Long-termpotentiation (LTP) is operationally defined as a long-lasting increase in synaptic efficacy following high-frequency stimulation of afferent fibers. Since the first full description of the phenomenon in 1973, exploration of the mechanisms underlying LTP induction has been one of the most active areas of research in neuroscience. Of principal interest to those who study LTP, particularly in the mammalian hippocampus, is its presumed role in the establishment of stable memories, a role consistent with descriptions of memory formation. (...) Other characteristics of LTP, including its rapid induction, persistence, and correlation with natural brain rhythms, provide circumstantial support for this connection to memory storage. Nonetheless, there is little empirical evidence that directly links LTP to the storage of memories. In this target article we review a range of cellular and behavioral characteristics of LTP and evaluate whether they are consistent with the purported role of hippocampal LTP in memory formation. We suggest that much of the present focus on LTP reflects a preconception that LTP is a learning mechanism, although the empirical evidence often suggests that LTP is unsuitable for such a role. As an alternative to serving as a memory storage device, we propose that LTP may serve as a neural equivalent to an arousal or attention device in the brain. Accordingly, LTP may increase in a nonspecific way the effective salience of discrete external stimuli and may thereby facilitate the induction of memories at distant synapses. Other hypotheses regarding the functional utility of this intensely studied mechanism are conceivable; the intent of this target article is not to promote a single hypothesis but rather to stimulate discussion about the neural mechanisms underlying memory storage and to appraise whether LTP can be considered a viable candidate for such a mechanism. (shrink)
The structuralist program has developed a useful metascientific resource: ontological reductive links (ORLs) between the constituents of the potential models of reduced and reducing theories. This resource was developed initially to overcome an objection to structuralist ``global'' accounts of the intertheoretic reduction relation. But it also illuminates the way that concepts at a higher level of scientific investigation (e.g., cognitive psychology) become ``structured through reduction'' to lower-level investigations (e.g., cellular/molecular neuroscience). After (briefly) explaining this structuralist background, I demonstrate how this (...) resource illuminates an actual, emerging scientific example: the link between the psychological concept of a ``consolidation switch'' from short-term to long-term memory and the cellular/molecular mechanisms of the transition from early- to late-phases of long-termpotentiation (LTP) (an important type of synaptic plasticity in mammalian hippocampus and cortex). (shrink)
The type I CaM-sensitive adenylyl cyclase is in a position to integrate signals from multiple inputs, consistent with the requirements for mediating long term potentiation (LTP). Biochemical and genetic evidence supports the idea that this enzyme plays an important role inc LTP. However, more work is needed before we will be certain of the role that CaM-sensitive adenylyl cyclases play in LTP.
Shors & Matzel's target article is a thought-provoking attempt to reconceptualise long-termpotentiation as an attentional or arousal mechanism rather than a memory storage mechanism. This is incompatible with the facts of the neurobiology of attention and of the behavioural neurophysiological properties of hippocampal neurons.
In the thirty years since its discovery by Terje Lomo and Tim Bliss, Long Term Potentiation has become one of the most extensively studied topics in contemporary neuroscience. In LTP the strength of synapses between neurons is potentiated following brief but intense activation. LTP is thought to play a central role in learning and memory, though the exact nature of its role is less clear. In spite of years of research, there are many questions about LTP regarding its functional (...) relevance that remain unanswered - for example, is it a model of memory formation, or is the actual neural mechanism used by the brain to store information? This volume presents a state of the art account of LTP. It begins with lively accounts, by the scientists most closely involved, of the discovery of LTP and of the experiments that established its basic properties and induction mechanisms. Later contributions contain reviews and new research that cover the range of molecular, cellular, physiological and behavioural approaches to the study of LTP. Provocative, accessible, and authoritative, this book makes it clear why LTP continues in equal measure to puzzle and beguile neuroscientists today. Advance praise for Long Term Potentiation: 'This book provides a definitive overview of the development of ideas about synaptic plasticity and about the wide range of current research in this fascinating field.' Colin Blakemore, University of OxfordReadership: Neuroscientists from postgraduate level upwards. (shrink)
The phenomenon of synesthesia has undergone an invigoration of research interest and empirical progress over the past decade. Studies investigating the cognitive mechanisms underlying synesthesia have yielded insight into neural processes behind such cognitive operations as attention, memory, spatial phenomenology and inter-modal processes. However, the structural and functional mechanisms underlying synesthesia still remain contentious and hypothetical. The first section of the present paper reviews recent research on grapheme-color synesthesia, one of the most common forms of synesthesia, and addresses the ongoing (...) debate concerning the role of selective attention in eliciting synesthetic experience. Drawing on conclusions of the first half, the paper’s second half examines the various models proposed to explain the cognitive mechanisms behind grapheme-color synesthesia, and discusses the explanatory virtues of a new model suggesting that grapheme-color synesthesia is grounded in memory. The last section offers an examination of some of the broader philosophical implications of synesthesia. (shrink)
Shors & Matzel set up a straw man, that LTP is a memory storage mechanism, and knock him down without due consideration of the important relations among different levels of organization and analysis regarding LTP, learning, and memory. Assessing these relationships requires analysis and hypotheses linking specific brain regions, neural circuits, plasticity mechanisms, and task demands. The issue addressed by the authors is important, but their analysis is off target.
