Review of The evolution of lateral asymmetries, language, tool use, and intellect and The lopsided ape: Evolution of the generative mind.

Reviews the books, The evolution of lateral asymmetries, language, tool use, and intellect by J. L. Bradshaw and L. J. Rogers (see record 1992-98933-000) and The lopsided ape: Evolution of the generative mind by M. C. Corballis (see record 1991-98134-000). We have come to think of the left cerebral hemisphere as being "analytic" and the right hemisphere as being "holistic". Just as there is an analytic-holistic distinction in functional brain asymmetry, there is also an analytic-holistic distinction in books, and these two books by Bradshaw and Rogers and by Corballis represent the ends of this continuum. The Bradshaw and Rogers book provides a thorough review of behavioural and morphological asymmetries in a wide variety of species, with a concentration on birds, rodents, and primates. They argue that there are not only behavioural and morphological asymmetries in many different species, but that these are frequently influenced by environmental factors and often show sex differences. Their basic message appears to be that there have long been many different forms of functional asymmetry, and that the present state of affairs in homo sapiens sapiens is the end product of the coevolution of many different interacting factors. In contrast, Corballis views human language and representation as a property that has evolved fairly recently and that is uniquely human. In Corballis' view, homo sapiens sapiens is the "lopsided ape", and, by implication, other apes are not lopsided. Of the two books, then, the primary contribution of the Corballis volume lies in its speculations about the emergence of complex thought and mental representation in humans; that of the Bradshaw and Rogers volume in its thorough review of the literature on animal laterality. As a story, Corballis makes far better reading, and may well generate more creative research; as a reference source, Bradshaw and Rogers may have more lasting usefulness. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The contribution of attention to the right visual field advantage for word recognition

Perceptual asymmetries have been explained by structural, attentional bias and attentional advantage models. Structural models focus on asymmetries in the physical access information has to the hemispheres, whereas attentional models focus on asymmetries in the operation of attentional processes. A series of experiments was conducted to assess the contribution of attentional mechanisms to the right visual field (RVF) advantage found for word recognition. Valid, invalid and neutral peripheral cues were presented at a variety of stimulus onset asynchronies to manipulate spatial attention. Results indicated a significant RVF advantage and cueing effect. The effect of the cue was stronger for the left visual field than the RVF. This interaction supports the attentional advantage model which suggests that the left hemisphere requires less attention to process words. The attentional asymmetry is interpreted in terms of the different word processing styles used by the left and right hemispheres. These results have ramifications for the methodology used in divided visual field research and the interpretation of this research.     

Handedness for tool use correlates with cerebellar asymmetries in chimpanzees (Pan troglodytes).

Recent studies have shown that great ape species possess patterns of macrostructural neocortical asymmetries that are similar to those found in humans. However, little is known about the asymmetry of subcortical structures in great apes. To address this lack of data, the authors assessed left-right asymmetry of the anterior and posterior aspects of cerebellum from MRI brain scans of 53 chimpanzees (Pan troglodytes). No population-level bias was found for either the anterior or the posterior region of the cerebellum. However, a significant inverse association was found in the asymmetry quotients of the anterior and posterior regions, indicating that the cerebellum was torqued at the individual level. Additionally, handedness for tool use but not other measures was associated with variation in cerebellar asymmetries. Last, older chimpanzees had a smaller cerebellum after brain volume was adjusted for. The results are discussed in the context of brain changes in primate evolution related to tool use. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hemispheric aymmetries in adults' perception of infant emotional expressions.

Accounts of emotion lateralization propose either overall right hemisphere (RH) advantage or differential RH vs left hemisphere (LH) involvement depending on the negative–positive valence of emotions. Perceptual studies generally show RH specialization. Yet viewer emotional responses may enhance valence effects. Because infant faces elicit heightened emotion in viewers, perceptual asymmetries with chimeric infant faces were assessed. First, it was determined that chimeras must be paired with their counterparts, not their mirror images, to tap viewers' sensitivity to adult facial asymmetries. Results showed an RH perceptual bias for infant cries but bihemispheric sensitivity to asymmetries in infant smiles. This effect was not due to LH featural vs RH holistic processing and held for additional, intensity-matched, spontaneous expressions. Specialized RH sensitivity to infant cries may reflect an evolutionary advantage for rapid response to infant distress. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lateral asymmetries in infant melody perception.

