span), and long-term strategic (free recall, temporal order, and self-ordered pointing) and nonstrategic (recognition) memory. Schizophrenia patients performed worse on all tests. Education, verbal intelligence, and immediate memory capacity did not account for deficits in working memory in schizophrenia patients. Reduced working memory capacity accounted for group differences in strategic memory but not in recognition memory. Working memory impairment may be central to the profile of impaired cognitive performance in schizophrenia and is consistent with hypothesized frontal lobe dysfunction associated with this disease. Additional medial-temporal dysfunction may account for the recognition memory deficit.     

Lateralization of receptive language in preschoolers: Test–retest reliability in a dichotic listening task.

On 2 occasions dichotic digit tapes were presented to 29 right-handed children (aged 33–65 mo). Results indicate that the dichotic listening tasks yielded measures with sufficient test–retest stability to permit reliable group comparisons, but that such indices may differ in terms of their contamination by sample-specific distributions of ability levels. It is suggested that conclusions not be drawn from such measures unless different indices of laterality show converging results and that when groups are compared, investigators include tabulations of both the difference and accuracy scores in their results. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cerebral laterality and depression: Differences in perceptual asymmetry among diagnostic subtypes.

Examined the influence of diagnostic subtype of depression on perceptual asymmetry for dichotic listening and visual tachistoscopic tasks. A total of 65 unmedicated patients with major depressive disorders and 30 normal controls were tested on a verbal and nonverbal task in each modality. Patients diagnosed according to the Diagnostic and Statistical Manual of Mental Disorders (DSM-III) with melancholia had abnormal perceptual asymmetry for dichotic nonsense syllable and complex tone tasks. In contrast, patients having a nonmelancholic "atypical depression" (reactivity of mood with preserved pleasure capacity and associated features) did not differ from normal controls on these tasks, but had an increased incidence of left handedness. Bipolar depression (history of hypomania) differed from unipolar depression in showing abnormal perceptual asymmetry for a tachistoscopic dot enumeration task. Alterations of perceptual asymmetry in melancholia and bipolar depression were consistent with hypothesized right hemisphere dysfunction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Developmental instability and cerebral lateralization

On the basis of prior studies of handedness, it was predicted that variations from modal asymmetry scores on cognitive tasks, in either direction from the mean, would be associated with an elevated incidence of classic markers of developmental instability (minor physical anomalies and fluctuating anatomic asymmetries). University students (N = 146) were administered 4 tasks that typically reveal functional asymmetries: the fused rhymed words dichotic listening task, the line bisection task, the chimeric faces task, and the cartoon faces task. A composite measure of developmental instability was computed from minor physical anomalies and fluctuating asymmetries. Participants with greater evidence of developmental instability had more atypical lateralization scores, deviating more from the sample mean, in either direction. Directional asymmetries were unrelated to developmental instability. These results suggest that developmental instability influences variation in the lateralization of cognitive skills as well as handedness.     

Working and strategic memory deficits in schizophrenia.

Working memory and its contribution to performance on strategic memory tests in schizophrenia were studied. Patients (n?=?18) and control participants (n?=?15), all men, received tests of immediate memory (forward digit span), working memory (listening, computation, and backward digit span), and long-term strategic (free recall, temporal order, and self-ordered pointing) and nonstrategic (recognition) memory. Schizophrenia patients performed worse on all tests. Education, verbal intelligence, and immediate memory capacity did not account for deficits in working memory in schizophrenia patients. Reduced working memory capacity accounted for group differences in strategic memory but not in recognition memory. Working memory impairment may be central to the profile of impaired cognitive performance in schizophrenia and is consistent with hypothesized frontal lobe dysfunction associated with this disease. Additional medial-temporal dysfunction may account for the recognition memory deficit. (PsycINFO Database Record (c) 2010 APA, all rights reserved)