Sumatran Orangutans and a Yellow-Cheeked Crested Gibbon Know What Is Where

In their natural habitats orangutans and gibbons have to solve spatial problems to find enough food, which is distributed over large areas and available at different times of the year. Therefore both species should evolve spatial memory skills to remember spatial locations and their content. We conducted 2 studies in a 1900-m² naturalistic outdoor enclosure. In the 1st study, we hid kiwi pieces in 10 different locations and placed kiwi pieces in a visible location. Individuals of both species approached significantly more food locations in the test condition than in the control condition in which no food was hidden. In the 2nd study, we hid 2 types of food in 10 different locations so that individuals had to remember which food type was where. We hid bananas on trees (banana condition) and grapes under bamboo shrubs (grape condition). We also placed oranges in full view (control condition) to rule out the possibility that finding food may automatically trigger an indiscriminate search. Individuals approached the banana locations more often in the banana than in the other 2 conditions. Some orangutans, but not the gibbon, also approached the grape locations more often in the grape than in the other 2 conditions. Individuals often returned to locations in which they previously found food and rarely revisited locations in the same session. We detected little influence of the food quantity and no influence of the distance to each location on the subjects' foraging behavior.     

Adding preferred color to a conventional reward method improves the memory of zebrafish in the T-maze behavior model

Zebrafish have become a useful model for studying behavior and cognitive functions. Recent studies have shown that zebrafish have natural color preference and the ability to form associative memories with visual perception. It is well known that visual perception enhances memory recall in humans, and we suggest that a similar phenomenon occurs in zebrafish. This study proposes that adding a visual perception component to a conventional reward method would enhance memory recall in zebrafish. We found that zebrafish showed greater preference for red cellophane over yellow in the training session but could not remember the preferred place in the memory test. However, the test memory recall was greater when the zebrafish were exposed to the red cellophane with a food reward during the training session, when compared with the use of food reward only. Furthermore, the red cellophane with food reward group showed more predictable memory recall than the food reward only group. These results propose that visual perception can increase memory recall by enhancing the consolidation processes. We suggest that color-cued learning with food reward is a more discriminative method than food reward alone for examining the cognitive changes in the zebrafish.

Abbreviations: WM: working memory; LTM: long-term memory     

Computer simulation of pigeons' performance on a spatial memory task

Delayed matching of key location is a useful paradigm for the study of pigeons' short-term memory for a spatial location. On each trial a randomly selected key from a matrix of keys is lit briefly as a sample and followed by a retention interval. During the ensuing choice period the sample and one of the non-sample keys are lit; choice of the sample is correct and rewarded whereas choice of the distractor key is not. The computer simulation of performance on this task is based on a simple model: We assume that the pigeon has knowledge of the location of the keys stored in a map-like reference memory. We also assume that short-term memory involves an attention focus or “pointer” that “drifts” on the surface of this map. The pointer migrates from a randomly determined position during the intertrial interval towards the location of the sample when this stimulus is presented. It wanders randomly from its previous position when this cue is no longer present in the retention interval. During the test for retention the bird selects the location (i.e., sample or distractor) closer to the location of the pointer on the map of the matrix. The simulation successfully reproduced several of the phenomena observed in delayed matching of location experiments and provided an account of some hitherto perplexing results. As well, the model successfully predicted some new empirical data.     

Three-dimensional space: locomotory style explains memory differences in rats and hummingbirds

While most animals live in a three-dimensional world, they move through it to different extents depending on their mode of locomotion: terrestrial animals move vertically less than do swimming and flying animals. As nearly everything we know about how animals learn and remember locations in space comes from two-dimensional experiments in the horizontal plane, here we determined whether the use of three-dimensional space by a terrestrial and a flying animal was correlated with memory for a rewarded location. In the cubic mazes in which we trained and tested rats and hummingbirds, rats moved more vertically than horizontally, whereas hummingbirds moved equally in the three dimensions. Consistent with their movement preferences, rats were more accurate in relocating the horizontal component of a rewarded location than they were in the vertical component. Hummingbirds, however, were more accurate in the vertical dimension than they were in the horizontal, a result that cannot be explained by their use of space. Either as a result of evolution or ontogeny, it appears that birds and rats prioritize horizontal versus vertical components differently when they remember three-dimensional space.     

