Inexperienced Animals Research Articles

Changes in the blood redox status of horses subjected to combat training

Combat training of police horses, involving physical activity in the presence of environmental stressors, poses a risk of oxidative stress. This study compared the oxidative imbalance after combat training in horses in the regular police service and in horses that had just been schooled. Blood collection was performed immediately after training and after 16 h rest. The activity of superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT), and total antioxidant status (TAS) were determined as the markers of enzymatic antioxidant defence. At the same time, lipid peroxidation (TBARS) and protein carbonylation (Carb) were assessed as oxidation biomarkers. Additionally, oxidative imbalance indexes such as SOD/CAT, SOD/GPx, TBARS/TAS and TBARS/GPx were calculated. Animals during schooling had significantly lower SOD activity in erythrocytes than those experienced. CAT activity in erythrocytes was insignificantly higher immediately after training than during recovery. The SOD/GPx ratio was higher in experienced animals, which may reflect the intra-erythrocyte imbalance between enzymes producing and degrading hydrogen peroxide towards the first one. The concentration of carbonyl groups was significantly higher after the combat training compared to the recovery period in all horses. In inexperienced animals slight increase in TBARS/TAS and TBARS/GPx indexes were observed during the recovery time after exercises, contrary to experienced horses, in which these markers decreased slightly. These results suggest that the oxidative imbalance in inexperienced horses, although less pronounced just after combat training, was more prolonged as compared to horses in regular service.

Dairy buffalo behaviour and welfare from calving to milking.

Abstract This review integrates recent scientific findings on the behaviour and welfare of buffalo dams during calving and the subsequent milking phase. These issues are discussed in relation to the level of welfare that buffalo dams and calves experience under different production systems. Key aspects are addressed including welfare issues related to dystocic parturitions and uterine prolapses, the formation of a selective dam-calf bonding, the habituation of inexperienced animals to the milking routine and the appropriate relationship to be developed with stock-people. All these aspects are also discussed in relation to farm profitability, in terms of calf vitality and milk production, and safety of the personnel involved in farm operations.

Concentration‐dependent chemosensory responses towards pheromones are influenced by receiver attributes in Asian elephants

AbstractThe physical structure of a signal is not sufficient to determine its meaning. For chemical signals between conspecifics, this concept is termed “pheromonal parsimony.” The function of a compound depends not only on its molecular structure but also on its context, which can include signal concentration and various receiver attributes. We sought to investigate the contextual flexibility of chemosensory responses through bioassays with Asian elephant (Elephas maximus) sex pheromones of various concentrations (frontalin, from males, and (Z)‐7‐dodecenyl acetate [Z7‐12:Ac], from females). We hypothesized that elephants would respond stronger to higher concentrations, especially towards the opposite‐sex pheromone, and that receiver age and sexual experience would modify responses. We examined responses of 73 captive elephants to both compounds. Pheromone concentration impacted the rate of chemosensory response, which was further modified by the sex, age and/or sexual experience of the receiver. Response rates increased with concentration for each compound across both sexes. Experience shaped male responses with older, physiologically primed males responding more often. The interaction between experience and age affected female response to frontalin, but not to Z7‐12:Ac. Furthermore, response thresholds were modified by sexual experience in most cases: experienced animals generally had lower thresholds than inexperienced animals. Elephants responded to each solution according to its perceived relevance, including concentration. These results also indicate that receiver attributes (e.g., sex, age and sexual experience) may modify seemingly fixed chemosensory responses and further emphasize the flexibility of vertebrate communication systems.

Effects of early experience and alternative feeds on medusahead (Taeniatherum caput-medusae ssp. asperum) intake by sheep

