Familiarity interferes with filial imprinting

The present study was performed to investigate whether and how pre-exposure to an object affects subsequent filial imprinting to that object. In Experiment 1 junglefowl chicks (Gallus gallus spadiceus) were first exposed to either a red object alone (control group), or a red and a yellow object simultaneously (experimental group; phase 1). Subsequently, all chicks were exposed to the yellow object in the presence of a black and blue one (phase 2). At the end of phase 1, most experimental chicks had developed a preference for the red object over the yellow one. At the end of phase 2, preferences of experimental chicks were shifted away from the yellow object towards the novel black and blue object, relative to preferences of control chicks. This shows that pre-exposure may interfere with imprinting. Experiment 2 revealed that when control chicks were tested with the yellow object at the end of phase 1, filial responses were as strong as in experimental chicks. This shows that the yellow object had not acquired control over filial behaviour during phase 1, and also that the relatively impaired imprinting on that object in phase 2 was not due to reduced generalization from the red object. One possible explanation why pre-exposure may interfere with imprinting is that familiarity alters the level of attention attracted by an object, a mechanism suggested to underlie ‘latent inhibition’ in conditioning.     

Predispositions and preferences. Effects on imprinting of lesions to the chick brain

Domestic chicks were exposed to a moving, stuffed jungle fowl or a rotating red box. The effects on the imprinting process of lesions to a restricted part of the hyperstriatum ventrale (IMHV) were studied in a series of experiments. Sham-operated control chicks developed a strong preference for the training object. Damage to IMHV impaired chicks' preferences for the training stimulus. However, the effect on chicks exposed to the red box was profound, whereas the effect on chicks exposed to the jungle fowl was relatively weak. The results suggest that information about a complex object, which in the experiments described resembled the chicks' own species, is stored in a different way from information derived from a relatively simple artificial object.     

Pecking: another measurement for filial attachment in group-reared domestic fowl chicks

This study examines different types of attachment measurements and pecking behavior in group-reared domestic chicks imprinted to a silent imprinting object. Immediately upon arriving from the hatchery, groups of heavy strain chicks were imprinted to a colored foam rubber ball for 72 h. The bond between these chicks and the imprinting object was then tested from 8 days until 5 weeks of age. Three days of imprinting sessions demonstrated that a strong attachment could be formed between the imprinted chicks and the imprinting object. In both experimental and control groups, the number of pecks was found to be significantly correlated with the latency measurements. It is, therefore, reasonable to consider the number of pecks of the imprinting object as another measurement for filial attachment.     

Stimulus Movement,Hen Behaviour and Filial Imprinting in Japanese Quail (Coturnix coturnix japonica)

A living hen is a very attractive imprinting stimulus compared to artificial stimuli. The present study examined to what extent this attractiveness is influenced by the behaviour of the hen. The effectiveness of a living quail hen as an imprinting stimulus was compared with that of a moving stuffed hen, a non-moving stuffed hen and an empty cage. Naive quail chicks were exposed to one of these stimuli for 2 h. Both during and after this period chicks exposed to the living hen showed the strongest attachment to the stimulus, next came chicks exposed to a moving stuffed hen, while chicks exposed to a non-moving stuffed hen showed no indication of any attachment, i.e. they behaved in the same way as chicks exposed to an empty cage. Also, among chicks exposed to the living hen a correlation was present between the strength of the attachment to the hen and the behaviour of this hen during the exposure. In particular pecking and behaviour directed at the chick seemed to stimulate the development of a filial bond. Together, these findings indicate that a living hen is attractive not just because she moved, but also because of specific qualities of this movement. The behaviour of the living hen differed in various ways from the movement of the moving stuffed hen. The influence of these differences on the filial imprinting process is discussed and compared with similar findings for sexual imprinting and song learning.     

Effects of beta-chlornaltrexamine on separation distress in chicks

Intraventricular B-chlornaltrexamine (2 micrograms) increased distress vocalizations (DVs) in chicks, and reduced the ability of intraventricular morphine (.1-.5 micrograms), to inhibit DVs. Object imprinting was not blocked by central CNA, but systemic naloxone (10 mg/kg) did attenuate imprinting to a green but not a red object.     

