Sex differences in dog corpus callosum.

Human studies reported sex differences in size and shape of the corpus callosum. These observations have been contested. The purpose of the present study is to investigate possible sex differences in the corpus callosum of dogs. The entire brains including the medulla from 12 female and 9 male adult mongrel dogs were removed and weighed. Total and partial area measurements of the callosum were made from photographic tracings of its outline. The callosum was partitioned into 3 regions; anterior half, posterior half, posterior one-fifth. The total corpus callosum, anterior half, posterior half, and posterior fifth or splenium areas were measured. Sex differences were found. The anterior half, the posterior half, the posterior fifth, and the total callosum were significantly greater in absolute area in males than in females.     

Lateralised behaviour in the domestic dog,Canis familiaris

Paw use on three tasks in 53 domestic dogs (Canis familiaris) was studied to determine whether the animals exhibited a significant paw preference, and, if so, to explore the direction and strength of the dogs' preferred paw use, both within, and between, tasks. The influence of the dogs' sex on their paw preferences was also explored. The findings revealed that lateralised behaviour was strongly sex related. Male and female showed paw preferences at the level of the population but in opposite directions. Female dogs had a greater preference for using their right paw on all tasks, whilst males were more inclined to adopt their left paw. Analysis revealed significant positive relationships for two of a possible three intertask correlations. Overall, the findings suggest that there are two distinct populations of paw preference in the domestic dog that cluster around the animals' sex. It is recommended that further work be conducted to explore the influence of pre-training on dogs' paw preferences before generalisations regarding laterality in this species are drawn.     

Morphology of the human corpus callosum: the shape of its mediosagittal section

The shape of the corpus callosum was studied on mediosagittal sections of 50 human brains. The terms "facies corticalis" and "facies profunda" are proposed for the sides of corpus callosum. Each of 50 brains had a different shape of callosal mediosagittal section and any available classification was not possible. In 94% of cases, the contour of callosal cortical surface exhibited a posterior depression and in 46% also an anterior one. Other details of callosal morphology influencing its shape on mediosagittal section (transverse folds, circumscribed depressions) were described. The junction of fornix and corpus callosum in 78% was in 3rd and in 14% in 4th quarter of callosal length. The possible significance of these findings for further studies of human brain morphology is discussed.     

Magnetic Resonance Findings of the Corpus Callosum in Canine and Feline Lysosomal Storage Diseases

Several reports have described magnetic resonance (MR) findings in canine and feline lysosomal storage diseases such as gangliosidoses and neuronal ceroid lipofuscinosis. Although most of those studies described the signal intensities of white matter in the cerebrum, findings of the corpus callosum were not described in detail. A retrospective study was conducted on MR findings of the corpus callosum as well as the rostral commissure and the fornix in 18 cases of canine and feline lysosomal storage diseases. This included 6 Shiba Inu dogs and 2 domestic shorthair cats with GM1 gangliosidosis; 2 domestic shorthair cats, 2 familial toy poodles, and a golden retriever with GM2 gangliosidosis; and 2 border collies and 3 chihuahuas with neuronal ceroid lipofuscinoses, to determine whether changes of the corpus callosum is an imaging indicator of those diseases. The corpus callosum and the rostral commissure were difficult to recognize in all cases of juvenile-onset gangliosidoses (GM1 gangliosidosis in Shiba Inu dogs and domestic shorthair cats and GM2 gangliosidosis in domestic shorthair cats) and GM2 gangliosidosis in toy poodles with late juvenile-onset. In contrast, the corpus callosum and the rostral commissure were confirmed in cases of GM2 gangliosidosis in a golden retriever and canine neuronal ceroid lipofuscinoses with late juvenile- to early adult-onset, but were extremely thin. Abnormal findings of the corpus callosum on midline sagittal images may be a useful imaging indicator for suspecting lysosomal storage diseases, especially hypoplasia (underdevelopment) of the corpus callosum in juvenile-onset gangliosidoses.     

First isolation of Neospora caninum from the feces of a naturally infected dog.