The goals of this study were to test the effects of early experience at grazing medusahead – an invasive unpalatable weed – and the availability of forage alternatives on intake of medusahead later in life by sheep. The study involved two experiments of 10 days each. During Experiment 1, 29 yearling sheep were penned individually in a 2×2 factorial design with early experience at grazing medusahead (yes [n=15], no [n=14]) and alfalfa hay availability (yes, no) as the main factors. All animals were fed ad libitum amounts of freshly harvested medusahead daily from 10:00 to 13:00h; additionally, eight experienced and seven inexperienced sheep received alfalfa hay (0.31% body weight) at the same time. All groups had a basal diet of tall fescue hay. Intake of the forages, NaCl and trace-mineralized salt blocks was measured. In Experiment 2, sheep were then clustered into nine groups of three yearlings each (n=5 early experience; n=4 experience gained during Experiment 1) and one group of two yearlings (experience gained during Experiment 1) and grazed 10 plots of medusahead-infested rangeland. Grazing events were recorded daily at 5min intervals from 08:30 to 11:00h and from 16:00 to 17:00h, and the defoliation proportion of medusahead tillers was determined every five days. During Experiment 1, medusahead intake was not affected by early experience or alfalfa availability (P>0.05) but medusahead intake across days was cyclic with more pronounced intake peaks at the beginning and end of the experiment for inexperienced animals (P<0.05). Experienced sheep showed a greater gain-to-feed ratio (P<0.05), and tended to have greater average daily body weight gains and salt intake (P<0.10) than inexperienced sheep. Sheep fed alfalfa tended to eat less trace-mineralized salt blocks than sheep that did not receive this forage (P<0.10). During Experiment 2, the proportion of grazing events recorded on medusahead by both groups (yes/no early experience) of animals was almost nil, although experienced animals tended to defoliate more medusahead tillers than inexperienced animals (P=0.10). In conclusion, when sheep were fed ad libitum amounts of medusahead, intake was low and cyclic with a more even consumption of the weed by experienced animals. Under these conditions, early experience also favored animal performance. However, it is likely that such high exposure to medusahead attenuated the subsequent use of the weed during grazing.

Role of cAMP signalling in winner and loser effects in crayfish agonistic encounters.

For territorial animals, establishment of status-dependent dominance order is essential to maintain social stability. In agonistic encounters of the crayfish Procambarus clarkii, a difference of body length of 3-7% is enough for larger animals to become dominant. Despite a physical disadvantage, small winners of the first pairings were more likely to win subsequent conflicts with larger inexperienced animals. In contrast, the losers of the first pairings rarely won subsequent conflicts with smaller naive animals. Such experiences of previous winning or losing affected agonistic outcomes for a long period. The winner effects lasted more than 2weeks and the loser effect lasted about 10days. Injection of 5HT1 receptor antagonist into the dominant animals 15-30min after establishment of dominance order blocked the formation of the winner effects. In contrast, injection of adrenergic-like octopamine receptor antagonist into subordinate animals blocked the formation of the loser. 5HT1 receptors are negatively coupled to adenylyl cyclase and adrenergic-like octopamine receptors are positively coupled. Consistent with this, dominant animals failed to show the winner effect when injected with pCPT-cAMP, a cAMP analogue, and subordinate animals failed to show a loser effect when injected with adenylyl cyclase inhibitor SQ 22536. These results suggest that an increase and decrease of cAMP concentration is essential in mediating loser and winner effects, respectively. Furthermore, formation of the loser effect was blocked by injection of protein kinase A (PKA) inhibitor H89, suggesting long-term memory of the loser effect is dependent on the cAMP-PKA signalling pathway.

Juvenile crab spiders (Mecaphesa asperata) use indirect cues to choose foraging sites

Direct assessment of food resources may be unreliable if those resources fluctuate or are not easily detected. Foragers under such conditions may instead use indirect cues to assess the quality of potential foraging sites. Young individuals may be particularly likely to use indirect cues to compensate for their inexperience and to reduce assessment costs. We investigated the cues juvenile crab spiders (Mecaphesa asperata) use when selecting foraging sites. First, we examined whether spiderlings' site preference was influenced by prey abundance, a direct cue of site quality. We next investigated whether juvenile crab spiders assessed potential sites using indirect cues, including flower quality, cues left by conspecifics, or conspecifics themselves. We found spiderlings did not use prey abundance to assess foraging sites, but instead used indirect cues when choosing where to forage. Spiderlings preferred sites that would attract larger numbers of their arthropod prey, choosing blooming inflorescences over both senescing inflorescences and inflorescences with buds. Hungry spiderlings, unlike individuals that had recently fed, also used cues left by conspecifics, preferring sites on which a conspecific had previously foraged. Finally, spiderlings avoided sites with larger numbers of conspecifics, but were attracted to sites with relatively low abundances of conspecifics, indicating that spiderlings are able to weigh the possibility of improving their foraging success by joining conspecifics against the potential costs of being in larger groups. We show here that young, relatively inexperienced animals do not always directly assess prey abundance when choosing foraging sites, but that these individuals are capable of detecting and using a variety of indirect cues to evaluate foraging site quality.

