Familial Sinistrality Research Articles

Left Hemisphere Lateralization for Language in Right-Handers Is Controlled in Part by Familial Sinistrality, Manual Preference Strength, and Head Size

We investigated the effects of familial sinistrality (FS+; presence of left-handedness in one's close relatives), manual preference strength (MPS), and head size on the hemispheric lateralization of language in right-handers. Functional magnetic resonance imaging was used to map 49 individuals while listening to a story in their mother tongue. We found that individuals who had both the FS+ trait and weak MPS had no left hemisphere dominance for this lexicosyntactic task, whereas others showed a leftward functional asymmetry. In addition, the smaller the brain size, the smaller the leftward asymmetry for language, independent of FS and MPS. None of these effects were observed when the same subjects performed a spatial attention task that elicited right hemispheric functional asymmetry. These results demonstrate that the left hemisphere dominance for language in right-handers is a variable controlled, in part, by a number of specific factors, including FS, MPS, and head size.

Quantitatively assessed familial sinistrality in right-, mixed-, and left-handers

Numerous manifestations of cerebral asymmetry in man depend on the presence of non-right-handers (NRHs) among the subject's biological relatives – familial sinistrality, FS. This study proposes a method for a quantitative assessment of FS, based on the coefficient of relatedness of the subject with every single one of his/her relatives with known handedness. Such an approach conforms much better with the genetic principles than the methods ignoring the degrees of genetic relationship. Contacting and including as many as possible living relatives enlarges the category of subjects with FS, even relative to studies where non-immediate family members have been included and this enlargement might be especially important for the right-handers. The method was applied on a sample of 870 subjects (264 right-, 246 mixed- and 360 left-handers). Handedness, either distributed in the three classical categories or presented by the raw handedness score as continua, showed a highly significant relationship with the index. A considerable excess of females over males in their FS was found and its possible genetic and psycho-sociological reasons were discussed. It was suggested that the proposed method mirrors an existing biological reality and could be applied in further studies of handedness in relation to its genetic grounds.

Effect of Familial Sinistrality on Planum Temporale Surface and Brain Tissue Asymmetries

The impact of having left-handers (LHs) among one's close relatives, called familial sinistrality (FS), on neuroanatomical markers of left-hemisphere language specialization was studied in 274 normal adults, including 199 men and 75 women, among whom 77 men and 27 women were positive for FS. Measurements of the surface of a phonological cortical area, the "planum temporale" (PT), and gray and white matter hemispheric volumes and asymmetries were made using brain magnetic resonance images. The size of the left PT of subjects with left-handed close relatives (FS+) was reduced by 10%, decreasing with the number of left-handed relatives, and lowest when the subject's mother was left-handed. Such findings had no counterparts in the right hemisphere, and the subject's handedness and sex were found to have no significant effect or interaction with FS on the left PT size. The FS+ subjects also exhibited increased gray matter volume, reduced hemispheric gray matter leftward asymmetry, and, in LHs, reduced strength of hand preference. These results add to the increasing body of evidence suggesting multiple and somewhat independent mechanisms for the inheritance of hand and language lateralization.

Brain, language, and handedness: a family affair

AbstractThe left planum temporale is a marker of left hemisphere language specialization. We investigated the effect of individual handedness and familial sinistrality on left planum temporale surface area and found the size is reduced in proportion with the number of left-handed immediate family members and is lowest when one's mother is left-handed. This reduction is independent of an individual's handedness or sex and has no counterpart in the right hemisphere.

Comparative Assessment of 13 of the Widely Used Hand Preference Items in a Bulgarian Sample

The hand preference items included into inventory were comparatively assessed concerning the frequencies of the answers given by Bulgarian right, mixed, and left handers, concerning the correlation of each item with the remaining 12, with eyedness and footedness scores. Relationships between writing hand, throwing hand, eyedness, and footedness were studied. Application of a cumulative index of familial sinistrality evidenced the biological significance of the main findings. All the results showed the inferiority of the writing hand as compared to the remaining items and evidenced the full inappropriateness of this item as a single predictor of handedness.

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 left-handedness 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.

