Sequences of feeding,sampling and exploration by wild and laboratory rats

Adult male wild rats and male laboratory rats, all Rattus norvegicus, were kept alone for 11 d is a residential maze. The maze had a central nest box and four arms radiating from it. Movement in the arms was automatically recorded. Three foods were supplied, one at the end of each of three arms; the fourth arm was empty. One food was usually much preferred to the othe two. Except on Days 1—3, access to the arms was for only 3h daily.The rate of visiting the arms declined during the first 3 d. The wild rats were more ‘active’ than the domestic in that they made more visits; but they spent less time in the arms. Visits were of two kinds: (a) short, usually < 1min; (b) long (> 4 min.: meals). The wild rats had shorter meals than the donestic.A 3-h period of access usually began with a bout of short visits to the arms. Each long visit to a food arm (a meal) was also typically followed by such a bout, sometimes after a period in the nest box (drinking). the first short visit after a meal by a wild rat was most often to the empty arm; but domestic rats distributed these visits evenly among the three arms in which they had not been feeding. In a given bout the second short visit by a wild rat, but not a domestic, tended to repeat the first.We interpret a bout of short visits as a patrol or re-exploration of the living space which may include sampling of all accessible foods. When a bout occured at the beginning of access to the maze arms, exploring was in ‘competition’ with eating; a bout after a meal may have represented ‘disinhibition’ of exploring.     

Radial maze performance in young and aged grey mouse lemurs (Microcebus murinus)

Young and aged grey mouse lemurs have been tested in an eight-arm radial maze out of which four arms were blind. An access to a nesting box was only feasible from the far end of the fourth arm, free to visit (= positive reinforcement). Both age groups memorized the position of the blind arms with an equal efficiency and learned very quickly to avoid them. However, repeated visits to the free arms already explored during the trial were noticed with the aged grey mouse lemurs, while the young group returned much less. These results corroborate the theory that age would preferably deteriorate working memory and less the reference memory.     

Measuring the drinking behaviour of individual pigs housed in group using radio frequency identification (RFID)

Changes in the drinking behaviour of pigs may indicate health, welfare or productivity problems. Automated monitoring and analysis of drinking behaviour could allow problems to be detected, thus improving farm productivity. A high frequency radio frequency identification (HF RFID) system was designed to register the drinking behaviour of individual pigs. HF RFID antennas were placed around four nipple drinkers and connected to a reader via a multiplexer. A total of 55 growing-finishing pigs were fitted with radio frequency identification (RFID) ear tags, one in each ear. RFID-based drinking visits were created from the RFID registrations using a bout criterion and a minimum and maximum duration criterion. The HF RFID system was successfully validated by comparing RFID-based visits with visual observations and flow meter measurements based on visit overlap. Sensitivity was at least 92%, specificity 93%, precision 90% and accuracy 93%. RFID-based drinking duration had a high correlation with observed drinking duration (R²=0.88) and water usage (R²=0.71). The number of registrations after applying the visit criteria had an even higher correlation with the same two variables (R²=0.90 and 0.75, respectively). There was also a correlation between number of RFID visits and number of observed visits (R²=0.84). The system provides good quality information about the drinking behaviour of individual pigs. As health or other problems affect the pigs’ drinking behaviour, analysis of the RFID data could allow problems to be detected and signalled to the farmer. This information can help to improve the productivity and economics of the farm as well as the health and welfare of the pigs.     

Growing pigs’ drinking behaviour: number of visits,duration, water intake and diurnal variation

