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Integrating cognitive psychology, neurology and neuroimaging.

In the last decade, there has been a dramatic increase in research effectively integrating cognitive psychology, functional neuroimaging, and behavioral neurology. This new work is typically conducting basic research into aspects of the human mind and brain. The present review features as examples of such integrations two series of studies by the author and his colleagues. One series, employing object recognition, mental motor imagery, and mental rotation paradigms, clarifies the nature of a cognitive process, imagined spatial transformations used in shape recognition. Among other implications, it suggests that when recognizing a hand's handedness, imagining one's body movement depends on cerebrally lateralized sensory-motor structures and deciding upon handedness depends on exact match shape confirmation. The other series, using cutaneous, tactile, and auditory pitch discrimination paradigms, elucidates the function of a brain structure, the cerebellum. It suggests that the cerebellum has non-motor sensory support functions upon which optimally fine sensory discriminations depend. In addition, six key issues for this integrative approach are reviewed. These include arguments for the value and greater use of: rigorous quantitative meta-analyses of neuroimaging studies; stereotactic coordinate-based data, as opposed to surface landmark-based data; standardized vocabularies capturing the elementary component operations of cognitive and behavioral tasks; functional hypotheses about brain areas that are consistent with underlying microcircuitry; an awareness that not all brain areas implicated by neuroimaging or neurology are necessarily directly involved in the associated cognitive or behavioral task; and systematic approaches to integrations of this kind.

Behavior↗

The umbilical cord twist: origin, direction, and relevance.

The purpose of this study was to evaluate the origin, direction, and relevance of the umbilical cord twist. We initially hypothesized that the direction of the helix or twist of the human umbilical cord at birth correlated with the eventual handedness of the child. Among 2801 singleton placentas in this study, only 5% had no twist, and the left twist outnumbered the right twist by 7 to 1, a ratio that is strikingly similar to the predominance of right-handed persons to non-right-handed persons in the general population. Forty-five 3- and 4-year-old children with previously documented cord twists were evaluated with respect to hand preference and performance. The direction of the cord twist was independent of the handedness of the child as well as the mother. We have documented an increased incidence of absent twist and right twist in association with single umbilical artery, suggesting that the impetus for the cord twist is independent on hemodynamic forces in the umbilical cord itself. We further document an increased incidence of absent twist among intrauterine fetal deaths and twins, suggesting that decreased fetal movement can impede the forces leading to normal twisting of the umbilical cord. Absence of cord twist may be associated with adverse prognosis.

Child, Preschool↗

Tooth eruption symmetry in functional lateralities.

Dental casts and oral photographs from a cross-sectional sample of 2092 young North Americans with detailed information on functional lateralities (eyedness, handedness and footedness) were examined to compare the proportions of symmetrical and asymmetrical eruption of the antimeric (left-right, contralateral pair) permanent teeth using a four-grade eruption scale. The proportion of symmetrically erupting antimeric teeth was higher for some teeth in those with non-right-sidedness of the feet and eyes, but not significantly so in the case of handedness. Left-footedness was significantly (95% confidence interval) associated with an increased proportion of symmetrical pairs of the maxillary first molar and mandibular lateral incisor, and non-right-eyedness with an increased proportion of symmetrical eruption and left/right non-balanced proportions of asymmetrical eruption in maxillary central incisors. True right-sidedness (hand, foot and eye) was significantly (P< or =0.05) associated with advanced eruption of the left mandibular first molar. It is suggested that while the timing of antimeric tooth emergence and clinical eruption is primarily programmed before crown mineralization, starting approximately at the 30th gestational week in the case of first permanent molars, symmetrical/asymmetrical tooth emergence and eruption may provide information a posteriori on prenatal and early postnatal growth and development.

Body Patterning↗

Hemispheric asymmetry in schizophrenia: a "dual deficits" model.