轻度认知损伤患者的联系记忆损伤特征

遗忘型轻度认知损伤患者(aMCI)在项目记忆和联系记忆上都有损伤．本文通过临床记忆量表中的项目记忆和联系记忆测验,研究aMCI的联系记忆是否比项目记忆有更显著的损伤．另外,通过分析配对联想学习测验,进一步研究aMCI联系记忆损伤的特点．25名aMCI和28名健康老人参与了两个联系记忆测验(配对联想学习测验和联想回忆测验)和两个项目记忆测验(图像自由回忆和无意义图形再认),aMCI患者在联系记忆测验上表现出了更显著的损伤,即使控制了项目记忆的损伤,aMCI的联系记忆仍然比健康老人显著降低．另外,ROC分析表明联系记忆测验比项目记忆测验对aMCI病人有更高的区分度．对配对联想学习测验的分析表明,相对于健康老人,aMCI患者在记忆有语言联系的词对要比记忆无语义联系的词对更为困难．本研究进一步表明aMCI患者的联系记忆比项目记忆有更大的损伤．相对于健康老人,aMCI患者不仅难以在两个无关项目间创建记忆连接,而且在有效利用项目间本身的语义联系方面存在更大的损伤．联系记忆测验比项目记忆测验对aMCI患者有更高的区分度．在神经心理评估中增加联系记忆测验,能更加有效地识别aMCI患者．     

Two-dimensional pattern discrimination by the honeybee

For a reward of sugar, bees will learn to prefer a pattern rather than an alternative similar one. This visual discrimination allows us to measure resolution, and to search for the cues that the bees remember and later use to recognize the rewarded pattern. Two systems in parallel, analogous to low pass and high pass filters, are distinguished. The first system discriminates the location and size of at least one area of contrast on each side of the target, with inputs from blue and green receptors, but the ability to discriminate the location of colour depends upon fixation. The bees remember less than a low resolution copy of the image, even when they fixate on a vertical pattern. The second system amplifies the contrast at edges in the pattern, ignoring the direction of contrast, and controls fixation upon the target. Edges are discriminated according to their orientation and radial or tangential arrangement. An axis of bilateral symmetry is detected. However, the relative locations of cues within the image are lost, apparently because the relevant neurones have very large fields. Only the cues, not the whole patterns, are preserved in memory. This system is colour blind because its input is restricted to the receptors with peak sensitivity in the green. The two systems together discriminate many simple patterns, but not all, because the filters are limited in variety.     

How Context Modification can Favor the Release of Past Experience in Vespula germanica Wasps,Enabling the Detection of a Novel Food Site

Vespula germanica wasps typically make consecutive trips between an undepleted food source and their nest. Hence, relocating a rewarded location is a recurrent activity during a wasp’s lifetime. While foraging, wasps continue searching over a previously rewarded location even when food is no longer available. Moreover, when food is displaced to a location nearby, wasps still visit the previously rewarded location. We aimed to study how the modification of the local context would affect the discovery of the novel food site. By displacing food and changing the local context after wasps had learned a certain task, we evaluated whether wasps found a new food location more rapidly than if contextual conditions remained unaltered. We found that when previously associated cues were modified, wasps were more likely to ‘give up’ searching at the old location than if these cues remained unaltered. Furthermore, we observed that a higher number of rewarding trials at the initial location resulted in greater time taken to detect the new feeder location.     

The effect of intertrial interval food presentions on pigeons' delayed matching to sample accuracy

Parallel effects of temporal variables on autoshaping and on delayed matching to sample performance suggest that delayed matching, like autoshaping, might depend upon the within-trial expectancy of reinforcement relative to the overall expectancy of reinforcement in the session. This possibility was assessed by presenting free food at different times during a 30-sec intertrial interval (ITI) in a delayed matching to sample procedure with pigeons. In three conditions a single free food presentation occurred, either early, mid-way, or late in each ITI; in another condition, three food presentations occurred during each ITI, one at each time location. Relative to a baseline condition, in which free food never occurred during the ITI, only food presentations late in the ITI produced a significant disruption in accuracy, and this effect occurred only at the longest of three delays tested. Three free food presentations in each ITI disrupted accuracy only to the same degree as a single, late, ITI food presentation. Thus, accuracy was affected by the temporal location rather than the frequency of ITI food presentations. These effects appear to differ from those of ITI food presentations on autoshaping and do not seem to be understandable in terms of changes in the background expectancy of reinforcement. It was suggested instead that food presented late in the ITI might disrupt subsequent memory processes.     