Neospora caninum is a major cause of abortion in cattle worldwide. Cattle become infected with N. caninum by ingesting oocysts from the environment or transplacentally from dam to fetus. Experimentally, dogs can act as definitive hosts, but dogs excrete few oocysts after ingesting tissue cysts. A natural definitive host was unknown until now. In the present study, N. caninum was isolated from the feces of a dog. Gerbils (Meriones unguiculatus) fed feces from the dog developed antibodies to N. caninum in the Neospora caninum agglutination test, and tissue cysts were found in their brains. Neospora caninum was isolated in cell culture and in gamma-interferon gene knockout mice inoculated with brain homogenates of infected gerbils. The DNA obtained from fecal oocysts of the dog, from the brains of gerbils fed dog feces, and from organisms isolated in cell cultures inoculated with gerbil brains was confirmed as N. caninum. The identification of N. caninum oocyst by bioassay and polymerase chain reaction demonstrates that the dog is a natural definitive host for N. caninum.     

Developmental Changes in the Corpus Callosum from Infancy to Early Adulthood: A Structural Magnetic Resonance Imaging Study

Previous research has reported on the development trajectory of the corpus callosum morphology. However, there have been only a few studies that have included data on infants. The goal of the present study was to examine the morphology of the corpus callosum in healthy participants of both sexes, from infancy to early adulthood. We sought to characterize normal development of the corpus callosum and possible sex differences in development. We performed a morphometric magnetic resonance imaging (MRI) study of 114 healthy individuals, aged 1 month to 25 years old, measuring the size of the corpus callosum. The corpus callosum was segmented into seven subareas of the rostrum, genu, rostral body, anterior midbody, posterior midbody, isthmus and splenium. Locally weighted regression analysis (LOESS) indicated significant non-linear age-related changes regardless of sex, particularly during the first few years of life. After this increase, curve slopes gradually became flat during adolescence and adulthood in both sexes. Age of local maximum for each subarea of the corpus callosum differed across the sexes. Ratios of total corpus callosum and genu, posterior midbody, as well as splenium to the whole brain were significantly higher in females compared with males. The present results demonstrate that the developmental trajectory of the corpus callosum during early life in healthy individuals is non-linear and dynamic. This pattern resembles that found for the cerebral cortex, further suggesting that this period plays a very important role in neural and functional development. In addition, developmental trajectories and changes in growth do show some sex differences.     

Corpus callosum morphology in capuchin monkeys is influenced by sex and handedness

Sex differences have been reported in both overall corpus callosum area and its regional subdivisions in humans. Some have suggested this reflects a unique adaptation in humans, as similar sex differences in corpus callosum morphology have not been reported in any other species of primate examined to date. Furthermore, an association between various measurements of corpus callosum morphology and handedness has been found in humans and chimpanzees. In the current study, we report measurements of corpus callosum cross-sectional area from midsagittal MR images collected in vivo from 14 adult capuchin monkeys, 9 of which were also characterized for hand preference on a coordinated bimanual task. Adult females were found to have a significantly larger corpus callosum: brain volume ratio, rostral body, posterior midbody, isthmus, and splenium than adult males. Left-handed individuals had a larger relative overall corpus callosum area than did right-handed individuals. Additionally, a significant sex and handedness interaction was found for anterior midbody, with right-handed males having a significantly smaller area than right-handed females. These results suggest that sex and handedness influences on corpus callosum morphology are not restricted to Homo sapiens.     

On the neurons with dendrites intermingling with the fibers of the human corpus callosum: a Golgi picture

Golgi preparations of the anterior part of the truncus of the corpus callosum from 11 adult human brains were investigated. The vertical plane of section was situated symmetrically between the frontal and sagittal plane. The use of this oblique plane of section enabled easy identification of the neurons with dendrites intermingling with transcallosal fibers, what was not possible in standard frontal sections. 2 types of such neurons (with features of other interstitial neurons) were described: fusiform and multipolar. Both types of neurons were more frequently impregnated in areas adjacent to induseum griseum, cingular cortex, and in the depth of the callosal sulcus. Multipolar neurons were also present in the central core and in ventral parts of the corpus callosum, but fusiform ones were not present in ventral parts of the corpus callosum truncus. The dentrites of both types of neurons usually were perpendicular to, sometimes also parallel to transcallosal fibers. The impregnation of these neurons in groups and pairs suggest their integrative role, and their planar orientation in mentioned oblique plane corresponds to oblique direction of transcallosal cingulostriatal decussating fibers.     