BACKGROUND: The aim was 1) to investigate left hemisphere functional integrity for auditory language processing in schizophrenic patients; and 2) to investigate the interaction between brain laterality and attentional processing by having subjects shift attention to the left or right ear. METHODS: The subjects were 33 schizophrenic inpatients, and 33 healthy comparison subjects with the same age, handedness, and gender distribution as the patient subjects. All subjects were tested with dichotic listening (DL) to consonant-vowel syllables, which is a measure of lateralized temporal lobe language processing. The subjects were tested under three different attentional conditions: a non-forced attention condition, attention focused to the right ear stimulus, and attention focused to the left ear stimulus. RESULTS: The main findings were 1) an absence of the expected right ear advantage in the schizophrenic group during the non-forced attention condition; and 2) a failure to modify DL performance through shifting of attention to either the right or left ear. The comparison group showed a right ear advantage during the non-forced and forced-right attention conditions (increased right ear advantage during the forced-right condition), and a left ear advantage during the forced-left attention condition. There were no significant effects of handedness. CONCLUSIONS: This pattern of results may indicate a "dual deficit" involving both automatic and controlled processing deficits in schizophrenia.

Adult↗

What does the haptic modality do during cognitive activities on letter shapes? A study with left- and right-handers.

This study was undertaken to analyze intermanual (interhemispheric) transfer in left and right handed subject and to assess how information was extracted during finger scanning of letter shape at the different levels of letter processing: shape recognition during a physical matching task, letter recognition in a verbal "meaning" matching task and letter naming. The dichhaptic procedure was used to study interhemispheric relations. It was hypothesized that cognitive activities have a feed-forward effect on the exploration of shapes, and that the performance is related to the nature of the task and to handedness. The exploratory strategies of the two types of handedness were also analyzed. The results showed that response latencies were generally similar for left- and right-handed subjects, but accuracy was better for left than right handers in "verbal" matching with the same overall exploratory strategies. In physical matching, left- and right-handed subjects performed equally but used different exploratory strategies. The naming task was very difficult for both groups but failed to discriminate their on accuracy, response latency, and exploratory strategy. The results are discussed with reference to the different exploratory strategies used and the interhemispheric interaction at work in different cognitive processes.

Adult↗

Predicting combinations of left and right asymmetries.

This paper explains how combinations of asymmetries for pairs of laterality variables may be predicted. It shows that many pairs combine as expected by chance, plus the influence of the RS+ gene hypothesised by Annett (1978, 1985). These include: eye dominance with writing hand, with throwing hand, and with foot for kicking; nonright handedness with planum temporale asymmetry, with asymmetry of the parietal operculum, and the association between these two anatomical asymmetries. Handedness for writing and throwing, and hand and foot preferences are more strongly associated, suggesting the presence of an additional influence. The reliability of the present analyses was supported by replication, especially in findings for hand preferences for writing and throwing described by Gilbert and Wysocki (1992). The relative frequencies of discordant patterns of preference, LR (writing, throwing) versus RL, are a function of the frequencies of the two variables in the population. These differ between age groups and also with the classification of 'either' hand preferences. Patterns of preference for writing, throwing and eye-dominance (RRR, RRL etc) are related in an orderly manner to differences between the hands for peg moving time. The success of the present application of the RS theory strengthens the argument that individual differences for hand preference depend on a continuous distribution of asymmetry, not on the 'types' commonly assumed in the literature.

Adult↗

Predicting hand preference with performance on motor tasks.

Handedness may be defined as preference or hand-differences in task performance. The strength and significance of the relationship between hand preference and hand performance asymmetries have been contested. To evaluate this relationship, we administered the Edinburgh Handedness Inventory and measured asymmetries in finger tapping, Purdue Pegboard, and grip strength in 30 subjects who prefer their right hand and 30 subjects who prefer their left hand. Hand asymmetries in finger tapping, Purdue Pegboard, and grip strength each predicted hand preference scores. However, a multiple regression equation best predicted hand preference by using performance of each task. Hand asymmetries in finger tapping correlated strongly with asymmetries in Purdue Pegboard performance, but neither of these asymmetries correlated strongly with asymmetries in grip strength. These findings indicate that hand preference and asymmetries in motor proficiency are strongly related, but suggest that preference and proficiency for different aspects of motor performance may be independently lateralized.

Adult↗

Cinema seating in right, mixed and left handers.