Neural bases of recognition memory investigated through an analysis of imprinting

Through a learning process known as imprinting, the young of some animals, including the domestic chick, come to recognize an object by being exposed to it. Visually naive chicks vigorously approach a wide range of objects. After an adequate period of exposure to one object chicks selectively approach it in a recognition test. The nervous system of dark-reared chicks is not a tabula rasa, as chicks have predispositions to approach some stimuli rather than others. Nevertheless, visual imprinting leads to changes in a nervous system that may not have been 'marked' by previous visual experience, and so encourages the hope of discovering the neural bases of the learning process. The intermediate and medial part of the hyperstriatum ventrale, a sheet of cells within the cerebral hemispheres, plays a crucial role in visual imprinting, particularly in the memory process of recognition. The cellular and sub-cellular changes that take place in this part of the hyperstriatum ventrale after imprinting are described. The right and left hyperstriatum ventrale regions play different roles in the imprinting process, and evidence is given for the existence of multiple memory systems in the chick brain.     

Stimulus-Evoked Increase of Glutamate in the Mediorostral Neostriatum/Hyperstriatum Ventrale of Domestic Chick After Auditory Filial Imprinting: An In Vivo Microdialysis Study

Abstract: Imprinting in chicks is a form of juvenile learning that has been used to study the basic cellular mechanisms of learning and memory. The forebrain area mediorostral neostriatum/hyperstriatum ventrale (MNH) is a center for acoustic imprinting. Electrophysiological and pharmacological behavioral studies in the MNH have demonstrated that the glutamatergic system and the associated receptors are critically involved in auditory filial imprinting. Accordingly, we investigated the hypothesis that stimulus-evoked glutamate release may be altered after this learning process. Using an in vivo microdialysis technique, we observed a significantly higher increase of extracellular glutamate level in tone-imprinted chicks during exposure to the previously imprinted tone than in socially imprinted control chicks. In a further series of experiments, where we exposed animals from both experimental groups to handling distress, glutamate levels in MNH showed only a slight increase, whereas we observed a pronounced increase of extracellular glutamate in the lobus parolfactorius (LPO), the avian analogue of the basal ganglia. No difference of distress-evoked glutamate release was found in MNH and LPO between tone-imprinted and socially imprinted chicks. The tone-evoked enhanced glutamate response in tone-imprinted chicks suggests that during auditory imprinting glutamatergic synapses develop the potential to increase transmitter release in response to the imprinting stimulus.     

Neurotransmitter Release from the Medial Hyperstriatum Ventrale of the Chick Forebrain Accompanying Filial Imprinting Behavior,Measured by In Vivo Microdialysis

The imprinting behavior of chicks was quantified as a preference score (correct response ratio) achieved in a running wheel apparatus. A total of 249 chicks were exposed to an imprinting stimulus and tested for stimulus-approaching behavior. The chicks were then classified as good learners (imprinted), poor learners (non-imprinted) and a gray-zone group, those were 46%, 31% and 23% of the total chicks respectively. Using the classified chicks, the acetylcholine (ACh) and glutamate releases from the medial hyperstriatum ventrale (MHV) of the chick forebrains were determined by in vivo microdialysis. The non-imprinted chicks were used as yoked controls. Increases of ACh and glutamate released were observed in the imprinted chicks during exposure to the imprinting stimulus, whereas there were no changes in the release of these neurotransmitters in the non-imprinted chicks during the imprinting exposure. These results might be indicated that cholinergic and glutamatergic synapses which are newly formed as functioning synapses with imprinting stimulus in the MHV are involved in the performance of imprinting behavior.     

Effects of prior exposure to light on chicks' behaviour in the imprinting situation

Day-old domestic chicks previously exposed to a constant light approached a flashing rotating light more rapidly than chicks previously kept in darkness. The speed of approach was inversely related to the length of exposure, and effects were apparent after 18 min of exposure. Responsiveness was not affected by a prior reduction in air temperature of 4°C for 60 min. After exposure in the dark to the sound of a chick loudly calling for 60 min, chicks were less responsive to the flashing light than those previously kept in relative silence.     

