Effects of rodent prefrontal lesions on object-based, visual scene memory

It has been suggested that certain prefrontal areas contribute to a neural circuit that mediates visual object memory. Using a successive go/no-go visual scene discrimination task, object-based long-term memory was assessed in two rodent prefrontal regions. Rewarded trials consisted of a standard scene of four toy objects placed over baited food wells. The objects and their locations composing the standard scene remained constant for the duration of the study. Trials in which one of the standard scene objects was replaced with a novel object were not rewarded. Following the establishment of a significant difference between latency to approach the rewarded standard scene compared to latency to approach non-rewarded scenes, quinolinic acid or control vehicle was infused into either the prelimbic and infralimbic cortices or the anterior cingulate cortex. Following a 1 week recovery period, subjects were retested. Animals with prelimbic/infralimbic cortex lesions displayed a profound and sustained deficit, whereas, animals with anterior cingulate cortex lesions showed a slight initial impairment but eventually recovered. Both lesion groups acquired a simple single object discrimination task as quickly as controls indicating that the deficits on the original scene discrimination task were not due to motivational, response inhibition, or perceptual problems.     

A model of episodic memory: Mental time travel along encoded trajectories using grid cells

The definition of episodic memory includes the concept of mental time travel: the ability to re-experience a previously experienced trajectory through continuous dimensions of space and time, and to recall specific events or stimuli along this trajectory. Lesions of the hippocampus and entorhinal cortex impair human episodic memory function and impair rat performance in tasks that could be solved by retrieval of trajectories. Recent physiological data suggests a novel model for encoding and retrieval of trajectories, and for associating specific stimuli with specific positions along the trajectory. During encoding in the model, external input drives the activity of head direction cells. Entorhinal grid cells integrate the head direction input to update an internal representation of location, and drive hippocampal place cells. Trajectories are encoded by Hebbian modification of excitatory synaptic connections between hippocampal place cells and head direction cells driven by external action. Associations are also formed between hippocampal cells and sensory stimuli. During retrieval, a sensory input cue activates hippocampal cells that drive head direction activity via previously modified synapses. Persistent spiking of head direction cells maintains the direction and speed of the action, updating the activity of entorhinal grid cells that thereby further update place cell activity. Additional cells, termed arc length cells, provide coding of trajectory segments based on the one-dimensional arc length from the context of prior actions or states, overcoming ambiguity where the overlap of trajectory segments causes multiple head directions to be associated with one place. These mechanisms allow retrieval of complex, self-crossing trajectories as continuous curves through space and time.     

What–Where–When memory in magpies (Pica pica)

Some animals have been shown to be able to remember which type of food they hoarded or encountered in which location and how long ago (what–where–when memory). In this study, we test whether magpies (Pica pica) also show evidence of remembering these different aspects of a past episode. Magpies hid red- and blue-dyed pellets of scrambled eggs in a large tray containing wood shavings. They were allowed to make as many caches as they wanted. The birds were then returned either the same day or the next day to retrieve the pellets. If they returned the same day, one colour of pellets was replaced with wooden beads of similar size and colour, while if they returned the next day this would happen to the other colour. Over just a few trials, the birds learned to only search for the food pellets, and ignore the beads, of the appropriate colour for the given retention interval. A probe trial in which all items were removed showed that the birds persisted in searching for the pellets and not the beads. This shows that magpies can remember which food item they hoarded where, and when, even if the food items only differ from each other in their colour and are dispersed throughout a continuous caching substrate.     

Flexible cue use in food-caching birds

An animal’s memory may be limited in capacity, which may result in competition among available memory cues. If such competition exists, natural selection may favor prioritization of different memory cues based on cue reliability and on associated differences in the environment and life history. Food-caching birds store numerous food items and appear to rely on memory to retrieve caches. Previous studies suggested that caching species should always prioritize spatial cues over non-spatial cues when both are available, because non-spatial cues may be unreliable in a changing environment; however, it remains unclear whether non-spatial cues should always be ignored when spatial cues are available. We tested whether mountain chickadees (Poecile gambeli), a food-caching species, prioritize memory for spatial cues over color cues when relocating previously found food in an associative learning task. In training trials, birds were exposed to food in a feeder where both spatial location and color were associated. During subsequent unrewarded test trials, color was dissociated from spatial location. Chickadees showed a significant pattern of inspecting feeders associated with correct color first, prior to visiting correct spatial locations. Our findings argue against the hypothesis that the memory of spatial cues should always take priority over any non-spatial cues, including color cues, in food-caching species, because in our experiment mountain chickadees chose color over spatial cues. Our results thus suggest that caching species may be more flexible in cue use than previously thought, possibly dependent upon the environment and complexity of available cues.     

