Neuronal correlate of pictorial short-term memory in the primate temporal cortex

It has been proposed that visual-memory traces are located in the temporal lobes of the cerebral cortex, as electric stimulation of this area in humans results in recall of imagery. Lesions in this area also affect recognition of an object after a delay in both humans and monkeys, indicating a role in short-term memory of images. Single-unit recordings from the temporal cortex have shown that some neurons continue to fire when one of two or four colours are to be remembered temporarily. But neuronal responses selective to specific complex objects, including hands and faces, cease soon after the offset of stimulus presentation. These results led to the question of whether any of these neurons could serve the memory of complex objects. We report here a group of shape-selective neurons in an anterior ventral part of the temporal cortex of monkeys that exhibited sustained activity during the delay period of a visual short-term memory task. The activity was highly selective for the pictorial information to be memorized and was independent of the physical attributes such as size, orientation, colour or position of the object. These observations show that the delay activity represents the short-term memory of the categorized percept of a picture.     

The primate amygdala represents the positive and negative value of visual stimuli during learning

Visual stimuli can acquire positive or negative value through their association with rewards and punishments, a process called reinforcement learning. Although we now know a great deal about how the brain analyses visual information, we know little about how visual representations become linked with values. To study this process, we turned to the amygdala, a brain structure implicated in reinforcement learning. We recorded the activity of individual amygdala neurons in monkeys while abstract images acquired either positive or negative value through conditioning. After monkeys had learned the initial associations, we reversed image value assignments. We examined neural responses in relation to these reversals in order to estimate the relative contribution to neural activity of the sensory properties of images and their conditioned values. Here we show that changes in the values of images modulate neural activity, and that this modulation occurs rapidly enough to account for, and correlates with, monkeys' learning. Furthermore, distinct populations of neurons encode the positive and negative values of visual stimuli. Behavioural and physiological responses to visual stimuli may therefore be based in part on the plastic representation of value provided by the amygdala.     

Glutamate-receptor-mediated encoding and retrieval of paired-associate learning

Paired-associate learning is often used to examine episodic memory in humans. Animal models include the recall of food-cache locations by scrub jays and sequential memory. Here we report a model in which rats encode, during successive sample trials, two paired associates (flavours of food and their spatial locations) and display better-than-chance recall of one item when cued by the other. In a first study, pairings of a particular foodstuff and its location were never repeated, so ensuring unique 'what-where' attributes. Blocking N-methyl-d-aspartate receptors in the hippocampus--crucial for the induction of certain forms of activity-dependent synaptic plasticity--impaired memory encoding but had no effect on recall. Inactivating hippocampal neural activity by blocking alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors impaired both encoding and recall. In a second study, two paired associates were trained repeatedly over 8 weeks in new pairs, but blocking of hippocampal AMPA receptors did not affect their recall. Thus we conclude that unique what-where paired associates depend on encoding and retrieval within a hippocampal memory space, with consolidation of the memory traces representing repeated paired associates in circuits elsewhere.     

Top-down signal from prefrontal cortex in executive control of memory retrieval.

Knowledge or experience is voluntarily recalled from memory by reactivation of the neural representations in the cerebral association cortex. In inferior temporal cortex, which serves as the storehouse of visual long-term memory, activation of mnemonic engrams through electric stimulation results in imagery recall in humans, and neurons can be dynamically activated by the necessity for memory recall in monkeys. Neuropsychological studies and previous split-brain experiments predicted that prefrontal cortex exerts executive control upon inferior temporal cortex in memory retrieval; however, no neuronal correlate of this process has ever been detected. Here we show evidence of the top-down signal from prefrontal cortex. In the absence of bottom-up visual inputs, single inferior temporal neurons were activated by the top-down signal, which conveyed information on semantic categorization imposed by visual stimulus-stimulus association. Behavioural performance was severely impaired with loss of the top-down signal. Control experiments confirmed that the signal was transmitted not through a subcortical but through a fronto-temporal cortical pathway. Thus, feedback projections from prefrontal cortex to the posterior association cortex appear to serve the executive control of voluntary recall.     