Alloparenting experience affects future parental behavior and reproductive success in prairie voles (Microtus ochrogaster).

Various hypotheses have been proposed to explain the function of alloparental behavior in cooperatively breeding species. We examined whether alloparental experience as juveniles enhanced later parental care and reproductive success in the prairie vole (Microtus ochrogaster), a cooperatively breeding rodent. Juveniles cared for one litter of siblings (1EX), two litters of siblings (2EX) or no siblings (0EX). As adults, these individuals were mated to other 0EX, 1EX or 2EX voles, yielding seven different pair combinations, and we recorded measures of parental behaviors, reproductive success, and pup development. As juveniles, individuals caring for siblings for the first time were more alloparental; and as adults, 0EX females paired with 0EX males spent more time in the nest with their pups. Taken together, these results suggest that inexperienced animals spend more time in infant care. As parents, 1EX males spent more time licking their pups than 2EX and 0EX males. Pups with either a 1EX or 2EX parent gained weight faster than pups with 0EX parents during certain developmental periods. While inexperienced animals may spend more time in pup care, long-term benefits of alloparenting may become apparent in the display of certain, particularly important parental behaviors such as licking pups, and in faster weight gain of offspring.

The effects of group size, rate of turnover and disruption to demonstration on the stability of foraging traditions in fish

There is considerable laboratory-based evidence that social learning plays a role in the behaviour of many animals, including fish. However, a weakness of such studies in fish, is that in virtually all to date, the behaviour showed could be learned asocially, with the social influence merely accelerating the rate of learning. Lefebvre & Palameta (1988. Social Learning: Psychological and Biological Perspectives. pp. 141–164) argued that the most compelling evidence for social learning comes from studies where inexperienced animals are unlikely to learn the target behaviour by themselves. The present study is designed to address this concern, by employing a feeding tube task in which fish gain access to food by swimming in a manner that they would not normally show. Employing a transmission chain design, we show foraging traditions in guppies, Poecilia reticulata, and southern platyfish, Xiphophorus maculatus, in which shoal members continue to exploit the food available in the feeding tube, in spite of changes in the composition of the shoal due to the gradual removal of demonstrators. Two experiments provide strong evidence for social learning underlying traditional behaviour, such as migratory routes, in fish, and reveal how the stability of such traditions (duration within a population) is affected by group size (2, 4 or 6 fish) and rate of turnover (16.5%, 25% or 50% per day). While larger shoals of fish showed more stable traditions than smaller shoals, this was found to be related to their slower rate of turnover rather than a direct effect of group size.

PATHOLOGICAL FEATURES IN MARINE BIRDS AFFECTED BY THE PRESTIGE'S OIL SPILL IN THE NORTH OF SPAIN

A total of 2,465 seabirds, mainly common murres (Uria aalge), razorbills (Alca torda), and puffins (Fratercula arctica) that beached in the northwestern part of Spain after the "Prestige" oil spill on 19 November 2002 were examined by pathological methods. Birds were divided into three groups: dead birds with the body covered (group 1) or uncovered (group 2) by oil and birds recovered alive but which died after being treated at a rescue center (group 3). The main gross lesions were severe dehydration and emaciation. Microscopically, hemosiderin deposits, related to cachexia and/or hemolytic anemia, were observed in those birds harboring oil in the intestine. Severe aspergillosis and ulcers in the ventriculus were found only in group 3 birds, probably because of stress associated with attempted rehabilitation at the rescue center. The mild character of the pathological changes suggests that petroleum oil toxicosis causes multiple sublethal changes that have an effect on the ability of the birds to survive at sea, especially weak and young, inexperienced animals. Dehydration and exhaustion seem to be the most likely cause of death.