Dynamics of Manual Skill: A Computerized Analysis of Single PEG Movements and Stochastic Resonance Hypothesis of Cerebral Laterality

Hand skill was analyzed using a computerized peg moving task. The durations of single hand movements (PMTs) were accurately measured in right-hand (RH) and left-hand (LH) writers. One trial consisted of 10 movements of the right hand and 10 movements of the left hand. Each participant performed five trials. Women showed significantly higher percentage than men in right-handedness; men showed higher percentage than women in left-handedness. This sex difference completely disappeared after taking the same height range in participants. The mean RH- and LH-PMTs decreased in 5 successive trials, even within a single trial during 10 successive hand movements, indicating a learning effect of repeated hand movements. The LH- minus RH-PMTs exhibited fluctuations within a single trial between positive (faster right hand) and negative (faster left hand) values. LH–RH PMTs were significantly greater than zero, in favor of right hand, in RH-writers, but not significantly different from zero in LH-writers, exhibiting a true fluctuating asymmetry. Participants with no familial sinistrality (FS-) were preponderantly right-handed (ca. 90%), those with left-handed mother and right-handed father (FS+1) showed stochastic distribution of hand preference (50:50). Participants with right-handed mother and left-hander father (FS+2) were not different from FS- individuals. LH–RH PMT was significantly greater than zero in FS- participants, almost equal to zero in FS+1 participants, and greater than zero in FS+2 participants exhibiting greater asymmetry than that in FS- participants. These results suggest a genetic inheritance of direction and degree of handedness, being a a X-linked trait originating from mother's genotype. It was suggested that fluctuating asymmetries may reflect interactions between stochastic resonance phenomena within right and left brains. This property of brain may genetically transmitted from mother's X chromosome; a net effect of stochastic interactions between hemispheres may result in right- or left-handedness, a predominantly unidirectional coupling creating right-handedness, in favor of left brain, and a stochastic bi-directional coupling between hemispheres would be a main trait of left-handers. This new “stochastic resonance hypothesis of cerebral laterality” concerns with stochastic fluctuations in hand-skill asymmetry and inter-hemispheric coupling through corpus callosum, and seems to be important for new developments in handedness research.

Laterality phenotypes in patients with schizophrenia, their siblings and controls: Associations with clinical and cognitive variables

Various behavioural indices of brain lateralisation significantly intercorrelate, but current research in this area still focuses on single behavioural asymmetries, such as handedness. To describe a novel approach, which simultaneously integrates various laterality indices and delineates complex phenotypes. Grade of membership analysis was used to describe latent, complex lateralisation phenotypes in patients with schizophrenia (n=157), their siblings (n=74) and controls (n=77). The indices used were asymmetries of eye, foot and hand; hand motor proficiency; and handedness of patient's first-degree relatives. Three distinct pure types of lateralisation ('right', 'left' and 'mixed') were evident in patients compared with two ('right' and 'left') in siblings and controls. The 'mixed' type in patients featured absence of eye and foot lateralisation and presence of familial sinistrality, despite a right-hand dominance for writing. Patients with schizophrenia expressing the 'left' phenotype had a more severe course of illness, significantly increased scores on two schizotypy factors and poorer neurocognitive performance. The pure types in the siblings were similar to those in healthy controls. The findings suggest that a leftward reversal, rather than a reduction in lateralisation, is associated with clinical severity and neurocognitive deficits in patients with schizophrenia.

Measuring familial sinistrality: Problems with dichotomous classification

Familial sinistrality (FS), or familial left-handedness, is usually measured as a presence/absence dichotomy (FS+/FS−). Measuring FS as a dichotomy is problematic in at least two ways: (1) magnitude data are discarded and (2) there is an increased risk of violating statistical assumptions. We hypothesised that using a non-dichotomised FS measure would allow more sensitive statistical tests than using a dichotomised measure. The non-dichotomised measure examined was proportion of family that is left-handed, or Proportional FS (FSP). FS measures of 60 healthy adults were consistent with our hypothesis: (1) The effect size was 2.3 times larger when FSP was used than when Dichotomised FS (FSD) was used; (2) the observed relationship was statistically significant when FSP was used but not when FSD was used; and (3) statistical assumptions were violated when FSD was used but not when FSP was used. When cases were weighted to account for an increased likelihood of FS in large families, results were similar. Next, bootstrapping methods were used to estimate empirically the long-term differences in power between analyses incorporating FSP and those incorporating FSD. Using FSP was associated with long-term increases in both power and effect size of over 50% relative to using FSD. We conclude that using a proportional rather than a dichotomous measure of FS will enhance the accuracy of observed effect sizes, increase the sensitivity of statistical tests, and reduce the likelihood of violating statistical assumptions.

CORRELATIONS BETWEEN NONVERBAL INTELLIGENCE AND NERVE CONDUCTION VELOCITIES IN RIGHT-HANDED MALE AND FEMALE SUBJECTS

A neurological theory of intelligence suggesting a direct correlation between nerve conduction velocity and psychometric intelligence was tested. Cattell's Culture Fair Intelligence Test was used to asses the nonverbal intelligence (IQ) of subjects. The motor median nerve conduction velocity from right hand of males was positively correlated with IQ. In subjects with no familial sinistrality (FS–), the motor ulnar-nerve conduction velocity from the right and left hands of males negatively correlated with IQ; there were inverse correlations between IQ and nerve conduction velocity (motor median nerve from right, sensory median nerve from right and left) in females. In subjects with familial sinistrality (FS+), IQ directly correlated with nerve conduction velocity from motor median (right and left), sensory median (right), and motor ulnar (right) nerves, but only in males. The speed hypothesis and neurological theory of intelligence were not supported by these results, which, in contrast, emphasized the importance of sex and familial sinistrality in any theory of intelligence.