Shors & Matzel propose that hippocampal LTP increases the effective salience of discrete external stimuli and thereby facilitates the induction of memories at distant places. In line with this suggestion, a neural network model of associative learning and hippocampal function assumes that LTP increases hippocampal error signals to the cortex, thereby facilitating stimulus configuration in association cortex. Computer simulations show that under these assumptions the model correctly describes the effect of LTP induction and blockade in classical discriminations and place learning.
Ethical consumption is on the rise, however little is known about the degree and the implications of the sometime conflicting sets of values held by the broad category of consumers who report consuming ethically. This paper explores convergence and divergence of ethical consumption values through a study of organic, fair trade, and local food consumers in Colorado. Using survey and focus group results, we first examine demographic and attitudinal correlates of ethical consumption. We then report evidence that while many organic, (...) fair trade, and local food consumers converge around similar values, some Colorado consumers support only local food, while opposing the consumption of organic and fair trade products. Next, we investigate how ethical consumers who converge and diverge frame their commitment to consuming ethically. The discussion and conclusion suggest that community development planners of projects that focus on ethical consumption will need to successfully traverse issues stemming from convergence and divergence to enjoy long-term sustained success. (shrink)
This paper tries to show that ontology is one of the important tendencies in the future philosophy. The author thinks that ontology as the basic spirit makes philosophy be different from other subjects. Ontology originates from people’s examination to essence of the world. However, ancient long-term argument couldn’t get any clear conclusion. So philosophers gradually understand that ontology is connected with epistemology. If we want to make a good explanation to ontology, we must return to check ourselves cognition. And (...) the epistemology turns into the main stream of the philosophy Since Descartes. But this doesn’t mean ontology being disappeared. It only tends from the stage to background. In fact, the discussion of the linguistic philosophy still belongs to epistemology. As a whole, we can say philosophy really goes though one negative development. According to dialectic, negation of negation is a universal law. The philosophy has to undergo another inevasible reform and return to ontology again. Many contemporary philosophers have regarded this and begin to do it effectively. (shrink)
The cellular basis of motor learning in the cerebellum has been attributed mostly to long-term depression (LTD) at excitatory parallel fiber (PF)-Purkinje cell (PC) synapses. LTD is induced when PFs are activated in conjunction with a climbing fiber (CF), the other excitatory input to PCs. Recently, by using whole-cell patch-clamp recording from PCs in cerebellar slices, a new form of synaptic plasticity was discovered. Stimulation of excitatory CFs induced a long-lasting (usually longer than 30 min) of 30 sec) and (...) the durations of RP (>30 min) strongly suggests that some intracellular biochemical machinery is involved. Pharmacological evidence suggests that protein kinases are involved in RP of inhibitory synapses and LTD of excitatory PF synapses. Besides the well-described LTD, RP could be a cellular mechanism that plays an important role in motor learning. (shrink)
Evidence from invertebrate systems including Aplysia and Drosophila, as well as studies carried out with mammalian brain, suggests that Ca2+-sensitive adenylyl cyclases may be important for long-term synaptic changes and learning and memory. Furthermore, some forms of long-termpotentiation (LTP) in the hippocampus elevate cyclic AMP (cAMP) signals, and activation of adenylyl cyclases and cAMP-dependent protein kinase may be required for late stages of LTP. We propose that long-term changes in neurons and at synapses may require (...) synergism between the cAMP and Ca2+ signal transduction systems which regulates transcription and synthesis of specific proteins required for long-term synaptic changes. During LTP, protein kinase C is activated and intraccllular Ca2+ increases. We hypothesize that the calmodulin (CaM)-regulated adenylyl cyclases may be activated during LTP because of increases in intracellular Ca2+, release of free CaM from neuromodulin, activation by protein kinase C, release of neurotransmitters, or a combination of these events. Synergistic activation of CaM-sensitive adenylyl cyclases may produce a robust or prolonged cAMP signal required for transcriptional control. Furthermore, the coupling of the Ca2+ and cAMP systems may provide positive feedback regulation of Ca2+ channels by cAMP-dependent protein kinase. (shrink)
Pains that persist long after damaged tissue hasrecovered remain a perplexing phenomenon. Theseso-called chronic pains serve no useful function foran organism and, given its disabling effects, mighteven be considered maladaptive. However, a remarkablesimilarity exists between the neural bases thatunderlie the hallmark symptoms of chronic pain andthose that subserve learning and memory. Bothphenomena, wind-up in the pain literature andlong-term potentiation (LTP) in the learning andmemory literature, are forms of neuroplasticity inwhich increased neural activity leads to a longlasting increase in the (...) excitability of neuronsthrough structural modifications at pre- andpost-synaptic sites. Moreover, the synapticmodifications of wind-up and LTP share a commonmechanism: a glutamate N -methyl-D-aspartate(NMDA) receptor interaction that initiates a calciummediated biochemical cascade that ultimately enhancessignal processing at the -amino-3-hydroxy-5-methyl-4-isoxazoleproprionic acid (AMPA) receptor. This paper arguesthat chronic pain, which has no adaptive value, canbe accounted for in terms of the highly adaptivephenomenon of activity-dependent neural plasticity;hence, some cases of chronic pain can beconceptualized as a memory trace in spinal neurons. (shrink)