Elements of episodic-like memory in animals

A number of psychologists have suggested that episodic memory is a uniquely human phenomenon and, until recently, there was little evidence that animals could recall a unique past experience and respond appropriately. Experiments on food-caching memory in scrub jays question this assumption. On the basis of a single caching episode, scrub jays can remember when and where they cached a variety of foods that differ in the rate at which they degrade, in a way that is inexplicable by relative familiarity. They can update their memory of the contents of a cache depending on whether or not they have emptied the cache site, and can also remember where another bird has hidden caches, suggesting that they encode rich representations of the caching event. They make temporal generalizations about when perishable items should degrade and also remember the relative time since caching when the same food is cached in distinct sites at different times. These results show that jays form integrated memories for the location, content and time of caching. This memory capability fulfils Tulving's behavioural criteria for episodic memory and is thus termed 'episodic-like'. We suggest that several features of episodic memory may not be unique to humans.     

Complex memories in honeybees: can there be more than two?

Foraging honeybees are likely to learn visual and chemical cues associated with many different food sources. Here, we explore how many such sources can be memorized and recalled. Marked bees were trained to visit two (or three) sugar feeders, each placed at a different outdoor location and carrying a different scent. We then tested the ability of the bees to recall these locations and fly to them, when the training scents were blown into the hive, and the scents and food at the feeders were removed. When trained on two feeder locations, each associated with a different scent, the bees could correctly recall the location associated with each scent. However, this ability broke down when the number of scents and feeder locations was increased to three. Performance was partially restored when each of the three training feeders was endowed with an additional cue, namely, a distinct colour. Our results suggest that bees can recall a maximum of two locations when each is associated with a different scent. However, this number can be increased if the scent cues are augmented by visual cues. These findings have implications for the ways in which associations are established and laid down in honeybee memory.     

Lateralization and unilateral transfer of spatial memory in marsh tits

Summary The results reported in this paper demonstrate lateralization and transfer of spatial memory processing in an adult, food-storig bird. The technique of monocular occlusion was used to investigate lateralization and memory transfer in food-storing marsh tits (Parus palustris) for two tasks, food-storing and one-trial associative learning, which rely on one-trial learning for the spatial location of hidden food items. In the food-storing task, marsh tits had to return to the sites where they had previously stored a seed; in the one-trial associative learning task, the birds had to return to sites where they had been allowed to eat some, but not all, of a piece of peanut. For both spatial memory tasks, it was demonstrated that although the visual systems fed by both eyes are involved in short-term storage, the right eye system is associated with long-term storage, and that memories are transferred from the left to the right eye system between 3 and 24 h after memory formation.     

Hippocampal Sharp Wave/Ripples during Sleep for Consolidation of Associative Memory

The beneficial effect of sleep on memory has been well-established by extensive research on humans, but the neurophysiological mechanisms remain a matter of speculation. This study addresses the hypothesis that the fast oscillations known as ripples recorded in the CA1 region of the hippocampus during slow wave sleep (SWS) may provide a physiological substrate for long term memory consolidation. We trained rats in a spatial discrimination task to retrieve palatable reward in three fixed locations. Hippocampal local field potentials and cortical EEG were recorded for 2 h after each daily training session. There was an increase in ripple density during SWS after early training sessions, in both trained rats and in rats randomly rewarded for exploring the maze. In rats learning the place -reward association, there was a striking further significant increase in ripple density correlated with subsequent improvements in behavioral performance as the rat learned the spatial discrimination aspect of the task. The results corroborate others showing an experience-dependent increase in ripple activity and associated ensemble replay after exploratory activity, but in addition, for the first time, reveal a clear further increase in ripple activity related to associative learning based on spatial discrimination.     

A Field Study of Spatial Memory in Green-Backed Firecrown Hummingbirds (Sephanoides sephaniodes)

The foraging ecology of hummingbirds involves the exploitation of a high number of patchily distributed flowers. This scenario seems to have influenced capabilities related to learning and memory, which help to avoid recently visited flowers and to allocate exploitation to the most rewarding flowers, once learning has occurred. We carried out two field experiments with the green‐backed firecrown hummingbird (Sephanoides sephaniodes, Trochilidae) in order to examine the ability of birds, first, to recall a nectar location, and secondly, to remember the location of the most rewarding flower among lower quality flowers. The first experiment showed that subjects were able to recall the location of nectar among flowers of identical appearance. In the second experiment, hummingbirds were also able to recall the location of the most rewarding nectar among less rewarding flowers with the same appearance. The results of this study suggest that S. sephaniodes can remember the location of the most rewarding patch, facilitating efficient exploitation of flowers in the absence of visual cues related to nectar quality.     

