Memory function in normal aging

Basic findings obtained on memory functions in normal aging are presented and discussed with respect to five separate but interacting memory systems. These systems are: episodic memory, semantic memory, short-term memory, perceptual representation system and procedural memory. All available evidence from cross-sectional research shows that there is a linear, decreasing memory performance as a function of age for episodic memory. Longitudinal studies suggest, however, that this age deficit may be an overestimation, by showing a relatively stable performance level up to middle age, followed by a sharp decline. Studies on semantic memory, short-term memory, perceptual representation system, and procedural memory show a relatively constant performance level across the adult life span, although some tasks used to assess short-term memory and procedural memory have revealed an age deficit. Disregarding the mixed results for these latter two memory systems, it can be concluded that episodic memory is unique in showing an age deficit. Episodic memory is also unique in the sense that it is the only memory system showing gender differences in performance throughout the adult life span with a significantly higher performance for women.     

睡眠剥夺对内隐记忆的影响

目的:探讨不同时间睡眠剥夺(sleep deprivation,SD)对内隐记忆的影响。方法:将32名青年男性随机分为4组:对照组、SD21、SD45和SD69组,每组8名。采用补笔测验和组词测验对4组被试进行测试。结果:SD 后无论知觉启动还是语义启动,启动量降低,并随SD 时间延长而减少。同一组内,两种测验进行比较,除对照组外,其他SD 组两两比较,语义启动的启动量大于知觉启动(P<0.05)。知觉启动中,SD45同SD69 相比无显著差异(P=0.245),其他两两比较差异均有统计学意义(P<0.01);语义启动中,SD21同对照组相比差异无统计学意义(P=0.316),其他两两比较差异均有统计学意义(P<0.01)。结论:SD 后内隐记忆受损,并同SD 时间有关;SD 后语义启动和知觉启动出现分离,知觉启动更受SD 影响。     

Electrocortical signs of word categorization in saccade-related brain potentials and visual evoked potentials

Visual evoked potentials (VEPs) elicited by foveal presentation of words were compared to brain potentials evoked by the same words in a condition where subjects had to make a saccadic eye movement in order to perceive the words (saccade-related brain potentials, SRPs). Subjects had to categorize the words responding with a button press to stimuli belonging to the target (infrequent, P = 0.2) category. The VEP and SRP waveforms showed divergences in the early (up to 250 ms) components, but a marked similarity between the late components. Principal Component Analysis also revealed the same relationship between the two types of brain responses. Peak latency of the late SRP components measured from saccade offset showed an apparent processing advantage over the corresponding late components of VEPs. The N3 component, indexing semantic processing of visual patterns, peaked between 310 and 375 ms in the SRPs, while in the VEPs it appeared between 410 and 470 ms. The P4 component, associated with final stimulus evaluation, showed a similar latency benefit in favour of SRPs (420-500 ms vs 530-590 ms in VEPs). The mean reaction time was 74 ms shorter in the eye movement condition (measured from saccade offset) than in the VEP condition (703 vs 777 ms). The question of what kind of processes may contribute to the differences in mean RTs and to the latencies of the late components between the two conditions are discussed. We suggest that the late components (P3, N3 and P4) of the VEP and the SRP, respectively, index identical brain processes.     

A String Matching Computer-Assisted System for Dolphin Photoidentification

This paper presents a syntactic/semantic string representation scheme as well as a string matching method as part of a computer-assisted system to identify dolphins from photographs of their dorsal fins. A low-level string representation is constructed from the curvature function of a dolphin's fin trailing edge, consisting of positive and negative curvature primitives. A high-level string representation is then built over the low-level string via merging appropriate groupings of primitives in order to have a less sensitive representation to curvature fluctuations or noise. A family of syntactic/semantic distance measures between two strings is introduced. A composite distance measure is then defined and used as a dissimilarity measure for database search, highlighting both the syntax (structure or sequence) and semantic (attribute or feature) differences. The syntax consists of an ordered sequence of significant protrusions and intrusions on the edge, while the semantics consist of seven attributes extracted from the edge and its curvature function. The matching results are reported for a database of 624 images corresponding to 164 individual dolphins. The identification results indicate that the developed string matching method performs better than the previous matching methods including dorsal ratio, curvature, and curve matching. The developed computer-assisted system can help marine mammalogists in their identification of dolphins, since it allows them to examine only a handful of candidate images instead of the currently used manual searching of the entire database. © 2000 Biomedical Engineering Society. PAC00: 8780Tq, 4230Sy, 0705Pj     

Cortical activation during retrieval of arithmetical facts and actual calculation: a functional magnetic resonance imaging study

By using functional magnetic resonance imaging (fMRI), the neural substrates involved in mental recitation of the single-digit multiplication table and serial subtraction were studied. The former depends mostly on well-learned arithmetical facts, while the latter requires arithmetic processing. Activation during each task was compared with that in a number counting control. During the recitation of single-digit multiplication, the activated regions included the area lying along the left intraparietal sulcus, the premotor and supplementary motor areas, and the posterior portion of the left inferior frontal gyrus. The areas activated during serial subtraction included these areas as well as the bilateral prefrontal and right parietal areas. From the results obtained during retrieval of the multiplication table in this study and previous studies, it was concluded that semantic memory of the multiplication table is stored in the area lying along the intraparietal sulcus and that the frontal areas play an executive role in utilizing the semantic memory of arithmetical facts. It was assumed that the arithmetical facts requiring actual calculation are also stored in the same region. The additional activation during serial subtraction compared with the activation during retrieval of the multiplication table is probably due to the processes of actual calculation. These processes include proper alignment of digits, which may have caused the right parietal activation, and maintaining digits needed for the mental serial subtractions, which may have caused the bilateral prefrontal activation.     

中医药学语言系统中语义类型的语境分析

目的:主题词表是可扩充的动态性叙词表,文献中的主题词标引具有很好的语义环境。因此,文章尝试从主题词集合的角度对中医药学语言系统(TCMLS)中的语义类型进行扩展研究。方法:对3515篇有关"腧穴"临床文献进行主题词的语义类型提取,采用聚类分析将语义类型聚成4个分类,组成一个大语境模板。结果:实验结果证明采用聚类分析得到的语义类型的语境模板,比较符合临床文献实际。该方法对TCMLS语义类型的加工和检索具有提示作用,是一个值得尝试的研究工作。     

基于“药性—功效知识元语义分析”探讨四气中的“平性”

四气,又称四性,即指药物具有的寒热温凉四种药性。四性之外,还有平性,是指药物寒热偏性不明显者,但有学者认为这只是相对而言,实际上仍有偏温偏凉之别,仍未超出四气范围。既然未超出寒热范围,那么为什么提出平性,并沿用至今呢?平性,到底有什么独特的之处呢?以2005年版《中国药典》所载的性、味、归经、齐全523味药物为研究对象,尝试基于药性—功效知识元语义分析,探讨平性的药性定位,并与"寒、凉、温、热"四性进行比较,从而论述"平"性与四气中其他四性的关系。     

评测纵览:面向“基因-疾病”的关联语义挖掘任务

介绍活跃基因注释语料库的设计目的和标注过程、特点,阐述标注规则、标签设计、标注实例,分析语料库在医药领域的应用场景,包括抗癫痫药物重定位、阿尔茨海默症关键基因提取等领域。