抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Research on moral judgment has been dominated by rationalist models, in which moral judgment is thought to be caused by moral reasoning. The author gives 4 reasons for considering the hypothesis that moral reasoning does not cause moral judgment; rather, moral reasoning is usually a post hoc construction, generated after a judgment has been reached. The social intuitionist model is presented as an alternative to rationalist models. The model is a social model in that it deemphasizes the private reasoning done by individuals and emphasizes instead the importance of social and cultural influences. The model is an intuitionist model in that it states that moral judgment is generally the result of quick, automatic evaluations (intuitions). The model is more consistent than rationalist models with recent findings in social, cultural, evolutionary, and biological psychology, as well as in anthropology and primatology.

https://www.motherjones.com/files/emotional_dog_and_rational_tail.pdf

The emotional dog and its rational tail: a social intuitionist approach to moral judgment.

How we raise young children is one of today's most highly personalized and sharply politicized issues, in part because each of us can claim some level of "expertise." The debate has intensified as discoveries about our development-in the womb and in the first months and years-have reached the popular media. How can we use our burgeoning knowledge to assure the well-being of all young children, for their own sake as well as for the sake of our nation? Drawing from new findings, this book presents important conclusions about nature-versus-nurture, the impact of being born into a working family, the effect of politics on programs for children, the costs and benefits of intervention, and other issues. The committee issues a series of challenges to decision makers regarding the quality of child care, issues of racial and ethnic diversity, the integration of children's cognitive and emotional development, and more. Authoritative yet accessible, From Neurons to Neighborhoods presents the evidence about "brain wiring" and how kids learn to speak, think, and regulate their behavior. It examines the effect of the climate-family, child care, community-within which the child grows.

/pdf/from-neurons-to-neighborhoods-the-science-of-early-childhood-3bfl5g72ow.pdf

From Neurons to Neighborhoods: The Science of Early Childhood Development

Prior to the twentieth century, theories of knowledge were inherently perceptual. Since then, developments in logic, statis- tics, and programming languages have inspired amodal theories that rest on principles fundamentally different from those underlying perception. In addition, perceptual approaches have become widely viewed as untenable because they are assumed to implement record- ing systems, not conceptual systems. A perceptual theory of knowledge is developed here in the context of current cognitive science and neuroscience. During perceptual experience, association areas in the brain capture bottom-up patterns of activation in sensory-motor areas. Later, in a top-down manner, association areas partially reactivate sensory-motor areas to implement perceptual symbols. The stor- age and reactivation of perceptual symbols operates at the level of perceptual components - not at the level of holistic perceptual expe- riences. Through the use of selective attention, schematic representations of perceptual components are extracted from experience and stored in memory (e.g., individual memories of green, purr, hot). As memories of the same component become organized around a com- mon frame, they implement a simulator that produces limitless simulations of the component (e.g., simulations of purr). Not only do such simulators develop for aspects of sensory experience, they also develop for aspects of proprioception (e.g., lift, run) and introspec- tion (e.g., compare, memory, happy, hungry). Once established, these simulators implement a basic conceptual system that represents types, supports categorization, and produces categorical inferences. These simulators further support productivity, propositions, and ab- stract concepts, thereby implementing a fully functional conceptual system. Productivity results from integrating simulators combinato- rially and recursively to produce complex simulations. Propositions result from binding simulators to perceived individuals to represent type-token relations. Abstract concepts are grounded in complex simulations of combined physical and introspective events. Thus, a per- ceptual theory of knowledge can implement a fully functional conceptual system while avoiding problems associated with amodal sym- bol systems. Implications for cognition, neuroscience, evolution, development, and artificial intelligence are explored.

/pdf/perceptual-symbol-systems-4spsk97r61.pdf

Perceptual symbol systems.

Despite decades of research, the functional neuroanatomy of speech processing has been difficult to characterize. A major impediment to progress may have been the failure to consider task effects when mapping speech-related processing systems. We outline a dual-stream model of speech processing that remedies this situation. In this model, a ventral stream processes speech signals for comprehension, and a dorsal stream maps acoustic speech signals to frontal lobe articulatory networks. The model assumes that the ventral stream is largely bilaterally organized--although there are important computational differences between the left- and right-hemisphere systems--and that the dorsal stream is strongly left-hemisphere dominant.

