Social effects on spatial choice in the radial arm maze

Social memory was investigated in the context of a spatial working memory task. Pairs of rats were tested in an eight-arm radial maze. Under most conditions, there was a tendency to choose maze locations that had been visited earlier by the other rat. The possibility that this tendency is produced by common preferences for particular maze locations was ruled out. An opposite tendency to avoid visits to locations that had been visited earlier during the trial by another rat was found only when the maze location contained two pellets (rather than an undepletable supply), the rats’ ability to see each other in the maze was restricted to the central arena, and the maze location had been previously visited by the focal rat. The amount of food available in maze locations did not otherwise modulate social influences on spatial choice. The results indicate that memory for a rat’s own previous choices is combined with memory for the choices made by another rat.     

Contextual cues and the retrieval of competing memories of goal events

In Experiment 1, four groups of rats were initially trained on a discrimination which established a stimulus as a signal for reinforcement. That signal was then presented during subsequent partial reinforcement training in a way that could potentially interfere with retrieval of the memory of nonreinforcement (S^N) on the preceding trial either because (1) thestorage and retrieval contexts for S^N were different (retrieval failure hypothesis), or (2) the memory of reinforcement produced by the signal acted as a competing memory (competing memory hypothesis). Experiment 1 supported the competing memory hypothesis. In Experiment 2, we investigated the effect of stimulus change on the capacity of the context to retrieve a competing memory of a temporally remote reinforcement event with which the context was strongly associated. Retrieval of a competing memory was impaired by differences between the storage and retrieval contexts in a manner analogous to the effect of context on retrieval of a reinforcement event memory from an immediately preceding trial.     

The development of nonverbal working memory and executive control processes in adolescents

The prefrontal cortex modulates executive control processes and structurally matures throughout adolescence. Consistent with these events, prefrontal functions that demand high levels of executive control may mature later than those that require working memory but decreased control. To test this hypothesis, adolescents (9 to 20 years old) completed nonverbal working memory tasks with varying levels of executive demands. Findings suggest that recall-guided action for single units of spatial information develops until 11 to 12 years. The ability to maintain and manipulate multiple spatial units develops until 13 to 15 years. Strategic self-organization develops until ages 16 to 17 years. Recognition memory did not appear to develop over this age range. Implications for prefrontal cortex organization by level of processing are discussed.     

Visual environment and delay affect cache retrieval accuracy in a food-storing rodent

Many scatter-hoarding species use spatial memory to relocate their food caches. Two factors can affect spatial memory: the availability of landmarks in the environment, and the latency between learning and recall. Using a 2 × 2 factorial design, we determined the effect of these factors on cache retrieval accuracy in Merriam’s kangaroo rats (Dipodomys merriami). Kangaroo rats cached seeds in an arena under conditions that varied by retrieval interval (1 or 10 days) and by number of landmarks (0 or 16 landmarks). After 1 day, they recovered equal proportions of caches in both landmark conditions. After 10 days, they recovered more caches in the 16-landmark condition than in the bare condition. This is the first study to show that landmarks are necessary for accurate cache recovery after long delays. This result is consistent with maze studies that have shown that landmarks reduce proactive interference and that delay increases proactive interference.     

The effects of rapid eye movement sleep deprivation and recovery on spatial reference memory of young rats

It is known that rapid eye movement (REM) sleep plays a crucial role in learning and memory. Previous studies have demonstrated that postlearning REM sleep deprivation (RSD) impairs memory consolidation. Most of these studies observed only the effects of RSD on learning and memory. In the present study, we not only investigated the impacts of 48-h RSD on the spatial reference memory of young rats in a Morris water maze, but also specifically examined whether an REM rebound for 24–48 h after 48-h RSD affected the maintenance of spatial reference memory. RSD was induced by the modified multiple platform method, and spatial reference memory was tested in a Morris water maze. The results demonstrated that, compared with the control groups, posttraining RSD for 48 h produced a significant impairment in the retention of acquired spatial reference memory, and the impairment continuously existed after 24 and 48 h of release from sleep deprivation, which indicates that REM sleep plays a critical role in reference memory maintenance and consolidation. Moreover, postlearning RSD may lead to a long-term impairment in the consolidation of newly acquired memories.     

Role of Mimeticism and Spatiality in Textual Recall

Four experiments were conducted to investigate the role of map spatiality and icon mimeticism in facilitating text recall. A secondary goal was to explore an assumption of the conjoint retention hypothesis, that the visuospatial component of working memory is involved in retrieving map information. We manipulated display conditions to evaluate the separate and combined effects of map spatiality and icon mimeticism on text recall. We also utilized a concurrent task paradigm to assess both the recognition of spatial displays and the recall of map feature information. The results of all four experiments point to the mimeticism of icons as the key attribute of maps for facilitating recall, rather than the spatial layout of the map when visual displays and text are presented simultaneously during encoding. We also found no evidence indicating that maps are processed in a more spatial manner than are lists. Copyright 2000 Academic Press.     