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.

Effects of brain laterality on accuracy of decoding facial displays of emotion

The human face is capable of producing numerous unique expressions and comprises the primary nonverbal channel for the communication of emotion. In this study, we investigated the effects of sex and neurological hemispheric dominance on the ability to decode facial expressions of emotion accurately. On the basis of a battery of measures assessing handedness, familial sinistrality, and immune disorders, we classified participants as having standard, anomalous, or mixed hemispheric dominance. Consistent with previous studies, we found that hemispheric dominance and sex interacted to influence participants' abilities to decode facial displays of affect from photographs. Specifically, mixed dominant females had the highest accuracy in the decoding of facial emotion, whereas mixed dominant males had the lowest accuracy. We discuss these findings within the context of communibiology and comment on their implications for the study of neurology and social behavior.

Crossed aphasia: An analysis of the symptoms, their frequency, and a comparison with left-hemisphere aphasia symptomatology

This study presents a thorough analysis of published crossed aphasia (CA) cases, including for the first time the cases published in Japanese. The frequency of specific symptoms was determined, and symptomatology differences based on gender, familial sinistrality, and CA subtype were investigated. Results suggested that the CA population is comparable to the left-hemisphere patient population. However, male were significantly more likely than female CA subjects to show a positive history of familial sinistrality. Typical right-hemisphere (i.e., nonlanguage-dominant) symptoms were frequent but rarely carefully reported or assessed. Results are compared with previous CA reviews and left-hemisphere aphasia. Suggestions for a more systematic assessment of the CA symptomatology are presented.

Re: Crossed Nonaphasia in a Dextral With Left Hemispheric Lesions: A Functional Magnetic Resonance Imaging Study of Mirrored Brain Organization

General conclusions concerning mechanisms of cerebral lateralization may be learned from the investigation of functional brain organization in patients with anomalous lateralization. The functional organization of language, attention, and motor performance was investigated in a 42-year-old patient with crossed nonaphasia by means of functional MRI. The strongly right-handed man experienced a left middle cerebral artery infarction documented by MRI without exhibition of aphasia. However, the left hemispheric stroke was accompanied by visuospatial impairment, right-sided slight sensory and motor paresis, and right homonymous hemianopia. No history of familial sinistrality or prior neurological illness was present. Functional MR language mapping revealed strong right hemispheric activation in inferior frontal and superior temporal cortices. Finger tapping with the right hand recruited ipsilateral premotor and motor areas as well as supplementary motor cortex. A Stroop task, usually strongly associated with left-sided inferior frontal activation in dextrals, resulted in strong right hemispheric frontal activation. From our data there is clear evidence that different modalities, such as language perception and production, attention, and motor performance, are processed exclusively by 1 hemisphere when atypical cerebral dominance is present.

Familial sinistrality in crossed aphasia: A new case and review of the available literature

From the earliest descriptions onwards, the phenomenon of familial sinistrality (FS) has been strongly implicated in the concept of crossed aphasia in dextrals (CAD). In the early literature on CAD, a positive tract of FS (FS+) was generally regarded as the most important cause of anomalous language lateralisation in dextrals. Although in the more recent literature FS+ is generally regarded a strong exclusion criterion for CAD, in a corpus of 180 published CAD cases we encountered 26 patients with FS+ (14.4%). Critical analysis revealed that only a minority of these cases (5/26; 19%) sufficiently met the adopted criteria for an unambiguous diagnosis of vascular CAD (reliable CAD). One personal observation, reported in this paper, also fulfilled these criteria and is added to this group. To evaluate the presumed impact of FS+ on the anatomoclinical configurations of vascular CAD, all "reliable" CAD cases with FS+ were analysed in a three-epoch time-frame model for aphasia and matched for both aphasia type and lesion-aphasia profile with a representative group of vascular "reliable" CAD cases with negative FS (FS-). Close analysis of the aphasia characteristics revealed that the FS variable did not induce semiological differences between both FS groups. Although the limited study sample does not allow strong conclusions to be drawn, our findings seem to indicate that FS does not act as a strong determinant of lesion- behaviour relationships in CAD.

