Spatio-temporal analysis of cortical activity evoked by gustatory stimulation in humans.

Gustatory activated regions in the cerebral cortex have not been identified precisely in humans. In this study we recorded the magnetic fields from the brain in response to two tastants, 1 M NaCl and 3 mM saccharin. We estimated the location of areas activated sequentially after the onset of stimulation with magnetic source imaging. We investigated the primary gustatory area (area G) precisely, and found it at the transition between the parietal operculum and the insular cortex. The central sulcus was activated less frequently than area G but with almost the same latency in cases of NaCl stimulation. Following area G, we found activation in several cortical regions, e.g. both the frontal operculum and the anterior part of the insula, the hippocampus, the parahippocampal gyrus and the superior temporal sulcus.     

Functional MRI detection of activation in the primary gustatory cortices in humans

Magnetoencephalography (MEG) has recently revealed that the transitions between the parietal operculum (Pop) and the insula (area G) and the ventral end of the central sulcus (cs) were activated with the shortest latency by instrumental gustatory stimulation, which suggests that the location of the primary gustatory area is in these two regions. However, studies using other noninvasive brain-imaging methods such as positron-emission tomography or functional magnetic resonance imaging (fMRI) with manual application of tastants into the mouth have been unable to confirm this. The present study examined cortical activation by repetitive stimulation of the tongue tip with 1 M NaCl with a computer-controlled stimulator and used fMRI to detect it. In individual brains, activations were detected with multiple comparisons (false discovery rate) across the whole brain corrected (threshold at P < 0.05) at both area G and frontal operculum (Fop) in 8 of 11 subjects and at the rolandic operculum (Rop) in 7 subjects. Activations were also found at the ventral end of the cs (n = 3). Group analysis with random-effect models (multiple comparison using familywise error in regions of interest, P < 0.02) revealed activation at area G in both hemispheres and in the Fop, Rop, and ventral end of the cs on the left side. The present study revealed no activation on the gyrus of the external cerebral surface except for the Rop. Taking MEG findings into consideration, the present findings strongly indicate that the primary gustatory area is present at both the transition between the Pop and insula and the Rop including the gray matter within a ventral part of the cs.     

Asymmetries of the Arcuate Fasciculus in Monozygotic Twins: Genetic and Nongenetic Influences

We assessed cerebral asymmetry for language in 35 monozygotic twin pairs. Using DTI, we reconstructed the arcuate fasciculus in each twin. Among the male twins, right-handed pairs showed greater left-sided asymmetry of connectivity in the arcuate fasciculus than did those with discordant handedness, and within the discordant group the right-handers had greater left-sided volume asymmetry of the arcuate fasciculus than did their left-handed co-twins. There were no such effects in the female twins. Cerebral asymmetry for language showed more consistent results, with the more left-cerebrally dominant twins also showing more leftward asymmetry of high anisotropic fibers in the arcuate fasciculus, a result applying equally to female as to male twins. Reversals of arcuate fasciculus asymmetry were restricted to pairs discordant for language dominance, with the left-cerebrally dominant twins showing leftward and the right-cerebrally dominant twins rightward asymmetry of anisotropic diffusion in the arcuate fasciculus. Because monozygotic twin pairs share the same genotype, our results indicate a strong nongenetic component in arcuate fasciculus asymmetry, particularly in those discordant for cerebral asymmetry.     

Multiple Sites of Gas Exchange

SYNOPSIS. For many years the general body surface has been recognizedas the primitive site of respiratory gas exchange in the animalkingdom. Even in simple animals such as the sea anemones, however,some specialization has occurred. In epifaunal species the tentacularcrown appears to be the major site of gas exchange while inone infaunal species dermal papillae are more important. Inboth, the columnar body wall remains an additional site of O₂uptake. In the polychaete annelids an evolutionary trend can be seenfrom the predominance of the general body surface over simple,metameric gills to the predominance of highly specialized andbranched anterior gills over the general body surface. n theoligochaetes reversion to the general body surface was followedin at least one species to specialization of the tail regionto form a "lung." Multiple sites clearly exist in the molluscs, but their relativeimportance is poorly known. Several sites exist in the echinoderms,the best known being the approximately equal allocation of O₂uptake between modified tube feet and respiratory trees in theholothurians. Multiple sites of gas exchange persist even inthe crustaceans, in temporal as well as spatial dimensions.Water breathers revert to cutaneous O₂ uptake following a molt,and air breathers have evolved an array of gas exchangers adaptedto their new medium. This array is so diverse that it does notprovide a single selection pressure for hemocyanin O₂ bindingproperties which, when compared broadly, remain indistinguishablefrom those of water breathers found in similar thermal regimes.     