Gender Differences in Eye Movements in Solving Text-and-Diagram Science Problems

The main purpose of this study was to examine possible gender differences in how junior high school students integrate printed texts and diagrams while solving science problems. We proposed the response style hypothesis and the spatial working memory hypothesis to explain possible gender differences in the integration process. Eye-tracking technique was used to explore these hypotheses. The results of eye-movement indices support the response style hypothesis. Compared to male students, female students spent more time and displayed more fixations in solving science problems. The female students took more time to read the print texts and compare the information between print-based texts and visual-based diagrams more frequently during the problem-solving process than the male students. However, no gender differences were found in the accuracy of their responses to the science problems or their performances in the spatial working memory task. Implications for psychological theory and educational practice are discussed.     

Toxicosis-based aversions to visual cues in rats: A test of the Testa and Ternes hypothesis

Testa and Ternes have proposed that the degree of spatial contiguity between a cue and a food object is an important determinant of the associability of that cue with toxicosis. We found, in accord with the Testa and Ternes hypothesis, that rats showed more profound illness-based aversions to the visual properties of food objects than to the visual properties of food bins or feeding chambers. This result has implications for the design of experiments undertaken to determine the relative associability of cues in different sensory modalities with toxicosis.     

Gender Differences in Eye Movements in Solving Text-and-Diagram Science Problems

The main purpose of this study was to examine possible gender differences in how junior high school students integrate printed texts and diagrams while solving science problems. We proposed the response style hypothesis and the spatial working memory hypothesis to explain possible gender differences in the integration process. Eye-tracking technique was used to explore these hypotheses. The results of eye-movement indices support the response style hypothesis. Compared to male students, female students spent more time and displayed more fixations in solving science problems. The female students took more time to read the print texts and compare the information between print-based texts and visual-based diagrams more frequently during the problem-solving process than the male students. However, no gender differences were found in the accuracy of their responses to the science problems or their performances in the spatial working memory task. Implications for psychological theory and educational practice are discussed.

     

Reactivation of an appetitive discrimination memory following retroactive interference

The present experiment employed an appetitive spatial discrimination response to examine alleviation of forgetting induced by retroactive interference. For separate groups of rats, a footshock that had occurred during acquisition contingent upon a correct response was tested for its effectiveness as a reactivation treatment. The results indicated that the footshock effectively alleviated forgetting, but only for rats experiencing the shock stimulus during original learning. These results suggest that a reactivation treatment may arouse affective or stimulus properties in common with the target memory to elicit retrieval of that memory.     

Short-term spatial memory in honeybees

Foraging honeybees were trained individually in two-choice spatial problems. Differentially rewarded for spatial alternation in Experiment 1 (“win-shift” training), they showed instead a clear tendency to perseverate—that is, to prefer on each trial the location of reward on the immediately preceding trial. On the basis of the results of Experiments 2 and 3, in which one location was rewarded over shorter or longer series of consecutive trials, an associative interpretation of the perseveration found in the first experiment was rejected in favor of an interpretation in terms of short-term spatial memory. Experiment 4, in which the animals were rewarded on each trial for choosing either location, also showed perseveration. Honeybees, like rats, seem to remember a rewarded location recently visited, but tend to return to it rather than, like rats, to avoid it.     

白藜芦醇对Aβ致大鼠堂学习记忆损伤的修复作用

通过观察白藜芦醇对淀粉样蛋白（Aβ25—35）诱导的空间学习记忆功能损伤的影响,探讨白藜芦醇对老年痴呆的治疗作用．方法是采用侧脑室注射Aβ25—35和腹腔注射白藜芦醇2周后进行Morris水迷宫测试．比较不同处理后的大鼠逃避潜伏期、到达平台游过距离以及目标象限内游泳所占的时间百分比．得到以下结果（1）Aβ25—35引起大鼠学习记忆的下降;（2）白藜芦醇有效地逆转Aβ25—35导致的学习记忆的损伤．因此,腹腔注射白藜芦醇有效地阻止了Aβ25—35对学习记忆的损伤．这些结果提示白藜芦醇是治疗AD学习记忆功能损伤的有效策略．     

Landmark geometry and identity controls spatial navigation in rats

In three experiments, a new reference memory procedure was used to examine how male rats search for consistently located food in a cue-controlled spatial environment. The animals searched the tops of 24 poles for six hidden baits in an enclosed circular arena containing a fixed configuration of six object landmarks. In Experiment 1, acquisition was faster and overall performance better for theconsistent group (10 rats), in which the six baited poles were fixed relative to the landmarks for each session, than for therandom group (4 rats), in which baited poles were randomly configured. Cue-control tests and computer simulations suggested that the consistent group relied on the landmarks to directly go to the baited poles, whereas the random group used them to employ a response strategy for searching the arena. Experiments 2 and 3 revealed that the number, identity, and geometric configuration of the landmarks were important to the consistent group’s search performance. Overall, these results are most consistent with the use of a geometric representation by male rats which includes information about both the identity and the relative geometry of discrete landmarks in the surrounding spatial environment.     