Responses to conspecific scent marks and the ontogeny of territorial marking in immature terrestrial salamanders

We investigated the ontogeny of responses to scent marks in immature terrestrial salamanders (Salamandra lanzai) that inhabit the southwest Alps. In this species, sexual maturity is usually reached at about 8 years, and adults exhibit territoriality. One should expect territoriality to take place largely before the acquisition of sexual maturity if sexual competition is not the main force driving territoriality. However, both the difficulties for inexperienced animals to find a suitable territory and size-related competition may delay the acquisition of territoriality in juveniles. We performed choice tests with juveniles belonging to two age groups (1±1 years old versus 4±1 years old). Each focal animal was offered, in random order, the choice between two shelters, one without scent and the other containing one of the following scents: own, same-aged animal, a juvenile belonging to the other age group, or adult female. We also performed choice tests with adult females for which the scents of two juveniles belonging to a different age group were successively offered in a random order. Older juveniles were strongly attracted toward their own shelter and mostly avoided the shelters that contained the scent of juveniles of about the same age and of adult females. Adult females avoided the scents of older juveniles but not younger juveniles. These results therefore suggest that older juveniles use territorial marking. Conversely, young juveniles behaved randomly with respect to their own scents and to those of a same-aged juvenile, and they were significantly attracted towards the odor of an older animal, especially adult females. Both older juveniles and adult females displayed a random behavior toward the scents of young juveniles. Our results suggest that young juveniles do not defend territories but use spaces occupied by older individuals.

Can information about solid food be transmitted from one piglet to another?

AbstractWhen weaned early, piglets commonly take some time to accept solid food, resulting in a growth check and reduced welfare. The transmission of information about food between animals has been demonstrated in other species and it would be advantageous if this occurred in piglets. This experiment investigated the effects of pairing piglets that were consuming solid food with newly weaned piglets. Six litters of piglets did not receive solid food until weaning. In each litter four piglets (3 plus 1 spare) were weaned at 21 days of age and housed together for 7 days and offered one of two foods (3 litters per food). At 28 days of age the remaining piglets were weaned and four pairs of piglets were formed, such that there were three experienced animals paired with three inexperienced observers, each pair having visual contact and varying degrees of physical contact (1: none, 2: through wire mesh, 3: housed together), and a pair of inexperienced piglets (4: housed together) to act as controls. Food intake and weight gain were recorded over a period of 7 days. There was no effect of food type on food intake or live-weight gain of the pairs but the inexperienced pigs had higher gains on food 1 than food 2. The inexperienced pairs ate less food than the other pairs and the experienced/observer pairs that were housed together had the greatest weight gain. The level of variation between piglets was such that there were no significant effects of pairing treatment on the weight gain of the inexperienced animals. Total time spent feeding increased with time from pair formation. The number of simultaneous feeding events was higher for the experienced/observer pairs housed together than for the inexperienced pairs. This experiment has indicated that food intake is stimulated when an inexperienced piglet is housed with an experienced piglet and, with further work, this could be exploited to alleviate the weaning check.

Food intake and performance of newly-weaned pigs: effect of pairing with an experienced pig

In intensive pig production systems piglets are weaned at between 21 and 28 days of age and it is common for piglets to take a few days to discover and accept solid food as a source of nutrients and this results in a loss of weight (the weaning growth lag). Therefore, if a means could be found to encourage the acceptance of solid food by piglets, benefits in terms of their growth and welfare would ensue. The transmission of information about foods from one animal to another has been demonstrated in the rat (Galef, 1993) and ruminants (Provenza and Balph, 1987) but there have been no studies with pigs at the time of weaning. Therefore, piglets were tested in pairs of experienced and inexperienced animals, with varying degrees of contact, with constant access to food over a period of seven days after weaning of the inexperienced animals.

Vomeronasal, olfactory, hormonal convergence in the brain. Cooperation or coincidence?

