Serial conditional discrimination and temporal bisection in rats selectively lesioned in the dentate gyrus

In positive serial conditional discrimination, animals respond during a target stimulus when it is preceded by a feature stimulus, but they do not respond when the same target stimulus is presented alone. Moreover, the feature and target stimuli are separated from each other by an empty interval. The present work aimed to investigate if two durations (4 or 16 s) of the same feature stimulus (light) could modulate the operant responses of rats to different levers (A and B) during a 5-s target stimulus (tone). In the present study, lever A was associated with the 4-s light, and lever B was associated with the 16-s light. A 5-s empty interval was included between the light and the tone. In the same training procedure, the rats were also presented with the 5-s tone without the preceding light stimuli. In these trials, the responses were not reinforced. We evaluated the hippocampal involvement of these behavioral processes by selectively lesioning the dentate gyrus with colchicine. Once trained, the rats were submitted to a test using probe trials without reinforcement. They were presented with intermediate durations of the feature stimulus (light) to obtain a temporal bisection curve recorded during the exposure to the target stimuli. The rats from both groups learned to respond with high rates during tones preceded by light and with low rates during tones presented alone, which indicated acquisition of the serial conditional discrimination. The rats were able to discriminate between the 4- and 16-s lights by correctly choosing lever A or B. In the test, the temporal bisection curves from both experimental groups showed a bisection point at the arithmetic mean between 4 and 16 s. Such processes were not impaired by the dentate gyrus lesion. Thus, our results showed that different durations of a feature stimulus could result in conditional properties. However, this processing did not appear to depend on the dentate gyrus alone.     

Perception or preference? Mediation of gene effects in the colour choices of naive quail chicks (C. coturnix japonica)

The purpose of this study was to examine gene effects in the peripheral and central neural mediation of colour preferences in artificially selected Japanese quail chicks (Coturnix coturnix japonica). Behavioural data indicated preferences of blue over red and red over blue in the respectively selected genetic lines, and general preferences for white in both lines. Preferences were influenced by luminance variations of testing stimuli. Choices between segmented stimuli that combined blue, red, and white, in various patterns of systematically varied hues and luminances, indicated perceptual discrimination of colours in each line. Preference values combined within stimuli summated additively in choice responses, suggesting no genetic association between colour preference and colour perception. Electrophysiological data indicated systematic differences between waveshapes of averaged evoked potentials according to hues of eliciting stimuli. These data also counterindicated the involvement of colour perception in the genetic variations of colour preference. However, no significant differences between waveshapes were found in relation to genetic variations in preferences.     

CONSUMERS REPORT PREFERENCES WHEN THEY SHOULD NOT: A CROSS-CULTURAL STUDY

If a chi‐squared analysis were to be performed to determine whether preferences were significant in a paired preference test, the appropriate expected frequencies in the analysis would represent those that would occur should the consumers have no preference. One way of determining these ‘no preference’frequencies, for a particular test situation, would be to note the preference responses obtained when the stimuli were putatively identical. Over 2000 consumers were given paired preference tests in which the stimuli were putatively identical. Response conditions and consumer groups were varied and the proportions of preference and no preference responses were noted. In a preliminary experiment, further research was seen to be justified when for putatively identical stimuli, judges did not exclusively express lack of preference; many expressed a preference for one or other of the stimuli. Further experiments were conducted using a written response condition and putatively identical potato chips (potato crisps) as stimuli. Using a single ‘no preference’option, variation in the placement of this option at either first, second or third place on the response sheet had no significant effect on the response frequencies. The proportion of ‘no preference’responses was approximately 30% in all cases. A previously reported 40‐20‐40 distribution was not always confirmed. The experiment was repeated with Korean consumers; these had fewer ‘no preference’responses. Deriving preferences from hedonic scales, rather than having judges respond to preference options, increased the proportion of ‘no preference’responses, with American judges still having more than Korean judges. Yet there are logical objections to extracting preference data from hedonic scales. Increasing the number of ‘no preference’options to two or three, had the effect of increasing the number of ‘no preference’responses up to as much as approximately 60%. Extending the results to Koreans, using two ‘no preference’options, it was seen that only the judges in an anonymous response condition had significantly fewer ‘no preference’responses than Americans. The use of these response frequencies as expected frequencies in chi squared analyses was illustrated, after adjustments for counterbalancing.     

