https://medicalxpress.com/ en-us Medical Xpress internet news portal provides the latest news on Health and Medicine. (Medical Xpress)—With thousands of basic and clinical neuroscience studies carried out over the past 15 years, the Default Mode Network (DMN) – a network of highly co-correlated interacting regions whose activity is very active during wakeful rest and distinct from that of other neural networks – is one of the most highly-investigated networks of the brain. Nevertheless, identifying the DMN's central role has remained elusive due to contradictory results: The dilemma is that while mind-wandering diverts attention from one's sensory environment and thereby creates unstable (i.e., variable) task performance, the DMN has been found to be active during what appear to be incompatible states. On the one hand, the DMN is active during intense mind-wandering (thinking about oneself or others, and recalling the past or planning the future), and on the other hand, the DMN is active during stable, rather than variable, behavior. Recently, however, scientists at Massachusetts General Hospital and Harvard Medical School as well as Boston University have demonstrated for the first time how these two explanations of DMN activity are more compatible than they might have seemed. In so doing – and while acknowledging that DMN fluctuations may reflect a higher-level function related to both stable behavior and mind-wandering (a potential example being memory reconsolodiation) – the researchers conclude that their findings call for a need to reinterpret the significance of DMN activity fluctuations in daily life as well as DMN disruption in disease. https://medicalxpress.com/news/2016-12-contradictions-basic-role-brain-default.html Mon, 12 Dec 2016 09:30:01 EST news400704802 (Medical Xpress)—While human infants, nonhuman primates and birds are capable of approximating or comparing rough arithmetic quantities, post-infant humans are unique in possessing precise mathematical cognition. Historically, what is known as the Triple Code model of numeric processing has hypothesized that symbolic, verbal, and abstract processing – for example, simple visual recognition of a numeral, determining the larger of two numerals, and verbal naming of a numeral, respectively – occur in well-defined coupled brain regions, all or some of which interact. Recently, however, scientists at Baylor College of Medicine, Houston employing electrocorticography (ECoG) electrophysiological recording – in which electrodes are placed directly on the exposed surface of the brain's cerebral cortex – not only reconfirmed math-selective hubs within the lateral parietal cortex (LPC) and ventral temporal cortex (VTC), but more significantly found what they describe as a remarkable diversity of neural responses within each region at both millimeter and millisecond scales. The researchers suggest that numerical processing involves multiple bidirectional functional loops in these, and perhaps nearby, sites – and while acknowledging that their new model does not take other brain regions into account (such as frontal lobe or subcortical structures like the thalamus or basal ganglia) that are likely to be involved in numerical cognition, it may serve as a framework for future mathematical cognition studies. https://medicalxpress.com/news/2016-11-brain-math-functional-coupling-neural.html Mon, 21 Nov 2016 10:00:01 EST news398933226 (Medical Xpress)—Parkinson's disease (PD) – an incurable, progressive illness caused by dysfunction and death of dopaminergic neurons in the brain (mainly in the substantia nigra) – results in a wide range of symptoms, motor system disorders such as tremors, akinesia (muscle rigidity), bradykinesia (slowed motion), and impaired balance (PD-related nonmotor symptoms include depression, gastrointestinal disorders, low blood pressure, and sleep disorders.) While PD can be managed with to varying degrees with medication and (less frequently) surgery, its precise cause has yet to be identified. At the same time, neuronal interconnection (or circuitry) models of Parkinson's disease are based on dopamine loss in a subcortical nucleus of the forebrain known as the striatum, as well as atypical striatal inputs into the basal ganglia (a neuronal network that plays a role in motor function and is thus relevant to PD and other neurological disorders manifesting with tremors and other involuntary movements). However, current research has been focused largely on extrastriatal mechanisms rather than striatal discharges in PD. Recently, however, scientists at Emory University School of Medicine, Atlanta, San Pablo University, Madrid and Instituto de Salud Carlos III, Madrid studied striatal projection neuron (SPN) patterns in PD patients undergoing deep brain stimulation (DBS) surgery, and compared that activity pattern with patients having the non-PD conditions essential tremor (ET) and isolated dystonia (ID) that lead to tremors and intermittent muscle contractions, respectively. The researchers found that their study provides significant insight into the role of striatal mechanisms in basal ganglia circuits and PD pathophysiology, as well as reports for the first time altered striatal SPN activity in dystonia and