Dog paw preference shows lability and sex differences

Paw preferences in domestic dogs were studied using three different behavioural tests, recording frequency, duration and latency of paw use. No overall population tendency to right- or left-paw preference was seen on any of the tests, nor could a sub-population of handed dogs be detected. This failure to replicate previous reports that male dogs tend to use their left paws while females use their right was counterbalanced by a significant tendency for male dogs to use their left paw when initially presented with one test, and for the latency of left paw use to be significantly shorter than that for right paw use on these initial presentations. This significant effect disappeared with repeated presentation of the test, and was not present in females. We conclude that behavioural lateralisation appears to be a labile category in dogs, and may be related to brain hemispheric effects in responding to novel stimuli.     

Vascularization of the corpus callosum in humans

The blood supply of the corpus callosum is studied in 20 brains by injecting the vascular system with gelatinous Indian ink. The arterial vascularization derives mainly from the anterior cerebral arteries, accessed from the median artery of the corpus callosum or from the terminal and choroidal branches of the posterior cerebral arteries. The various arteries give off perforating branches which are direct or indirect, short, of middle length or long. All these arteries concentrate on the peripheral wall of the corpus callosum. Inside of it these various arteries give off numerous terminal and collateral branches running between the nervous fibres and forming a characteristic vascular network which nourishes the capillary network. The venous vascularization of the corpus callosum is tributary to the deep venous system of the brain and concentrates on the central wall of the commissure.     

A comparative MRI-based morphometric study of the corpus callosum in term and preterm infants

A comparative morphometric study was performed with MRI brain scans of term- and preterm-born infants. The structural characteristics of the brain were analyzed using conventional morphometric indices, and a novel quantitative parameter, the corpus callosum coefficient (kCC), was introduced based on patterns of the prenatal cortex ontogeny. All these quantitative indices reflected anatomical features of the preterm brain. It was found that reduced kCC values in preterm infants were associated with an altered proportion between the rostral and caudal segments of the corpus callosum. The threshold kCC value was established that allowed significant discrimination between the brains of full-term and preterm infants.     

Hemispheric specialization in domestic dogs (Canis familiaris) for processing different types of acoustic stimuli

Lateralization is considered to be a fundamental feature of vertebrate brains. The aim of the present study was to examine the impact of functional cerebral asymmetry on processing of auditory stimuli in the domestic dog (Canis familiaris) during the orientation reaction. The experiment was conducted on 46 dogs (25 females and 21 males). Four types of auditory stimuli were used in the experiment (three meaningful stimuli: cat meowing, dog barking, the "sit" command ("siad" in Polish), and a neutral word ("wir", meaning "whirl" in Polish). It was predicted that the orientation reaction (turning the head towards the stimuli) would take place only in the case of meaningful sounds. It was also expected that dogs would show consistent lateralization. As predicted, all three meaningful stimuli elicited the orientation reaction. The response of the examined dogs to cat meowing showed significant lateralization with dominant leftwards movement, which hints towards activation of the right cerebral hemisphere and may be related to strong emotions evoked by this stimulus. Contrary to results of previous studies, dogs reacting to dog barking turned their heads leftwards more often, which suggests activation of the right cerebral hemisphere, probably related to the emotional meaning of the stimulus. The "sit" command consistently evoked the orientation reaction but there was no significant lateralization of this movement.     