基于分块主颜色的图像检索方法研究与实现

颜色直方图法是基于内容的图像检索系统通常采用的方法。提出了一种基于分块主颜色的检索方法，克服了颜色直方图无法表达颜色空间分布信息的缺陷，将简化的二次式距离计算方法应用到分块主颜色的匹配中，降低了算法复杂度，提高了计算效率和对图像相似度判断的准确率，从而提高了图像检索的效率。据此实现的图像检索系统的运行结果表明，该方法的查准率和查全率比颜色直方图法有明显提高。     

Online Metric Learning for Relevance Feedback in E-Commerce Image Retrieval Applications

Relevance feedback plays a key role in multiple feature-based image retrieval applications. This paper describes an online metric learning approach for a set of ranking functions. In the feedback round, the most relevant and most nonrelevant images related to the target image are selected to construct a relative comparison triplet. The weighting parameters of the multiple ranking functions are updated by minimizing a quadratic objective function constrained by the triplet. The approach unifies the learning algorithm for the most commonly used ranking functions. Thus, multiple features with their own ranking function can easily be employed in the ranking module without feature reconstruction. The method is computationally inexpensive and appropriate for large-scale e-commerce image retrieval applications. Customized ranking functions are well supported. Practically, simplified ranking functions yield better results when the number of query rounds is relatively small. Experiments with an image dataset from a real e-commerce platform show the superiority of the proposed approach.     

Neuronal correlate of visual associative long-term memory in the primate temporal cortex

In human long-term memory, ideas and concepts become associated in the learning process. No neuronal correlate for this cognitive function has so far been described, except that memory traces are thought to be localized in the cerebral cortex; the temporal lobe has been assigned as the site for visual experience because electric stimulation of this area results in imagery recall and lesions produce deficits in visual recognition of objects. We previously reported that in the anterior ventral temporal cortex of monkeys, individual neurons have a sustained activity that is highly selective for a few of the 100 coloured fractal patterns used in a visual working-memory task. Here I report the development of this selectivity through repeated trials involving the working memory. The few patterns for which a neuron was conjointly selective were frequently related to each other through stimulus-stimulus association imposed during training. The results indicate that the selectivity acquired by these cells represents a neuronal correlate of the associative long-term memory of pictures.     

系列顺序短时记忆任务中时间分离效应及理论解释

时间分离效应是指在系列顺序短时记忆任务中,时间间隔越长的项目越容易被一起回忆的现象.介绍了时间分离效应的两种相反理论解释:事件理论和时间理论.前者认为对项目的回忆依赖过去项目信息加工过程中的认知操作,与项目时间属性无关;后者则强调项目在时间维度上分离性会影响项目回忆成绩.剖析了在整合了两种理论的基础上提出的SIMPLE理论对时间分离效应的拟合,拟合结果表明系列顺序短时记忆并不包含时间信息表征.     

Updating verbal and visuospatial working memory： Are the processes parallel？

The current study compared the processes of updating verbal and visuospatial working memory （WM） and examined the roles of central executive and slave systems in working memory updating tasks, by changing the number of items updated simultaneously to manipulate the load on central executive. Experiment 1 used the verbal WM updating task, and the results validated the efficiency of the paradigm to manipulate the load on central executive. Experiment 2 employed the verbal WM updating task, with the articulatory suppression task to interfere with the phonological loop. The results supported the study by Morris and Jones, revealing that the central executive system played an important role in the updating component of verbal WM, while the phonological loop was responsible for the serial recall component. Experiment 3 employed the visuospatial WM updating task, with the spatial tapping task to interfere with the visuospatial sketchpad. The results suggested that the visuospatial sketchpad and the central executive together dealt with the updating component, while the visuospatial sketchpad was responsible for the serial recall component by itself. These results are consistent with the findings that visuospatial sketchpad has close links with central executive, while the phonological loop is separated from the central executive. It suggests that updating visuospatial and verbal WM are not two parallel processes.     