Two experiments investigated lateral asymmetries in infants' perception of contour-altered and contour-preserved melody changes. In the first study, 40 infants (8.5 months old) of right-handed parents were trained to respond to binaural melody changes with a head turn toward mechanized toy reinforcers. The subsequent test phase included monaural left-ear and right-ear presentations of the familiar melody and of a changed melody. Infants who heard a contour-altered change showed a left-ear advantage, whereas infants who heard a contour-preserved change showed a right-ear advantage. These effects were replicated with a different set of melodies in the second study. The pattern of lateralization for detection of melody changes in infants of right-handed parents resembles that previously found in right-handed adults and may reflect more general hemispheric processing differences in the early organization of auditory information processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

General Intelligence as a Domain-Specific Adaptation.

General intelligence (g) poses a problem for evolutionary psychology's modular view of the human brain. The author advances a new evolutionary psychological theory of the evolution of general intelligence and argues that general intelligence evolved as a domain-specific adaptation for the originally limited sphere of evolutionary novelty in the ancestral environment. It has accidentally become universally important merely because we now live in an evolutionarily novel world. The available data seem to support the author's contention that intelligent people can solve problems better than less intelligent people only if the problems are evolutionarily novel, and they have no advantage in solving evolutionarily familiar problems. This perspective can also solve some empirical anomalies, such as the "central theoretical problem of human sociobiology" (D. R. Vining, 1986, p. 167) and the geographic distribution of general intelligence throughout the world. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Primary motor cortex asymmetry is correlated with handedness in capuchin monkeys (cebus apella).

Humans exhibit a population-wide tendency toward right-handedness, and structural asymmetries of the primary motor cortex are associated with hand preference. Reported are similar asymmetries correlated with hand preference in a New World monkey (Cebus apella) that does not display population-level handedness. Asymmetry of central sulcus depth is significantly different between left-handed and right-handed individuals as determined by a coordinated bimanual task. Left-handed individuals have a deeper central sulcus in the contralateral hemisphere; right-handed individuals have a more symmetrical central sulcus depth. Cerebral hemispheric specialization for hand preference is not uniquely human and may be more common among primates in general. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

How and why do the two cerebral hemispheres interact?

Research on the anatomical bases of interhemispheric interaction, including individual differences in corpus callosum (CC) anatomy, is reviewed. These anatomical findings form the basis for the discussion of 2 major themes. The 1st considers interhemispheric transfer time (IHTT) and related issues. These include varieties of IHTT and possible directional asymmetries of IHTT. Evidence suggests that pathological variations in IHTT may have cognitive consequences. The 2nd involves conditions under which interhemispheric interaction is necessary and beneficial. The data suggest that when both hemispheres have some competence at a difficult task, there is a benefit to interhemispheric interaction. The role of the CC in the dynamic distribution of attention may be particularly relevant to this advantage. Throughout the article reference is made to individual differences and developmental changes associated with interhemispheric interaction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cerebral lateralization and cognitive functioning in patients with congenital adrenal hyperplasia.

A battery of tests was administered to 17 patients with congenital adrenal hyperplasia (CAH) and 17 normal controls to investigate the effect of prenatal androgen exposure on cerebral lateralization and cognitive performance. Individuals were compared on measures of hand preference, verbal and performance IQ, and temporal processing asymmetry. A higher incidence of left-handedness was found among CAH participants. CAH individuals exhibited higher performance IQs as opposed to verbal IQs. Temporal processing asymmetries were investigated using an auditory gap detection task. Measures of reaction time and response error revealed a right-ear, therefore left-hemisphere, advantage for gap detection. This right-ear advantage did not differ between CAH individuals and controls. Results partially support the hypothesis that prenatal androgen exposure causes a shift in cerebral lateralization toward right-hemisphere dominance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Baseline asymmetries in brain electrical activity predict dichotic listening performance.

