A computer simulation of oscillatory behavior in primary visual cortex

Periodic variations in correlated cellular activity have been observed in many regions of the cerebral cortex. The recent discovery of stimulus-dependent, spatially-coherent oscillations in primary visual cortex of the cat has led to suggestions of neural information encoding schemes based on phase and/or frequency variation. To explore the mechanisms underlying this behavior and their possible functional consequences, we have developed a realistic neural model, based on structural features of visual cortex, which replicates observed oscillatory phenomena. In the model, this oscillatory behavior emerges directly from the structure of the cortical network and the properties of its intrinsic neurons; however, phase coherence is shown to be an average phenomenon seen only when measurements are made over multiple trials. Because average coherence does not ensure synchrony of firing over the course of single stimuli, oscillatory phase may not be a robust strategy for directly encoding stimulus-specific information. Instead, the phase and frequency of cortical oscillations may reflect the coordination of general computational processes within and between cortical areas. Under this interpretation, coherence emerges as a result of horizontal interactions that could be involved in the formation of receptive field properties

Making enactivism even more embodied

The full scope of enactivist approaches to cognition includes not only a focus on sensory-motor contingencies and physical affordances for action, but also an emphasis on affective factors of embodiment and intersubjective affordances for social interaction. This strong conception of embodied cognition calls for a new way to think about the role of the brain in the larger system of brain-body-environment. We ask whether recent work on predictive coding offers a way to think about brain function in an enactive system, and we suggest that a positive answer is possible if we interpret predictive coding in a more enactive way, i.e., as involved in the organism’s dynamic adjustments to its environment

Computer Simulation of Oscillatory Behavior in Cerebral Cortical Networks

It has been known for many years that specific regions of the working cerebral cortex display periodic variations in correlated cellular activity. While the olfactory system has been the focus of much of this work, similar behavior has recently been observed in primary visual cortex. We have developed models of both the olfactory and visual cortex which replicate the observed oscillatory properties of these networks. Using these models we have examined the dependence of oscillatory behavior on single cell properties and network architectures. We discuss the idea that the oscillatory events recorded from cerebral cortex may be intrinsic to the architecture of cerebral cortex as a whole, and that these rhythmic patterns may be important in coordinating neuronal activity during sensory processing

A Computer Simulation of Olfactory Cortex with Functional Implications for Storage and Retrieval of Olfactory Information

Based on anatomical and physiological data, we have developed a computer simulation of piriform (olfactory) cortex which is capable of reproducing spatial and temporal patterns of actual cortical activity under a variety of conditions. Using a simple Hebb-type learning rule in conjunction with the cortical dynamics which emerge from the anatomical and physiological organization of the model, the simulations are capable of establishing cortical representations for different input patterns. The basis of these representations lies in the interaction of sparsely distributed, highly divergent/convergent interconnections between modeled neurons. We have shown that different representations can be stored with minimal interference. and that following learning these representations are resistant to input degradation, allowing reconstruction of a representation following only a partial presentation of an original training stimulus. Further, we have demonstrated that the degree of overlap of cortical representations for different stimuli can also be modulated. For instance similar input patterns can be induced to generate distinct cortical representations (discrimination). while dissimilar inputs can be induced to generate overlapping representations (accommodation). Both features are presumably important in classifying olfactory stimuli

Early Initiation of Oral Antihypertensives Reduces Intensive Care Unit Stay and Hospital Cost for Patients with Hypertensive Intracerebral Hemorrhage.

Background/objectiveIntravenous nicardipine infusion is effective for rapid blood pressure control. However, its use requires hemodynamic monitoring in the intensive care unit (ICU) and is associated with high hospital cost. This study aimed to examine the effect of early versus late initiation of oral antihypertensives on ICU length of stay (LOS) and cost of hospitalization in patients with hypertensive intracerebral hemorrhage (ICH).MethodsThis is a single-center retrospective study of patients with hypertensive ICH treated with nicardipine infusion from January 1, 2013, to December 31, 2017. Patients were dichotomized into study and control groups, based on receiving oral antihypertensives within 24 h versus after 24 h of emergency department arrival. Baseline characteristics, duration of nicardipine infusion, LOS in the ICU and hospital, functional outcome at discharge, and hospital cost were compared between the two groups using univariate and multivariate analysis.ResultsA total of 90 patients in the study group and 76 in the control group were identified. There was no significant difference in demographics, past medical history, and initial SBP between the two groups. After adjusting for confounding factors with multivariate regression models, early initiation of oral antihypertensives was associated with significant reductions in duration of nicardipine infusion (55.5 ± 60.1 vs 121.6 ± 141.3 h, p <0.005), nicardipine cost ($14,207 vs$29,299, p < 0.01), ICU LOS (2 vs 5 days, p < 0.005), and cost of hospitalization ($24,564 vs$47,366, p < 0.01). There was no significant difference in adversary renal events, favorable outcomes, and mortality between the two groups.ConclusionsEarly initiation of oral antihypertensives is safe and may have a significant financial impact on patients with hypertensive ICH