activity compatible with unchanged striatal function in ET. https://medicalxpress.com/news/2016-08-curtain-abnormal-discharge-striatal-neurons.html Tue, 30 Aug 2016 09:30:02 EDT news391746949 (Medical Xpress)—In dynamic neuronal networks, pervasive oscillatory activity is usually explained by pointing to pacemaking elements that synchronize and drive the network. Recently, however, scientists at The Weizmann Institute of Science in Israel studied synchronized periodic bursting that emerged spontaneously in a network of in vitro rat hippocampus and cortex neurons, finding that roughly 60% of all active neurons were self-sustained oscillators when disconnected from the network – and that each neuron oscillated at its own frequency, which is controlled by the neuron's excitability. The researchers say that neuronal oscillations are widespread in the brain, not only in processes that require timing but also observed over natural activity characteristic of many areas – and that their realization that single neurons operating in default mode with no relevant input tend to oscillate may be important in deciphering the activity in these areas. Similarly, they state, the ability to couple and create large ensembles of synchronized oscillations will be important to understand how the activity spread to larger areas. https://medicalxpress.com/news/2016-03-hippocampal-cortical-neurons-oscillate-individually.html Thu, 31 Mar 2016 09:30:01 EDT news378615562 (Medical Xpress)—One of the most fascinating and fast-growing areas in neuroscience is evolutionary neurobiology - an interdisciplinary scientific research field at the intersection of neuroscience, evolutionary biology, and – after the so-called neo-Darwinian synthesis in the 20th century – comparative neuroanatomy and developmental genetics. Recently, a collaboration of scientists at The George Washington University, Washington, DC, Massachusetts General Hospital, and The National University of Singapore drew on an even wider range of disciplines, adding graph theory, molecular neurobiology, human cognitive neuroscience, and phylogenetic comparative brain evolution to determine if the expansion of the brain's cortical surface and associated long-range cortical connections in the supragranular layers of the cortex might be related to changes in underlying molecular architecture and thereby related genetic expression. They demonstrated that transcriptional expression of certain genes reflects the classic subdivision of the cerebral cortex into different types (sensory/motor, paralimbic, and heteromodal association), and that while the genes that best distinguish these subdivisions are selectively enriched in upper layers of the cortex in humans but not in mice, the researchers noted that the question of whether their findings apply only to humans or are common to other great apes or primates remains a hypothesis to be tested in future work. https://medicalxpress.com/news/2016-02-gene-specific-transcription-humans-linked-long-range.html Wed, 24 Feb 2016 09:30:02 EST news375514820 (Medical Xpress)—A number of lung diseases are resistant to, or only marginally handled by, conventional therapies. Thanks to the discovery of numerous genetic targets, gene therapy provides an alternative or complementary therapeutic option. Over the past two decades or more, a large number of gene delivery systems, based on viruses or man-made nanoparticles, have been developed in order to deliver therapeutic nucleic acids to the target cells in the lung, while preventing these cargos from being degraded by the body's protective enzymes before they reach the target. However, while it is readily accessible via inhalation, the mucus lining the lung airways typically traps inhaled foreign matter that is then removed from the lung by being rapidly and continuously swept up towards the larynx to be swallowed into the stomach and degraded. Although this is a critical host defense mechanism, the same airway mucus also traps inhaled therapeutic nanoparticles, such as gene delivery systems, through steric obstruction and/or adhesive interactions, meaning that therapeutic nanoparticles trapped in airway mucus will be rapidly cleared from the lung and so not be able to reach their target cells in the lung. Indeed, several clinically tested viral and non-viral gene delivery systems have been shown unable to efficiently penetrate human airway mucus. In addition, the physiological environment in the lung renders it hard to retain stability of therapeutic nanoparticles until they reach the target cells. Thus, despite over two decades of effort, therapeutically effective lung gene therapy is yet to be realized. https://medicalxpress.com/news/2015-09-deep-biodegradable-dna-nanoparticles-rapidly.html Tue, 01 Sep 2015 09:30:03 EDT news360293009 Standard models of perception are stimulus-driven, meaning that the external perceptual event drives the brain's perception-related activity. However, the tide may be turning: recent ideas suggest that our perceptual experiences and visually guided behaviors are influenced by top-down processes in the brain – specifically, the brain's predictions about the external world. Recently, scientists at University of Wisconsin–Madison demonstrated that