Assessment of mate preference in the house mouse with reference to investigations on assortative mating

This study analysed patterns of mate choice based on different types of laboratory test, and points out the advantages of combined methods to assess mate preference. We compared dyadic encounters and two-way choice tests involving a pair of mice or their urinary signature. Preference was assessed in males and females of the two European subspecies of the house mouse Mus musculus that share a secondary hybrid zone. A preference was deduced from directional choice or behavioural discrimination in favour of a mouse. Our results show discrepancies between the outcomes of the different types of test, which we discuss in terms of the quality of the stimuli involved, and of physical access to the information carried by those stimuli. Despite variation, our results indicate that M. m. domesticus did not show a preference, but could discriminate between stimuli of the two subspecies and tended to direct sexual behaviour assortatively. In contrast, both male and female M. m. musculus showed positive discrimination and preference for potential mates and signals carried by their own subspecies. Additionally, our results confirm that subspecies informative signals are present in mouse urine and suggest that they may be molecules of low volatility, necessitating contact for preference to be displayed.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 84 , 461–471.     

Play as a reinforcer for maze-learning in juvenile rats

The reinforcing value of play for juvenile rats was examined, relative to that of other social experiences. Successive experimental groups chose, in a T-maze, between normal companions and companions whose social behaviour had been rendered abnormal by physical confinement or by amphetamine or chlorpromazine treatment. Both these drugs inhibited play, as did physical restriction, but they had opposing effects on other social behaviours, so that the choice presented was between social experiences with and without play. Young rats learnt these social discriminations as easily as a food/no food discrimination in the same apparatus, developing a preference for the playing partner. Non-playing partners indulging in large amounts of amicable social behaviour were chosen more frequently than unsociable animals.     

Development of a novel stall design for dairy cattle: Part I. The effect of an increased slope on lying behavior,rumination, cleanliness,and preference

The longitudinal slope of a stall is important for positioning cows in the stall and maintaining cleanliness of the stall surface. The objectives of this study were to determine the short-term effect of increasing free-stall slope from 4.5% to 9.3% on dairy cow lying behavior, rumination, milk production, cleanliness, and preference. In experiment 1, 60 multiparous Holstein cows were divided randomly into two groups and exposed to a 4.5% stall slope (standard in the research facility) and a 9.3% stall slope in a replicated crossover design with four 7-day periods. Each group of cows were housed in a pen with 30 free-stalls and switched between treatments weekly. Lying behavior and rumination were recorded continuously, milk yields were recorded twice per day, and cleanliness scores were collected on the last day of each week. Experiment 2 consisted of an 8-day preference test conducted with 14 cows from experiment 1 in an experimental pen with 32 stalls (16 stalls with a 4.5% slope and 16 stalls with a 9.3% slope). Continuous video monitoring was used to record time spent lying, standing, and perching in each treatment during the last 5 days, and lying time was used to assess preference. In experiment 1, cows spent 12 min/day less time lying down (12.8 vs 12.6 ± 0.28 h/d) and had 0.6 more bouts/day (9.5 vs 10.1 ± 0.38 no./d) with a shorter duration by 6 min/day (1.4 vs 1.3 ± 0.03 h/bout) in stalls with a 9.3% slope. Rumination was 5.5 min less per day in stalls with a 9.3% slope (578.4 vs 572.9 ± 16.56 min/d) and milk yield did not differ between treatments (33.6 vs 33.4 ± 0.78 kg/d). Stall slope did not affect cow cleanliness (1.6 vs 1.6 ± 0.05 points on a 1–5 scale). In experiment 2, cows showed no clear preference for lying, standing, or perching in either stall slope (4.5% and 9.3%) when given a choice. These results indicate that increasing stall slope from 4.5% to 9.3% marginally altered lying behavior, but did not interfere with stall use or influence cow preferences.     

