Philosophical Transactions of the Royal Society B: Biological Sciences
0962-8436
1471-2970
Anh Quốc
Cơ quản chủ quản: ROYAL SOC , The Royal Society
Lĩnh vực:
Agricultural and Biological Sciences (miscellaneous)Biochemistry, Genetics and Molecular Biology (miscellaneous)
Các bài báo tiêu biểu
The cognitive neuroscience of constructive memory: remembering the past and imagining the future
Episodic memory is widely conceived as a fundamentally constructive, rather than reproductive, process that is prone to various kinds of errors and illusions. With a view towards examining the functions served by a constructive episodic memory system, we consider recent neuropsychological and neuroimaging studies indicating that some types of memory distortions reflect the operation of adaptive processes. An important function of a constructive episodic memory is to allow individuals to simulate or imagine future episodes, happenings and scenarios. Since the future is not an exact repetition of the past, simulation of future episodes requires a system that can draw on the past in a manner that flexibly extracts and recombines elements of previous experiences. Consistent with this
constructive episodic simulation
hypothesis, we consider cognitive, neuropsychological and neuroimaging evidence showing that there is considerable overlap in the psychological and neural processes involved in remembering the past and imagining the future.
Tập 362 Số 1481 - Trang 773-786 - 2007
Before and below ‘theory of mind’: embodied simulation and the neural correlates of social cognition The automatic translation of folk psychology into newly formed brain modules specifically dedicated to mind-reading and other social cognitive abilities should be carefully scrutinized. Searching for the brain location of intentions, beliefs and desires—as such —might not be the best epistemic strategy to disclose what social cognition really is. The results of neurocognitive research suggest that in the brain of primates, mirror neurons, and more generally the premotor system, play a major role in several aspects of social cognition, from action and intention understanding to language processing. This evidence is presented and discussed within the theoretical frame of an embodied simulation account of social cognition. Embodied simulation and the mirror neuron system underpinning it provide the means to share communicative intentions, meaning and reference, thus granting the parity requirements of social communication.
Tập 362 Số 1480 - Trang 659-669 - 2007
Complementary learning systems within the hippocampus: a neural network modelling approach to reconciling episodic memory with statistical learning A growing literature suggests that the hippocampus is critical for the rapid extraction of regularities from the environment. Although this fits with the known role of the hippocampus in rapid learning, it seems at odds with the idea that the hippocampus specializes in memorizing individual episodes. In particular, the Complementary Learning Systems theory argues that there is a computational trade-off between learning the specifics of individual experiences and regularities that hold across those experiences. We asked whether it is possible for the hippocampus to handle both statistical learning and memorization of individual episodes. We exposed a neural network model that instantiates known properties of hippocampal projections and subfields to sequences of items with temporal regularities. We found that the monosynaptic pathway—the pathway connecting entorhinal cortex directly to region CA1—was able to support statistical learning, while the trisynaptic pathway—connecting entorhinal cortex to CA1 through dentate gyrus and CA3—learned individual episodes, with apparent representations of regularities resulting from associative reactivation through recurrence. Thus, in paradigms involving rapid learning, the computational trade-off between learning episodes and regularities may be handled by separate anatomical pathways within the hippocampus itself. This article is part of the themed issue ‘New frontiers for statistical learning in the cognitive sciences’.
Tập 372 Số 1711 - Trang 20160049 - 2017
Sensory gain control (amplification) as a mechanism of selective attention: electrophysiological and neuroimaging evidence Both physiological and behavioral studies have suggested that stimulus–driven neural activity in the sensory pathways can be modulated in amplitude during selective attention. Recordings of event–related brain potentials indicate that such sensory gain control or amplification processes play an important role in visual–spatial attention. Combined event–related brain potential and neuroimaging experiments provide strong evidence that attentional gain control operates at an early stage of visual processing in extrastriate cortical areas. These data support early selection theories of attention and provide a basis for distinguishing between separate mechanisms of attentional suppression (of unattended inputs) and attentional facilitation (of attended inputs).