Two hundred and sixty four right-handed, 246 mixed-handed and 360 left-handed students were requested to indicate on five maps of cinema halls what place they would choose. All three handedness groups showed a preference for the right and a corresponding directional bias towards the left space. However, they differed significantly from each other on the magnitude of this bias which was most pronounced in right and less in left handers. It is assumed that lateralized mechanisms underlying such biases have developed evolutionarily and serve right-handed persons best. Non-dextrality considerably reduces their phenotypic expressions, but even left-handedness does not reverse the directional bias towards the left. It is also hypothesized that right, mixed and left handers differ in a large number of behavioral choices and strategies, modeled by cerebrally lateralized mechanisms and that the cinema seating preference is only one of them.

Adolescent↗

Manual asymmetries in reaching movement control. II: Study of left-handers.

Two experiments performed with left-handed subjects investigated how the manual asymmetries and hemispheric specialization involved in visuo-manual coordination are associated with handedness. Pro and retroactive processes involved in rapid movement control were analyzed according to the different movement parameters to be controlled, similar to studies performed with right-handers (Boulinguez, Nougier and Velay, 2001). Manual performances and kinematic properties of reaching movements showed that the left and right hands of left-handers behaved in the same way as the left and right hands of right-handers. Results are discussed in the light of the independence of handedness and other forms of cerebral dominance in sensori-motor information processing involved in hand movements.

Adult↗

Directionality in right, mixed and left handers.

Directionality in right, mixed and left handers was studied, asking subjects to draw 6 familiar objects. All three handedness classes showed left directional bias, but they differed significantly in this respect, right handers being the most and left handers the least left directed. Directionality is related to handedness, but it seems to be governed by an autonomous underlying mechanism, which probably developed in the course of evolution to facilitate the perceptuo-motor relationships of the subject with the environment.

Adolescent↗

Hand preference consistency and fine motor performance in young children.

Recent investigations suggest that children who establish handedness early are better coordinated than those who lack this characteristic. To test this assumption, 160 4- to 6-year-olds were classified by consistent (established) and inconsistent (mixed) hand preference behavior and tested for fine motor performance using a finger tapping task. Analysis of the data revealed no significant differences existed between groups in finger tapping performance in relation to total sample, age or sex. Thus, contrary to recent reports, children with consistent and inconsistent hand preferences do not appear to differ in motor behavior as revealed by performance on a fine motor task. Furthermore, it appears that the performance of those with inconsistent hand preference presents a significant challenge to current theoretical notions of the genesis of handedness.

Child↗

Problems in the assessment of hand preference.

Hand preference for the original items proposed by Oldfield (1971) and information concerning age, sex, familial sinistrality were obtained from a population of 1694 subjects. An item analysis was performed which resulted in the elimination of some of the items. Handedness distribution derived on the basis of the selected items was compared with the distribution obtained on the basis of the Oldfield's selection. Results show that handedness distributions depend on item selection, familial sinistrality and age, while no effect of sex is found.

Adolescent↗

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.

Adolescent↗

Not all sinistrality is pathological.

Information regarding age, sex, birth stress, and handedness was obtained form 762 university faculty members and 1869 undergraduate and medical students, who also provided age, sex, and handedness information for their first-degree relatives. In addition, students reported the occupations and educational levels of their parents. Analyses of the effects of birth order, reported birth stress, and maternal, paternal, and joint parental age showed that an increased incidence of sinistrality was only rarely associated with high birth risk; in all cases, the effects were confined to male subjects, most frequently male faculty members. Sinistrality was not associated with low socioeconomic status; on the contrary, there were significantly more sinistrals among parents of high than of low educational and occupational levels. The pathogenic hypothesis has other implications which fail to find support in the current literature, thus casting further doubt on the proposition that all sinistrality is pathological in origin.

Adolescent↗

Hand preference in a population of Swedish college students.

