Models of hemispheric specialization.

Reviews the literature on models of human laterality, including unilateral specialization models (dealing with language, visuospatial functions, motor functions, manipulospatial functions, and focal vs diffuse representation), cooperative interaction models, negative interaction models, parallel models, and allocation models. Although local models designed to deal with smaller, specific topic domains exist, there is currently no general model of hemispheric specialization. It is suggested that the theoretical mechanisms invoked by laterality theorists might serve as the basis for development of a more general theoretical viewpoint. In most current theoretical formulations, the basic unit of analysis is the hemisphere. The author proposes a reformation in terms of smaller neural processing entities, labeled subprocessors. The methodological and theoretical consequences of adopting a subprocessor point of view and the relationships between subprocessors and existing local models are considered. (6 p ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Developmental changes in hemispheric specialization for tactile spatial ability.

64 1st-, 3rd, and 5th-grade children and adults (16 in each group) performed a tactile shape-discrimination task. On each of 40 trials, after exploring a randomly generated nonsense form using only finger motion, Ss judged a tactually presented comparison form as either the same as or different from the 1st stimulus. In Condition 1, a single stimulus form and the comparison form were successively presented to the same hand. In Condition 2, stimulus forms were simultaneously presented to both hands; however, a comparison form was presented to only one hand. Results indicate that the left hand (right hemisphere) was more accurate than the right hand (left hemisphere) for 5th-grade Ss and adults, but no significant differences between hands were found for 1st- and 3rd-grade Ss. Overall, Condition 2 was more difficult than Condition 1, but similar laterality effects were found in both groups. Sex differences were found only in the adult group in which males made somewhat fewer errors than females. These results suggest that the right hemisphere becomes progressively more specialized for tactile spatial ability with increasing age. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sex differences and lateral specialization of hemispheric functioning

Acute renal failure developed in nine of 78 patients who were subjected to hepatic artery ligation for nonresectable and extensive malignant tumor of the liver. Of those nine, six had hepatomas, one cholangiocarcinoma, one metastatic islet-cell carcinoma and one metastatic melanoma. Preoperative renal function as reflected in blood-urea-nitrogen and serum creatinine values was within normal limits. There were marked elevations of serum glutamic-oxalacetic transaminase and lactic dehydrogenase levels after hepatic artery ligation, an indication of massive ischemic injury of the tumor and the liver. A diagnosis of acute renal failure was established within 14 to 70 hours after hepatic artery ligation. In five patients, oliguric renal failure developed, and in four, high urinary output renal failure. In only three patients did systemic hypotension and hypovolemia precede acute renal failure. Seven of the nine patients died. Postmortem examination was done in five patients, and in only two was there evidence of renal tubular necrosis. The factors contributing to acute renal failure appear to be extensive involvement of the liver by tumor, presence of ascites and jaundice, occlusion of the portal vein and hyperuricemia. The presence of any one of the foregoing contraindicates the procedure.     

Lateralized word recognition: Assessing the role of hemispheric specialization, modes of lexical access, and perceptual asymmetry.

The processing advantage for words in the right visual field (RVF) has often been assigned to parallel orthographic analysis by the left hemisphere and sequential by the right. The authors investigated this notion using the Reicher-Wheeler task to suppress influences of guesswork and an eye-tracker to ensure central fixation. RVF advantages obtained for all serial positions and identical U-shaped serial-position curves obtained for both visual fields (Experiments 1–4). These findings were not influenced by lexical constraint (Experiment 2) and were obtained with masked and nonmasked displays (Experiment 3). Moreover, words and nonwords produced similar serial-position effects in each field, but only RVF stimuli produced a word-nonword effect (Experiment 4). These findings support the notion that left-hemisphere function underlies the RVF advantage but not the notion that each hemisphere uses a different mode of orthographic analysis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Integration and interference in the cerebral hemispheres: relations with hemispheric specialization

The two hemispheres of the brain often perform complementary computations and make unique contributions to task performance. This study examines the interaction of linguistic (left hemisphere) and prosodic (right hemisphere) information in speech processing. An individual differences approach is used in which interference between linguistic and prosodic processes in a Stroop-like task is compared between individuals who process the two dimensions in opposite hemispheres (complementary specialization) vs. those who process both dimensions in the same hemisphere (noncomplementary specialization). Complementarity was not related to interference in any way. This finding is consistent with the hypothesis of Chiarello and Maxfield (1996) that interference is equivalent between and within hemispheres when it arises in a response selection stage.     

Developmental changes in hemispheric specialization for tactual processing in very young children: Evidence from cross-modal transfer.