Asymmetric regional cerebral blood flow in sedated baboons measured by positron emission tomography (PET)

The analysis of structural brain asymmetry has been a focal point in anthropological theories of human brain evolution and the development of lateralized behaviors. While physiological brain asymmetries have been documented for humans and animals presenting with pathological conditions or under certain activation tasks, published studies on baseline asymmetries in healthy individuals have produced conflicting results. We tested for the presence of cerebral blood flow asymmetries in 7 healthy, sedated baboons using positron emission tomography, a method of in vivo autoradiography. Five of the 7 baboons exhibited hemispheric asymmetries in which left-sided flow was significantly greater than right-sided flow. Furthermore, the degree of asymmetry in 8 of 24 brain regions was found to be significantly correlated with age; older individuals exhibited a higher degree of asymmetry than younger individuals. Cerebral blood flow itself was uncorrelated with age, and differences between males and females were not significant.     

The epidermal and inner epithelial lining of the operculum inClarias batrachus (Clariidae,Siluriformes)

The operculum may be divided into the proximal, the distal and the intermediate regions. The epithelium lining the inner surface of the operculum (EISO) and the opercular epidermis (OE) of these regions inClarias batrachus show significant differences in their thickness, in the density, in the dimensions of mucous cells and club cells, and in the distribution of lymphocytes, melanocytes, taste buds and ampullary organs. These differences in structural organization are associated with the different conditions prevailing at these locations. Rich vascularization observed in the tissues underlying the OE has been correlated with assisting the fish in accessory respiration. In contrast, the tissues underlying the EISO are poorly vascularized. Accessory respiration in this region may not be so advantageous.     

Anatomical asymmetry as the basis for cerebral dominance

Despite repeated assertions by some critics of the impossibility of linking behaviour to study of the brain, there have been major, although not always continuous advances in this field over the past 100 years, some of them based on simple techniques. One example is the study of cerebral dominance, for which it was believed until quite recently that no anatomical basis had been specified. The paper summarizes the findings of striking anatomical asymmetry of the upper surface of the temporal lobe, in an area known to be involved in speech functions. Asymmetries observed in autopsy brains of adults and fetuses, both by gross and by cytoarchitectonic techniques, are reported. By use of radiological methods asymmetries have been shown in the brains and skills of living persons. Asymmetries also appear to be present in the endocasts of skulls of ancient humans, and in nonhuman primates. The distribution of asymmetries is different in left and right handers. The implications of these findings are discussed.     

Individual quantitative differences in the structure of the human hippocampus

The volume of the hippocampal grey substance (Corpus Ammoni--CA) and that of the denticulated plate (Fasciculus dentatus--FD) have been studied in mature persons of various sex and age (17 subjects, 22 cerebral hemispheres) under cytoarchitectonic control defining the borders of the cerebral formations mentioned. Certain quantitative and spatial differences of CA and FD have been revealed in some subjects. Especially great differences are noted between more seldom occurring extreme individual variants, their difference being as great as three times. The differences revealed are demonstrated to be independent on the brain mass of the human beings studied. The observation performed causes to revise the competency of the principle concerning a constant proportional dependence between the reference points on the cerebral surface and the internal cerebral structures. These data are used in neurosurgery when surgical interventions are performed on brains with different dimensions. A suggestion is made that the individual volumetric differences revealed in the hippocamp of various persons are defined by its functional specificity.     

Dynamic modeling of multivariate dimensions and their temporal relationships using latent processes: Application to Alzheimer's disease

Alzheimer's disease gradually affects several components including the cerebral dimension with brain atrophies, the cognitive dimension with a decline in various functions, and the functional dimension with impairment in the daily living activities. Understanding how such dimensions interconnect is crucial for Alzheimer's disease research. However, it requires to simultaneously capture the dynamic and multidimensional aspects and to explore temporal relationships between dimensions. We propose an original dynamic structural model that accounts for all these features. The model defines dimensions as latent processes and combines a multivariate linear mixed model and a system of difference equations to model trajectories and temporal relationships between latent processes in finely discrete time. Dimensions are simultaneously related to their observed (possibly multivariate) markers through nonlinear equations of observation. Parameters are estimated in the maximum likelihood framework enjoying a closed form for the likelihood. We demonstrate in a simulation study that this dynamic model in discrete time benefits the same causal interpretation of temporal relationships as models defined in continuous time as long as the discretization step remains small. The model is then applied to the data of the Alzheimer's Disease Neuroimaging Initiative. Three longitudinal dimensions (cerebral anatomy, cognitive ability, and functional autonomy) measured by six markers are analyzed, and their temporal structure is contrasted between different clinical stages of Alzheimer's disease.     