Transfer of stimulus control from a TFT to CRT screen

The use of television and computer screens for presenting stimuli to animals is increasing as it is non-invasive and can provide precise control over stimuli. Past studies have used cathode ray tube (CRT) screens; however, there is some evidence that these give different results to non-flickering thin film transistor (TFT) screens. Hens’ critical flicker fusion frequency ranges between 80 and 90 Hz - above standard CRT screens. Thus, stimuli presented on CRT screens may appear distorted to hens. This study aimed to investigate whether changing the flicker rate of CRT screens altered hens’ discrimination. Hens were trained (in a conditional discrimination) to discriminate between two stimuli on a TFT (flickerless) screen, and tested with the stimuli on a CRT screen at four flicker rates (60, 75, 85, and 100 Hz). The hens’ accuracy generally decreased as the refresh rate of the CRT screen decreased. These results imply that the change in flicker rate changed the appearance of the stimuli enough to affect the hens’ discrimination and stimulus control is disrupted when the stimuli appear to flicker.     

Visual and auditory conditional position discrimination in chimpanzees (Pan troglodytes)

Chimpanzee cognition has been studied predominantly through the visual modality, and much less through the auditory modality. The aim of this study was to explore possible differences in chimpanzees’ processing of visual and auditory stimuli. We developed a new conditional position discrimination (CPD) task requiring the association between a stimulus (from either the auditory or the visual modality), and a spatial position (left or right). The stimuli consisted of the face and voice of two individuals well known to the subjects (one chimpanzee and one human). Six chimpanzees participated in both the visual and the auditory conditions. We found contrasting results between the two conditions: the subjects acquired the CPD more easily in the visual than in the auditory condition. This supports previous findings on the difficulties encountered by chimpanzees in learning tasks involving auditory stimuli. Our experiments also revealed individual differences: the chimpanzee with the most extensive experience in symbolic visual matching tasks showed good performance in both conditions. In contrast, the chimpanzee expert in an auditory-visual intermodal matching task showed no sign of learning in either condition. Future work should focus on finding the most appropriate procedure for exploring chimpanzees’ auditory-visual cognitive skills.     

Variation in female guppy preference for male olfactory and visual traits

Animals often use different sensory systems to assess different sexually selected signals from potential mates. However, the relative importance of different signals on mate choice is not well understood in many animal species. In this study, we examined the relative importance of male olfactory and visual cues on female preference in the guppy Poecilia reticulata. We used digitally modified male images to standardize visual stimuli. We found that, regardless of whether females were presented without male visual stimuli or with identical male visual stimuli, they preferred stimuli with the odor of males to those without. However, when females were allowed to choose between dull male visual stimuli with male odor, and brightly colored male visual stimuli without male odor, there was no clear preference for either. Some females preferred the dull male visual stimuli with male odor, whereas some other females preferred the brightly colored male visual stimuli without male odor. These results indicate that the relative importance of olfactory and visual cues in female mate preference varied between individuals.     

Role of Muscarinic Acetylcholine Receptors in Serial Feature-Positive Discrimination Task during Eyeblink Conditioning in Mice

We investigated the role of muscarinic acetylcholine receptors (mAChRs) in eyeblink serial feature-positive discrimination learning in mice using the mAChR antagonist. A 2-s light cue was delivered 5 or 6 s before the presentation of a 350-ms tone paired with a 100-ms periorbital electrical shock (cued trial) but not before the tone-alone presentation (non-cued trial). Mice received 30 cued and 30 non-cued trials each day in a random order. We found that saline-injected control mice were successfully discriminating between cued and non-cued trials within a few days of conditioning. The mice responded more frequently to the tone in cued trials than in non-cued trials. Analysis of conditioned response (CR) dynamics revealed that the CR onset latency was shorter in cued trials than in non-cued trials, despite the CR peak amplitude not differing significantly between the two conditions. In contrast, scopolamine-injected mice developed an equal number of CRs with similar temporal patterns irrespective of the presence of the cue during the 7 days of conditioning, indicating in a failure to acquire conditional discrimination. In addition, the scopolamine administration to the control mice after they had successfully acquired discrimination did not impair the conditional discrimination and expression of pre-acquired CR. These results suggest that mAChRs may play a pivotal role in memory formation in the conditional brain state associated with the feature cue; however they are unlikely to be involved in the development of discrimination after conditional memory had formed in the serial feature-positive discrimination task during eyeblink conditioning.     