Individual drinking patterns are a potential tool for disease monitoring in pigs. However, to date, individual pig drinking behaviour has not been described, and effects of external factors have not been examined. The aim of this study was to perform detailed quantification of drinking behaviour of growing pigs and to examine effects of period of day and effects of competition for access to the drinking nipple on the drinking behaviour, amount of water used and water wastage. In all, 52 cross-bred castrated male pigs (live weight 20.5±1.7 kg; mean±s.d.) maintained as either 3 (N3) or 10 (N10) pigs per pen and water nipple (four groups/treatment) were used. All pigs were fitted with a transponder ear tag. A radio frequency identification reader recorded and time stamped visits at the nipple. In each pen, water flow was logged every second. The drinking behaviour was recorded for 4 consecutive days and analysed using a linear mixed model. Overall, the pigs spent 594 s at the nipple during 24 h distributed among 44 visits. During this period, 5 l of water were used, of which >30% was wasted. Social competition did not affect the drinking behaviour over 24 h, except for the proportion of interrupted visits where pigs, kept with recommended nipple availability (N10), showed an increased proportion of interrupted drinking bouts compared with pigs kept at very low level of competition (N3) (0.18±0.01 v. 0.11±0.01; P<0.01). However, splitting data into 8-h periods (P1, P2, P3) starting from 0600 h revealed differences between treatments, showing that in N3, water use per visit was lower in P1 than P2 and P3 (110±10 v. 126±7 and 132±7 ml; P<0.05), whereas in N10, the water used per visit was higher during P3 than during the other periods (P1: 107±14 ml, P2: 112±10 ml v. P3: 151±10 ml; P<0.001). A similar pattern was found for visit duration. In N3, fewer nipple visits were observed in P2 than P1 (15.6±1.2 v. 22.0±1.2; P<0.001), whereas no difference was found between P1 and P2 in N10. The results demonstrate that growing pigs at the two levels of competition maintained a comparable level of 24 h water intake by changing behavioural variables involved in drinking. This dynamic characteristic of drinking behaviour means that if individual drinking patterns are to be used as disease monitoring tools, it is important to consider effects of external factors and include data on period level to allow rapid detection of behavioural changes.     

Conditioning of gray crows (Corvus cornix L.) in a "giant" eight-arm radial maze

Twelve adult hooded crows (Corvus cornix) were trained to perform a standard radial-maze task in a giant eight-arm outdoor radial maze constructed at the "Chistyi les" Biological Station (Tver oblast) for comparative investigations of spatial memory in birds and mammals. The maze consists of a central part of 250 cm diameter, and has arms of 650 cm length, 170 cm height and 80 cm width. The examined hooded crows showed good task performance. Errors (repeated visits to empty arms) were few in number and were predominantly connected with the tendency to avoid arms close to an observer.     

Use of an Eight-arm Radial Water Maze to Assess Working and Reference Memory Following Neonatal Brain Injury

Working and reference memory are commonly assessed using the land based radial arm maze. However, this paradigm requires pretraining, food deprivation, and may introduce scent cue confounds. The eight-arm radial water maze is designed to evaluate reference and working memory performance simultaneously by requiring subjects to use extra-maze cues to locate escape platforms and remedies the limitations observed in land based radial arm maze designs. Specifically, subjects are required to avoid the arms previously used for escape during each testing day (working memory) as well as avoid the fixed arms, which never contain escape platforms (reference memory). Re-entries into arms that have already been used for escape during a testing session (and thus the escape platform has been removed) and re-entries into reference memory arms are indicative of working memory deficits. Alternatively, first entries into reference memory arms are indicative of reference memory deficits. We used this maze to compare performance of rats with neonatal brain injury and sham controls following induction of hypoxia-ischemia and show significant deficits in both working and reference memory after eleven days of testing. This protocol could be easily modified to examine many other models of learning impairment.     

Exploratory behavior of juvenile roach <Emphasis Type="Italic">Rutilus rutilus</Emphasis> (L.) (Teleostei: Cyprinidae) in a maze after different magnetic impacts on embryos

We have investigated a sequence of visits to arms in a cross maze in juvenile (1-year-old) roach Rutilus rutilus (L.). Fish embryos of one group are raised under a natural geomagnetic field. The embryos of another group are exposed to the main phase of a simulated geomagnetic storm (changes in geomagnetic field up to 100 nT for each component). It turns out that the sequence of visits does not differ from random in both groups. Thus, the exploratory behavior in juvenile roach differs from other animal taxa investigated earlier. In the latter taxa a spontaneous alternation was observed: a tendency to visit the arm which was visited least recently.     