Ultrastructure of Licea kleistobolus (Myxomycetes) and its bearing on the taxonomic affinity of the species

The peridium of Licea kleistobolus Martin consists of two distinct layers. Abundant refuse matter is evenly distributed on the surface of the fructification. The upper surface of the operculum is smooth and punctated by pores of variable size. The internal structure of the operculum is essentially the same as that of the peridium. Processes along the periphery of the lower surface of the operculum and along the upper edge of the sporangium function as an opening mechanism. The operculum bears hollow finger-like outgrowths and rounded warts, both being continuous with the inner wall of the operculum. The results of a SEM- and TEM-study indicate that the two different types of processes are homologous structures. Similarity between aberrant cap-illitial outgrowths along the margin of lobes in Listerella paradoxa Jahn and the processes bordering the sporangial edge and periphery of the operculum in L. kleistobolus , indicates affinity of the two species.     

Hemispheric asymmetries in cortical electrical activity during sleep. I

The hypothesis of a predominance of the right hemisphere in stage REM as compared to NREM has been tested through a spectral analysis of the EEG recorded from left (T3) and right (T4) temporal sites in 5 young healthy right-handed male subjects. Variations in the asymmetry coefficient R - L/R + L in different sleep stages have been analyzed by one way ANOVAs and Sheffé's tests. The hypothesis of a progressive increase in left hemisphere activity throughout different REM cycles as one approaches final awakenings have been investigated by comparing variations in the asymmetry coefficient for epochs of REM and stage 2 NREM sampled in different phases of the REM cycle. EEG results do not support either the hypothesized stage dependent or cycle dependent variation in EEG activity during sleep. We question whether variations in EEG amplitude and synchronization can be used as indices of hemispheric asymmetries during sleep.     

The relationship of handedness to asymmetry in the occlusal morphology of first permanent molars.

Handedness has been shown to be related to a number of systematic asymmetries in body dimensions, dermatoglyphic patterns and cerebral morphology. The aim here was to compare linear and angular tooth crown asymmetries of the permanent molars in healthy right-handed and left-handed subjects. The material comprised 27 children with recorded concordant left-side dominance of hand, eye and foot. The controls were an age- and sex-matched group with right side dominance. The material is based on the Collaborative Perinatal Project where detailed medical records and the dentitions, including accurate dental impressions, of over two thousand American children were examined in the USA in the sixties. Machine vision technique was used to obtain accurate three-dimensional information from the occlusal surfaces of the first permanent upper and lower molars. The directional asymmetry values of angular measurements of mandibular first molars showed evidence of asymmetry of opposite direction between the two examined groups. The results indicate that occlusal morphology of first permanent molars may be affected by handedness, and this tendency is most evident in the angular measurements of the mandibular molars. Fluctuating asymmetry did not differ significantly between the examined groups.     

A three‐dimensional analysis of bilateral directional asymmetry in the human clavicle

This study presents a novel three‐dimensional analysis using statistical atlases and automated measurements to assess diaphyseal morphology of the clavicle and its relationship to muscle asymmetry. A sample of 505 individuals (285 males, 220 females) from the William McCormick Clavicle Collection was CT scanned, segmented, and added to a statistical bone atlas that captures correspondence between homologous points on the bone surfaces. Muscle attachment sites were localized on the atlas and then propagated across the entire population. Cross‐sectional contours were extracted at 5% increments along the entire bone, as well as at muscle attachment sites and the clavicle waist; maximum and minimum dimensions of each cross‐sectional contour were calculated. In addition, the entire three‐dimensional surface was examined for asymmetry by analyzing the magnitude and directional differences between homologous points across all bone surfaces in the dataset. The results confirm the existing studies on clavicle asymmetry, namely that the left clavicle is longer than the right, but the right is more robust than the left. However, the patterns of asymmetry are sexually dimorphic. Males are significantly asymmetric in all dimensions and at muscle and ligament attachment sites (P < 0.05), whereas female asymmetry is more variable. We hypothesize that this is related to absolute and relative differences in male muscle strength compared to females. However, an area with no muscle attachments on the posterior midshaft was significantly asymmetric in both sexes. We suggest that this is a curvature difference caused by opposing muscle actions at the medial and lateral ends of the bone. Am J Phys Anthropol 2012. © 2012 Wiley Periodicals, Inc.     