Examined whether young children show any evidence of right hemispheric specialization for tactual processing. 72 1-, 2-, and 3-yr-old right-handed children were each administered 6 cross-modal tasks in which they palpated a shape with either their left or right hand for 25 sec and then viewed the familiar and a novel shape in a 10-sec test of visual recognition. Although Ss of all 3 ages showed significantly more visual fixation to novel shapes, regardless of which hand had been used for palpation, scores were enhanced among 2- and 3-yr-olds following palpation with the left as compared with the right hand. This left-hand (right hemisphere) superiority was not evident in 1-yr-olds. These results are the first to demonstrate a left-hand superiority for information processing in children as young as 2 yrs and to suggest that this adultlike pattern is developed by at least the 2nd year of life. Left-hand superiority may be due to asymmetries in tactual sensitivity, motor control, and/or information processing. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Left hemisphere specialization for response to positive emotional expressions: A divided output methodology.

An extensive literature credits the right hemisphere with dominance for processing emotion. Conflicting literature finds left hemisphere dominance for positive emotions. This conflict may be resolved by attending to processing stage. A divided output (bimanual) reaction time paradigm in which response hand was varied for emotion (angry; happy) in Experiments 1 and 2 and for gender (male; female) in Experiment 3 focused on response to emotion rather than perception. In Experiments 1 and 2, reaction time was shorter when right-hand responses indicated a happy face and left-hand responses an angry face, as compared to reversed assignment. This dissociation did not obtain with incidental emotion (Experiment 3). Results support the view that response preparation to positive emotional stimuli is left lateralized. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of hemispheric specialization in sensory processing on reaching in infants: Age and gender related effects.

Music or speech were presented separately to the right or left ears of 48 6- and 8-mo-old infants as they reached for an object. Examination of the latency to contact the object revealed a complex relationship between type of auditory input and locus of presentation as a function of age and gender. In younger males, presentation of speech to the left ear resulted in longer contact latencies than did presentation of music. Younger females showed no asymmetries. Older males took significantly longer to contact when music was presented to their right than to their left ear; older females exhibited a tendency toward the typical adult pattern of specialization in that there was a greater effect of speech at their right than at their left ear, and vice versa for music. Data are discussed in terms of possible sequences in the development of hemispheric specialization. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Torque, hemispheric dominance, and psychosocial adjustment.

The relationships between torque (drawing of circles in a clockwise direction), 2 measures of hemispheric dominance, and measures of anxiety and social competency were examined in 225 unselected male college students. Torque occurred for 33.8% of the sample and was associated with handedness and conjugate lateral eye movement tendencies in a manner consistent with T. H. Blau's (see record 1978-29447-001) mixed cerebral dominance theory of the effect. Eye movement data from torque Ss were consistent with those reported for hospitalized schizophrenics. Multiple ANOVA conducted on the adjustment measures did not reveal significant differences associated with torque, alone or in interaction with S handedness or experimenter sex. Torque, a behavioral indicator of peculiarities in hemispheric functioning, is a potentially valuable tool for schizophrenia research. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Left hemispheric neuronal heterotopia: a PET, MRI, EEG, and neuropsychological investigation of a university student

A 21-year-old left-handed medical student had a prominent unilateral cerebral cortical malformation due to an ontogenetic migration disorder. We performed neuropsychological studies, EEG, T1- and T2-weighted and proton-density MRI, and positron emission tomography (PET) (under both the resting condition and neuropsychological activation). Neuropsychological testing revealed normal intelligence and generally normal memory functioning but selective deficits in tests of verbal fluency and spatial-figural relationships. Proton-density and T2-weighted MRI revealed extensive left cortical heterotopia that included parts of the Wernicke area. PET under the resting condition revealed a small interhemispheric difference with slightly reduced glucose metabolism in the left temporoparietal cortical zone. An activation PET (with the patient performing a verbal fluency test) resulted in a normal overall increase in metabolism but marked deviations in cortical areas. The highest activity changes were in the Broca and Wernicke areas of the right hemisphere, and there was very little activation in those regions of the left hemisphere that were expected to respond well to the activation--the temporal, parietal, and temporo-occipital cortical zones. We conclude that there can be large compensations for unilateral heterotopia.     

Onset of duplicated syllable babbling and unimanual handedness in infancy: Evidence for developmental change in hemispheric specialization?

A longitudinal design was used to test for a developmental relation between unimanual handedness and duplicated syllable babbling (SB). 30 infants were tested for a unimanual hand preference in their manipulation of 8 toys at weekly intervals from 5 mo of age through 8 wks after the onset of duplicated SB. Measures of Ss' unimanual handedness across weekly sessions were analyzed with respect to SB onset (mean age of onset 6.7 mo; range 5.4–8.7 mo). Ss began to demonstrate unimanual right handedness on the week of SB, whereas they did not show any significant hand preference on the preceding week(s). Ss also demonstrated a temporary loss of this hand preference for a brief period approximately 3–4 wks after SB onset. This discontinuity may reflect a disconnection syndrome of the brain hemispheres or a disruption caused by new skills mediated by the nondominant hemisphere. The developmental synchrony between unimanual handedness and duplicated SB and the curvilinear trend in unimanual handedness following SB onset suggest the presence of developmental change in hemispheric specialization or, at least, in asymmetrical organization at some brain level(s) at this point in development. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prediction, control, and learned helplessness.

