Weaknesses in reports of "fertility" for horses and other species

Apparent fertility of a male or group of females is considered frequently by veterinarians or animal scientists. Unfortunately, concepts of experimental design and statistics impacting validity and interpretation of values for average pregnancy rate frequently are ignored. The magnitude of this problem was documented by examination of published papers; 51 of 67 (76%) were considered flawed for one or more reasons. The discussion considers why: (a) conclusions from most published fertility studies reporting no significant difference due to treatment(s) are suspect, because too few males and/or females were used; (b) the experimental unit in an IVF study should be a droplet of co-incubating gametes rather than an ovum; (c) apparent fertility of a male is profoundly influenced by the range in actual fertility of the females with which he was mated, and thus might shift over a two- to three-fold range; and (d) scientists should refrain from conduct of studies destined to be inconclusive, and should be candid in reporting each fertility trial. It was emphasized that no fertility data were better than an imprecise average value for a given male or a conclusion based on an inadequate research study or incomplete report of what was done.     

Differences in brain function and changes with intervention in children with poor spelling and reading abilities

Previous fMRI studies in English-speaking samples suggested that specific interventions may alter brain function in language-relevant networks in children with reading and spelling difficulties, but this research strongly focused on reading impaired individuals. Only few studies so far investigated characteristics of brain activation associated with poor spelling ability and whether a specific spelling intervention may also be associated with distinct changes in brain activity patterns. We here investigated such effects of a morpheme-based spelling intervention on brain function in 20 children with comparatively poor spelling and reading abilities using repeated fMRI. Relative to 10 matched controls, children with comparatively poor spelling and reading abilities showed increased activation in frontal medial and right hemispheric regions and decreased activation in left occipito-temporal regions prior to the intervention, during processing of a lexical decision task. After five weeks of intervention, spelling and reading comprehension significantly improved in the training group, along with increased activation in the left temporal, parahippocampal and hippocampal regions. Conversely, the waiting group showed increases in right posterior regions. Our findings could indicate an increased left temporal activation associated with the recollection of the new learnt morpheme-based strategy related to successful training.     

Mechanisms of Selective Attention during Competitive Discrimination of Visual and Auditory Verbal Information: Positron Emission Tomography and Cortical Evoked Potential Studies

The mechanisms of selective verbal attention were studied under conditions of simultaneous delivery of speech signals via the visual and auditory channels. The investigation was based on the comparison and synthesis of data obtained by two methods: positron emission tomography (PET) and brain evoked potentials (EPs). A new approach was developed: complementary tasks were constructed in such a way that, despite principal methodological problems, the same phenomenon could be investigated in one paradigm in EP and PET studies. The results obtained by the two methods are in rather good agreement with respect to topography: the secondary and tertiary areas, as well as the associative brain areas, are involved in attention concentration, that is, selection of verbal information occurs at the level of cognitive processes. The combination of two complementary methods, PET and EP, allowed the processes of processing of sensory information and brain mechanisms of selective attention to be investigated much more completely. The PET studies contributed to further understanding of brain mechanisms evidencing where processing occurs and the EP method provided insight into the mechanism of how this information is processed inside the corresponding cortical areas. The finding that the activation of primary areas of the visual cortex is accompanied by the inhibition of visual information deserves attention. This conclusion can be considered highly significant because of the concordance of the two independent methods. How to interpret it is not yet clear. It is possible that, in the case of primary importance of verbal information and priority of the visual channel for the repression from consciousness of artificially irrelevant information, a safety mechanism is activated: the amplified signal enters the brain cortex, where it is retained in the short-term iconic memory. This enables a reaction to this stimulus (if necessary), in the presence of any additional sign involving selective attention.     

What can functional brain imaging studies tell us about typical and atypical cognitive development in children?

Functional brain imaging has been largely reserved for adults. However, in recent years there have been increasing attempts to use functional brain imaging to inform our understanding of child development. These have taken three main forms: (1) Children with known or suspected neurological disorders may undergo brain imaging for medical diagnostic purposes and/or for the purpose of research into the nature of the disorders. (2) There have been a few studies where children, usually over the age of 8, have undergone functional brain imaging. (3) Results from brain imaging studies of adults have influenced theories about children's development. This chapter discusses the impact of brain imaging studies on our understanding of working memory; reading; and arithmetic. The different forms of brain imaging converge in demonstrating that different brain regions show differential activation for different domains and for different components within the domains: e.g. different reading strategies and different components of arithmetic. They show important similarities between children and adults, though it must be remembered that very few studies have involved young children. They also indicate that experience influences brain function, as well as the other way around.     