Superquadric modeling of cranial and cerebral shape and asymmetry

A new method for quantifying cranial and cerebral shape and asymmetry fits symmetric superquadric geometric models to three-dimensional coordinate measurements. Asymmetry is quantified as radial residuals of the surface data points from their best-fit superquadric models. Twenty human crania, 10 magnetic resonance imaging (MRI) exocranial surfaces, and 10 corresponding MRI cerebral surfaces as well as two infant head casts were digitized and modeled using superquadrics. Superquadric parameters have simple geometric interpretation, are very reproducible, and demonstrated statistically significant differences between crania of Amerindian ancestry and MRI exocranial surfaces of European ancestry used in this study. Superquadric models demonstrated strong congruence between MRI exocranial and cerebral surfaces. Typical asymmetry was 1-5 mm. Lastly, polar contour plots of radial residuals for head casts before and after orthotic cranioplasty demonstrated the efficacy of using superquadrics to quantify positional plagiocephaly and synostosis of infant crania.     

Time course of the involvement of the right anterior superior temporal gyrus and the right fronto-parietal operculum in emotional prosody perception

In verbal communication, not only the meaning of the words convey information, but also the tone of voice (prosody) conveys crucial information about the emotional state and intentions of others. In various studies right frontal and right temporal regions have been found to play a role in emotional prosody perception. Here, we used triple-pulse repetitive transcranial magnetic stimulation (rTMS) to shed light on the precise time course of involvement of the right anterior superior temporal gyrus and the right fronto-parietal operculum. We hypothesized that information would be processed in the right anterior superior temporal gyrus before being processed in the right fronto-parietal operculum. Right-handed healthy subjects performed an emotional prosody task. During listening to each sentence a triplet of TMS pulses was applied to one of the regions at one of six time points (400-1900 ms). Results showed a significant main effect of Time for right anterior superior temporal gyrus and right fronto-parietal operculum. The largest interference was observed half-way through the sentence. This effect was stronger for withdrawal emotions than for the approach emotion. A further experiment with the inclusion of an active control condition, TMS over the EEG site POz (midline parietal-occipital junction), revealed stronger effects at the fronto-parietal operculum and anterior superior temporal gyrus relative to the active control condition. No evidence was found for sequential processing of emotional prosodic information from right anterior superior temporal gyrus to the right fronto-parietal operculum, but the results revealed more parallel processing. Our results suggest that both right fronto-parietal operculum and right anterior superior temporal gyrus are critical for emotional prosody perception at a relatively late time period after sentence onset. This may reflect that emotional cues can still be ambiguous at the beginning of sentences, but become more apparent half-way through the sentence.     

Limb bone bilateral asymmetry: variability and commonality among modern humans

Humans demonstrate species-wide bilateral asymmetry in long bone dimensions. Previous studies have documented greater right-biases in upper limb bone dimensions--especially in length and diaphyseal breadth--as well as more asymmetry in the upper limb when compared with the lower limb. Some studies have reported left-bias in lower limb bone dimensions, which, combined with the contralateral asymmetry in upper limbs, has been termed "crossed symmetry." The examination of sexual dimorphism and population variation in asymmetry has been limited. This study re-examines these topics in a large, geographically and temporally diverse sample of 780 Holocene adult humans. Fourteen bilateral measures were taken, including maximum lengths, articular and peri-articular breadths, and diaphyseal breadths of the femur, tibia, humerus, and radius. Dimensions were converted into percentage directional (%DA) and absolute (%AA) asymmetries. Results reveal that average diaphyseal breadths in both the upper and lower limbs have the greatest absolute and directional asymmetry among all populations, with lower asymmetry evident in maximum lengths or articular dimensions. Upper limb bones demonstrate a systematic right-bias in all dimensions, while lower limb elements have biases closer to zero %DA, but with slight left-bias in diaphyseal breadths and femoral length. Crossed symmetry exists within individuals between similar dimensions of the upper and lower limbs. Females have more asymmetric and right-biased upper limb maximum lengths, while males have greater humeral diaphyseal and head breadth %DAs. The lower limb demonstrates little sexual dimorphism in asymmetry. Industrial groups exhibit relatively less asymmetry than pre-industrial humans and less dimorphism in asymmetry. A mixture of influences from both genetic and behavioral factors is implicated as the source of these patterns.     