perceptual expectations about when a stimulus will appear are instantiated in the brain by optimally configuring prestimulus alpha-band oscillations in order to optimize the effectiveness of subsequent neural processing. The researchers state that their findings provide direct evidence that forming temporal predictions about when a stimulus will appear can bias the phase of ongoing alpha-band oscillations (one of the dominant oscillations in the human brain) toward an optimal phase for visual processing, and so may be the means for the top-down control of visual processing guided by temporal predictions. https://medicalxpress.com/news/2015-07-human-brain-alpha-band-oscillation-phase.html Wed, 22 Jul 2015 06:00:02 EDT news356684858 The brain is an exceedingly complex and active organ in which most neural activity is not directly evoked by, and thereby linked to, specific external events. Moreover, intrinsic activity occurring in one location exhibits functional connectivity – that is, being correlated with other brain regions – but there has been only limited direct evidence of these continuous large-scale connectivity dynamics having behavioral relevance. Recently, however, scientists at University of California, Berkeley demonstrated that these ongoing changes correlate with behavior by using functional magnetic resonance imaging (fMRI). The researchers conclude that moment-to-moment changes in baseline functional connectivity may shape subsequent behavioral performance. Their findings suggest that a highly modular network structure is beneficial to perceptual efficiency. https://medicalxpress.com/news/2015-07-william-james-revisited-ongoing-brain.html Tue, 21 Jul 2015 06:00:01 EDT news356676967 (Medical Xpress)—Myelin is an electrically insulating layer, or sheath, made of protein and fatty molecules, and synthesized by cholesterol-rich oligodendrocytes, that forms around neurons and allows electrical impulses to propagate rapidly along the axon. (Oligodendrocytes are glial cells – non-neuronal cells that maintain homeostasis, form myelin, and provide support and protection for neurons in the central and peripheral nervous systems.) The myelin sheath is critical to normal central nervous system behavior, but oligodendrocyte cell death or injury can lead to demyelination, which if not followed by normal remyelination typically leads to axonal degeneration, functional impairments, and clinical disability. Taking a novel approach to the myelination and remyelination processes, scientists at Paris Descartes University studied Liver X Receptor, or LXR, isoforms LXRα and LXRβ – oxysterol-activated proteins able to modulate gene expression – to investigate their possible role in the myelin physiology of the cerebellum. (Isoforms are any of several different forms of the same protein.) They found – for the first time – that mice genetically invalidated for both LXRs exhibit alteration in motor coordination and spatial learning linked with myelination deficits, and moreover demonstrated that LXRs intervene both in oligodendroglial cell maturation and in the transcriptional control of myelin gene expression during both myelination and remyelination processes. The researchers state that their findings could potentially lead to the development of pharmacological and translational therapies for conditions resulting from demyelination, such as multiple sclerosis. https://medicalxpress.com/news/2015-07-myelin-liver-receptors-key-cerebellar.html Fri, 10 Jul 2015 09:30:01 EDT news355722193 (Medical Xpress)—One of the most challenging problems in biology is the extreme difficulty in predicting phenotype from genotype – and the questions it creates: If we could rear genetically identical individuals from a variety of genetic backgrounds and rear them in the same environment, how much phenotypic variation between individuals of the same genotype would we see? Would different genetic backgrounds differ in their degree of variability? What would account for these differences? Recently, scientists at Harvard University, Cambridge and Cornell University, Ithaca used Drosophila (fruit flies) inbred lines to address these questions focusing on variability in locomotor handedness. They demonstrated that different genotypes vary significantly in phenotype variability; that this phenotypic variability itself, as a trait, can be heritable; and that genomic locations affecting variability can be mapped. Moreover, taken together with a companion study1, the papers demonstrate a rare example of linkage between genetic variation for a complex behavioral trait and a neural center of behavioral control. https://medicalxpress.com/news/2015-06-gene-phene-scientists-genetic-phenotypic.html Tue, 02 Jun 2015 09:20:02 EDT news352431754 (Medical Xpress)—The adaptive immune system – a subsystem of the overall immune system – comprises specialized cells and processes that eliminate or prevent pathogen growth by using the experience of past infections to prepare its limited repertoire of specialized receptors to protect organisms from future threats. Recently, scientists at CNRS and Ecole Normale Superieure, Paris and the University of Pennsylvania developed a general theoretical framework from first principles that allowed