Forty-four right-handed participants were assessed on 2 occasions 6 weeks apart on electrophysiological measures of activation asymmetry derived from spectral estimates of electroencephalogram (EEG) alpha power in homologous scalp electrodes. Approximately 4 months following the final EEG assessment. participants were administered a dichotic listening CV-syllables task. Overall, participants exhibited a highly significant right-ear advantage. Differences among individuals in ear asymmetry were predicted by the earlier recorded electrophysiological data. Participants with greater activation in left-sided posterior temporal and parietal regions showed a larger right-ear advantage. In addition, a larger right-ear advantage was predicted by right-sided prefrontal activation. These data indicate that some of the variance in dichotic listening performance can be explained by dispositional activation asymmetries and is associated with a complex pattern of posterior and anterior activation asymmetries. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

D-subgenome bias of Xcm resistance genes in tetraploid Gossypium (cotton) suggests that polyploid formation has created novel avenues for evolution

A detailed RFLP map was used to determine the chromosomal locations and subgenomic distributions of cotton (Gossypium) genes/QTLs that confer resistance to the bacterial blight pathogen, Xanthomonas campestris pv. malvacearum (Xcm). Genetic mapping generally corroborated classic predictions regarding the number and dosage effects of genes conferring Xcm resistance. One recessive allele (b6) was a noteworthy exception to the genetic dominance of most plant resistance alleles. This recessive allele appeared to uncover additional QTLs from both resistant and ostensibly susceptible genotypes, some of which corresponded in location to resistance (R)-genes effective against other Xcm races. One putatively "defeated" resistance allele (B3) reduced severity of Xcm damage by "virulent" races. Among the six resistance genes derived from tetraploid cottons, five (83%) mapped to D-subgenome chromosomes-if each subgenome were equally likely to evolve new R-gene alleles, this level of bias would occur in only about 1.6% of cases. Possible explanations of this bias include biogeographic factors, differences in evolutionary rates between subgenomes, gene conversion or other intergenomic exchanges that escaped detection by genetic mapping, or other factors. A significant D-subgenome bias of Xcm resistance genes may suggest that polyploid formation has offered novel avenues for phenotypic response to selection.     

Observational learning of a left-right behavioral asymmetry in mice (Mus musculus).

B6D2F? hybrid mice that were allowed to observe a trained female mouse open a pendulum door to the right (or to the left) to enter a food compartment later solved this problem faster than pupils that had been placed behind a visual barrier. Male pupils that had observed a "left-handed" teacher performed sinistrally; males that had observed a "right-handed" model performed dextrally. Female pupils did not exhibit their demonstrator's laterality. Observational learning may provide a means to maintain certain lateralized behaviors. Such social learning may lead to the emergence of local traditions and to the cultural diffusion of behavioral asymmetries. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Asymmetries in Global-Local Processing Ability in Elderly People With the Apolipoprotein E-ε4 Allele.

Previous studies have identified cognitive asymmetries in elderly people at increased risk for Alzheimer's disease (AD) by comparing standardized neuropsychological tests of verbal and spatial abilities in both preclinical AD and apolipoprotein ε4+ elderly groups. This prospective study investigated cognitive asymmetries within a single test by comparing cognitively intact elderly (with and without the ε4+ allele) on a learning and memory measure that uses global and local visuospatial stimuli. Both groups demonstrated comparable overall learning and recall. But the ε4+ group had a significantly larger discrepancy between their global and local learning scores and had a greater proportion of individuals with more than a one standard deviation difference between their immediate recall of the global and local elements, relative to the ε4- group. These findings build on previous studies identifying subgroups of elderly people at greater risk for AD who often demonstrate increased cognitive asymmetries relative to groups without significant risk factors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Supports crisis phone services.