Examined the independent effects of perceived control over and perceived predictability of an aversive event on 100 undergraduates' performance on a memory task and depressive affect. All Ss completed the Multiple Affect Adjective Check List and the Desirability of Control Scale. Ss who received noise blasts that were both uncontrollable and unpredictable displayed performance decrements and depressive affect relative to a no-noise group, whereas Ss who were able either to control or to predict the aversive event did not. The perception of control or predictability concerning the aversive event was thus sufficient to mitigate learned helplessness, suggesting the functional equivalence of perceived control and predictability. Finally, results reveal that Ss high in the "desire for control over events" reacted to the aversive noise more than did Ss low in the desire for control. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Crime specialization, seriousness progression, and Markov chains.

Sequences of violent and nonviolent offenses by 300 male offenders (mean age 26.47 yrs) were subjected to log-linear analyses of the stabilities and magnitudes of their transition probabilities (TPs). Results show that all patterns resembled a Markov process wherein the TPs were stable. The relative magnitude of these TPs indicated that there was specialization in nonviolent offenses and little tendency toward consistently violent behavior. Seriousness progression from nonviolent to violent misconduct was infrequent; however, there was substantial retrogression from violent to nonviolent offenses. (11 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Generality and modifiability of working memory among skilled and less skilled readers.

Investigated whether individual differences in working memory are related to a general system and whether the predictability of working memory to academic achievement is enhanced under dynamic testing conditions. Exp 1 correlated 11 working memory tasks with short-term memory and achievement measures. Convergent and discriminant validity for the working memory measures was established. Although a confirmatory factor analysis supported the notion that the working memory tasks reflect 2 operations, these operations produced similar correlational patterns to achievement. Exp 2 supported a 2-factor model under dynamic testing procedures, and those procedures contribute significant variance to reading performance. Overall, the results suggest that (1) working memory operates as a general system independent of reading skill and (2) dynamic testing procedures enhance the prediction of reading performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

How far does the brain lateralize?: an unbiased method for determining the optimum degree of hemispheric specialization

The relationship between measures (of size or function) on one side of the brain, in relation to the difference between the two sides on that measure, are important components of theories of hemispheric asymmetry. For example, it has been concluded that increasing lateralization (e.g., of hand skill or planum temporale area) occurs at the expense of the non-dominant hemisphere. Here it is demonstrated that such relationships could merely be a necessary consequence of relating components of a laterality index to the index (L - R)/(L + R) itself, or indeed to L - R. An alternative approach (using random data to exemplify the null hypothesis) is presented together with an application to data on hand skill from 12,782 11-year-olds in a cohort study. This demonstrates a symmetry hitherto undocumented of maximal hand skill in left and right hands in left- and right-hand writers respectively, the point of the maximum falling short of the population mean for relative hand skill in either case. If degrees of laterality are what is genetically determined, this suggests that selection is present for a function (perhaps language) associated with a greater magnitude of lateralization than is represented by hand skill.     

Sources of vocalization latency differences between skilled and less skilled young readers.

Vocalization latencies of 16 skilled and 16 less skilled 3rd-grade readers were found to be a function of set size, number of syllables, and stimulus material. Differences between skilled and less skilled readers were absent for naming colors, digits, and pictures. Differences were found for words, and differences increased with number of syllables (and letters). While set-size effects were observed equally for skilled and less skilled Ss for colors and digits, only less skilled readers were substantially affected by set-size increases with words. Inefficiency in alphabetic verbal coding rather than use of information constraint or word retrieval seems to be the major source of reader differences in vocalization latencies. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Motivation, affect, and hemispheric asymmetry: Power versus affiliation.

In 4 experiments, the authors examined to what extent information related to different social needs (i.e., power vs. affiliation) is associated with hemispheric laterality. Response latencies to a lateralized dot-probe task following lateralized pictures or verbal labels that were associated with positive or negative episodes related to power, affiliation, or achievement revealed clear-cut laterality effects. These effects were a function of need content rather than of valence: Power-related stimuli were associated with right visual field (left hemisphere) superiority, whereas affiliation-related stimuli were associated with left visual field (right hemisphere) superiority. Additional results demonstrated that in contrast to power, affiliation primes were associated with better discrimination between coherent word triads (e.g., goat, pass, and green, all related to mountain) and noncoherent triads, a remote associate task known to activate areas of the right hemisphere. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Manual and hemispheric specialization in the manipulation of a joystick by baboons (Papio papio).

Manual performance asymmetries were examined in 8 baboons (Papio papio). Using a joystick, monkeys had to track and hit with a cursor a randomly moving target on a monitor. The left or right hand was tested first, depending on group assignment, followed by a transfer to the other hand. A transfer effect is reported for the total number of trials to criterion and total number of successful trials. No effect was found for response time. However, for both test and transfer, the group initially tested with the left hand exhibited more controlled movements as demonstrated by shorter cursor's paths. Overall, it appears that the spatial components of the task are more sensitive to laterality effects than response times or learning scores. (PsycINFO Database Record (c) 2010 APA, all rights reserved)