Role of stimulus-stimulus pairing in matching-to-sample procedure: cross-species comparison of humans and pigeons

The present experiment examined whether, in a matching-to-sample (MTS) procedure, a relation between two stimuli, a sample and a comparison, could be established as a result of just stimulus–stimulus pairing, even if back up reinforcers were never provided for the conditional relation between the sample and comparison stimuli, but rather only for the comparison stimulus. A procedure called “pseudo matching-to-sample” was used in which, when S1 was presented as a sample stimulus, two comparison stimuli (C1 and C2) were presented, and only responses to C1 were reinforced. Conversely, when S2 was presented, only responses to C3 (and not C4) were reinforced. In other words, organisms experiencing this procedure could discriminate C1 from C2, and C3 from C4, by simple discrimination without regard to the conditional sample stimuli. In order to examine cross-species differences, responding by humans in this procedure was compared to that by pigeons. Although the humans developed a discriminative function for the sample stimuli, that is, the humans’ responding was affected by both the sample stimuli and the reinforcers, responding by the pigeons was affected solely by the reinforcers. These data suggest that, in this procedure, humans (but not pigeons) are able to learn relations among stimuli simply as a result of stimulus–stimulus pairing.     

SOURCES OF ERROR AND THE NO-PREFERENCE OPTION IN DAIRY PRODUCT TESTING

When products are physically identical, consumers will choose a no‐preference option in a paired preference test only about 30% of the time, giving a nonintuitive result. We evaluated the no‐preference false alarm rate in dairy products and the potential sources of error in panelist behavior, including discrimination problems and poor repeatability of judgments. Paired preference tests were conducted with milk (2% versus nonfat or skim), with cottage cheese (4% versus nonfat) and with identical samples. Triangle, dual standard and same/different discrimination tests were also conducted. The no‐preference option was chosen by about 30% of the consumers when samples were identical, and less frequently when samples were different. Discrimination performance, although statistically significant, was poorer than expected with about 30% discriminators (d′ of 1.7) in most tests. Even in the dual standard tests on milk (visually obvious and with references present), performance was only 88% correct (76% discriminators). Repeatability in preference tests was also poorer than expected, with only 56% choosing the same preference option for different samples on repeat trials although the group preferences were stable. Same/different tests indicated that over 50% of the consumers called identical samples different, although this fell short of explaining the 70% average false alarm rate in preferences. Even with apparently discriminable consumer products, accurate discrimination of the samples and repeatability of preferences should not be assumed. Random responding may contribute to error variance and produce nonsensical results such as the expression of choice between identical samples.     

Recycle hollow fiber enzyme reactor with flow swing

The hollow fiber enzyme reactor with pulsation developed by Kim and Chang (1983) was operated in a differential mode by recycling a substrate solution, in order to assess the efficiency of ultrafiltration swing. The rates of lactose conversion by beta-galactosidase contained in the shell side of the reactor were measured to determine the effects of recirculation rate, pulsation period, and amplitude. The conversion increased with the increase of recirculation flow rate and the amplitude while variation in period affected the conversion relatively little. The maximum increase of 113% in the activity was observed in the reactor with pulsation as compared to that without pulsation. The two-compartment model well described the experimental data obtained in this study. Square-wave pulsation was theoretically more effective in increasing conversion than sine wave pulsation. However, in experimental operation the damping effect of the hollow fiber wall narrowed the difference between these two wave forms.     