Bodily Affects as Prenoetic Elements in Enactive Perception

In this paper we attempt to advance the enactive discourse on perception by highlighting the role of bodily affects as prenoetic constraints on perceptual experience. Enactivists argue for an essential connection between perception and action, where action primarily means skillful bodily intervention in one’s surroundings. Analyses of sensory-motor contingencies (as in Noë 2004) are important contributions to the enactive account. Yet this is an incomplete story since sensory-motor contingencies are of no avail to the perceiving agent without motivational pull in one direction or another or a sense of the pertinent affective contingencies. Before directly addressing the issue of affect in perception, we explain our peculiar, low-level conception of affect as a form of worldinvolving intentionality that modulates (minimally) bodily behavior without necessarily possessing informational value of any kind. We then address the deficiency concerning affect in enactive accounts of perception by examining some exemplary forms of bodily affect that constrain perception. We show that bodily affect significantly contributes to (either limiting or enabling) our contact with the world in our perceptually operative attentive outlook, in a kind of perceptual interest or investment, and in social perception

GENESIS: A System for Simulating Neural Networks

We have developed a graphically oriented, general purpose simulation system to facilitate the modeling of neural networks. The simulator is implemented under UNIX and X-windows and is designed to support simulations at many levels of detail. Specifically, it is intended for use in both applied network modeling and in the simulation of detailed, realistic, biologically-based models. Examples of current models developed under this system include mammalian olfactory bulb and cortex, invertebrate central pattern generators, as well as more abstract connectionist simulations

Accurate Determination of Phenotypic Information from Historic Thoroughbred Horses by Single Base Extension

Historic DNA have the potential to identify phenotypic information otherwise invisible in the historical, archaeological and palaeontological record. In order to determine whether a single nucleotide polymorphism typing protocol based on single based extension (SNaPshot™) could produce reliable phenotypic data from historic samples, we genotyped three coat colour markers for a sample of historic Thoroughbred horses for which both phenotypic and correct geotypic information were known from pedigree information in the General Stud Book. Experimental results were consistent with the pedigrees in all cases. Thus we demonstrate that historic DNA techniques can produce reliable phenotypic information from museum specimens.© 2010 Campana et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Viral Single-Strand DNA Induces p53-Dependent Apoptosis in Human Embryonic Stem Cells

Human embryonic stem cells (hESCs) are primed for rapid apoptosis following mild forms of genotoxic stress. A natural form of such cellular stress occurs in response to recombinant adeno-associated virus (rAAV) single-strand DNA genomes, which exploit the host DNA damage response for replication and genome persistence. Herein, we discovered a unique DNA damage response induced by rAAV transduction specific to pluripotent hESCs. Within hours following rAAV transduction, host DNA damage signaling was elicited as measured by increased gamma-H2AX, ser15-p53 phosphorylation, and subsequent p53-dependent transcriptional activation. Nucleotide incorporation assays demonstrated that rAAV transduced cells accumulated in early S-phase followed by the induction of apoptosis. This lethal signaling sequalae required p53 in a manner independent of transcriptional induction of Puma, Bax and Bcl-2 and was not evident in cells differentiated towards a neural lineage. Consistent with a lethal DNA damage response induced upon rAAV transduction of hESCs, empty AAV protein capsids demonstrated no toxicity. In contrast, DNA microinjections demonstrated that the minimal AAV origin of replication and, in particular, a 40 nucleotide G-rich tetrad repeat sequence, was sufficient for hESC apoptosis. Our data support a model in which rAAV transduction of hESCs induces a p53-dependent lethal response that is elicited by a telomeric sequence within the AAV origin of replication

Antimicrobial activity of silver nanoparticles incorporated in a cryogel matrix

Hospital acquired infections are a major financial and societal burden with high mortality, morbidity and cost. Such infections are caused by a number of pathogenic and opportunistic bacteria, many of which are resistant to front line antibiotics. To combat their emergence and spread, new approaches have been developed such as adding biocides to wound dressings and surgical implants, but have met with limited success. We proposed an innovative technology capable of improving the clinical outcomes associated with bacterial infection of skin, deep wounds and surgical implants. This approach will exploit the ability of silver nanoparticles (NPs)1 to produce antibacterial radicals and reactive compounds. To begin with, antimicrobial activity of NPs and cytotoxicity of materials were tested