Morphological asymmetry of insular freshwater populations of threespine stickleback

Fluctuating asymmetry (FA), random deviations from perfect symmetry in a bilateral organism, has been widely used as a proxy for developmental instability in stressed populations. In order to test the utility of FA of resident freshwater threespine stickleback (Gasterosteus aculeatus) as a biomonitoring tool for contaminated sites, we compared levels of asymmetry of seven morphological traits of threespine stickleback collected from lakes at three islands with a history of military contamination and three islands with no military history, in the Aleutian Archipelago, Alaska. Traits examined include eye diameter, operculum width, pectoral fin ray number, pectoral fin width, lateral plate number, lateral plate length, and pelvic spine length. All morphometric traits demonstrated some degree of FA or directional asymmetry (DA), but the military history of a lake was not a predictor of the degree or type of asymmetry. Overall, the patterns of asymmetry were similar for all traits, irrespective of military contamination at a lake. Our results demonstrate that the suite of threespine stickleback traits measured are not suitable for examination of FA as a proxy for aquatic pollution in this region. DA also does not appear to be suitable as an indicator of aquatic pollution, but may instead be driven by local ecological factors such as predation.     

Influence of neural grafting on rat brain with damaged temporal cortex

This study investigated the feasibility and certain aspects of grafting nerve tissue from 15- and 21-day embryo rats into the left temporal rat cortex damaged by a solution (1 µg/1 µliter) of kainic acid (KA). After unilateral damage induced in the temporal cortex by KA, extensive lesions were found in a number of brain structures (the hippocampus, thalamus, etc.) removed from the KA application site; asymmetry between hemispheres was also revealed from the areas of cross-sections of these structures. In the presence of temporal cortex from 21-day embryos grafted into the lesioned area and setting up axonal connections with the host brain, damage to brain structures removed from the lesioned site was either prevented or substantially reduced. Asymmetry between hemispheres as gauged from the area of their cross sections was no longer present in brain with such grafts; moreover, grafts from 15-day embryos transplanted into a cortex lesioned by KA projected out onto the brain surface, growing and compressing the latter. The damaging action of KA on the host brain extended in the presence of these grafts. A viable graft located within the damaged area is thought to inactivate excitatory transmitters accumulating due to KA action, probably fulfilling the function of the damaged cortex in some measure once connections with the host brain have been set up.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 22, No. 5, pp. 586–595, October–September, 1990.     

DSA-Based Quantitative Assessment of Cerebral Hypoperfusion in Patients with Asymmetric Carotid Stenosis

Digital subtraction angiography (DSA) is often used to evaluate the morphological and pathological changes of cerebral arteries in clinical practice. This study aims to explore the possibility of assessing cerebral hypoperfusion with DSA in patients with carotid stenosis. Thirty patients with a mild to severe stenosis on one side, and a mild stenosis on the other side of the carotid artery were recruited. Frontal, parietal, temporal and occipital lobes were chosen as regions of interest for measuring the quantitative perfusion parameters from their time-density curves (TDCs) of DSA images. The perfusion parameters were compared between the two hemispheres by using paired t-test. In addition, the bilateral asymmetry of these parameters was calculated and its correlation with the bilateral asymmetry in stenosis was analyzed. The parameters included mean transit time (MTT), time of contrast uptake (TU), time taken to the half peak value (1/2TMAX), area under the curve (AUC) were significantly prolonged at the severe stenosis side than those at the mild stenosis side in frontal lobe (P=0.013; P=0.041; P=0.009; P=0.027) and parietal lobe (P=0.008; P=0.041; P=0.002; P=0.012). The asymmetric ratios of MTT and AUC showed statistically significant correlations with stenosis asymmetry in all four lobes. MTT, TU, 1/2TMAX and AUC could reflect the bilateral asymmetry of the cerebral perfusion. These DSA parameters, therefore, may be used for the evaluation of cerebral hypoperfusion caused by carotid stenosis.