利用多尺度条件熵和记忆性度量估计图像无损压缩极限

为估计利用各类成像传感器自然获取图像的无损压缩极限 ,提出一个利用多尺度条件熵和记忆性度量的实用方法。传统方法进行高阶概率估计时由于上下文稀释问题而需要大量的训练数据 ,该方法借助多尺度的策略有效地缓解了这一个问题 ,从而可以利用有限的观测数据进行高阶条件熵分析 ,进而对无损压缩极限作出更为准确的估计。已进行的实验结果表明 ,该文提出的估计方法可以较好地适用于扫描仪、遥感、医学等各类成像传感器 ,为相关应用提供了可靠参考。     

Chunking by a pigeon in a serial learning task

A basic principle of human memory is that lists that can be organized into memorable 'chunks' are easier to remember. Memory span is limited to a roughly constant number of chunks and is to a large extent independent of the amount of informaton contained in each chunk. Depending on the ingenuity of the code used to integrate discrete items into chunks, one can substantially increase the number of items that can be recalled correctly. Newly developed paradigms for studying memory in non-verbal organisms allow comparison of the abilities of human and non-human subjects to memorize lists. Here I present two types of evidence that pigeons 'chunk' 5-element lists whose components (colours and achromatic geometric forms) are clustered into distinct groups. Those lists were learned twice as rapidly as a homogeneous list of colours or heterogeneous lists in which the elements are not clustered. The pigeons were also tested for knowledge of the order of two elements drawn from the 5-element lists. They responded in the correct order only to those subsets that contained a chunk boundary. Thus chunking can be studied profitably in animal subjects; the cognitive processes that allow an organism to form chunks do no presuppose linguistic competence.     

分配注意对短时记忆编码和提取的影响

以大学生为被试,采用分配注意范式探讨了短时记忆编码和提取所需的注意资源。研究发现：与集中注意相比,编码阶段进行第二作业导致记忆成绩显著降低,而提取阶段进行第二作业则对记忆成绩没有影响。自由回忆和顺序回忆的结果一致。本研究表明,短时记忆编码是需要较多注意资源的控制加工,而短时记忆提取则是相对无需注意资源的自动加工。这与当前关于长时记忆的研究结果类似,而与早期以第二作业成绩为测量指标的短时记忆研究结果有所不同。     

谈钢琴演奏技巧与音乐表现的关系

钢琴演奏作品,为达到艺术最高层的意境表现,应具备正确的弹奏方法。本文提出音乐形象与演奏技巧相辅相承的辩证观点。通过诠释音乐形象的产生,以及对演奏技巧的影响,结合分析钢琴触键技巧,细致地对中国古曲改编的钢琴作品《春江花月夜》进行分析,总结乐曲处理的三个阶段,说明乐曲意境处理的重要性。     

Neuronal correlates of parametric working memory in the prefrontal cortex.

Humans and monkeys have similar abilities to discriminate the difference in frequency between two mechanical vibrations applied sequentially to the fingertips. A key component of this sensory task is that the second stimulus is compared with the trace left by the first (base) stimulus, which must involve working memory. Where and how is this trace held in the brain? This question was investigated by recording from single neurons in the prefrontal cortex of monkeys while they performed the somatosensory discrimination task. Here we describe neurons in the inferior convexity of the prefrontal cortex whose discharge rates varied, during the delay period between the two stimuli, as a monotonic function of the base stimulus frequency. We describe this as 'monotonic stimulus encoding', and we suggest that the result may generalize: monotonic stimulus encoding may be the basic representation of one-dimensional sensory stimulus quantities in working memory. Thus we predict that other behavioural tasks that require ordinal comparisons between scalar analogue stimuli would give rise to monotonic responses similar to those reported here.     