them to predict the composition of receptor repertoires optimally adapted to minimize the biological cost of infections from a given pathogenic environment. Their theory predicts that the immune system will have more receptors for rare antigens; individuals exposed to the same infections will have largely different repertoires; and competitive antigen/receptor binding and selective amplification of stimulated receptors are key to creating optimal repertoires. Their findings explain how limited populations of immune receptors can self-organize to provide effective immunity against highly diverse pathogens, and moreover inform the design and interpretation of experiments surveying immune repertoires. https://medicalxpress.com/news/2015-05-host-thyself-immune-self-organizes-minimize.html Thu, 14 May 2015 09:20:01 EDT news350798310 (Phys.org)—In vivo neural electrical activity is the essence of nervous system function, controlling sensory modalities, emotion, memory, behavior, and basic survival functions. Therefore, to study neurons in the laboratory it is important that in vitro neuronal models also support such electrical activity to reflect fundamental brain functions – and most human neuronal cultures are currently grown in vitro using the classic culture media DMEM (Dulbecco's Modified Eagle Medium), Neurobasal, or a mixture of the two. In contrast, laboratory experiments employing electrophysiological techniques – such as patch clamping (which allows the study of single or multiple ion channels in cells), calcium imaging – on brain slices or in culture are performed in a medium of artificial cerebrospinal fluid (aCSF). https://medicalxpress.com/news/2015-05-brain-bottle-culture-medium-neuronal.html Tue, 05 May 2015 09:30:02 EDT news350010868 (Medical Xpress)—In chaos theory – the study of dynamical systems highly sensitive to initial conditions – was first described in 1890 by Henri Poincaré1, followed by work by Jacques Hadamard in 1898 and Pierre Duhem in 1908. Then, in his 1963 paper2, meteorologist Edward N. Lorenz theoretically demonstrated how in deterministic nonlinear systems, slightly differing initial states can evolve into very different later states – an effect commonly known as the butterfly effect. (While Lorenz did not use the term in his paper – it was previously introduced by Ray Bradbury in his 1952 science fiction story, A Sound of Thunder – it is attributed to him: the title of his talk at the 139th meeting of the American Association for the Advancement of Science in 1972, Does the flap of a butterfly's wings in Brazil set off a tornado in Texas?, was anecdotally coined by fellow meteorologist Philip Merilees.) That said, while chaotic behavior in many natural systems can be studied through analysis of a chaotic mathematical model or analytical techniques such as recurrence plots and Poincaré maps, there is not universal agreement that weather systems are so exquisitely sensitive to initial conditions, with alternative explanations including model error and oversimplified Lorenz equations. https://medicalxpress.com/news/2015-02-cancer-chaos-base-mutation-cancer-like.html Tue, 10 Feb 2015 09:30:02 EST news342766432 (Medical Xpress)—A long-standing assumption in aging research, and therefore in resulting antiaging interventions, is that modifying genetic and environmental factors to extend lifespan also increases healthspan – the length of time an organism is in optimal health. As it turns out, however, that assumption has escaped scientific scrutiny due largely to its apparent validity. Recently, scientists at University of Massachusetts Medical School (UMMS) examined this assumption, and thereby the life-/healthspan relationship, by investigating multiple lifespan-modulating signaling pathways – mechanisms in which ligands (ions or molecules) bind to receptors, resulting in altered cellular responses – in the wild type and four long-lived mutants (insulin/insulin-like growth factor-1, dietary restriction, protein translation, and mitochondrial signaling) of the roundworm Caenorhabditis elegans, a species studied for over two decades in aging research. They found that all long-lived mutants spent a higher percentage of their extended lifespan in a frail, rather than healthy, state. The scientists therefore conclude that aging research must include additional factors beyond lifespan alone. https://medicalxpress.com/news/2015-01-prosper-decoupling-lifespan-healthspan-aging.html Mon, 26 Jan 2015 09:20:01 EST news341470515 (Medical Xpress)—In 1949, Donald O. Hebb (often called the father of neuropsychology and neural networks) published The Organization of Behavior: A Neuropsychological Theory1, connecting the two previously distinct areas of higher cognitive brain function and neural biology. His theory, known as Hebbian learning – and which came to be known as the Hebbian plasticity hypothesis – posited that "when an axon of cell A is near enough to excite a cell B and repeatedly or persistently takes part in firing it, some growth process or metabolic change takes place in one or both cells such that A's efficiency, as one of the cells firing B, is increased." (While often described in lay terms as cells that fire together, wire together, this omits the