Tập 353 Số 1373 - Trang 1257-1270 - 1998
Consequences of human modification of the global nitrogen cycle
The demand for more food is increasing fertilizer and land use, and the demand for more energy is increasing fossil fuel combustion, leading to enhanced losses of reactive nitrogen (N
r
) to the environment. Many thresholds for human and ecosystem health have been exceeded owing to N
r
pollution, including those for drinking water (nitrates), air quality (smog, particulate matter, ground-level ozone), freshwater eutrophication, biodiversity loss, stratospheric ozone depletion, climate change and coastal ecosystems (dead zones). Each of these environmental effects can be magnified by the ‘nitrogen cascade’: a single atom of N
r
can trigger a cascade of negative environmental impacts in sequence. Here, we provide an overview of the impact of N
r
on the environment and human health, including an assessment of the magnitude of different environmental problems, and the relative importance of N
r
as a contributor to each problem. In some cases, N
r
loss to the environment is the key driver of effects (e.g. terrestrial and coastal eutrophication, nitrous oxide emissions), whereas in some other situations nitrogen represents a key contributor exacerbating a wider problem (e.g. freshwater pollution, biodiversity loss). In this way, the central role of nitrogen can remain hidden, even though it actually underpins many trans-boundary pollution problems.
Tập 368 Số 1621 - Trang 20130116 - 2013
The global nitrogen cycle in the twenty-first century Global nitrogen fixation contributes 413 Tg of reactive nitrogen (Nr ) to terrestrial and marine ecosystems annually of which anthropogenic activities are responsible for half, 210 Tg N. The majority of the transformations of anthropogenic Nr are on land (240 Tg N yr−1 ) within soils and vegetation where reduced Nr contributes most of the input through the use of fertilizer nitrogen in agriculture. Leakages from the use of fertilizer Nr contribute to nitrate (NO3 − ) in drainage waters from agricultural land and emissions of trace Nr compounds to the atmosphere. Emissions, mainly of ammonia (NH3 ) from land together with combustion related emissions of nitrogen oxides (NOx −1 to the atmosphere, which are transported between countries and processed within the atmosphere, generating secondary pollutants, including ozone and other photochemical oxidants and aerosols, especially ammonium nitrate (NH4 NO3 ) and ammonium sulfate (NH4 )2 SO4 . Leaching and riverine transport of NO3 contribute 40–70 Tg N yr−1 to coastal waters and the open ocean, which together with the 30 Tg input to oceans from atmospheric deposition combine with marine biological nitrogen fixation (140 Tg N yr−1 ) to double the ocean processing of Nr . Some of the marine Nr is buried in sediments, the remainder being denitrified back to the atmosphere as N2 or N2 O. The marine processing is of a similar magnitude to that in terrestrial soils and vegetation, but has a larger fraction of natural origin. The lifetime of Nr in the atmosphere, with the exception of N2 O, is only a few weeks, while in terrestrial ecosystems, with the exception of peatlands (where it can be 102 –103 years), the lifetime is a few decades. In the ocean, the lifetime of Nr is less well known but seems to be longer than in terrestrial ecosystems and may represent an important long-term source of N2 O that will respond very slowly to control measures on the sources of Nr from which it is produced.
Tập 368 Số 1621 - Trang 20130164 - 2013
A chronology of human understanding of the nitrogen cycle <sup />
Nitrogen over the ages! It was discovered in the eighteenth century. The following century, its importance in agriculture was documented and the basic components of its cycle were elucidated. In the twentieth century, a process to provide an inexhaustible supply of reactive N (N
r
; all N species except N
2
) for agricultural, industrial and military uses was invented. This discovery and the extensive burning of fossil fuels meant that by the beginning of the twenty-first century, anthropogenic sources of newly created N
r
were two to three times that of natural terrestrial sources. This caused a fundamental change in the nitrogen cycle; for the first time, there was the potential for enough food to sustain growing populations and changing dietary patterns. However, most N
r
created by humans is lost to the environment, resulting in a cascade of negative earth systems impacts—including enhanced acid rain, smog, eutrophication, greenhouse effect and stratospheric ozone depletion, with associated impacts on human and ecosystem health. The impacts continue and will be magnified, as N
r
is lost to the environment at an even greater rate. Thus, the challenge for the current century is how to optimize the uses of N while minimizing the negative impacts.
