Myth, Memory, and the Oral Tradition: Cicero in the Trobriands

In nonliterate societies, myths are often linked to specific geographical locations. Using Malinowski's Trobriand material and taking a lead from Cicero's De oratore, it is argued that spatial location functions (1) as a mnemonic device for the recall of a corpus of myth, (2) as a structural marker dividing a corpus into separate thinkable units, and (3) as a means of restricting social change at least temporarily to specific institutions. Malinowski's instrumental theory of myth is contrasted with the cognitive theory advanced by LéviStrauss, and certain didactic functions of myth are also discussed . [myth, memory, oral tradition, social space, Trobriands]     

Estrogens and age-related memory decline in rodents: what have we learned and where do we go from here?

The question of whether ovarian hormone therapy can prevent or reduce age-related memory decline in menopausal women has been the subject of much recent debate. Although numerous studies have demonstrated a beneficial effect of estrogen and/or progestin therapy for certain types of memory in menopausal women, recent clinical trials suggest that such therapy actually increases the risk of cognitive decline and dementia. Because rodent models have been frequently used to examine the effects of age and/or ovarian hormone deficiency on mnemonic function, rodent models of age-related hormone and memory decline may be useful in helping to resolve this issue. This review will focus on evidence suggesting that estradiol modulates memory, particularly hippocampal-dependent memory, in young and aging female rats and mice. Various factors affecting the mnemonic response to estradiol in aging females will be highlighted to illustrate the complications inherent to studies of estrogen therapy in aging females. Avenues for future development of estradiol-based therapies will also be discussed, and it is argued that an approach to drug development based on identifying the molecular mechanisms underlying estrogenic modulation of memory may lead to promising future treatments for reducing age-related mnemonic decline.     

Enzyme Isomerization and Concentration Oscillations in Five-Component Biochemical Systems

The kinetic behavior of mnemonic enzymes is analyzed. Based on sufficient conditions for initiation of oscillations, the possibility of concentration oscillations in an open five-component enzymatic system is shown.     

Semimicrotitration device for cholinesterase assay

A semimicrotitration device for reaction volumes of 0.5 to 2 ml and effective stirring of reaction solution or suspension is described. The principal part of the device is a combined glass electrode functioning as a reaction vessel (combined "cup"-glass electrode). Characteristics of the device are small volumes and great reliability. Nonspecific cholinesterase activities measured in rat plasma and liver tissue homogenates and compared with the activities of the same tissue and plasma samples measured radiometrically and spectrophotometrically illustrate the applicability of the device. The method is best suited for kinetic studies with multiple substrates of esterases, either in the soluble form or in tissue homogenates.     

The credibility of movement‐writing

The author first defended the credibility of movement‐writing in Chapter 2, Section 3, of a B.Litt.¹ thesis entitled Social Anthropology and [the] Dance, [Oxford, U.K., 1972]. Seven theoretical criteria from Nelson Goodman's Languages of Art [1969] were used to illustrate to examiners who knew nothing about movement‐writing in any form that Laban's system was not merely a mnemonic device. The guts of the chapter are revived in the following essay because of long‐standing, still‐existing confusion about the relations between movement‐writing and research and between “notation” and “writing” with regard to human movement studies.     

Neuronal firing rates account for distractor effects on mnemonic accuracy in a visuo-spatial working memory task

Persistent neural activity constitutes one neuronal correlate of working memory, the ability to hold and manipulate information across time, a prerequisite for cognition. Yet, the underlying neuronal mechanisms are still elusive. Here, we design a visuo- spatial delayed-response task to identify the relationship between the cue-distractor spatial distance and mnemonic accuracy. Using a shared experimental and computational test protocol, we probe human subjects in computer experiments, and subsequently we evaluate different neural mechanisms underlying persistent activity using an in silico prefrontal network model. Five modes of action of the network were tested: weak or strong synaptic interactions, wide synaptic arborization, cellular bistability and reduced synaptic NMDA component. The five neural mechanisms and the human behavioral data, all exhibited a significant deterioration of the mnemonic accuracy with decreased spatial distance between the distractor and the cue. A subsequent computational analysis revealed that the firing rate and not the neural mechanism per se, accounted for the positive correlation between mnemonic accuracy and spatial distance. Moreover, the computational modeling predicts an inverse correlation between accuracy and distractibility. In conclusion, any pharmacological modulation, pathological condition or memory training paradigm targeting the underlying neural circuitry and altering the net population firing rate during the delay is predicted to determine the amount of influence of a visual distraction.     