The cortical organization of speech processing

Previous work in which we compared English infants, English adults, and Hindi adults on their ability to discriminate two pairs of Hindi (non-English) speech contrasts has indicated that infants discriminate speech sounds according to phonetic category without prior specific language experience (Werker, Gilbert, Humphrey, & Tees, 1981), whereas adults and children as young as age 4 (Werker & Tees, in press), may lose this ability as a function of age and or linguistic experience. The present work was designed to (a) determine the generalizability of such a decline by comparing adult English, adult Salish, and English infant subjects on their perception of a new non-English (Salish) speech contrast, and (b) delineate the time course of the developmental decline in this ability. The results of these experiments replicate our original findings by showing that infants can discriminate non-native speech contrasts without relevant experience, and that there is a decline in this ability during ontogeny. Furthermore, data from both cross-sectional and longitudinal studies shows that this decline occurs within the first year of life, and that it is a function of specific language experience. © 2002 Published by Elsevier Science Inc.

Cross-language speech perception: Evidence for perceptual reorganization during the first year of life

Infant sensitivity to distributional information can affect phonetic discrimination.

Infants aged 4–6 months discriminate the fine phonetic differences that distinguish syllables in both their native and unfamiliar languages1,2,3, but by 10–12 months their perceptual sensitivities are reorganized so that they discriminate only the phonetic variations that are used to distinguish meaning in their native language12. It would seem, then, that infants apply their well honed phonetic sensitivities as they advance and begin to associate words with objects, but the question of how speech perception sensitivities are used in early word learning has not yet been answered. Here we use a recently developed technique to show that when they are required to pair words with objects, infants of 14 months fail to use the fine phonetic detail they detect in syllable discrimination tasks. In contrast, infants of 8 months—who are not yet readily learning words—successfully discriminate phonetic detail in the same task in which infants aged 14 months fail. Taken together, these results suggest a second reorganization in infants's use of phonetic detail as they move from listening to syllables to learning words.

/pdf/infants-listen-for-more-phonetic-detail-in-speech-perception-14e2684ow4.pdf

Infants listen for more phonetic detail in speech perception than in word-learning tasks

Discrimination of 2 German vowel contrasts was examined in English-learning infants of 6-8 and 10-12 months of age using a head turn procedure. The younger infants were better able than the older infants to discriminate the nonnative contrasts, but performance at 6-8 months was below levels that have been reported for nonnative consonant contrasts. A 2nd experiment using a habituation looking procedure showed that 4-month-old infants discriminated both German vowel contrasts, but the 6-month-olds could not. The findings are consistent with previous consonant work, revealing a shift from a language-general toward a language-specific pattern during the 1st year of life. However, that shift begins earlier in development for vowels than for consonants. There is a substantial body of research on developmental differences in discriminatio n of nonnative phonetic contrasts, but the research to date has focused almost exclusively on the perception of consonants. In the present study, we investigated developmental changes across infancy in discrimination of nonnative vowel contrasts. The existing cross-language research suggests that an important part of early language acquisition involves the tuning of perceptual sensitivities to map on to those required in the native language. For example, cross-language studies of consonant discrimination have revealed that young infants can discriminate nearly every phonetic contrast on which they have been tested, including those contrasts that comprise phones that are not used to distinguish meaning in their language-learning environment (for a review, see Best, in press; Werker, 1991). In an early study, Streeter (1976) showed that Kikuyu-learning infants aged 4 months could discriminate the English voiced-voiceless distinction even though it is not used phonemically in their native language. Similar findings have been reported for many other nonnative consonant contrasts (Aslin, Pisoni,

Developmental Changes in Perception of Nonnative Vowel Contrasts

Over the past few years, there has been an increasing emphasis on studying the link between infant speech perception and later language acquisition. This research has yielded some seemingly contradictory findings: In some studies infants appear to use phonetic and indexical detail that they fail to use in other studies. In this article we present a new, unified framework for accounting for these divergent findings. PRIMIR (a developmental framework for Processing Rich Information from Multidimensional Interactive Representations) assumes there is rich information available in the speech input and that the child picks up and organizes this information along a number of multidimensional interactive planes. Use of this rich information depends on the joint activity of 3 dynamic filters. These filters-the initial biases, the developmental level of the child, and requirements of the specific language task the child is facing-work together to differentially direct attention to 1 (or more) plane. In this article...

Janet F. Werker

Papers

Cross-language speech perception: Evidence for perceptual reorganization during the first year of life

Infant sensitivity to distributional information can affect phonetic discrimination.

Infants listen for more phonetic detail in speech perception than in word-learning tasks

Developmental Changes in Perception of Nonnative Vowel Contrasts

PRIMIR: A Developmental Framework of Infant Speech Processing