Erythropoietin treatment alleviates ultrastructural myelin changes induced by murine cerebral malaria

ABSTRACT: BACKGROUND: Cerebral malaria (CM) is a severe complication of malaria with considerable mortality. In addition to acute encephalopathy, survivors frequently suffer from neurological sequelae. The pathogenesis is incompletely understood, hampering the development of an effective, adjunctive therapy, which is not available at present. Previously, erythropoietin (EPO) was reported to significantly improve the survival and outcome in a murine CM model. The study objectives were to assess myelin thickness and ultrastructural morphology in the corpus callosum in murine CM and to adress the effects of EPO treatment in this context. METHODS: The study consisted of two groups of Plasmodium berghei-infected mice and two groups of uninfected controls that were either treated with EPO or placebo (n = 4 mice/group). In the terminal phase of murine CM the brains were removed and processed for electron microscopy. Myelin sheaths in the corpus callosum were analysed with transmission electron microscopy and stereology. RESULTS: The infection caused clinical CM, which was counteracted by EPO. The total number of myelinated axons was identical in the four groups and mice with CM did not have reduced mean thickness of the myelin sheaths. Instead, CM mice had significantly increased numbers of abnormal myelin sheaths, whereas EPO-treated mice were indistinguishable from uninfected mice. Furthermore, mice with CM had frequent and severe axonal injury, pseudopodic endothelial cells, perivascular oedemas and intracerebral haemorrhages. CONCLUSIONS: EPO treatment reduced clinical signs of CM and reduced cerebral pathology. Murine CM does not reduce the general thickness of myelin sheaths in the corpus callosum.     

Subregional and Intracellular Distribution of NADP-Linked Malic Enzyme in Human Brain

High total activity (expressed as μmol/min/g of wet tissue or per milligram of DNA) and differential subregional distribution of NADP-linked malic enzyme was found in autopsy specimens of human brain. Striatum showed the highest activity of malic enzyme, which was two to five-fold higher than that in other human organs tested. High activity was also found in frontal cortex, while the lowest activity of the enzyme in the central nervous system was found in cerebellum, substantia alba, and corpus callosum. In striatum, frontal cortex, pens, and cerebellum more than 80% of total malic enzyme activity was localized in the mitochondrial fraction, while in substantia alba and corpus callosum approximately 60% of the enzyme activity was present in the mitochondrial fraction. Relatively high specific activity of malic enzyme was found in a crude mitochondrial fraction isolated from various regions of human brain. The highest specific activity was found in the mitochondria isolated from striatum (more than 100 nmol/min/mg of mitochondrial protein); the lowest, but still high (approximately 32 nmol/min/mg of mitochondrial protein) was present in corpus callosum. These data and the different ratios of citrate synthase to mitochondrial malic enzyme activities found in different regions of brain suggest that human brain mitochondria, like the mitochondria isolated from other mammalian brains, are extremely heterogenous. A possible role of mitochondrial malic enzyme in human brain metabolism is discussed.     

Size and position of the human adhaesio interthalamica

In 50 human brains, we investigated the size of the adhaesio interthalamica, length of CA-CP line, position of the centre of adhaesio interthalamica, and the distance between the corpus callosum and adhaesio interthalamica. Interthalamic adhesion was absent in 11 brains (22%) and was duplicated in 1 brain. In all 50 brains, length of the intercommissural line (CA-CP) had a mean value of 2.56 cm, in brains with the interthalamic adhesion 2.48 cm, and 2.56 cm in brains without it. t-test for this difference showed no significant result for a probability of 0.05 (t = 1.95). Midsagittal section area of adhaesio interthalamica had a mean value of 13.1 mm2 (min = 1.5 mm2; max = 34 mm2). There is no correlation between the length of CA-CP line and the size of the midsagittal section area of adhaesio interthalamica (the correlation coefficient was 0.06). The centre of adhaesio interthalamica was most often situated above the CA-CP line and around the perpendicular line through its middle portion. The distance between the corpus callosum and interthalamic adhesion, measured in standardized system of CA-CP line, had a mean value 1.4 cm (min = 0.7 cm; max = 2.3 cm). Our results confirm the opinions that the presence of size of the interthalamic adhaesion depends not directly on the size of the corresponding brain (diencephalon).     