The author takes issue with comments made by D. Lester (see record 1990-57067-001) that hotline telephone counseling is unsupervised, executed by poorly trained individuals, and potentially dangerous in that such agencies may violate professional ethics. This type of attitude toward paraprofessional efforts represents an elitism within the mental health field that posits nonacademically trained individuals as being unable to lend constructive support and help to other human beings. The ability to empathize, listen, offer suggestions, and simply to "be there" in a time of crisis are not "trainable" qualities, nor qualities that need "supervision" as Lester implies, but rather constitute the best of being human. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

In vitro differentiation of chick spinal cord neurons in the presence of Reissner''s fibre, an ependymal brain secretion

Variation on the Y chromosome may permit our understanding the evolution of the human paternal lineage and male gene flow. This study reports upon the distribution and non random association of alleles at four Y-chromosome specific loci in four populations, three Caucasoid (Italian, Greek and Slav) and one Asian. The markers include insertion/deletion (p12f), point mutation (92R7 and pY alpha I), and repeat sequence (p21A1) polymorphisms. Our data confirm that the p12f/TaqI 8 kb allele is a Caucasoid marker and that Asians are monomorphic at three of the loci (p12f, 92R7, and pY alpha I). The alleles at 92R7 and pY alpha I were found to be in complete disequilibrium in Europeans. Y-haplotype diversity was highly significant between Asians and all three European groups (P < 0.001), but the Greeks and Italians were also significantly different with respect to some alleles and haplotypes (P < 0.02). We find strong evidence that the p12f/TaqI 8 kb allele may have arisen only once, as a deletion event, and, additionally, that the present-day frequency distribution of Y chromosomes carrying the p12f/8 kb allele suggests that it may have been spread by colonising sea-faring peoples from the Near East, possibly the Phoenicians, rather than by expansion of Neolithic farmers into continental Europe. The p12f deletion is the key marker of a unique Y chromosome, found only in Caucasians to date, labelled 'Mediterranean' and this further increases the level of Y-chromosome diversity seen among Caucasoids when compared to the other major population groups.     

Paediatric reference values for urinary catecholamine metabolites evaluated by high performance liquid chromatography and electrochemical detection

This report summarizes our experiences with the subjective visual vertical (SVV) as a clinical neuro-otological tool. In the SVV test, patients have to orient a dim light bar in an otherwise dark surrounding earth-vertical, using a remote-control. Normal subjects in an upright position did not deviate more than 2 degrees from true vertical. After vestibular neurectomy, the SVV was consistently tilted by some 12 degrees toward the affected ear. Smaller tilts (approximately 7 degrees) of the SVV occurred in patients with spontaneous peripheral vestibular diseases. This shift in SVV disappeared within weeks to months, similar to the spontaneous nystagmus. After stapes surgery slight deviations of the SVV towards the unoperated ear were seen in about 20% of the patients, indicating a slight irritation of the otolith organs. Assessed in an upright position, the SVV thus may be regarded as reflecting tonic otolithic input differences between the two ears. Asymmetries in the shifts of the SVV induced by roll tilts of the gravito-inertial vector by eccentric rotations of the subject have been proposed as a test for otolithic sensitivity. In our studies such asymmetries in the shifts of the SVV could not be induced by 26 degrees or 90 degrees roll tilts of subjects towards the affected or healthy ears. A simple clinical test to reveal unilateral otolithic sensitivity (comparable to an otolithic "caloric test") thus still has to be found.     

Aging on the input versus output side: Theoretical implications of age-linked asymmetries between detecting versus retrieving orthographic information.