Tập 368 Số 1621 - Trang 20130120 - 2013
Approximating the coalescent with recombination The coalescent with recombination describes the distribution of genealogical histories and resulting patterns of genetic variation in samples of DNA sequences from natural populations. However, using the model as the basis for inference is currently severely restricted by the computational challenge of estimating the likelihood. We discuss why the coalescent with recombination is so challenging to work with and explore whether simpler models, under which inference is more tractable, may prove useful for genealogy-based inference. We introduce a simplification of the coalescent process in which coalescence between lineages with no overlapping ancestral material is banned. The resulting process has a simple Markovian structure when generating genealogies sequentially along a sequence, yet has very similar properties to the full model, both in terms of describing patterns of genetic variation and as the basis for statistical inference.
Tập 360 Số 1459 - Trang 1387-1393 - 2005
Alloantigen–induced specific immunological unresponsiveness When the immune system encounters alloantigen it can respond in any one of a number of different ways. The choice that is made will take into account factors such as where, when and how the contact with the alloantigen takes place, as well as the environmental conditions that prevail at the time the alloantigen is encountered. Alloantigen administration before transplantation either alone or in combination with therapeutic agents that modulate the functional activity of the responding leucocytes can be a powerful way of inducing specific unresponsiveness to alloantigensin vivo .The molecular mechanisms that influence the way the outcome of the immune response to alloantigen develops, either activation or unresponsiveness to the triggering antigen, hold the key to our ability to manipulate the immune system effectively by exposing it to donor antigen for therapeutic purposes. This review will focus on alloantigen–induced immunological unresponsiveness and how insights into the mechanisms of unresponsiveness have driven the development of novel tolerance–induction strategies that show promise for translation into the clinic in the future.
Tập 356 Số 1409 - Trang 665-680 - 2001
Pathological and microbiological findings from incidents of unusual mortality of the common frog ( <i>Rana temporaria</i> )
In 1992 we began an investigation into incidents of unusual and mass mortalities of the common frog (
Rana temporaria
) in Britain which were being reported unsolicited to us in increasing numbers by members of the public. Investigations conducted at ten sites of unusual mortality resulted in two main disease syndromes being found: one characterized by skin ulceration and one characterized by systemic haemorrhages. However, frogs also were found with lesions common to both of these syndromes and microscopic skin lesions common to both syndromes were seen. The bacterium Aeromonas hydrophila, which has been described previously as causing similar lesions, was isolated significantly more frequently from haemorrhagic frogs than from those with skin ulceration only. However, as many of the latter were euthanased, this may have been due to differences in
post mortem
bacterial invasion. An iridovirus-like particle has been identified on electron microscopical examination of skin lesions from frogs with each syndrome and iridovirus-like inclusions have been detected in the livers of frogs with systemic haemorrhages. Also, an adenovirus-like particle has been cultured from one haemorrhagic frog. A poxvirus-like particle described previously from diseased frogs has now been found also in control animals and has been identified as a melanosome. Both the prevalence of the iridovirus-like particle and its association with lesions indicate that it may be implicated in the aetiology of the disease syndromes observed. Specifically, we hypothesize that primary iridovirus infection, with or without secondary infection with opportunistic pathogens such as
A. hydrophila
, may cause natural outbreaks of ‘red-leg’, a disease considered previously to be due to bacterial infection only.
Tập 351 Số 1347 - Trang 1539-1557 - 1996