Dog experts' brains distinguish socially relevant body postures similarly in dogs and humans

We read conspecifics' social cues effortlessly, but little is known about our abilities to understand social gestures of other species. To investigate the neural underpinnings of such skills, we used functional magnetic resonance imaging to study the brain activity of experts and non-experts of dog behavior while they observed humans or dogs either interacting with, or facing away from a conspecific. The posterior superior temporal sulcus (pSTS) of both subject groups dissociated humans facing toward each other from humans facing away, and in dog experts, a distinction also occurred for dogs facing toward vs. away in a bilateral area extending from the pSTS to the inferior temporo-occipital cortex: the dissociation of dog behavior was significantly stronger in expert than control group. Furthermore, the control group had stronger pSTS responses to humans than dogs facing toward a conspecific, whereas in dog experts, the responses were of similar magnitude. These findings suggest that dog experts' brains distinguish socially relevant body postures similarly in dogs and humans.     

Dogs' expectation about signalers' body size by virtue of their growls

Several studies suggest that dogs, as well as primates, utilize a mental representation of the signaler after hearing its vocalization and can match this representation with other features provided by the visual modality. Recently it was found that a dogs' growl is context specific and contains information about the caller's body size. Whether dogs can use the encoded information is as yet unclear. In this experiment, we tested whether dogs can assess the size of another dog if they hear an agonistic growl paired with simultaneous video projection of two dog pictures. One of them matched the size of the growling dog, while the other one was either 30% larger or smaller. In control groups, noise, cat pictures or projections of geometric shapes (triangles) were used. The results showed that dogs look sooner and longer at the dog picture matching the size of the caller. No such preference was found with any of the control stimuli, suggesting that dogs have a mental representation of the caller when hearing its vocalization.     

In-Kennel Behavior Predicts Length of Stay in Shelter Dogs

Previous empirical evaluations of training programs aimed at improving dog adoption rates assume that dogs exhibiting certain behaviors are more adoptable. However, no systematic data are available to indicate that the spontaneous behavior of shelter dogs has an effect on adopter preference. The aim of the present study was to determine whether any behaviors that dogs exhibit spontaneously in the presence of potential adopters were associated with the dogs'' length of stay in the shelter. A sample of 289 dogs was videotaped for 1 min daily throughout their stay at a county shelter. To account for differences in adopter behavior, experimenters varied from solitary passive observers to pairs of interactive observers. Dogs behaved more attentively to active observers. To account for adopter preference for morphology, dogs were divided into “morphologically preferred” and “non-preferred” groups. Morphologically preferred dogs were small, long coated, ratters, herders, and lap dogs. No theoretically significant differences in behavior were observed between the two different dog morphologies. When accounting for morphological preference, three behaviors were found to have a significant effect on length of stay in all dogs: leaning or rubbing on the enclosure wall (increased median length of stay by 30 days), facing away from the front of the enclosure (increased by 15 days), and standing (increased by 7 days). When combinations of behaviors were assessed, back and forth motion was found to predict a longer stay (increased by 24 days). No consistent behavioral changes were observed due to time spent at the shelter. These findings will allow shelters to focus behavioral modification efforts only on behaviors likely to influence adopters'' choices.     

Transient cellular structures in developing corpus callosum of the human brain

The corpus callosum connects two cerebral hemispheres as the most voluminous fiber system in the human brain. The developing callosal fibers originate from immature pyramidal neurons, grow through complex pathways and cross the midline using different substrates in transient fetal structures. We analyzed cellular structures in the human corpus callosum on postmortem brains from the age of 18 weeks post conception to adult, using glial fibrillary acidic protein, neuron-specific nuclear protein, and chondroitin sulphate immunocytochemistry. We found the presence of transient cellular structures, callosal septa, which divide major fiber bundles and ventrally merge with subcallosal zone forming grooves for callosal axons. The callosal septa are composed of glial fibrillary acidic protein reactive meshwork, neurones and the chondroitin sulphate immunoreactive extracellular matrix. The developmental window of prominence of the callosal septa is between 18-34 weeks post conception which corresponds to the period of most intensive growth of callosal axons in human. During the early postnatal period the callosal septa become thinner and shorter, lose their neuronal and chondroitin sulphate content. In conclusion, transient expression of neuronal, glial and extracellular, growing substrate in the callosal septa, as septa itself, indicates their role in guidance during intensive growth of callosal fibers in the human brain. These findings shed some light on the complex morphogenetic events during the growth of the corpus callosum and represent normative parameters necessary for studies of structural plasticity after perinatal lesions.