Monolithic microfluidic mixing–spraying devices for time-resolved cryo-electron microscopy

The goal of time-resolved cryo-electron microscopy is to determine structural models for transient functional states of large macromolecular complexes such as ribosomes and viruses. The challenge of time-resolved cryo-electron microscopy is to rapidly mix reactants, and then, following a defined time interval, to rapidly deposit them as a thin film and freeze the sample to the vitreous state. Here we describe a methodology in which reaction components are mixed and allowed to react, and are then sprayed onto an EM grid as it is being plunged into cryogen. All steps are accomplished by a monolithic, microfabricated silicon device that incorporates a mixer, reaction channel, and pneumatic sprayer in a single chip. We have found that microdroplets produced by air atomization spread to sufficiently thin films on a millisecond time scale provided that the carbon supporting film is made suitably hydrophilic. The device incorporates two T-mixers flowing into a single channel of four butterfly-shaped mixing elements that ensure effective mixing, followed by a microfluidic reaction channel whose length can be varied to achieve the desired reaction time. The reaction channel is flanked by two ports connected to compressed humidified nitrogen gas (at 50 psi) to generate the spray. The monolithic mixer-sprayer is incorporated into a computer-controlled plunging apparatus. To test the mixing performance and the suitability of the device for preparation of biological macromolecules for cryo-EM, ribosomes and ferritin were mixed in the device and sprayed onto grids. Three-dimensional reconstructions of the ribosomes demonstrated retention of native structure, and 30S and 50S subunits were shown to be capable of reassociation into ribosomes after passage through the device.     

Bilateral Eye Movements, Attentional Flexibility and Metaphor Comprehension: The Substrate of REM Dreaming?

Explanations for the effects of the rapid eye movements induced during Eye Movement Desensitization Reprocessing (EMDR; Shapiro, 2001) have drawn upon an analogy with the eye movements of REM sleep (Kuiken, Bears, Miall, and Smith, 2002). An extension of that analogy posits two orienting systems, one involving threat-fear related mnemonic contextualization and another involving loss-pain related monitoring of conflicting response alternatives. In a study involving individuals who had recently experienced significant loss or trauma, we found that experimentally induced saccadic eye movements decreased reaction times to unexpected stimuli among those reporting traumatic distress (characterized by hyperarousal and intrusive thoughts) and increased reaction times among those reporting separation distress (characterized by vivid reminiscences and the sense of a foreshortened future). Also, we found that saccadic eye movements increased the perceived strikingness of metaphoric sentence endings among those reporting amnesia for events related to either loss or trauma. The eye movements of both EMDR and REM sleep may differently affect the attentional and cognitive reorienting activity of those living with the consequences of loss or trauma. These differences may be evident in their waking reflections and in their dreams. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Integrating memories in the human brain: hippocampal-midbrain encoding of overlapping events

Decisions are often guided by generalizing from past experiences. Fundamental questions remain regarding the cognitive and neural mechanisms by which generalization takes place. Prior data suggest that generalization may stem from inference-based processes at the time of generalization. By contrast, generalization may emerge from mnemonic processes occurring while premise events are encoded. Here, participants engaged in a two-phase learning and generalization task, wherein they learned a series of overlapping associations and subsequently generalized what they learned to novel stimulus combinations. Functional MRI revealed that successful generalization was associated with coupled changes in learning-phase activity in the hippocampus and midbrain (ventral tegmental area/substantia nigra). These findings provide evidence for generalization based on integrative encoding, whereby overlapping past events are integrated into a linked mnemonic representation. Hippocampal-midbrain interactions support the dynamic integration of experiences, providing a powerful mechanism for building a rich associative history that extends beyond individual events.     