This paper briefly reviews three topics: (a) Convergent vomeronasal and olfactory chemosensory input into a common circuit considered important for mating in male golden hamsters; (b) Apparent activation of this circuit by intracerebral luteinizing hormone-releasing hormone (LHRH) and (c) Interaction of the LHRH and the two chemosensory inputs. Mapping of c-fos protein in male hamsters mating with females or exposed to female pheromones indicates intense activation in the central vomeronasal pathways, induced by both olfactory and vomeronasal input. This input appears to activate the medial preoptic area, where chemosensory activation is greater in experienced than in inexperienced animals. Intracerebral injection of LHRH facilitates mating behavior and increases Fos expression in the medial preoptic area of mating males. Despite evidence that the release of LHRH in response to female chemosignals is dependent on vomeronasal input, no activation of LHRH neurons has been demonstrated in males exposed to such chemosignals. Electrical stimulation of the vomeronasal organ can induce Fos expression in chemosensory pathways and in medial preoptic LHRH neurons.

On the nature of mammalian and human pheromones.

Communication by chemical (pheromone) signals is important in many species, including mammals. Chemosensory and hormonal systems can interact in at least two ways: (i) chemosensory input, especially but not exclusively that through the vomeronasal organ, may elicit hormonal release, which, in turn, may facilitate behavioral or physiological responses; and (ii) hormones, especially steroids, may be essential for some responses to chemosensory, including vomeronasal, input. Recent, still controversial reports, suggest that chemosensory communication may occur in humans via a residual vomeronasal organ and that chemosensory/hormonal interactions also operate in humans. In this symposium these matters are examined critically. Johnston explores the concept of pheromone communication and suggests that the notion of a single-chemical 'magic bullet' irresistibly leading to a preprogrammed result is too simplistic despite documented examples of special stimuli acting via the vomeronasal organ. Meredith briefly reviews evidence for hormonal mediation of the effects of vomeronasal input; including a situation where vomeronasal and hormonal facilitation of a behavior appear to be interchangeable--but where vomeronasal input appears important only in inexperienced animals. Wood discusses evidence that the effectiveness of chemosensory input to particular brain nuclei depends critically on the simultaneous presence of a steroid hormone within the same nucleus. Monti-Bloch presents his evidence that steroids may act as gender-specific chemical signals in humans, exciting an electrical response from the residual human vomeronasal organ and affecting human hormone levels.

Vocalisations between mother and young in sheep: effects of breed and maternal experience

This experiment was designed to investigate the function of vocalisations of the parturient ewe to her lambs in two breeds of sheep, a highly selected lowland breed (Suffolk), and a less selected hill breed (Scottish Blackface). Sheep have a specific lambing vocalisation, the low-pitched bleat or "rumble", that is made almost exclusively to the lamb. The hypothesis was that this "care-giver" bleat will be important in the formation of the ewe-lamb bond. Ewes also make high-pitched bleats, considered to be "protest" or distress bleats, after the birth of the lamb. Vocalisation data were collected from inexperienced and experienced ewes of both breeds, and their lambs. Additionally, an embryo transfer study between the two breeds was carried out to investigate interactions between ewe and lamb bleating. Low-pitched bleating was higher in primiparous ewes than multiparous ewes, and highest in primiparous Blackface ewes (mean bleat rate: primiparous Blackface=7.04, multiparous Blackface=2.73, primiparous Suffolk=3.99, multiparous Suffolk=2.18; P<0.005). An increase in litter size, or raising lambs of a different breed, had no effect on the rate of low-pitched bleating. The number of Suffolk ewes making high-pitched bleats was greater than Blackface ewes (61.4% vs. 35% for Suffolk and Blackface ewes respectively, P<0.01) and the rate of bleating increased with twin litters. Suffolk lambs had a higher bleat rate than Blackface lambs (mean bleat rate: Blackface=0.252, Suffolk=0.622, P<0.01), and lambs born to a primiparous ewe had a higher bleat rate than lambs with a multiparous dam (P<0.05). Birth of the second twin lamb caused a doubling in individual lamb bleat rate in both breeds. Ewe low-pitched bleat rate is, therefore, affected by intrinsic factors, ewe breed and experience, but not by characteristics of the lamb in the immediate postnatal period. The function of the bleat may be to strengthen bonding with the lamb, and the higher rate in primiparous ewes may reflect both the immaturity of the system in inexperienced animals and a slower rate of bond formation. High-pitched bleating is affected by ewe breed and may reflect the likelihood of separation of the ewe from the lamb. Lamb vocalisations are modified by their rearing experience, and appear to represent a signal of need. Increased domestication of the Suffolk breed may have led to an increase in lamb vocalisations.