necessary causality involved: Hebbian learning requires that cell A fires just before, not coincident with, cell B – an important factor that presaged spike-timing-dependent plasticity, which adjusts the strength of connections between neurons in the brain based on the relative timing of a particular neuron's output and input action potentials, the latter referred to as spikes.) https://medicalxpress.com/news/2014-12-rethinking-hebbian-plasticity-neuromodulation-essential.html Tue, 30 Dec 2014 09:30:01 EST news339141282 (Medical Xpress)—What do rheumatoid arthritis, type I diabetes, myasthenia gravis, multiple sclerosis, rheumatic heart disease, and narcolepsy have in common? All of these (and many other) apparently unrelated disorders are caused by autoimmunity, in which the immune system produces antibodies that attack normal, healthy cells and tissues. Currently considered incurable, these autoimmune diseases can be managed – albeit with varying efficacy and sometimes serious side effects – by immunosuppressive (reducing the activation or efficacy of the immune system), anti-inflammatory (steroids), or palliative (for example, insulin injections if type 1 diabetes) treatment. Moreover, autoimmune diseases include a wide range of dysfunctional immune responses known as type II, type III, and type IV immune hypersensitivity reactions. https://medicalxpress.com/news/2014-09-diminutive-decoys-membrane-cloaked-nanoparticles-disrupt.html Fri, 19 Sep 2014 11:20:04 EDT news330341394 (Medical Xpress)—Current therapies for cancer, wound healing, inflammation, and many other diseases – as well as protocols for drug reloading of vascular grafts and stents – often rely on so-called drug delivery depots, which are infused with medication and surgically implanted proximate to the site being treated. However, drug delivery depots in clinical use today are single-use, with no ability to be refilled once exhausted. Moreover, once all medication has been released they sometimes require removal by way of additional invasive surgery, thereby exposing the patient to additional risk. A long-sought solution to these drawbacks is localized drug delivery that would allow for minimally invasive refilling of drug depots for repeat drug dosing over the course of weeks or months. Refilling local drug delivery would also obviate the need for surgical removal. Recently, scientists at Wyss Institute for Biologically Inspired Engineering, Harvard University devised a DNA nanotechnology-based approach for blood-based drug refilling of hydrogel intratumor drug depots using nucleic acid sequence complementarity. More specifically, oligodeoxynucleotide-conjugated alginate drug payloads were used for refilling drug-delivering hydrogels containing the complementary sequence and exploited for tumor treatment. (An oligodeoxynucleotide, or ODN, is a short sequence of nucleotides – RNA or DNA – that contain deoxyribose; alginate is an anionic polysaccharide distributed widely in the cell walls of brown algae.) The researchers conclude that their proof-of-concept study demonstrates the potential application of refilling other drug-delivery devices in the treatment of a wide range of diseases. https://medicalxpress.com/news/2014-08-medicinal-gps-dna-nanotechnology-based-approach.html Fri, 29 Aug 2014 09:20:01 EDT news328510329 (Medical Xpress)—Type 1 diabetes is a chronic autoimmune disease in which viral infection1,2, genetics and environmental factors conspire to impact the immune system's T-cells, which then attack and destroy the pancreatic insulin-producing islets of Langerhans (also known as beta cells). There is no vaccine or cure, only management – and while a successful islet or pancreas transplant may address Type I diabetes and its associated long-term complications, the procedure requires a lifelong regimen of immunosuppressive drugs that may be only partially efficacious, have a negative impact on the islets themselves and create an increased risk of infection and cancer. Given these caveats, research has long focused on encapsulating islets in a manner that obviates the need for post-transplantation immunosuppression. That being said, current microencapsulation techniques have been shown to interfere with various islet functions, such as cellular hypoxia (lack of oxygen), delayed GSIR (glucose-stimulated insulin release), and transplant site size limitations. Recently, however, scientists at the Diabetes Research Institute, University of Miami Miller School of Medicine have designed and optimized a conformal encapsulation technique based on biocompatible permeable hydrogels, resulting in thin, complete, uniform coatings on islets of various sizes in which the coating conforms to each islet's individual shape. Moreover, syngeneic (genetically identical or sufficiently identical, and thereby immunologically compatible) diabetic mice receiving transplanted conformally coated islets achieved and maintained euglycemia – that is, normal blood glucose levels – for over 100 days without foreign body response to the encapsulating material or abnormal revascularization. https://medicalxpress.com/news/2014-08-t-cell-conformal-hydrogel-coating-immunosuppression-free.html Tue, 12 Aug 2014 10:50:01 EDT news327058059 (Medical