Imprinting on time-structured acoustic stimuli in ducklings

Filial imprinting is a dedicated learning process that lacks explicit reinforcement. The phenomenon itself is narrowly heritably canalized, but its content, the representation of the parental object, reflects the circumstances of the newborn. Imprinting has recently been shown to be even more subtle and complex than previously envisaged, since ducklings and chicks are now known to select and represent for later generalization abstract conceptual properties of the objects they perceive as neonates, including movement pattern, heterogeneity and inter-component relationships of same or different. Here, we investigate day-old Mallard (Anas platyrhynchos) ducklings’ bias towards imprinting on acoustic stimuli made from mallards’ vocalizations as opposed to white noise, whether they imprint on the temporal structure of brief acoustic stimuli of either kind, and whether they generalize timing information across the two sounds. Our data are consistent with a strong innate preference for natural sounds, but do not reliably establish sensitivity to temporal relations. This fits with the view that imprinting includes the establishment of representations of both primary percepts and selective abstract properties of their early perceptual input, meshing together genetically transmitted prior pre-dispositions with active selection and processing of the perceptual input.     

Social recognition and approach in the chick: lateralization and effect of visual experience

Chicks, Gallus gallus domesticus, tested monocularly on day 3 after hatching recognize familiar versus unfamiliar conspecifics and choose to approach one or other when they use the left eye, whereas they approach familiar and unfamiliar chicks at random when they use the right eye. In experiment 1 we investigated the effects of light exposure of embryos prior to hatching on this particular form of lateralization. Irrespective of whether they hatched from eggs incubated in the dark or from eggs exposed to light during the final days of incubation, chicks using the left eye had higher choice scores (meaning they chose to approach either a familiar or an unfamiliar chick) than chicks using the right eye or both eyes. Therefore, light experience prior to hatching did not influence the lateralization of individual recognition or choice behaviour, although it did affect latency to move out of, and time spent in, the centre of the runway. Experiment 2 showed that visual/social experience posthatching influences choice behaviour: chicks housed in a group in the light for 12 h on day 1 posthatching made a clear choice between familiar and unfamiliar chicks when tested on day 3, but chicks kept in a group in the dark on day 1 did not make a choice, instead alternating between the two stimuli. In experiment 3 we found that posthatching visual/social experience increased the choice scores of chicks using the right eye and thereby removed any lateralization of choice behaviour. The results suggest that visual experience of a social group is required before chicks using their right eye (and left hemisphere) will pay attention to the cues that distinguish one chick from another. Chicks using their left eye (and right hemisphere) recognize the difference between individuals without requiring visual experience with other chicks. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Intuitive physical reasoning about occluded objects by inexperienced chicks

Questions concerning the role of nature and nurture in higher cognition appear to be intractable if one restricts one's attention to development in humans. However, in other domains, such as sensory development, much information has been gained from controlled rearing studies with animals. Here, we used a similar experimental strategy to investigate intuitive reasoning about occluded objects. Newborn domestic chicks (Gallus gallus) were reared singly with a small object that became their social partner. They were then accustomed to rejoin such an imprinting object when it was made to move and disappear behind either one of two identical opaque screens. After disappearance of the imprinting object, chicks were faced with two screens of different slants, or of different height or different width, which may or may not have been compatible with the presence of the imprinting object hidden beneath/behind them. Chicks consistently chose the screen of slant/height/width compatible with the presence of the object beneath/behind it. Preventing chicks from touching and pecking at the imprinting object before testing did not affect the results, suggesting that intuitive reasoning about physical objects is largely independent of specific experience of interaction with objects and of objects' occluding events.     

Visual lateralization and development of spatial and social spacing behaviour of chicks (Gallus gallus domesticus)

We investigated whether the development of spatial behaviour of the domestic chicken is influenced by light exposure of the embryo, as is known to be the case for some other lateralized visual functions. Ninety-six chicks were incubated in the dark or exposed to light during the final days of incubation. Half of the chicks in each group had the experience of moving behind opaque screens from 10 to 12 days of age. The other half were given transparent screens as a control. Chicks were tested in a detour test and a rotated floor test and their dispersal in groups was observed in larger pens. In the rotated floor test, chicks that had had experience with opaque screens used distal cues significantly more often than chicks that had experience with transparent screens (P = 0.042), regardless of whether they had been exposed to light before hatching or incubated in the dark. There were no significant differences between treatments in the detour test or in the dispersal behaviour. Hence, visual lateralization has no influence on the development of the spatial behaviour that we tested, whereas the occlusion experience is quite specific and results in shifted attention to distal spatial cues.     