Cognitive Strategy Use and Measured Numeric Ability in Immediate- and Long-Term Recall of Everyday Numeric Information

The goals of this study were to assess the primary effects of the use of cognitive strategy and a combined measure of numeric ability on recall of every-day numeric information (i.e. prices). Additionally, numeric ability was assessed as a moderator in the relationship between strategy use and memory for prices. One hundred participants memorized twelve prices that varied from 1 to 6 digits; they recalled these immediately and after 7 days. The use of strategies, assessed through self-report, was associated with better overall recall, but not forgetting. Numeric ability was not associated with either better overall recall or forgetting. A small moderating interaction was found, in which higher levels of numeric ability enhanced the beneficial effects of strategy use on overall recall. Exploratory analyses found two further small moderating interactions: simple strategy use enhanced overall recall at higher levels of numeric ability, compared to complex strategy use; and complex strategy use was associated with lower levels of forgetting, but only at higher levels of numeric ability, compared to the simple strategy use. These results provide support for an objective measure of numeric ability, as well as adding to the literature on memory and the benefits of cognitive strategy use.     

Sex differences in the long-term effect of preweanling isolation stress on memory retention

Social experiences during development can powerfully modulate later neuroendocrine and behavioral system. In the present study, male and female rat pups experienced daily bouts of social isolation for 6 h per day or control conditions during the third postnatal week. Performance on a 12-arm radial maze with 8 arms consistently baited with food reward was examined in adulthood. During the social isolation, both male and female pups exhibited a significant increase in plasma corticosterone levels. When tested on the radial arm maze as adults, the performance of female rats that had experienced social isolation during development was not affected; however, male rats in the isolation condition initially exhibited impairments in working memory but not reference memory. Despite achieving comparable asymptotic levels of performance on the maze, male rats that experienced social isolation during the third week demonstrated disruption in working memory retention when radial arm maze trials were interrupted after the fourth arm choice. Thus, while male rats that experience social isolation during the third week of life eventually perform comparably to controls on the standard radial arm maze task, their ability to retain information over a delay remains impaired. These findings highlight an important sex difference in the long-term effects of stress during this period of late preweanling development.     

The Effect of Single or Repeated Home Visits on the Hanging and Use of Insecticide-Treated Mosquito Nets following a Mass Distribution Campaign - A Cluster Randomized,Controlled Trial

Background

Study objective was to evaluate the effectiveness of commonly used post-campaign hang-up visits on the hanging and use of campaign nets.

Methods

A cluster-randomized trial was carried out in Uganda following an ITN distribution campaign. Five clusters (parishes, consisting of ∼11 villages each) were randomly selected for each of the three study arms with between 7,534 and 9,401 households per arm. Arm 1 received one hang-up visit, while Arm 2 received two visits by volunteers four and seven months after the campaign. Visits consisted of assistance hanging the net and education on net use. The control arm was only exposed to messages during the campaign itself. Three cross-sectional surveys with a two-stage cluster sampling design, representative of the study populations, were carried out to capture the two key outcome variables of net hanging and ITN use. Sample size was calculated to detect at least a 15 percentage-points change in net use, and was 1811 at endline. The analysis used an intention-to-treat approach.

Findings

Both hanging and use of ITN increased during follow-up in a similar way in all three study arms. The proportion of the population using an ITN the previous night was 64.0% (95% CI 60.8, 67.2), for one additional visit, 68.2% (63.8, 72.2) for two visits and 64.0% (59.4, 68.5) for the control. The proportion of households with all campaign nets hanging increased from 55.7% to 72.5% at endline (p<0.0005 for trend), with no difference between study arms. Financial cost per household visited was estimated as USD 2.33 for the first visit and USD 2.24 for the second.

Conclusions

Behavior change communication provided during the campaign or through other channels was sufficient to induce high levels of net hanging and use and additional “hang-up” activities were not cost-effective.     