Xpress)—In the ongoing quest to design new beneficial molecules or identify potential drugs catalogued in pharmaceutically databases, a critical requirement is determining how a ligand (typically a modulator, or signal-triggering molecule) binds to a therapeutic protein. Currently, most drug design protocols the most potent ligand is chosen – but at the cost of diminished target protein specificity. On the other hand, such small-molecule ligands having what is known as a high TC50 value, meaning that a larger amount of the drug is needed to be effective – and they may therefore be rejected. Recently, however, scientists at Jawaharlal Nehru Centre for Advanced Scientific Research, India combined surface-enhanced Raman spectroscopy (SERS) and molecular dynamics (MD) simulation to identify the precise location on a target protein where modulators bind. (SERS is a surface-sensitive technique used to analyze nanoscale composition that enhances normal Raman signals by up to eight orders of magnitude; MD simulates physical movements of atoms and molecules to refine three-dimensional structures of proteins and other macromolecules.) https://medicalxpress.com/news/2014-07-proteins-scientists-drug-discovery-tool.html Tue, 22 Jul 2014 09:30:02 EDT news325232594 (Medical Xpress)—Located at the forward end of the brain's frontal lobe, the mammalian prefrontal cortex (PFC) is the seat of many of our most unique cognitive abilities – collectively referred to as executive function – including planning, decision-making, and coordinating thoughts and actions with internal goals. That said, perhaps its most important attribute – one that is apparently unique to H. sapiens – is reasoning which, based on Bayesian, or probabilistic, inference, mitigates uncertainty by informing adaptive behavior. While the structural details of this remarkable process have historically remained elusive, scientists at Institut National de la Santé et de la Recherche Médicale, Paris, and Ecole Normale Supérieure, Paris and Université Pierre et Marie Curie, Paris have recently employed computational modeling and neuroimaging to show that the human prefrontal cortex involves two interactive reasoning pathways that embody hypothesis testing for evaluating, accepting and rejecting behavioral strategies. More specifically, their model describes behavior guided by reason in the form of an online algorithm combining Bayesian inference applied to multiple stored strategies with hypothesis testing that can update these strategies. In addition – as proposed in a previous work1 – the scientists conclude that since the frontopolar cortex (FPC), located in the anterior-most portion of the frontal lobes, is human-specific and is a key component in executive function decision-making, the ability to make inferences on concurrent strategies and decide to switch directly to one of these alternative strategies is unique to humans as well. https://medicalxpress.com/news/2014-06-upfront-personal-scientists-human-brain.html Fri, 27 Jun 2014 09:20:05 EDT news323064658 (Medical Xpress)—On the one hand, the nervous has limited computational capability – but at the same time, the sensory environment contains an immense amount of information. In this demanding situation, the brain somehow manages to selectively focus attention on relevant stimuli. Recently, scientists at Technische Universität München, Munich and Ruhr University Bochum, Bochum investigated thalamic tactile sensory relay by employing optogenetics (the use of light to control neurons which have been genetically sensitized to light) to control specific cortical input to the thalamus. They show that the deepest cortical layer (known as layer six, or simply L6) plays a key role in controlling thalamic signal transformation (specifically, by controlling adaptive responses of thalamic neurons) and thalamic gating of dynamic sensory input patterns by changing the firing mode. https://medicalxpress.com/news/2014-05-focused-cortico-thalamic-pathway-filters-relevant.html Tue, 13 May 2014 15:00:01 EDT news319210213 (Medical Xpress)—Cortical information is carried by axonal spike timing, which is also a key factor in synaptic plasticity. Spike timing, in turn, can be synchronized by cortical oscillations, thereby regulating cortical information processing. That said, oscillations in the cerebral cortex are the subject of much debate – and in the case of their regulatory mechanisms, not well understood. Addressing this problem, scientists at Howard Hughes Medical Institute and University of California at San Diego used a model cortical circuit to propose that such a regulatory mechanism links the dynamical state of the cortex to interactions between sensory and behavioral context during information processing. Moreover, their proposed regulatory mechanism explains a wide range of heretofore paradoxical empirical results. https://medicalxpress.com/news/2014-05-good-vibrations-cortical-oscillations-modulated.html Thu, 01 May 2014 12:30:01 EDT news318163087 (Medical Xpress)—The fruit fly Drosophila melanogaster is a model organism (a non-human species that is extensively studied to understand particular biological phenomena) studied in a wide range of laboratory experiments for several reasons, including