Microbiota-gut-brain axis in autism spectrum disorder

Extensive studies, largely during the past decade, identify the dynamic and bidirectional interaction between the bacteria resident in the intestines and their host brain along the "microbiota-gut-brain axis". This interaction modulates the development and function of the central nervous system and is implicated in neurological disorders. As a neurodevelopmental disorder, autism spectrum disorder (ASD) is considered a historically defect in the brain. With accumulating evidence showing how the microorganisms modulate neural activities, more and more research is focusing on the role of the gut microbiota in mitigating ASD symptoms and the underlying mechanisms. In this review, we describe the intricate and crucial pathways via which the gut microbiota communicates with the brain, the microbiota-gut-brain axis, and summarize the specific pathways that mediate the crosstalk of the gut microbiota to the brain in ASD.     

Sensory inputs stimulate progenitor cell proliferation in an adult insect brain

Although most brain neurons are produced during embryonic and early postnatal development, recent studies clearly demonstrated in a wide range of species from invertebrates to humans that new neurons are added to specific brain structures throughout adult life. Hormones, neurotransmitters, and growth factors as well as environmental conditions modulate this neurogenesis. In this study, we address the role of sensory inputs in the regulation of adult neural progenitor cell proliferation in an insect model. In some insect species, adult neurogenesis occurs in the mushroom bodies, the main sensory integrative centers of the brain, receiving multimodal information and often considered as the analog of the vertebrate hippocampus. We recently showed that rearing adult crickets in enriched sensory and social conditions enhanced neuroblast proliferation in the mushroom bodies. Here, by manipulating hormonal levels and affecting olfactory and/or visual inputs, we show that environmental regulation of neurogenesis is in direct response to olfactory and visual stimuli rather than being mediated via hormonal control. Experiments of unilateral sensory deprivation reveal that neuroblast proliferation can be inhibited in one brain hemisphere only. These results, obtained in a relatively simple brain, emphasize the role of sensory inputs on stem cell division.     

"Thinking about not-thinking": neural correlates of conceptual processing during Zen meditation

Recent neuroimaging studies have identified a set of brain regions that are metabolically active during wakeful rest and consistently deactivate in a variety the performance of demanding tasks. This "default network" has been functionally linked to the stream of thoughts occurring automatically in the absence of goal-directed activity and which constitutes an aspect of mental behavior specifically addressed by many meditative practices. Zen meditation, in particular, is traditionally associated with a mental state of full awareness but reduced conceptual content, to be attained via a disciplined regulation of attention and bodily posture. Using fMRI and a simplified meditative condition interspersed with a lexical decision task, we investigated the neural correlates of conceptual processing during meditation in regular Zen practitioners and matched control subjects. While behavioral performance did not differ between groups, Zen practitioners displayed a reduced duration of the neural response linked to conceptual processing in regions of the default network, suggesting that meditative training may foster the ability to control the automatic cascade of semantic associations triggered by a stimulus and, by extension, to voluntarily regulate the flow of spontaneous mentation.     

Category differences in brain activation studies: where do they come from?

Differences in the neural processing of six categories of pictorial stimuli (maps, body parts, objects, animals, famous faces and colours) were investigated using positron emission tomography. Stimuli were presented either with or without the written name of the picture, thereby creating a naming condition and a reading condition. As predicted, naming increased the demands on lexical processes. This was demonstrated by activation of the left temporal lobe in a posterior region associated with name retrieval in several previous studies. This lexical effect was common to all meaningful stimuli and no category-specific effects were observed for naming relative to reading. Nevertheless, category differences were found when naming and reading were considered together. Stimuli with greater visual complexity (animals, faces and maps) enhanced activation in the left extrastriate cortex. Furthermore, map recognition, which requires greater spatio-topographical processing, also activated the right occipito-parietal and parahippocampal cortices. These effects in the visuo-spatial regions emphasize inevitable differences in the perceptual properties of pictorial stimuli. In the semantic temporal regions, famous faces and objects enhanced activation in the left antero-lateral and postero-lateral cortices, respectively. In addition, we showed that the same posterior left temporal region is also activated by body parts. We conclude that category-specific brain activations depend more on differential processing at the perceptual and semantic levels rather than at the lexical retrieval level.     