Rat spatial memory tasks adapted for humans: characterization in subjects with intact brain and subjects with selective medial temporal lobe thermal lesions

In the present paper we describe five tests, 3 of which were designed to be similar to tasks used with rodents. Results obtained from control subjects, patients with selective thermo-coagulation lesions to the medial temporal lobe and results from non-human primates and rodents are discussed. The tests involve memory for spatial locations acquired by moving around in a room, memory for objects subjects interacted with, or memory for objects and their locations. Two of the spatial memory tasks were designed specifically as analogs of the Morris water task and the 8-arm radial-maze tasks used with rats. The Morris water task was modeled by hiding a sensor under the carpet of a room (Invisible Sensor Task). Subjects had to learn its location by using an array of visual cues available in the room. A path integration task was developed in order to study the non-visual acquisition of a cognitive representation of the spatial location of objects. In the non-visual spatial memory task, we blindfolded subjects and led them to a room where they had to find 3 objects and remember their locations. We designed an object location task by placing 4 objects in a room that subjects observed for later recall of their locations. A recognition task, and a novelty detection task were given subsequent to the recall task. An 8-arm radial-maze was recreated by placing stands at equal distance from each other around the room, and asking subjects to visit each stand once, from a central point. A non-spatial working memory task was designed to be the non-spatial equivalent of the radial maze. Search paths recorded on the first trial of the Invisible Sensor Task, when subjects search for the target by trial and error are reported. An analysis of the search paths revealed that patients with lesions to the right or left hippocampus or parahippocampal cortex employed the same type of search strategies as normal controls did, showing similarities and differences to the search behavior recorded in rats. Interestingly, patients with lesions that included the right parahippocampal cortex were impaired relative to patients with lesions to the right hippocampus that spared the parahippocampal cortex, when recall of the sensor was tested after a 30 min delay (Bohbot et al. 1998). No differences were obtained between control subjects and patients with selective thermal lesions to the medial temporal lobe, when tested on the radial-maze, the non-spatial analogue to the radial-maze and the path integration tasks. Differences in methodological procedures, learning strategies and lesion location could account for some of the discrepant results between humans and non-human species. Patients with lesions to the right hippocampus, irrespective of whether the right parahippocampal cortex was spared or damaged, had difficulties remembering the particular configuration and identity of objects in the novelty detection of the object location task. This supports the role of the human right hippocampus for spatial memory, in this case, involving memory for the location of elements in the room; learning known to require the hippocampus in the rat.     

Chimpanzees (Pan troglodytes) fail a what-where-when task but find rewards by using a location-based association strategy

Recollecting the what-where-when of an episode, or episodic-like memory, has been established in corvids and rodents. In humans, a linkage between remembering the past and imagining the future has been recognised. While chimpanzees can plan for the future, their episodic-like memory has hardly been investigated. We tested chimpanzees (Pan troglodytes) with an adapted food-catching paradigm. They observed the baiting of two locations amongst four and chose one after a given delay (15 min, 1 h or 5 h). We used two combinations of food types, a preferred and a less preferred food that disappeared at different rates. The subjects had to base their choices on the time elapsed since baiting, and on their memory of which food was where. They could recover either their preferred food or the one that remained present. All animals failed to obtain the preferred or present foods above chance levels. They were like-wise unsuccessful at choosing baited cups above chance levels. The subjects, thus, failed to use any feature of the baiting events to guide their choices. Nonetheless, their choices were not random, but the result of a developed location-based association strategy. Choices in the second half of the study correlated with the rewards obtained at each location in the first half of the study, independent from the choices made for each location in the first half of the study. This simple location-based strategy yielded a fair amount of food. The animals' failure to remember the what-where-when in the presented set-up may be due to the complexity of the task, rather than an inability to form episodic-like memories, as they even failed to remember what was where after 15 minutes.     