being easy to grow, presenting various visible congenital traits, and having an extremely large salivary gland chromosome. In particular, studies of how neural circuits process sensory information make use of Drosophila's visually-driven behaviors as a model system. Recently, scientists at the University of Washington have demonstrated that one of the computations performed by this system is temporal integration of visual motion. Moreover, by measuring the activity of identified visual interneurons during tethered flight, they describe the way this computation might be performed. https://medicalxpress.com/news/2014-04-fruit-visual-interneurons-temporal-motion.html Mon, 21 Apr 2014 11:48:05 EDT news317299627 (Medical Xpress)—Neuroplasticity (also referred to as brain plasticity, or simply plasticity) is the ability of the brain's neurons and neural networks – previously counter to what scientists believed – to change their connections and behavior when presented with a range of conditions, including neurodevelopment, novel information, sensory stimulation, and trauma. Moreover, modular brain areas can self-reorganize and perform activities differing from their typical functions. In the lab, researchers can induce site-specific plasticity through an established experimental method known as repetitive transcranial magnetic stimulation (rTMS), in which a pulsed noninvasive magnetic field roughly the same strength as a magnetic resonance imaging (MRI) scan depolarizes or hyperpolarizes the neurons in the target brain site. Compared with non-repetitive transcranial magnetic stimulation, rTMS produces longer-lasting effects that persist past after the stimulation has stopped, and has been used as a treatment modality in stroke, Parkinson's disease, depression, and other neurological and psychiatric disorders. https://medicalxpress.com/news/2014-03-dots-diffusion-mri-reveals-plasticity.html Mon, 31 Mar 2014 09:10:04 EDT news315461874 (Medical Xpress)—Light is inextricably intertwined in myriad ways with most life on Earth. In humans, for example, light stimulates alertness and cognition, improving performance and increasing wakefulness. In a recent study, scientists at University of Liège, Belgium and Stem Cell and Brain Research Institute, France demonstrated that exposure to longer wavelength light, relative to shorter wavelength, subsequently enhances the impact of light on executive brain function through the recently-discovered photopigment melanopsin, an invertebrate-like, even plant-like, photoreceptor. By combining melanopsin responses combined with functional Magnetic Resonance Imaging (fMRI) recording, the researchers concluded that since photic memory – the effects of prior light on subsequent responses to light – is typical not only of melanopsin, but of certain invertebrate and plant photopigments as well, humans may therefore have an invertebrate or plant-like machinery within the eyes that participates to regulate cognition. Moreover, they state that their findings may explain a type of long-term adaptation to previous lighting conditions known as the previous light history effect, and support the design of cognitive performance-optimizing lighting systems. https://medicalxpress.com/news/2014-03-memories-plant-like-photopigment-eye-key.html Tue, 25 Mar 2014 09:30:01 EDT news314949409 (Medical Xpress)—Key cognitive functions such as working memory (which combines temporary storage and manipulation of information) and executive function (a set of mental processes that helps connect past experience with present action) are associated with the brain's prefrontal cortex. Unlike other brain regions, the prefrontal cortex does not mature until early adulthood, with the most pronounced changes being seen between its peripubertal (onset of puberty) and postpubertal developmental states. Moreover, this maturation period is correlated with cognitive maturation – but the physical neuronal changes during this transition have remained for the most part unknown. Recently, however, scientists at the Wake Forest School of Medicine in Winston-Salem, NC recorded and compared prefrontal cortical activity peripubertal and adult monkeys. https://medicalxpress.com/news/2014-03-childhood-adhd-autism-schizophrenia-tied.html Fri, 14 Mar 2014 11:02:00 EDT news314013688 (Medical Xpress)—Extensive research effort has been focused on determining the genetic and cellular factors leading to neurodevelopmental illnesses such autism, Asperger's syndrome and schizophrenia. Oftentimes, however, while a given factor – for example, a microdeletion (the loss of a chromosomal fragment) or a particular cell type such as microglia (which infiltrate the developing brain and help prune synapses during brain maturation) – is associate with neurodevelopmental illnesses, the actual phenotypical mechanism remains unknown. Recently, however scientists at the European Molecular Biology Laboratory (EMBL) in Monterotondo, Italy made the genotype-phenotype connection, demonstrating that laboratory mice in which the Cx3cr1 gene is removed, or knocked out (KO) – referred to as Cx3cr1KO mice – exhibit a microglia deficit during development that, in turn, causes reduced functional brain connectivity and autism-linked