Development of a novel stall design for dairy cattle: Part II. The effect of minimal stall partitioning on lying behavior,rumination, stall cleanliness,and preference

Free-stalls for dairy cows promote cleanliness, provide cows with a defined space to lie down, and decrease labor and bedding required for maintenance. However, current stall features can restrict behavior and reduce stall use. The objective of this study was to assess the short-term effect of a novel free-stall design (flexible single-bar partition, no neck rail, increased slope) on stall cleanliness and the lying behavior, rumination, milk production, and preferences of dairy cows in comparison to standard free-stalls (metal loop partitions, neck rail). In the first experiment, 60 Holstein cows were randomly divided into two groups and switched between standard and novel stalls in a replicated crossover design with four 7-day periods. Lying behavior and rumination were recorded continuously. Milk yields were recorded 2x/day, and stall cleanliness scores were collected on the last four days of weeks 3 and 4. The second experiment was a 6-day preference test where 14 cows from experiment 1 were given free access to 16 standard and 16 novel stalls. Lying behavior was recorded continuously. On day 6, standing, perching, and intention, lying, and rising movements were recorded. In experiment 1, cows spent 12 min less time lying down (14.1 vs 14.3 ± 0.48 h/d), had one fewer lying bouts (8.8 vs 9.8 ± 0.23 bouts/d), and had longer lying bouts by 6 min (1.4 vs 1.5 ± 0.05 h/bout) in novel stalls. Rumination time (547.3 vs 548.9 ± 4.66 min/d) and milk yield (35.0 vs 35.2 ± 0.51 kg/d) did not differ between stall types. However, novel stalls were more than twice as soiled as standard stalls (32.8 vs 14.2 ± 1.38% of rear half soiled). In experiment 2, the cows most recently housed in the novel stalls showed a clear preference for lying down in those stalls, whereas cows most recently housed in standard stalls showed no preference. Intention and lying down movements were longer in standard stalls when other cows were present in diagonally opposite stalls, but were similar between stall types when not occupied. All cows preferred standing in novel stalls. Novel stalls may have improved stall use compared to standard free-stalls, and the design requires further development to address cleanliness concerns. Future work is required to provide comfortable stalls without sacrificing cleanliness.     

A comparison of two methods for assessing critical flicker fusion frequency in hens

This paper compared two general methods for assessing critical fusion frequency in hens (gallus gallus domesticus). The first method was a conditional discrimination procedure with the stimuli presented successively. The second was a two-alternative forced-choice procedure with the stimuli presented simultaneously. It was found that both methods of stimulus presentation gave comparable results suggesting that either method is useful when investigating psychophysics in animals. The results also show that hens’ critical fusion frequency is considerably higher than that of humans which may account for hens’ inability to recognise images presented on standard computer or television monitors.     

Effect of mating stimuli on LH release in bulls

Fourteen crossbred beef bulls were assigned at random to receive one of four sexual stimuli treatments. Treatments consisted of: (1) controls (four bulls), no visual or physical contact with any cows; (2) false mount (two bulls), allowed to mount an estrual cow; (3) mated (four bulls), allowed to mount an estrual cow with intromission and ejaculation; (4) electroejaculated (four bulls), no exposure to cows. Serum from blood samples taken at 15-min intervals from -15 min to 2 hr from sexual stimuli were radioimmunoassayed for luteinizing hormone (LH). Four bulls had elevated levels at the pretreatment bleeding, but none of the stimuli induced or were associated with LH releases. Basal levels of LH were consistent within bulls but varied considerably among bulls. Conclusion is that stimuli associated with mating do not cause a release of LH.     