The influence of barley food rewards on sheep movement through a handling system

The use of barley food rewards to improve sheep handling was evaluated in two experiments. In Experiment 1, six groups of sheep were trained to run through a race system and into a sheep-handling machine. Three groups were rewarded and three were not. After 10 days of training over 1 month, rewarded and unrewarded groups were either not handled, clamped in the machine, or clamped and inverted in the machine, and the efficiency of handling was measured. Food rewards significantly reduced the amount of labour required for sheep handling. Less time was spent pushing up rewarded sheep than unrewarded sheep for all handling treatments, and the race system was more than 90% efficient in 9 out of 15 tests with rewarded sheep compared with 1 out of 15 for unrewarded sheep.In Experiment 2, long-term memory was assessed by re-testing the same sheep 1 year later. Similar results to the first test were obtained for control (not handled) and clamped groups, but for inverted sheep there was no significant difference in push-up time between rewarded and unrewarded groups. These results suggest that sheep have excellent long-term memories of sheep handling procedures, both when rewarded and unrewarded. Although the effectiveness of food rewards was diminished as the severity of the handling treatment increased, the results indicate that rewarding sheep could lead to long-term improvement in sheep handling efficiency, especially when severe treatments are performed rarely.     

Therapy Dogs Improve Student Affect but Not Memory

ABSTRACT

While students are increasingly struggling with anxiety and depression, the effects of therapy dogs on student stress has only recently been explored. This study was conducted to investigate whether therapy dogs can improve student affect and to determine if these benefits extend to cognition in the form of enhanced ability to remember information. Forty-four college students were randomly assigned to interact with a therapy dog or not during both learning (session 1) and testing (session 2) in a paired-associates procedure. Arousal, stress, and mood were measured at the beginning and end of each session. As predicted, therapy dogs increased happiness and decreased stress and arousal. However, there was no difference in recognition memory for the paired associates between the therapy dog and control conditions. Mood was a significant predictor of memory, such that decreased happiness in session 2 predicted better recognition performance. These findings indicate that the benefits of therapy dogs are primarily affective and not cognitive.     

Neural Population-Level Memory Traces in the Mouse Hippocampus

One of the fundamental goals in neurosciences is to elucidate the formation and retrieval of brain''s associative memory traces in real-time. Here, we describe real-time neural ensemble transient dynamics in the mouse hippocampal CA1 region and demonstrate their relationships with behavioral performances during both learning and recall. We employed the classic trace fear conditioning paradigm involving a neutral tone followed by a mild foot-shock 20 seconds later. Our large-scale recording and decoding methods revealed that conditioned tone responses and tone-shock association patterns were not present in CA1 during the first pairing, but emerged quickly after multiple pairings. These encoding patterns showed increased immediate-replay, correlating tightly with increased immediate-freezing during learning. Moreover, during contextual recall, these patterns reappeared in tandem six-to-fourteen times per minute, again correlating tightly with behavioral recall. Upon traced tone recall, while various fear memories were retrieved, the shock traces exhibited a unique recall-peak around the 20-second trace interval, further signifying the memory of time for the expected shock. Therefore, our study has revealed various real-time associative memory traces during learning and recall in CA1, and demonstrates that real-time memory traces can be decoded on a moment-to-moment basis over any single trial.     

One-trial instrumental conditioning in rats

A new method for a single-trial operant conditioning task with food reward in rats is described. The non-contingent reward of the first random lever press resulted in a higher response rate in both 24 and 48-hour retention tests as compared to contingently rewarded individuals. The latency to press the lever was shorter in non-contingently rewarded subjects than in contingently rewarded rats. The response rate in the first 5-min interval of the 24-hour retention test was higher in non-contingently rewarded subjects. The neuroleptic haloperidol (500 micrograms/kg., i.p.) given immediately following the "event to be remembered" significantly depresses the response rate compared to that for saline-treated controls. The advantages of the new method are discussed with respect to its applicability for memory research in animals and especially in neurophysiology and psychopharmacology.     

Validation of a rodent model of source memory

Source memory represents the origin (source) of information. Recently, we proposed that rats (Rattus norvegicus) remember the source of information. However, an alternative to source memory is the possibility that rats selectively encoded some, but not all, information rather than retrieving an episodic memory. We directly tested this ‘encoding failure’ hypothesis. Here, we show that rats remember the source of information, under conditions that cannot be attributed to encoding failure. Moreover, source memory lasted at least seven days but was no longer present 14 days after studying. Our findings suggest that long-lasting source memory may be modelled in non-humans. Our model should facilitate attempts to elucidate the biological underpinnings of source memory impairments in human memory disorders such as Alzheimer''s disease.