Subjects classified visible 2-digit numbers as larger or smaller than 55. Target numbers were preceded by masked 2-digit primes that were either congruent (same relation to 55) or incongruent. Experiments 1 and 2 showed prime congruency effects for stimuli never included in the set of classified visible targets, indicating subliminal priming based on long-term semantic memory. Experiments 2 and 3 went further to demonstrate paradoxical unconscious priming effects resulting from task context. For example, after repeated practice classifying 73 as (...) larger than 55, the novel masked prime 37 paradoxically facilitated the “larger” response. In these experiments task context could induce subjects to unconsciously process only the leftmost masked prime digit, only the rightmost digit, or both independently. Across 3 experiments, subliminal priming was governed by both task context and long-term semantic memory. (shrink)
As an explicit organizing metaphor, memory aid, and conceptual framework, the prefrontal cortex may be viewed as a five-member ‘Executive Committee,’ as the prefrontal-control extensions of five sub-and-posterior-cortical systems: the ‘Perceiver’ is the frontal extension of the ventral perceptual stream which represents the world and self in object coordinates; the ‘Verbalizer’ is the frontal extension of the language stream which represents the world and self in language coordinates; the ‘Motivator’ is the frontal cortical extension of a subcortical extended-amygdala stream which (...) represents the world and self in motivational/emotional coordinates; the ‘Attender’ is the frontal cortical extension of a subcortical extended-hippocampal stream which represents the world and self in spatiotemporal coordinates and directs attention to internal and external events; and the ‘Coordinator’ is the frontal extension of the dorsal perceptual stream which represents the world and self in body- and eye-coordinates and controls willed action and working memory. This tutorial review examines the interacting roles of these five systems in perception, working memory, attention, long - term memory, motor control, and thinking. (shrink)
While researchers have examined the types of ethical issues that arise in long-term care, few studies have explored long-term care nurses’ experiences of moral distress and fewer still have examined responses to initial moral distress. Using an interpretive description approach, 15 nurses working in long-term care settings within one city in Canada were interviewed about their responses to experiences of initial moral distress, resources or supports they identified as helpful or potentially helpful in dealing with these situations, (...) and factors that hindered nurses in their responses. Using a thematic analysis process, three major themes were identified from the nurses’ experiences: (i) the context of the situation matters; (ii) the value of coming together as a team; and (iii) looking for outside direction. The work of responding to initial moral distress was more fruitful if opportunities existed to discuss conflicts with other team members and if managers supported nurses in moving their concerns forward through meetings or conversations with the team, physician, or family. Access to objective others and opportunities for education about ethics were also identified as important for dealing with value conflicts. (shrink)
High temporal resolution event-related brain potential and electroencephalographic coherence studies of the neural substrate of short-term storage in working memory indicate that the sustained coactivation of both prefrontal cortex and the posterior cortical systems that participate in the initial perception and comprehension of the retained information are involved in its storage. These studies further show that short-term storage mechanisms involve an increase in neural synchrony between prefrontal cortex and posterior cortex and the enhanced activation of long-term memory representations of (...) material held in short-term memory. This activation begins during the encoding/comprehension phase and evidently is prolonged into the retention phase by attentional drive from prefrontal cortex control systems. A parsimonious interpretation of these findings is that the long-term memory systems associated with the posterior cortical processors provide the necessary representational basis for working memory, with the property of short-term memory decay being primarily due to the posterior system. In this view, there is no reason to posit specialized neural systems whose functions are limited to those of short-term storage buffers. Prefrontal cortex provides the attentional pointer system for maintaining activation in the appropriate posterior processing systems. Short-term memory capacity and phenomena such as displacement of information in short-term memory are determined by limitations on the number of pointers that can be sustained by the prefrontal control systems. Key Words: coherence; event-related potentials; imaging; long-term memory; memory; short-term memory; working memory. (shrink)
The realities and myths of long-term care and the challenges it poses for the ethics of autonomy are analyzed in this perceptive work. The book defends the concept of autonomy, but argues that the standard view of autonomy as non-interference and independence has only a limited applicability for long term care. The treatment of actual autonomy stresses the developmental and social nature of human persons and the priority of identification over autonomous choice. The work balances analysis of the ethical (...) concepts associated with autonomy with discussion of the implications of the ethical analysis for long term care. A central chapter involves a phenomenological analysis of four general features of everyday experience (space, time, communication, and affectivity) and explores their practical implications for long term care. This work concludes with a discussion of the advantages associated with a phenomenologically-inspired treatment of actual autonomy for the ethics of long-term care. (shrink)