A versatile apparatus for performing anaerobic optical titrations with provision for multiple sampling of the reaction mixture.

An all-glass device sultable for the oxido-reductive titrations of air-sensitive compounds is deseribed. The device has a provision for monltoring the optical spectrum and for sampling the reaction mixture with direct transfers of the sample into electron-paramagnetic resonance sample tubes. The performance of the device is evaluated and an example of its use is given.     

The Dependence of Mnemonic Processes on the Structure of Formal Teaching

The investigation described in this report was carried out within the general context of an inquiry into the problem of the correlation between formal schooling and development; it was not our objective to study mnemonic processes as such.     

A simple and easy-to-assemble device for polymerase chain reaction

In this paper we describe an efficient polymerase chain reaction device which is easy to assemble and requires minimal investment in dedicated equipment. The polymerase chain reaction device consists of three waterbaths, three dual-head peristaltic pumps, an electronic timer and a fabricated water jacket capable of holding microcentrifuge tubes. This device has been successfully used to amplify human factor X genomic DNA in our laboratory.     

Mental imagery and visual working memory

Visual working memory provides an essential link between past and future events. Despite recent efforts, capacity limits, their genesis and the underlying neural structures of visual working memory remain unclear. Here we show that performance in visual working memory--but not iconic visual memory--can be predicted by the strength of mental imagery as assessed with binocular rivalry in a given individual. In addition, for individuals with strong imagery, modulating the background luminance diminished performance on visual working memory and imagery tasks, but not working memory for number strings. This suggests that luminance signals were disrupting sensory-based imagery mechanisms and not a general working memory system. Individuals with poor imagery still performed above chance in the visual working memory task, but their performance was not affected by the background luminance, suggesting a dichotomy in strategies for visual working memory: individuals with strong mental imagery rely on sensory-based imagery to support mnemonic performance, while those with poor imagery rely on different strategies. These findings could help reconcile current controversy regarding the mechanism and location of visual mnemonic storage.     

Memory retrieval: reactivating sensory cortex

Associating information with vivid sensory cues aids recall of that information. New experiments help shed some light on the brain mechanisms of memory retrieval that make this mnemonic technique so effective.     

Working smarter,not harder

The ability to chunk, or to strategically organize, information is one of the most powerful ways people have to encode experience into memory. A functional brain imaging study by Bor and colleagues, in this issue of Neuron, provides evidence that prefrontal cortex contributes to this essential mnemonic process.     

Neuro-genetic optimization of temperature control for a continuous flow polymerase chain reaction microdevice

In this study, a hybridized neuro-genetic optimization methodology realized by embedding finite element analysis (FEA) trained artificial neural networks (ANN) into genetic algorithms (GA), is used to optimize temperature control in a ceramic based continuous flow polymerase chain reaction (CPCR) device. The CPCR device requires three thermally isolated reaction zones of 94 degrees C, 65 degrees C, and 72 degrees C for the denaturing, annealing, and extension processes, respectively, to complete a cycle of polymerase chain reaction. The most important aspect of temperature control in the CPCR is to maintain temperature distribution at each reaction zone with a precision of +/-1 degree C or better, irrespective of changing ambient conditions. Results obtained from the FEA simulation shows good comparison with published experimental work for the temperature control in each reaction zone of the microfluidic channels. The simulation data are then used to train the ANN to predict the temperature distribution of the microfluidic channel for various heater input power and fluid flow rate. Once trained, the ANN analysis is able to predict the temperature distribution in the microchannel in less than 20 min, whereas the FEA simulation takes approximately 7 h to do so. The final optimization of temperature control in the CPCR device is achieved by embedding the trained ANN results as a fitness function into GA. Finally, the GA optimized results are used to build a new FEA model for numerical simulation analysis. The simulation results for the neuro-genetic optimized CPCR model and the initial CPCR model are then compared. The neuro-genetic optimized model shows a significant improvement from the initial model, establishing the optimization method's superiority.     