Differential Involvement of the Dentate Gyrus in Adaptive Forgetting in the Rat

How does the brain discriminate essential information aimed to be stored permanently from information required only temporarily, and that needs to be cleared away for not saturating our precious memory space? Reference Memory (RM) refers to the long-term storage of invariable information whereas Working Memory (WM) depends on the short-term storage of trial-unique information. Previous work has revealed that WM tasks are very sensitive to proactive interference. In order to prevent such interference, irrelevant old memories must be forgotten to give new ones the opportunity to be stabilized. However, unlike memory, physiological processes underlying this adaptive form of forgetting are still poorly understood. Here, we precisely ask what specific brain structure(s) could be responsible for such process to occur. To answer this question, we trained rats in a radial maze using three paradigms, a RM task and two WM tasks involving or not the processing of interference but strictly identical in terms of locomotion or motivation. We showed that an inhibition of the expression of Zif268 and c-Fos, two indirect markers of neuronal activity and synaptic plasticity, was observed in the dentate gyrus of the dorsal hippocampus when processing such interfering previously stored information. Conversely, we showed that inactivating the dentate gyrus impairs both RM and WM, but improves the processing of interference. Altogether, these results strongly suggest for the first time that the dentate gyrus could be a key structure involved in adaptive forgetting.     

The influence of drinker location and colour on drinking behaviour and water intake of newborn pigs under hot environments

The effect of drinker location within the farrowing crate in relation to its microenvironment and the effect of dispenser colour on drinking behaviour and water intake of newborn pigs for the first two days of their lives were studied. In the first trial, 16 sows were randomly assigned to four treatment groups with the piglet's water dispenser placed in the front right (FR), front left (FL), back right (BR) or back left (BL) corner of the farrowing pen, respectively. In the second trial nine sows were randomly assigned to three treatment groups with the piglets’ water dispenser, placed in the front left corner of the farrowing pen, and coloured as red (CR), green (CG) or blue (CB), respectively. Trials commenced between 08:00 and 10:00 h on the first morning after the litters were born and the piglets’ age was considered to be zero (“age”) by that time.The average age of the piglets at their first visit to water dispensers was 15.9 ± 1.8 h. The newborn pigs visited the drinker more frequently (P < 0.001) during daytime than during night, with two peaks soon after sow feeding time. The duration of drinking time was long at the time of higher (noon) and shorter at the time of lowest (early morning) temperatures (P < 0.01) in the farrowing house, respectively. The greatest attention at the drinkers occurred soon after suckling (P < 0.001). The longest time spends at the drinker during the first visits and decreased as the pigs visited dispensers repeatedly. The profile of visit frequency and duration differed between piglet sexes (P < 0.001). The pigs that did not visit the drinker grew slower and were lighter at 48 h of age than the pigs visited the drinker. First visit and overall mean visit age were significantly shorter for BL than for FR and BR groups. Piglets visited the FL drinker for shorter time than the others. Water consumption per pig/24 h was lower for FL and higher for BL groups (P < 0.05). Water consumption was higher for CR and CB groups than for CG group. The overall mean visit age was shorter for CG than for CB group. Significant interactions were observed between sex and colour groups for the number of visits (P < 0.05). The results of the present study revealed that water dispenser use by newborn piglets is characterised by diurnal and between two successive milk consumptions distributions. Water consumption by piglets from birth to 48 h of their lives is strongly influenced by water dispenser location in the farrowing pen and the dispenser colour. It also appears that males and females behave differently to the three colour dispensers used in this study.     

Spatial navigation on the radial maze with trial-unique intramaze cues and restricted extramaze cues

We investigated the use of extramaze and intramaze cues on the eight-arm radial maze. The rats received daily training consisting of forced-choice visits to four baited arms, a retention interval, and the availability of all eight arms with baits available at arms that did not appear in the forced-choice phase. The radial maze was placed in a featureless octagonal enclosure to minimize the availability of extramaze cues. Intramaze cues were provided at the distal end of each arm by placing a small object in front of the food trough; unique objects were randomly sampled from a large pool of objects. The use of extramaze and intramaze cues was assessed by rotating the objects, after the retention interval, on occasional non-rewarded probes, thereby dissociating the location of extramaze and intramaze cues. The rats used extramaze rather than intramaze cues. Implications for spatial representations are discussed.     