Home Range Analysis of <Emphasis Type="Italic">Perodicticus potto edwardsi</Emphasis> and <Emphasis Type="Italic">Sciurocheirus cameronensis</Emphasis>

Because the spatial arrangements of nocturnal prosimians are often used to indicate their social systems, it is important to assess the reliability of methods used to analyze ranging patterns. We compared methods of home range analysis for 2 species of nocturnal prosimians: central pottos (Perodicticus potto edwardsi) and Cross River Allens galagos ({Sciurocheirus cameronensis}). We conducted radio-tracking studies of 10 pottos and 8 galagos from October 1999 – November 2000 in the montane rain forests of southwest Cameroon. We calculated home ranges via minimum convex polygon (MCPs) and kernel analyses. Adult potto home ranges averaged 145.2 ha (MCPs) versus only 28.4 ha via kernel analysis; the difference is statistically significant. The mean home range of galagos is 18.3 ha via MCPs and 2.19 ha via kernel analysis; the difference is statistically significant. Neither MCP nor kernel analyses revealed a sex difference in adult home ranges for pottos and galagos. Kernel analysis gave more reliable estimates of home ranges than the minimum convex polygon method used in many studies of nocturnal prosimians. Minimum convex polygon analysis tended to overestimate the range sizes and to include many areas not traversed by the animal. We compared our findings with those from an earlier study of similar species in Gabon, where little attention was given to the home range analysis, technique. Together with studies of lemur spatial systems they highlight the importance of considering the method of home range analysis when it is to be applied to understanding social systems.     

Assessment of α-synuclein secretion in mouse and human brain parenchyma

Genetic, biochemical, and animal model studies strongly suggest a central role for α-synuclein in the pathogenesis of Parkinson's disease. α-synuclein lacks a signal peptide sequence and has thus been considered a cytosolic protein. Recent data has suggested that the protein may be released from cells via a non-classical secretory pathway and may therefore exert paracrine effects in the extracellular environment. However, proof that α-synuclein is actually secreted into the brain extracellular space in vivo has not been obtained. We developed a novel highly sensitive ELISA in conjugation with an in vivo microdialysis technique to measure α-synuclein in brain interstitial fluid. We show for the first time that α-synuclein is readily detected in the interstitial fluid of both α-synuclein transgenic mice and human patients with traumatic brain injury. Our data suggest that α-synuclein is physiologically secreted by neurons in vivo. This interstitial fluid pool of the protein may have a role in the propagation of synuclein pathology and progression of Parkinson's disease.     

Current concepts on the "dark" cells of human and animal brains

The latest current literature is reviewed on the dark cells of the brain and internal organs of animals and man. The following questions are considered: shrinked and picnomorphic neurons; dark neurons and glyocytes--structure and function; and perspectives of research into the problem of dark cells. A conclusion has been made that in most cases dark cells of the animal and human nervous tissue constitute functionally conditioned elements emerging during the life span.     

视觉信息处理:阅读中文和英文时眼动模式的对比研究

文字阅读是一个复杂的视觉模式识别过程,虽然客观测量阅读过程中的脑的活动比较困难,但用记录分析阅读中由脑部控制的眼球活动来研究脑的信息处理特点却是可行的.本文采用两种不同结构的文字——以空间图象为基础的方块汉字和以发音序列为基础的横行英文——作为输入,用红外眼动仪测量阅读时的眼动曲线,再由计算机分析其异同.结果表明:1)阅读注视时程对中文及英文分别为0.260及0.265秒;2)阅读辨认跨度对中文及英文分别为1.7及1.8信息单位.由两者的相似性提示我们:整段理解阅读信息处理能力决定于神经系统高级阅读中枢的解码速率.     

Lactate and pH in the Brain: Association and Dissociation in Different Pathophysiological States

Brain tissue pH and lactate content were measured in rats under three different experimental conditions, namely: during complete global cerebral ischemia; after reversible near-complete cerebral ischemia; and in experimental brain tumors. At the end of the experiments brains were frozen with liquid nitrogen. A series of 20-microns thick coronal sections was prepared in a cryostat and then used for the regional determination of tissue pH (umbelliferone technique) and tissue lactate (bioluminescent technique). In addition, tissue samples were taken for the quantitative measurement of brain lactate (enzymatic fluorometric technique). The relationship between lactate content and tissue pH was different for each of the three experimental models studied: only after short-term global cerebral ischemia did an increase in the lactate content correlate with a decrease in tissue pH (r = 0.94; p less than 0.001). A highly significant increase in the lactate content (p less than 0.001) was accompanied by physiological pH values (6.96 +/- 0.08 in comparison to 6.97 +/- 0.04 in controls) during recirculation after transient cerebral ischemia and in brain tumors even by an alkaline pH shift. In view of these observations the term "lactacidosis" should not be used without measuring both the lactate content and the pH. The observed dissociation between pH and lactate is due to the fact that both parameters are regulated independently. During anaerobiosis the main source of proton production is ATP hydrolysis rather than glycolysis. It is, therefore, suggested that the terms "acidosis" and "lactosis" should be used instead of "lactacidosis."     