behaviors that persist into adulthood. https://medicalxpress.com/news/2014-02-microglial-deficit-mice-impairs-functional.html Thu, 13 Feb 2014 13:32:12 EST news311520692 (Medical Xpress)—Autism Spectrum Disorder (ASD) refers to a group of developmental disorders (such as autism and Asperger's syndrome) characterized by impairments in the ability to communicate and interact socially. ASD has a generally well-accepted brain signature – namely, the reduced integrity of long-range white-matter fiber tracts consisting mostly of glial cells and myelinated axons that transmit signals from one region of the cerebrum to another and between the cerebrum and lower brain centers. These tracts are investigated primarily through diffusion imaging studies. (Based on the random thermal motion of molecules, diffusion imaging – specifically, Diffusion Magnetic Resonance Imaging or dMRI – enables the imaging of white matter in the brain by measuring the magnitude and orientation of water diffusion in multiple directions to calculate a three-dimensional water diffusion profile, which in the case of dense white matter tracks is highly anisotropic, or ovoid, pointing in the direction of the fiber bundle.) Recently, scientists at Massachusetts Institute of Technology and Massachusetts General Hospital assessed known white matter tracts in children with ASD by using Diffusion-Weighted Imaging (DWI-MRI), where the image contrast is determined by the Brownian (random) microscopic motion of water protons. Unlike most previous studies, however, the researchers carefully matched head motion between groups, and in doing so demonstrated that there was no evidence of widespread changes in white-matter tracts in the ASD group – rather, differences were present only in the right inferior longitudinal fasciculus (rILF), a white matter tract that connects the temporal and occipital lobes. They conclude that their data challenge the idea that widespread changes in white-matter integrity are a signature of ASD and highlight the importance of matching for data quality in future diffusion studies of ASD and other clinical disorders. https://medicalxpress.com/news/2014-02-diffusion-precise-neural-autism-spectrum.html Fri, 07 Feb 2014 09:00:08 EST news310973841 (Medical Xpress)—The oldest well-established procedure for somatic treatment of unipolar and bipolar disorders, electroconvulsive therapy (ECT) has, at best, a variegated reputation – and not just in its reputation for being a "barbaric" treatment modality (which, as it turns out, it is not). The scientific, clinical, and ethical controversy extends to unanswered questions about its precise mechanism of action – that is, how major electrical discharge over half the brain shows efficacy in recovery from a range of sometimes quite distinct psychological and psychiatric disorders. Recently, however, scientists at Université de Lausanne, Lausanne, Switzerland and Charité University Medicine, Berlin, Germany found local but not general anatomical brain changes following electroconvulsive therapy that are differently distributed in each disease, and are actually the areas believed to be abnormal in each disorder. Since interaction between ECT and specific pathology appears to be therapeutically causal, the researchers state that their results have implications for deep brain stimulation, transcranial magnetic stimulation and other electrically-based brain treatments. https://medicalxpress.com/news/2014-01-electroconvulsive-therapy-mood-disorder-specific-therapeutic.html Thu, 30 Jan 2014 10:30:01 EST news310280546 (Medical Xpress)—A recent neurological addressing one of the most fundamental issues in sleep rhythm generation study underscores an inconvenient truth—namely, that established scientific facts have and will continue to change. Researchers at Institute for Basic Science (Daejeon), Korea Institute of Science and Technology (Seoul) and Yonsei University (Seoul) have demonstrated significant exceptions to the theory, long accepted as dogma, that low-threshold burst firing mediated by T-type Ca2+ channels in thalamocortical neurons is the key component for sleep spindles. (A T-type Ca2+channel is a type of voltage-gated ion channel that displays selective permeability to calcium ions with a transient length of activation. Burst firing refers to periods of rapid neural spiking followed by quiescent, silent, periods. Sleep spindles are bursts of oscillatory brain activity visible on an EEG that occurs during non-rapid eye movement stage 2, or NREM-2, sleep, during which no eye movement occurs, and dreaming is very rare.) The scientists presented both in vivo and in vitro evidence that sleep spindles are generated normally in the absence of T-type channels and burst firing (periods of rapid neural spiking followed by quiescent, silent, periods) in thalamocortical neurons. Moreover, their results show what they describe as a potentially important role of tonic (constant) firing in this rhythm generation. They conclude that future studies should be aimed at investigating the detailed mechanism through which each type of thalamocortical oscillation is generated. https://medicalxpress.com/news/2013-12-channel-neurology-vigilance.html Mon, 30 Dec 2013 09:00:01 EST news307611776