Capacity of working memory in rats as determined by performance on a radial maze

Capacity of the working memory was tested in 12 rats highly overtrained in the 12- and 24-arm radial mazes. Asymptotic performance levels were characterized by 1.01 and 2.78 errors/trial in the 12- and 24-arm mazes, respectively. The incidence of errors increased from 31% on the last choice in the 12-arm maze to 51% on choices 23 and 24 in the 24-arm maze, but remained significantly below the expected error probability of about 85%. Linear extrapolation of the above trend to mazes with more arms suggests working memory capacity of 40 to 50 items. When two trials in a 12-arm maze were repeated in immediate succession, error incidence increased from 1.17 in the first trial to 2.13 in the second trial. The tendency to avoid choice repetition could be observed in any string of 12 continuous choices, but was weakest in segments divided by trial boundary (2.48 errors in choices 7 to 18). With a different trial separation (choices 1–6 and 19–24 in maze A, choices 7–18 in an adjacent maze B) errors dropped to 1.09 in B but increased to 2.30 in A. It is concluded that radial maze performance reflects avoidance of choice repetition which is improved by recognition of trial boundaries and is adversely influenced by forgetting and interference.     

Mirroring intentional forgetting in a shared-goal learning situation

Background

Intentional forgetting refers to the surprising phenomenon that we can forget previously successfully encoded memories if we are instructed to do so. Here, we show that participants cannot only intentionally forget episodic memories but they can also mirror the “forgetting performance” of an observed model.

Methodology/Principal Findings

In four experiments a participant observed a model who took part in a memory experiment. In Experiment 1 and 2 observers saw a movie about the experiment, whereas in Experiment 3 and 4 the observers and the models took part together in a real laboratory experiment. The observed memory experiment was a directed forgetting experiment where the models learned two lists of items and were instructed either to forget or to remember the first list. In Experiment 1 and 3 observers were instructed to simply observe the experiment (“simple observation” instruction). In Experiment 2 and 4, observers received instructions aimed to induce the same learning goal for the observers and the models (“observation with goal-sharing” instruction). A directed forgetting effect (the reliably lower recall of to-be-forgotten items) emerged only when models received the “observation with goal-sharing” instruction (P<.001 in Experiment 2, and P<.05 in Experiment 4), and it was absent when observers received the “simple observation” instruction (P>.1 in Experiment 1 and 3).

Conclusion

If people observe another person with the same intention to learn, and see that this person is instructed to forget previously studied information, then they will produce the same intentional forgetting effect as the person they observed. This seems to be a an important aspect of human learning: if we can understand the goal of an observed person and this is in line with our behavioural goals then our learning performance will mirror the learning performance of the model.     

Helpful amnesia: Neuroscience unravels the role of forgetting as a prerequisite for establishing new long‐term memories

As neuroscience has been analysing the mechanisms behind long‐term memory, it demonstrated that forgetting is crucial for being able to remember.

“To be able to forget means sanity,” explained American writer Jack London (The Star Rover) referring to our sometimes infuriating inability to recall past events. In fact, being able to remember everything ever said and done might drive even the strongest mind insane. It is through forgetting and letting go of memories that the brain is able to acquire fresh impressions and new experience to move on, instead of being mired in the past.The importance of forgetting also fits well into and has inspired research to understand the molecular and cognitive basis of long‐term memory and how all the components and processes fit together. This puzzle of what is being remembered and why has been a long‐standing challenge for neuroscience; while progress has been made identifying more of the mechanisms and some of the existential drivers of memory formation, it is only recently that work has begun analyzing how these interact in animal models, often focusing on how the brain “decides” which things to remember and which things to send into oblivion.

This puzzle of what is being remembered and why has been a long‐standing challenge for neuroscience…

As a result, the field now sees collaboration across disciplines, driven by the realization that different parts and processes all play a part in memory formation and long‐term consolidation. This has led to one tangible if still tentative conclusion about long‐term memory, namely that forgetting occurs through loss of retrieval capability rather than erasure. It would appear to confirm the observation attributed to German philosopher Friedrich Nietzsche that “the existence of forgetting has never been proved: we only know that some things do not come to our mind when we want them to.”

The existence of forgetting has never been proved: we only know that some things do not come to our mind when we want them to.