Cross-modal and cross-temporal association in neurons of frontal cortex

The prefrontal cortex is essential for the temporal integration of sensory information in behavioural and linguistic sequences. Such information is commonly encoded in more than one sense modality, notably sight and sound. Connections from sensory cortices to the prefrontal cortex support its integrative function. Here we present the first evidence that prefrontal cortex cells associate visual and auditory stimuli across time. We gave monkeys the task of remembering a tone of a certain pitch for 10 s and then choosing the colour associated with it. In this task, prefrontal cortex cells responded selectively to tones, and most of them also responded to colours according to the task rule. Thus, their reaction to a tone was correlated with their subsequent reaction to the associated colour. This correlation faltered in trials ending in behavioural error. We conclude that prefrontal cortex neurons are part of integrative networks that represent behaviourally meaningful cross-modal associations. The orderly and timely activation of neurons in such networks is crucial for the temporal transfer of information in the structuring of behaviour, reasoning and language.     

基于图像感知哈希技术的钓鱼网页检测

文中提出一种基于图像感知哈希技术的钓鱼检测方法,简称Phash———将网页以图像格式保存,提取图像的主要可视信息的像素点,由这些像素点组成感知哈希序列,再进行哈希序列的相似度匹配。该方法既克服了钓鱼网页存活时间短的问题,又能快速地与特征库进行匹配。实验表明,该方法是有效的,在保证一定误判率和召回率的情况下大大提高了匹配速度。     

讨论方式对目击证人记忆的影响

以54名大学生为被试,采用模拟事件范式,创设共同目击者讨论、问题讨论和无讨论3种讨论方式,探讨讨论方式对目击证人自由回忆不同类型案件信息的效果、信心及其确信度的影响.研究显示:相比细节信息,被试对动作信息的回忆正确率、信心更高,校准和信心准确率得分更低;相比问题讨论组和无讨论组,共同目击者讨论组被试回忆的信息总数和正确数更高.表明目击证人对动作信息的记忆和确信度好于对细节信息的记忆,对细节信息的记忆过于自信;共同目击者讨论仅增加了自由回忆的信息量,并没有提高自由回忆效果.     

Fault-Tolerant Mechanism of the Distributed Cluster Computers

The distributed system with high performance and stability is commonly adopted in large scale scientific and engineering computing. In this paper, we discuss a fault-tolerant mechanism under Linux circumstance to improve the fault-tolerant ability of the system, namely a scheme and frame to form the stable computing platform. In terms of the structure and function of the distributed system, active list and file invocation strategies are employed in the task management. System multilevel fault-tolerance can be achieved by repeated processes in a single node and task migration on multi-nodes. Manager node agent introduced in this paper administrates the nodes using the list, disposes of the tasks according to the nodes' performance, and hence, to be able to make full use of the cluster resources. An evaluation method is proposed to appraise the performance. The analyzed results show the usefulness of the scheme proposed except for some additional overhead of memory consumption.     

基于色彩通道融合的火焰图像分割

提出了基于色彩通道融合的回转窑火焰图像分割方法,由彩色火焰图像的红绿通道、红蓝通和绿蓝通道构成三幅新的图像,分别从中提取训练样本集,对三个神经网络进行训练,神经网络收敛后,各自对相应的图像进行分割,会得到三种不同的结果,采用均值、中值、模糊逻辑和神经网络四种方法将其进行融合,会得到很高的分割准确率,实验结果表明该方法是可行的。     

影响短期时序记忆加工的因素研究

短期时序记忆不但要记忆项目本身,同时还具有顺序、位置、间隔等属性,属于短期记忆或工作记忆的范畴。本文采用对项目进行时序判断的方法考察短期时序记忆的加工方式,同时也考察了短期时序记忆过程中是否存在系列位置效应。结果表明：短期时序记忆的加工过程属于序列加工;在短期时序记忆的加工过程中存在首因效应和近因效应;相同记忆容量的短期时序记忆的绩效显著好于非时序记忆。