In vivo Microdialysis of 5-Hydroxyindoleacetic Acid and Glutamic Acid in the Hamster Suprachiasmatic Nuclei

SYNOPSIS. The technique of in vivo brain microdialysis rapidlyis becoming a popular tool for research on the neurochemicalbasis of physiological and behavioral functions. The presentstudy describes the application of microdialysis to investigatethe endogenous release of 5-hydroxyindoleacetic acid (5-HIAA)and glutamic acid in the suprachiasmatic nuclei (SCN) of hamsters.There were apparent circadian patterns of release of both ofthese neurosecretions, with peak levels occurring during thedark phase. Pharmacological manipulations of serotonin releaseand reuptake, using tetrodotoxin and citalopram, respectively,provided evidence that the nocturnal increase in 5-HIAA reflectsan increase in serotonergic synaptic activity, rather than intraneuronalmetabolism of unreleased serotonin. These results illustratethe usefulness of the microdialysis technique for studies onthe neurochemistry of central pacemaker function.     

Principles of diffusion tensor imaging and its applications to basic neuroscience research

The brain contains more than 100 billion neurons that communicate with each other via axons for the formation of complex neural networks. The structural mapping of such networks during health and disease states is essential for understanding brain function. However, our understanding of brain structural connectivity is surprisingly limited, due in part to the lack of noninvasive methodologies to study axonal anatomy. Diffusion tensor imaging (DTI) is a recently developed MRI technique that can measure macroscopic axonal organization in nervous system tissues. In this article, the principles of DTI methodologies are explained, and several applications introduced, including visualization of axonal tracts in myelin and axonal injuries as well as human brain and mouse embryonic development. The strengths and limitations of DTI and key areas for future research and development are also discussed.     

Brain cholesterol in representatives of different vertebrate classes

Studies have been made on the cholesterol content of the brain in 73 species of vertebrates. Cholesterol content increases in both aquatic and terrestrial animals in evolutionary row. Significant variations in cholesterol content were noted within the same class. Comparative studies revealed correlation between changes in phospholipids and cholesterol on one hand and various glycolipids on the other. It is suggested that cholesterol content of the brain in vertebrates depends on ecological factors rather than on taxonomic position of animals.     

Top-down modulations from dorsal stream in lexical recognition: an effective connectivity FMRI study

Both the ventral and dorsal visual streams in the human brain are known to be involved in reading. However, the interaction of these two pathways and their responses to different cognitive demands remains unclear. In this study, activation of neural pathways during Chinese character reading was acquired by using a functional magnetic resonance imaging (fMRI) technique. Visual-spatial analysis (mediated by the dorsal pathway) was disassociated from lexical recognition (mediated by the ventral pathway) via a spatial-based lexical decision task and effective connectivity analysis. Connectivity results revealed that, during spatial processing, the left superior parietal lobule (SPL) positively modulated the left fusiform gyrus (FG), while during lexical processing, the left SPL received positive modulatory input from the left inferior frontal gyrus (IFG) and sent negative modulatory output to the left FG. These findings suggest that the dorsal stream is highly involved in lexical recognition and acts as a top-down modulator for lexical processing.     

Surface-based and probabilistic atlases of primate cerebral cortex

Brain atlases play an increasingly important role in neuroimaging, as they are invaluable for analysis, visualization, and comparison of results across studies. For both humans and macaque monkeys, digital brain atlases of many varieties are in widespread use, each having its own strengths and limitations. For studies of cerebral cortex there is particular utility in hybrid atlases that capitalize on the complementary nature of surface and volume representations, are based on a population average rather than an individual brain, and include measures of variation as well as averages. Linking different brain atlases to one another and to online databases containing a growing body of neuroimaging data will enable powerful forms of data mining that accelerate discovery and improve research efficiency.