惊恐障碍的认知偏向研究

文章综述了惊恐障碍患者对威胁性信息的注意偏向、解释偏向、记忆偏向等认知偏向。对威胁性信息的优先注意激发焦虑体验,对模糊信息的灾难化解释增加焦虑水平,对引起焦虑感信息的记忆保持促使惊恐体验更易于提取,这3种认知偏向促使具有焦虑倾向的个体对惊恐障碍更易感,也是惊恐障碍形成和保持的关键因素     

眼睛运动如何与记忆相关？

很久以来,人们一直在致力于研究人的眼动与心理活动之间的关系,从而揭示其间的奥妙。众多研究表明,睡眠时的快速眼动（RapidEyeMovements,REM）及其周期对记忆的形成与巩固有重要作用。在清醒状态下,人的眼动就是为了获得视觉信息,如果涉及记忆任务,这就是编码阶段的具体行动。另外,问题解决过程也有眼动参与。总体看来,眼动和记忆之间是一种双向的关系,适当的眼动训练或许能够提高记忆成绩。     

情绪记忆的神经基础

情绪记忆具有强烈、持久的特点,在记忆中具有优势地位。杏仁核是情绪记忆的关键脑区,其外侧核被认为是情绪回路建立的中心部位。恐惧条件反射是情绪记忆,特别是情绪回路研究的有效手段。情绪记忆的编码,储存与提取受到杏仁核与各相关脑区共同影响,其中激素调节在这些过程中发挥重要作用。文中结合最新的研究成果对情绪记忆的神经机制进行讨论     

Flexible use of spatial cues in the southern flying squirrel (<Emphasis Type="Italic">Glaucomys volans</Emphasis>)

Insects, birds, and mammals have been shown capable of encoding spatial information in memory using multiple strategies or frames of reference simultaneously. These strategies include orientation to a goal-specific cue or beacon, to the position of the goal in an array of local landmarks, or to its position in the array of distant landmarks, also known as the global frame of reference. From previous experiments, it appears that birds and mammals that scatter hoard rely primarily on a global frame of reference, but this generalization depends on evidence from only a few species. Here we examined spatial memory in a previously unstudied scatter hoarder, the southern flying squirrel. We dissociated the relative weighting of three potential spatial strategies (beacon, global, or relative array strategy) with three probe tests: transposition of beacon and the rotation or the expansion of the array. The squirrels’ choices were consistent with a spatial averaging strategy, where they chose the location dictated by at least two of the three strategies, rather than using a single preferred frame of reference. This adaptive and flexible heuristic has not been previously described in animal orientation studies, yet it may be a common solution to the universal problem of encoding and recalling spatial locations in an ephemeral physical landscape.     

Episodic memory development: theory of mind is part of re‐experiencing experienced events

Two experiments with 3½‐ to 6½‐year‐old children showed that theory‐of‐mind development is associated with the growth of episodic memory. Episodic memory was assessed by manipulating informational conditions such that they permit or prevent the formation of episodic memories in terms of re‐experiencing the recalled event. Only experienced events, e.g. seeing how one puts a picture of a frog into a box, can be remembered by re‐experience. Events known through indirect information cannot be re‐experienced, e.g. putting pictures into the box when blindfolded and being later shown on video what was on these cards. Children were also tested on a battery of theory‐of‐mind tasks assessing their understanding of the origins of knowledge. There was a significant interaction in both experiments showing that recall of directly experienced items improved in relation to indirectly presented items the higher children's theory‐of‐mind scores. The discussion suggests that episodic memory development is specifically linked to the growing ability to introspect an ongoing experience and interpret it as representing an actual past event. Copyright © 2007 John Wiley & Sons, Ltd.     

无关声音效应研究述评

无关声音效应是在对注意与记忆进行研究时所发现的一个现象,有益于探讨噪音等无关声音刺激对个体认知过程、工作绩效及身心健康的影响作用。在简要回顾ISE现象的界定与理论解释争论的基础上,重点从对刺激强度不同的ISE现象之理论分析、应用价值及一些相关的近期研究方面作了介绍,从对ISE现象的理论解释、无关声音刺激的选取、研究方法的综合使用、ISE现象中的个体差异等方面做了展望。