A hand preference inventory was administered to a population of 921 Swedish college students. The questions concern writing, drawing, throwing a ball, cutting with scissors, tooth brushing, cutting with a knife, and using a hammer, each with five response alternatives: always right, mostly right, either hand, mostly left and always left. A consistent preference over all activities for the left hand was rare (4%), but common for the right hand (62%). Corresponding percentages for writing hand were 9% and 89%, thus contradicting recent reports of a dramatic increase of left-handedness. There were no sex differences. Hand preference for writing was highly correlated with that for the other activities. Self-reported parental sinistrality was more common in respondents with a consistent left hand preference. There was no association between nonright-handedness and self-reported early learning difficulties, although among females mixed handers tended to report a higher frequency of difficulties in learning to write.

Adolescent↗

Between-species variation in the development of hand preference among macaques.

This research examined between-species variation in the development of hand preference among Macaca. Specifically, we examined hand preference using juveniles and adults of three macaque species that differ in social and reactive tendencies in order to examine whether the correlation between temperament and handedness that has been noted within Macaca mulatta occurs between closely related species. Each of the species studied exhibited a different pattern of hand preference development. Both juvenile and adult M. mulatta exhibited group-level left-hand bias. Juvenile Macaca nemestrina were not biased towards either hand at the group-level, whereas adults exhibited a group-level left-hand bias. Neither juvenile nor adult Macaca fascicularis exhibited manual bias at the group-level. Analysis of variance indicated statistically significant main effects of species and age class on hand preference measures. Post-hoc analysis indicated greater use of the left- versus right-hand, and greater hand preference strength independent of direction, among M. mulatta and M. nemestrina than among M. fascicularis, and among adults than among juveniles. These results indicate significant between-species variation in the development of hand preference within the genus Macaca, and are inconsistent with any one single-factor theory yet offered to explain the etiology of primate laterality. We hypothesize that the relationship between handedness and temperament that has been shown within M. mulatta may generalize across closely related primate species.

Age Factors↗

Pitch perception: a difference between right- and left-handed listeners.

Various results indicate that the perception of a complex tone's "virtual" pitch is generally lateralized in the right cerebral hemisphere. The primary aim of this work was to test the hypothesis that this is not the case for the "spectral" pitch percepts induced by complex tones. Forty right-handed and 18 left-handed listeners were monaurally presented with pairs of successive tones made up of n consecutive equal-amplitude harmonics of a missing fundamental (F0). n varied from two to four across subjects. In "test" conditions, the paired tones differed in F0 but the spectral components of the tone with the lower F0 were higher in frequency than the corresponding components of the other tone (except for one component, which was identical). The subjects had to say if, from one tone to the other, pitch rose or fell. From such judgements, one could infer that the pitch dominantly perceived in each tone was a virtual pitch (corresponding to F0) or a spectral pitch (i.e., the pitch of a single spectral component, or a perceptual quality corresponding to the centroid of the power spectrum). For n = 2, the results indicated that virtual pitch was less salient than spectral pitch; the opposite occurred for n = 3 and n = 4. The ear (left or right) to which the stimuli were presented had some influence on the judgements, in the expected direction. However, this influence was not a robust one. Unexpectedly, a reliable effect of the listeners' handedness was observed: for each value of n, the judgements indicating virtual pitch perception were less frequent in the left-handers than in the right-handers. Discrimination performances measured in "control" conditions showed that the handedness factor was not confounded with a factor of frequency discrimination ability.

Acoustic Stimulation↗

The effects of hand preference and gender on finger tapping performance asymmetry by the use of an infra-red light measurement device.

We used an infra-red device to study the effects of gender and handwriting preference on manual asymmetry in tapping rate and intertap variability. Our sample (n=102) consisted of approximately equal number of subjects with respect to gender (52 women and 50 men) and handedness (52 right-handers and 50 left-handers). Data on overall performance indicated that men performed more quickly and regularly than women. The index used for measuring manual asymmetry was the difference between the hands as a proportion of the total. Therefore, the asymmetry index was adjusted to remove the influence of overall performance. The analyses based on asymmetry scores indicated a significant handedness effect: right-handers showed greater manual asymmetries than left-handers for both tapping rate and intertap variability. In addition, right handers exhibited a significant greater asymmetry for intertap variability than tapping rate. Taken together, these data may reflect greater hemispheric differences in right-handers, specially for intertap variability.

Adolescent↗