This experiment tested for age-linked asymmetries predicted under Node Structure theory (NST; D.G. MacKay & D. M. Burke, 1990) between detecting versus retrieving orthographic information. Older adults detected that briefly presented words were correctly spelled (e.g., endeavor) or misspelled (e.g., endeavuor) as readily as did young adults. However, they were less able than young adults to retrieve the correctly and incorrectly spelled words that they had seen. These age-linked asymmetries were not due to educational factors, stimulus characteristics, sensory-level factors, task complexity, floor or ceiling effects, general slowing, or cohort-related activities, but they were consistent with NST predictions and with similar asymmetries in a wide range of other studies. By contrast, repetition deficits in detecting and retrieving repeated- versus unrepeated-letter misspellings (e.g., elderdly vs. elderkly) were symmetrical or equivalent in magnitude for young and older adults. Implications for a wide range of theories of cognitive aging and of repetition deficits are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Asymmetries in spontaneous head orientation in infant chimpanzees (Pan troglodytes).

Behavioral laterality in head orientation while sleeping in either a supine or prone posture was examined in 43 chimpanzees (Pan troglodytes) for the first 3 months of life. An overall significant right-side lateral bias was found for head orientation in the supine posture. A trend toward greater right-side bias in females compared with males was observed but failed to reach significance. These data suggest that asymmetries in head orientation are present early in life in chimpanzees, and they may be correlated with functional asymmetries observed in adulthood. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Increased asymmetries in 2-deoxyglucose uptake in the brain of freely moving congenitally acallosal mice

To investigate the role of the corpus callosum in the expression of functional brain asymmetries, we compared left and right uptake of [14C]2-deoxyglucose in 43 brain regions measured in 10 C57B1/6 mice with a normal corpus callosum and in 12 congenitally acallosal mice, after 45 min of free activity in a novel, large open-field arena. The metabolic patterns across the brain appeared to be similar in the two groups of mice, as well as the average direction of asymmetry in tracer incorporation, which was higher at right in most of the brain regions for both acallosals and controls. However, the direction of the metabolic asymmetries of any given region was not consistent across individual animals. The largest asymmetries were found in the central auditory nuclei in both groups of mice, with extreme values in some acallosals. Significantly larger asymmetries were found in acallosal mice for the brain and the cortex as a whole, as well as for the lateral geniculate and pretectal nuclei, the olfactory tubercles, and retrosplenial, infrarhinal and perirhinal cortices. The metabolic asymmetries of the thalamic sensory nuclei were correlated with the asymmetries of the corresponding sensory cortical fields in the acallosal, but not in control mice. On the other hand, asymmetries of the cortical regions were largely intercorrelated in control mice, resulting in a general activation of one hemisphere over the other, while in acallosals they were more independent, resulting in a "patchy" pattern of cortical asymmetries. These results suggest that callosal agenesis, combined with the occurrence of ipsilateral Probst bundles, leads to a loss of co-ordination in the activation of different sensory and motor areas. The impaired co-ordination might then be distributed through cortico-subcortical loops, resulting in larger asymmetries throughout the brain. Thus, a normal corpus callosum appears to balance and synchronize metabolic brain activity, perhaps by smoothing the effects of asymmetrically activated ascending systems.     

Rotation of mental images and asymmetries in word recognition in disabled readers.

Two experiments with 72 right-handed children (9–11 yrs old) revealed marked dissimilarities in perceptual coding between impaired and fluent readers. In Exp I, 26 boys with reading disabilities and average intelligence were compared to 26 good readers on a test of visual–spatial, short-term memory. Both groups performed equally well in their spatial recall on transformed visual fields. However, poor readers coded the test stimuli differently, in a nonanalytic and synchronous fashion. In a follow-up experiment, 10 disabled readers compared with 10 good readers showed a lower right- over left-field advantage when reporting single words presented tachistoscopically. Taken together, results disconfirm the widely held ideas that poor readers are suffering from spatial disorientation, left–right confusion, mirror-image equivalence, or lack of cerebral dominance. Findings suggest that the perceptual "anormalies" often linked with reading disability may result from nonpathological variations in the structural operations used to encode visual information. This difference in the organization of encodings in visual memory may be related to asymmetries in brain functioning. (42 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)