Effects of androgens and estrogens on crowings and distress callings in male Japanese quail, Coturnix japonica

In male Japanese quail, crowing behavior is considered to be strictly androgen-dependent. It was previously shown that in chicks, treatment with either testosterone or 5alpha-dihydrotestosterone (5alpha-DHT; a non-aromatizable androgen) induced crowing with motivation for distress calling in acutely isolated conditions. Many studies, however, have shown that the potencies of testosterone and 5alpha-DHT in activating crowing in castrated males are different. To clarify the effects of androgenic and estrogenic actions on the production of crows and distress calls, we injected quail daily from 11 to 42 days after hatching (Day 11 to 42) with testosterone propionate (TP), 5alpha-DHT, estradiol benzoate (EB) or vehicle and examined their calling behaviors both in a recording chamber (acutely isolated conditions) and in their home-cages (well-acclimated conditions). Both TP- and 5alpha-DHT-treated birds began to crow by Day 13 when isolated in the recording chamber. The TP-treated birds, however, crowed less frequently than 5alpha-DHT-treated ones. This, combined with the observations that distress calling was strongly inhibited in EB-treated birds, suggests that estrogen converted from testosterone may inhibit the motivation for distress calling. On the other hand, after chronic treatment of TP, but not of 5alpha-DHT, birds began to crow intensely in their home-cages earlier than vehicle treated controls, suggesting that estrogen is needed to initiate crowing behavior in sexually active males. Taken together, it is suggested that estrogenic actions affect the motivation underlying vocal behaviors, while the androgenic action is indispensable in generating crowing.     

Activity patterns of breeding Hen Harriers Circus cyaneus assessed using nest cameras

Nest camera footage from 13 Hen Harrier Circus cyaneus nests was analysed to document patterns of adult attendance, incubation, brooding and prey delivery rates. Nest attendance was high throughout the incubation stage and began to decrease when chicks were five days old. Chick provisioning increased gradually after hatching and peaked when the chicks were five days old. Daily activity rates were highest during the middle of the day, from 08:00 to 19:00 hours.     

Activity rhythms and position preferences of domestic chicks which can see a moving object

The activity levels of isolated domestic chicks in home pens maintained at constant light and temperature were monitored for 4–6 days after hatching. The data were analysed using correlograms, spectrograms and multiple regression. Most chicks showed 24 h periodicities and also shorter periodicities of 1.5–4 h and about 30 min, but there was considerable individual variation. The importance of short-term rhythms in studies of responsiveness is emphasized. Chicks which could see a small, rotating ball from their home pens were more active than those which could not see a moving object and spent more time near it. The more pronounced 24 h periodicities, shown when a moving object could be seen, were partly due to greater activity, especially that near the object.     

Effect of filial imprinting procedure on cell proliferation in the chick brain

In the present study we tested the hypothesis that memory formation during visual imprinting might be related to generation of new cells in the brain of newborn domestic chicks. Cell proliferation was examined in the intermediate medial mesopallium (IMM), arcopallium intermedium (AI), medial part of nidopallium and mesopallium (MNM), nidopallium dorso-caudalis (Ndc), hippocampus (Hp) and area parahippocampalis (APH), as well as in corresponding ventricular zones. Number of new cells was measured by BrdU incorporation 24 h or 7 days after training, BrdU was injected before training. 24 h after imprinting the number of BrdU-positive cells increased significantly in IMM. 7 days after training no changes were observed in IMM, while the number of new cells decreased in MNM and Ndc in comparison to the control group. These data suggest that newly generated cells in the brain of young chicks are influenced by imprinting procedure, which has opposite short-term and long-term effects. A possible reason for such double action of imprinting in contrast to conventional learning can be its additional stimulation of development of predisposition for features of natural parents.     