Repeated failures in reducing rat’s spontaneous alternation through the intertrial disruption of spatial orientation

Three experiments examined the contention that an extramaze cue representing relative spatial direction controls rats’ spontaneous alternation. Attempts to eliminate this short-term directional memory by horizontally rotating the Ss were without effect. These data, along with other recent findings, cast doubt upon the completeness of Douglas’s model of spontaneous alternation.     

Memories of reward events and expectancies of reward events may work in tandem

A common assumption is that expectancies of reward events in instrumental tasks are established on the basis of Pavlovian conditioning. According to the tandem hypothesis, tested in the four runway investigations reported here employing rats, memories of reward events may serve as the conditioned stimuli eliciting expectancies. In Experiments 1–3, rats were trained under a schedule of partial reward (P), which did not produce increased resistance to extinction, and subsequently shifted to consistent reward (C). According to the tandem hypothesis, the shift to the C schedule should result in increased resistance to extinction if, as hypothesized, under the P schedule the memory of reward, S^R, came to elicit the expectancy of nonreward,_EN. This hypothesis was confirmed under a variety of conditions. It was shown that increased resistance to extinction could not be attributed to the P schedule alone, to the rats receiving two schedules, P and C, to stimuli other than S^R eliciting E_N, or to the rats forgetting reward-produced memories when expecting nonreward (Experiment 4). It was shown that the tandem hypothesis could explain the divergent findings obtained in prior studies employing a shift from P to C as well as in the present study.     

Comparing spatial memory in two species of tit: Recalling a single positive location

The performance of a food-storing species, the marsh tit(Parus palustris), was compared with that of a nonstorer, the blue tit(P. caeruleus), in a spatial memory task in which birds had to return to a site where they had previously been allowed to eat part of a piece of peanut. No differences were found between species’ overall performance, but increasing retention interval from 1 min to 24 h brought about a decrease in performance. The results are discussed in relationship to the hypothesis that food-storing birds have a specialized spatial memory capacity.     

Social working memory: Memory for another rat's spatial choices can increase or decrease choice tendencies

In two experiments using a radial-arm maze, pairs of rats made choices among eight maze locations, each containing a large quantity of one of two food types. The choices made by 1 rat affected the choices made by the other rat. Under most conditions, visits by 1 rat increased the tendency of the other rat to subsequently choose that maze location. However, the effect depended on the quality of the food available in a particular location. When it was possible for the rats to observe each other on the maze arms and a rat had experienced that a location contained the less preferred food type, a previous visit to that location by the foraging partner decreased the tendency to visit that location. These effects are attributed to working memory for the spatial choices of another rat, and they indicate that memory produced by a rat’s own visit to a maze location is integrated with memory for the behavior of another rat to determine spatial choice     

How is radial arm maze behavior in rats related to locomotor search tactics?

Norway rats have been shown to depend on short-term spatial memory to find food on a radial arm maze (RAM), but what locomotor search tactics are involved in using this memory effectively? Four experiments distinguished tactics of distance minimizing, central-place search, trail following, thigmotactic search, and random search by using different configurations of a RAM placed flat on the floor of an arena. These search tactics make similar predictions on an elevated RAM but predict different outcomes on a floor RAM because the rats are free to approach the food from any direction. After initial trials dominated by exploration, rats traveled along arms to food, even when the resultant distance was up to three times the minimum distance. With no food present, rats also traveled along arms; with no arms up to present, they traveled along walls to food. It appears that both maze arms and arena walls engage mechanisms related to trail following in rats.     

Differential effects of delay of reinforcement on acquisition of affective and instrumental responses

Thirsty rats were allowed to choose between a striped arm of a T-maze that contained water and a black arm that contained a saccharin solution. After each exposure to the saccharin solution, half of the animals received a lithium chloride injection 1 min later and half received the same injection 30 min later. Comparable saline injections at these same delays were given after each exposure to the striped, water, arm. The results from saccharin aversion, spatial aversion, and instrumental learning tests generally supported the hypothesis that delayed reinforcement has a substantially greater negative impact on the acquisition of an instrumental response than it has on affective conditioning.