Calorimetric biosensors with integrated microfluidic channels

A microfluidic device capable of measuring real-time enthalpy changes of biochemical reactions and thermal properties of biological fluids is presented in this paper. The device consists of a freestanding microthermopile integrated with a glass microfluidic reaction chamber. The p-type polysilicon/gold microthermopiles fabricated on a 2 μm thick thermally isolated membrane showed a sensitivity of 0.94 V/W and a thermal time constant of less than 100 ms. Although the device is not restricted to enzymatic reactions, in this paper measurements of the heat of reaction from the catalytic action of glucose oxidase, catalase, and urease on glucose, hydrogen peroxide, and urea, respectively, are reported. Reactions were performed in open air using liquid batch testing and in enclosed fluidic reaction chamber by continuous flow experiments. A sensitivity of 53.5 μV/M for glucose, 26.5 μV/M for hydrogen peroxide and 17 μV/M for urea was obtained. Detection limit for glucose in the continuous flow mode is 2 mM (30 pmol). The aim of this work is to demonstrate the potential of the integrated calorimetric microfluidic device for fundamental thermodynamic studies in biochemical reactions. Using arrays of such devices with immobilized enzymes multi-analyte detection can be accomplished and the effects of interferents from competing substrates can be compensated. This paper presents the design, fabrication and initial testing results from such a microthermopile-based thermal biosensor.     

Sequence specific visual detection of LAMP reactions by addition of cationic polymers

Background  

Development of a practical gene point-of-care testing device (g-POCT device) requires innovative detection methods for demonstrating the results of the gene amplification reaction without the use of expensive equipment. We have studied a new method for the sequence-specific visual detection of minute amounts of nucleic acids using precipitation reaction by addition of cationic polymers to amplicons of Loop mediated isothermal Amplification (LAMP).     

Functional Roles of Slow Enzyme Conformational Changes in Network Dynamics

Extensive studies from different fields reveal that many macromolecules, especially enzymes, show slow transitions among different conformations. This phenomenon is named such things as dynamic disorder, heterogeneity, hysteretic or mnemonic enzymes across these different fields, and has been directly demonstrated by single molecule enzymology and NMR studies recently. We analyzed enzyme slow conformational changes in the context of regulatory networks. A single enzymatic reaction with slow conformational changes can filter upstream network noises, and can either resonantly respond to the system stimulus at certain frequencies or respond adaptively for sustained input signals of the network fluctuations. It thus can serve as a basic functional motif with properties that are normally for larger intermolecular networks in the field of systems biology. We further analyzed examples including enzymes functioning against pH fluctuations, metabolic state change of Artemia embryos, and kinetic insulation of fluctuations in metabolic networks. The study also suggests that hysteretic enzymes may be building blocks of synthetic networks with various properties such as narrow-banded filtering. The work fills the missing gap between studies on enzyme biophysics and network level dynamics, and reveals that the coupling between the two is functionally important; it also suggests that the conformational dynamics of some enzymes may be evolutionally selected.     

Kinetics of an enzyme-catalyzed reaction measured by electrospray ionization mass spectrometry using a simple rapid mixing attachment

Mass spectrometry offers a potential means of measuring virtually all enzyme-catalyzed reactions by simultaneously measuring the concentrations of substrates, products, and intermediates where there are differences in mass between them. To perform these measurements the reaction mixture must be aged for different times and then ionized. Electrospray ionization mass spectrometry provides the most direct means of measuring these reactions. Here we describe a simple reaction mixing and ageing attachment for an electrospray ionization mass spectrometer, built from commercially available components. We have employed this device to measure the kinetics of a model reaction, namely the hydrolysis of N2-(carbobenzyloxy)-L-lysine-p-nitrophenyl ester-catalyzed by trypsin. In this way we were able to measure the kinetics of substrate depletion, product formation, and changes in both free enzyme and acyl-enzyme intermediate concentration in the approach to steady state. With this device we were able to measure reaction times down to about 640 ms.