Crossed Nonaphasia in a Dextral With Left Hemispheric Lesions

Background — General conclusions concerning mechanisms of cerebral lateralization may be learned from the investigation of functional brain organization in patients with anomalous lateralization. Case Description — The functional organization of language, attention, and motor performance was investigated in a 42-year-old patient with crossed nonaphasia by means of functional MRI. The strongly right-handed man experienced a left middle cerebral artery infarction documented by MRI without exhibition of aphasia. However, the left hemispheric stroke was accompanied by visuospatial impairment, right-sided slight sensory and motor paresis, and right homonymous hemianopia. No history of familial sinistrality or prior neurological illness was present. Functional MR language mapping revealed strong right hemispheric activation in inferior frontal and superior temporal cortices. Finger tapping with the right hand recruited ipsilateral premotor and motor areas as well as supplementary motor cortex. A Stroop task, usually strongly associated with left-sided inferior frontal activation in dextrals, resulted in strong right hemispheric frontal activation. Conclusions — From our data there is clear evidence that different modalities, such as language perception and production, attention, and motor performance, are processed exclusively by 1 hemisphere when atypical cerebral dominance is present.

Motor Control of the Hands: The Effect of Familial Sinistrality

Left-and right-handed subjects, selected on the basis of degree of hand preference and for the presence or absence of familial sinistrality, responded to monaurally presented tonal stimuli (440 Hz note played on four different instruments) using their right and left hands on separate occasions. It was found that in both the strong left-handers and the inconsistent strong right-handers, motor control of the hands was related to familial sinistrality (FS). Specifically, strong left-handers and inconsistent strong right-handers with FS have a difference in the motor control of the hands in the left hemisphere, with a left hemisphere-left hand advantage. Strong left-handers and inconsistent strong righthanders with no FS have a difference in the motor control of the hands in the right hemisphere, with a right hemisphere-left hand advantage.

Superior episodic memory is associated with interhemispheric processing.

The dependence of episodic memories on interhemispheric processing was tested. In Experiment 1, positive familial sinistrality (FS+; e.g., presence of left-handed relatives) was associated with superior episodic memory and inferior implicit memory in comparison with negative familial sinistrality (i.e., FS-). This reflected a greater degree of interhemispheric interaction in FS+ participants, which was hypothesized as facilitating episodic memory. In Experiment 2, the authors directly manipulated inter- versus intrahemispheric processing using tests of episodic (recognition) and semantic (lexical decision) memory in which letter strings were presented twice within trial blocks. Semantic memory was superior when the 2nd presentation went to the same hemisphere as the 1st. Episodic memory, however, was superior when the 2nd presentation of a stimulus went to the opposite hemisphere. Results support an interhemispheric processing basis for episodic memories.

Do Environmental and Hereditary Factors Affect the Psychophysiology and Left-Right Shift in Left-Handers?

The principal objective of this study was to investigate the reality of sinistrality in left-handed subjects. The subjects were assessed by a 20-item questionnaire with two groups taken from Oldfield's and Yetkin questionnaires. The relation of different effects on left-hand preference was studied in men and women considering familial information and writing hand. The degree of hand preference was determined by Geshwind scores (GSs). The GS degrees of hand preferences were divided into weak and strong left-hand ranging from -20% to - 100%.After assessing the GSs we asked the subjects to answer 22 questions with different aims. which were especially written for only left-handers. Some of them were based on familial sinistrality and hereditary relation to left-handers. The others concerned hand, foot, eye, shoulder, and ear preferences; the psychology of left-handedness; the knowledge concerned with left-handedness; the success, ability, and interest education and skill, and morphological differences in hand and foot sizes.In the present study, it was found that the subjects have had at least one left-handed person in their family or among their relatives. Some subjects had shifted their left hand preference in favor of their right hands. Nevertheless, the left-handers have been found as a presence with their own peculiarities.

The Effect of Familial Sinistrality on the Relation between Schizophrenialike Thinking and Pseudoneglect

We have recently reported a correlation between schizophrenialike symptoms and the degree of pseudoneglect in healthy right-handers. We aimed to investigate the effect of familial sinistrality (FS) on this relation. Seventy-six healthy right-handers were divided into four groups on the basis of gender and FS. A computerized version of Corsi's task was used as the visuospatial task. Subjects filled in the Magical Ideation Scale (MI), which asked for delusionlike beliefs, and performed the Corsi's task using each hand. Performance of both hemispaces was separately evaluated. In all groups, performance of the left hemispace was better than that of the right hemispace and FS+ subjects performed better than FS− subjects. When the right hand was used, performance was correlated to MI scores only for FS− groups. Findings suggest that the correlation between right-sided neglect and proneness to schizotypy in normal right-handers is affected by FS.