     

Pigs shift too: foraging strategies and spatial memory in the domestic pig

In a previous experiment, we showed that domestic pigs, Sus scrofa, unlike many other species, performed accurately in a spatial memory task, where visits to a previously baited food trough were rewarded (win-stay). We investigated whether pigs have a predisposition for this strategy, by comparing their performance in a radial arm maze under either win-stay (N=10) or win-shift (N=10) reward contingencies. Contrary to our earlier results, only one of the animals in the win-stay condition was able to reach the imposed criterion level of accuracy. The performances of the other win-stay pigs did not deviate from random. All pigs in the win-shift condition reached criterion by day 25 of the experiment, and performed better than expected by chance. Analysis of the types of errors made matched our a priori predictions that shift movements would occur more frequently, especially within visits to the maze. We suggest that the difference in learning rates may reflect the fact that win-stay pigs needed to use two different rules, stay between trials and shift within trials, while win-shift pigs only needed to use the shift rule. In our previous study, win-stay pigs did not experience a conflict of rules and this may have facilitated stay learning. We found evidence of a recency effect in win-shift animals and a primacy effect in the win-stay group. However, we discuss the unsuitability of these specific terms in this type of experiment, and propose an alternative interpretation of the results. Copyright 2000 The Association for the Study of Animal Behaviour.     

Contextual control of rats' foraging behaviour in a radial maze

This study demonstrated that with experience rats were able to discriminate the background contextual cues in order to foraging correctly in an eight-arm radial maze if the background contexts signaled to the rats which of two bait patterns was in effect in that context. Four of the eight arms were context-dependent: two arms were baited in the "night" context, while the other two were baited in the "daytime" context. The remaining four arms were context-independent: three of them were never baited, while the remaining one was baited in both contexts. The rats gradually began to avoid the arms that were uniquely baited in the other context, suggesting a contextual or conditional control of arm selection. Interestingly, these rats also showed better performance in avoiding the never-baited arms, compared with control rats. Namely, disambiguating the incentive values of the four arms by contextual cues collaterally facilitated the context-independent arm performance. Another interesting finding of the present study is that the rats did not visit the always-baited arm earlier than the arms uniquely baited in that context.     

Analysis of the Optimal Duration of Behavioral Observations Based on an Automated Continuous Monitoring System in Tree Swallows (Tachycineta bicolor): Is One Hour Good Enough?

Studies of animal behavior often rely on human observation, which introduces a number of limitations on sampling. Recent developments in automated logging of behaviors make it possible to circumvent some of these problems. Once verified for efficacy and accuracy, these automated systems can be used to determine optimal sampling regimes for behavioral studies. Here, we used a radio-frequency identification (RFID) system to quantify parental effort in a bi-parental songbird species: the tree swallow (Tachycineta bicolor). We found that the accuracy of the RFID monitoring system was similar to that of video-recorded behavioral observations for quantifying parental visits. Using RFID monitoring, we also quantified the optimum duration of sampling periods for male and female parental effort by looking at the relationship between nest visit rates estimated from sampling periods with different durations and the total visit numbers for the day. The optimum sampling duration (the shortest observation time that explained the most variation in total daily visits per unit time) was 1h for both sexes. These results show that RFID and other automated technologies can be used to quantify behavior when human observation is constrained, and the information from these monitoring technologies can be useful for evaluating the efficacy of human observation methods.     

A Normative Theory of Forgetting: Lessons from the Fruit Fly

Recent experiments revealed that the fruit fly Drosophila melanogaster has a dedicated mechanism for forgetting: blocking the G-protein Rac leads to slower and activating Rac to faster forgetting. This active form of forgetting lacks a satisfactory functional explanation. We investigated optimal decision making for an agent adapting to a stochastic environment where a stimulus may switch between being indicative of reward or punishment. Like Drosophila, an optimal agent shows forgetting with a rate that is linked to the time scale of changes in the environment. Moreover, to reduce the odds of missing future reward, an optimal agent may trade the risk of immediate pain for information gain and thus forget faster after aversive conditioning. A simple neuronal network reproduces these features. Our theory shows that forgetting in Drosophila appears as an optimal adaptive behavior in a changing environment. This is in line with the view that forgetting is adaptive rather than a consequence of limitations of the memory system.