Development of spatial memory in occlusion-experienced domestic chicks

At around day 11 of life, domestic chicks show a tendency to move out of sight of their mother before returning and regaining social and visual contact. We conducted a series of experiments to investigate the role of this voluntary ‘out-of-sight’ behaviour on the development of spatial memory in young chicks. We compared the behaviour of chicks that were reared in environments that provided opportunities to move out of sight of an imprinting stimulus (occlusion-experienced chicks) with the behaviour of chicks that were given minimal occlusion experience (controls). As in natural conditions, out-of-sight behaviour peaked on day 11. When chicks were released into larger pens at 14 days of age, occlusion-experienced chicks walked more than control chicks, but otherwise showed similar degrees of dispersal. Occlusion-experienced chicks tended to show better (although not significant, P=0.09) retrieval of a visually displaced imprinting stimulus than control chicks. Time spent out of sight in the rearing pens was negatively related to the number of orientation errors in a detour test. Occlusion-experienced chicks also tended to make fewer orientation errors in the first trial (P=0.07) and in subsequent trials (P=0.05). In contrast, experimentally manipulating the amount of time that chicks were out of sight of an imprinting stimulus (by confining the chicks) had no effect on their performance in displacement or detour tests. The results presented here suggest that active experience of occlusion around day 11 improved egocentric orientation towards an out-of-sight goal, supporting the hypothesis that enrichment-induced behavioural changes are dependent on the interaction with objects.     

Influence of a maternal odorant on copying strategies in chicks facing isolation and novelty during a standardized test

A synthetic analogue of a mother-hen odour named MHUSA (Mother Hen Uropygial Secretion Analogue) reduces stress-related behaviour in the chicken. We hypothesize that MHUSA may have an attractant effect on chicks. In order to test this, 30 chicks were individually exposed to MHUSA, placebo or neutral when self isolated in a straight shuttle box. The location of the chicks within the test chamber was recorded with 360 consecutive scan-sampled images. During the first three minutes immediately after introduction to the test area chicks spent more time in the neutral zone (p<0.05). However, taking the results from the total observation period, chicks spent more time in the MHUSA and placebo zones combined than in the neutral zone (p=0.07). They were more often observed in the MHUSA zone compared to the placebo zone (p<0.05). These results suggest that during the first three minutes in the shuttle, individuals were adapting to their new environment. After this period, chicks directed themselves towards specific local stimuli, as they tried to reach their group or something that resembled it. After a stressor was introduced, we observed a return to the same situation as during the first three minutes of the test, with chicks returning to the neutral zone, suggesting that the chick had its confidence in the environment. Three main conclusions may be drawn. Firstly, MHUSA has an attractant effect on na?ve chicks. Secondly, it appears to play a role in the reaction of chicks faced with a stressful event, and finally, the reaction to MHUSA seems innate and does not require previous experience.     

Activation of cholecystokinin neurons in the dorsal pallium of the telencephalon is indispensable for the acquisition of chick imprinting behavior

Chick imprinting behavior is a good model for the study of learning and memory. Imprinting object is recognized and processed in the visual wulst, and the memory is stored in the intermediate medial mesopallium in the dorsal pallium of the telencephalon. We identified chicken cholecystokinin (CCK)-expressing cells localized in these area. The number of CCK mRNA-positive cells increased in chicks underwent imprinting training, and these cells expressed nuclear Fos immunoreactivity at high frequency in these regions. Most of these CCK-positive cells were glutamatergic and negative for parvalbumin immunoreactivity. Semi-quantitative PCR analysis revealed that the CCK mRNA levels were significantly increased in the trained chicks compared with untrained chicks. In contrast, the increase in CCK- and c-Fos-double-positive cells associated with the training was not observed after closure of the critical period. These results indicate that CCK cells in the dorsal pallium are activated acutely by visual training that can elicit imprinting. In addition, the CCK receptor antagonist significantly suppressed the acquisition of memory. These results suggest that the activation of CCK cells in the visual wulst as well as in the intermediate medial mesopallium by visual stimuli is indispensable for the acquisition of visual imprinting.