It has become common in medical ethics to discuss difficult cases in terms of the principles of respect for autonomy, beneficence, nonmaleficence, and justice. These moral concepts or principles serve as maxims that are suggestive of appropriate clinical behavior. Because this language evolved primarily in the acute care setting, I consider whether it is in need of supplementation in order to be useful in the long-term care setting. Through analysis of two typical cases involving residents of long-term care (...) facilities, I argue for the additional principles of candor and responsibility for narrative integrity. (shrink)
The assessment and management of pain is a significant public health problem in the United States. Long-term care facilities face unique barriers and challenges to pain management due to the large population of cognitively impaired residents, little physician contact and poor pain education for nurses and nurse assistants. In addition, common misconceptions about pain and pain treatment in the elderly along with health professional and resident fears of addiction and drug toxicity, add to the problem of pain management. The (...) basic principles of pain treatment in long-term care are identical to all other health care settings – utilizing a combination of drug and non-drug treatments. Recent efforts to institutionalize improved pain management practices, through assessment procedures and defined pain management policies, standards and education programming, is a promising venue for systemically improving pain treatment in long-term care settings. (shrink)
In this paper, I consider the question of where illegal immigrants should go once their lives have been saved in hospitals and they are ready to be transferred to long-term care situations. I highlight three recent cases in which such a decision was made. In one case, the patient was kept at the hospital, in another the patient was repatriated to his home country, and in the third, the patient was discharged to his family. I consider the relevant moral (...) values and argue that for reasons of fairness we must develop a policy that treats similar cases in similar ways. In order to best uphold patient well-being and minimize costs, the plan proposed here calls for illegal immigrants to be covered by insurance for long-term care. (shrink)
Many Western countries have introduced market principles in healthcare. The newly introduced financial instrument of “care-intensity packages” in the Dutch long-term care sector fit this development since they have some characteristics of a market device. However, policy makers and care providers positioned these instruments as explicitly not belonging to the general trend of marketisation in healthcare. Using a qualitative case study approach, we study the work that the two providers have done to fit these instruments to their organisations and (...) how that enables and legitimatises market development. Both providers have done various types of work that could be classified as market development, including creating accounting systems suitable for markets, redefining public values in the context of markets, and starting commercial initiatives. Paradoxically, denying the existence of markets for long-term care and thus avoiding ideological debates on the marketisation of healthcare has made the use of market devices all the more likely. Making the market invisible seems to be an operative element in making the market work. Our findings suggest that Dutch long-term care reform points to the need to study the ‘making’ rather than the ‘liberalising’ of markets and that the study of healthcare markets should not be confined to those practices that explicitly label themselves as such. (shrink)
Regardless of the increased interest in technological innovation in universities, relatively little is known about the technology developed by academic scientists. Long-term analyses of researchers’ technological contribution are notably missing. This paper examines university-based technology in Finland during the period 1900–85. The focus is on the quantity and technological specialization of applications created inside the universities and in the changes that occurred in scientists’ technological output over nine decades. In the long-term analysis several aspects in universities’ technological contribution, (...) which are typically considered a recent phenomenon, turn out to have long historical roots. Thus the empirical evidence provided in the article challenges views emphasising that the world of science has faced a drastic change in recent decades. (shrink)
Various studies on the impact of religiousness on consumer ethics have produced mixed results and suggested further clarification on the issue. Therefore, this article examines the effect of religiousness, materialism, and long-term orientation on consumer ethics in Indonesia. The results from 356 respondents in Indonesia, the largest Muslim population in the world, showed that intrinsic religiousness positively affected consumer ethics, while extrinsic social religiousness negatively affected consumer ethics. However, extrinsic personal religiousness did not affect consumer ethical beliefs dimensions. Unlike (...) other studies in developed countries, materialism and long-term orientation influenced only a few of the consumer ethical beliefs dimensions in this study. To date, the study is one of the first empirical studies to explore the impact of religiousness on consumer ethics in Indonesia. The study contributes to the debate on the impact of religiousness on consumer ethics and can assist managers and public policymakers in their effort to mitigate unethical consumer activities in Indonesia. (shrink)