Spontaneous behaviour,training and discrimination training in goldfish using chemosensory stimuli

The present behavioural experimental paradigm made use of the responsiveness of goldfish to natural and non-familiar chemosensory stimuli in the context of feeding. With the exception of Tubifex food extract, which was spontaneously preferred, goldfish exhibited no spontaneously recordable response to low concentrations of the stimuli tested. Training experiments using non-familiar stimuli (amyl acetate, -ionone, -phenylethanol, 10^-6, 10^-7 M) required 2–3 months of daily training prior to the animals reaching a 70% positive response level for discrimination. This discrimination was dependent upon a functioning olfactory system as no responses were recorded after bilateral exclusion of olfaction, e.g. dissection of olfactory nerve or olfactory tracts. Amino acids (Ala, Arg, Gln, Gly, Lys), more natural stimuli than those listed above, were preferred when applied at concentrations < 10^-5 M. Goldfish were able to discriminate amino acid odours applied at 10^-6 or 10^-7 M, but these stimuli elicited no spontaneous response below 10^-5 M. Ten to twenty reinforcements were sufficient to achieve discrimination between amino acids, which again was eliminated after bilateral exclusion of olfactory pathways. In contrast to the 4-week period for long-term memory to non-familiar odours, long-term memory for amino acids lasted at least 3 months.Abbreviations FB funnel biting - FO funnel orientation     

Consistency of side choice in the milking parlour by Holstein-Friesian cows and its relationship with their reactivity and milk yield

Dairy cows often have to choose which of two sides to enter in the milking parlour. Some cows are very consistent in this choice, and it is common to assume that when these cows are more disturbed are being milked in their non-preferred side. Such disturbance might involve significantly poor welfare. In order to assess this assumption, we decided to study the behaviour and milk yield of dairy cows and their relationships with side preference in the milking parlour. The study was carried out at Cambridge University Farm, in a two-sided tandem milking parlour. The data collection followed the daily management routine. We recorded the side chosen by each cow (left or right) during 40 milking sessions. Data from 70 cows, which were present in at least 25 milking sessions (mode=36), were included in the statistical analysis. Cows' reactivity (CR) during premilking udder preparation, time spent fitting the milking cluster (FT), milk yield (MY) and duration of milking (DM) were measured. There was evident individual variation in the consistency of side choice. Individual differences (ANOVA, P<0.001) were also found in CR, FT, MY and DM; although these variables were not significantly affected by the side or the interaction animalxside (ANOVA, P>0.05). The comparison between left and right side means (paired t-test) of these variables did not show significant differences (P>0.05). We concluded that there is no evidence that the cows were discomforted or stressed when milked in the non-preferred side of the milking parlour.     

Female mate recognition and sexual isolation depending on courtship song in Drosophila sechellia and its siblings

In Drosophila sechellia, females accept males that sing heterospecific songs less than those that do not sing, whereas in D. melanogaster and D. simulans, females accept males that sing heterospecific song more than those that do not sing. Here we studied the sexual isolation of D. sechellia and its siblings using interspecific hybrids to reveal the mechanisms underlying female mate recognition. The females of hybrids mated more with winged males of the parent species than with wingless ones, suggesting that the discrimination against heterospecific songs by D. sechellia females is recessive. Female preference for courtship songs seems to be inherited additively or semidominantly. In addition, we examined female receptivity without the stimuli of courtship songs by comparing the mating frequencies between the crosses using wingless males and found that it is also inherited additively or semidominantly.     

Reliability criteria of a bioassay using rats trained to detect estrus-specific odor in cow urine

An odor discrimination apparatus was used to quantify the reaction of rats against odor differences of estrous and diestrous urine of cows. Rats were trained to release impulses from a microswitch when they came into contact with estrous but not diestrous urine. After training, the discrimination ability was highly significant (P≤ 0.001) between both urine types. The reaction was specific for cow urine, and no significant discrimination occurred for estrous and diestrous urine from pigs or goats, or that of women. The discrimination of urine diluted with water was still highly significant up to 1:25. Another group of rats was trained to detect camphor. Decreasing concentrations were detected down to 0.1/ug/ml when diluted in water, and down to 1/ug/ml when diluted in estrous urine. Once trained to discriminate between estrous and diestrous urine, rats maintained this ability for 12 mo. Thus, a bioassay was set up to accompany fractionation steps in the laboratory which could lead to the isolation of estrous pheromones in cow urine.