Reproductive Performance of Female Antarctic Fur Seals: The Influence of Age, Breeding Experience, Environmental Variation and Individual Quality

1. The reproductive performance of female Antarctic fur seals was examined in relation to age, reproductive experience and environmental variation over 10 consecutive years (1983-92) at Bird Island, South Georgia. 2. The age at which females first gave birth varied from 3 to 6 years; over 90% of these females were 3 or 4 years of age. We found no evidence to suggest that age at primiparity had significant effects on subsequent reproduction; however, 3-year-old primiparae were less likely to be seen in subsequent years than 4-year-old primparae which may indicate a cost, in terms of survival, for females that first give birth at an early age. 3. Age-specific reproductive rates increased rapidly from ages 2 to 6 years, reached a peak of 0.80 at 7-9 years, remained above 0.75 until 11 years and then began to decline with increasing age. 4. The mean duration of foraging trips in the current year (which was used as a measure of the availability of food resources) consistently improved models of the likelihood of pupping and of weaning success. When these trips were long (indicating reduced local food resources), females returned to the breeding beaches later, fewer females pupped, they gave birth to lighter pups and weaning success was reduced. 5. The reproductive performance of older, experienced Antarctic fur seals was greater than that of younger, inexperienced animals because they had higher natality rates, gave birth to heavier pups earlier in the season, had greater weaning success and were more likely to pup the next season.

Vomeronasal system, LHRH, and sex behaviour

Vomeronasal chemosensory input is important for male hamster mating behavior, especially in inexperienced animals. Experiments reviewed here showed that intracerebroventricular injection of luteinizing hormone-releasing hormone (LHRH) substantially restores mating behavior impaired by removal of vomeronasal organs in inexperienced hamsters. An analogue molecule Ac 5–10LHRH, which fails to release luteinizing hormone (LH) from the pituitary, has similar behavioural effects. These findings are consistent with the idea that vomeronasal sensory input may trigger intracerebral release of LHRH which then facilitates mating behaviour. Immunocytochemistry for the immediate-early gene-product Fos, used as an indicator of regional brain activation, indicates a selective activation of central vomeronasal pathways during mating behaviour. Chemosensory and other sensory inputs contribute to activation in medial amygdala and bed-nucleus of stria terminalis, but medial preoptic/anterior hypothalamic area activation appears more closely tied to mating behavior itself. Any of these areas may be sites of interaction between vomeronasal chemosensory input and LHRH-containing cells and fibers.

Male Sexual Behaviour: Further Studies on the Role of Alpha 2-Adrenoceptors

The role of central alpha 2-adrenoceptors in male sexual behaviour was investigated by administering the selective agonist, guanabenz, and the selective antagonist, efaroxan, to both sexually experienced and sexually inexperienced male rats. In sexually experienced animals, guanabenz, at the dose of 1 mg/kg i.p., increased mount and intromission latencies (ML, IL), intercopulatory interval (ICI) and post-ejaculation interval (PEI), and reduced mount and intromission frequencies (MF, IF) and copulatory efficacy (CE). Efaroxan, at the dose of 10 mg/kg i.p, reduced ML and IL. In sexually inexperienced animals, guanabenz, at the dose of 1 mg/kg i.p., slightly reduced the percent of animals achieving ejaculation and increased PEI. Efaroxan, either at the dose of 3 or 10 mg/kg i.p., increased the percent of animals achieving ejaculation and—only at the dose of 10 mg/kg i.p.—reduced EL. Finally, in sexually experienced animals, efaroxan (10 mg/kg i.p.) prevented the effect of guanabenz (1 mg/kg i.p.). On the whole, these data further indicate that, in rats, male sexual behaviour is positively modulated by brain noradrenergic systems.

Reverse-Hebb plasticity leads to optimization and association in a simulated visual cortex

The effects of a variable-phase synaptic modification rule on the experience-dependent development of a simulated visual cortex were investigated. Of interest were the process of optimization of the internal representation with respect to orientation, through which the weakly tuned neurons of visually inexperienced animals attain their tightly tuned adult characteristics, and the process of association by which identical stimuli presented to either eye come to evoke identical cortical representations. In its general form, the synaptic modification rule was Hebbian. However, it was not assumed that positive correlation of presynaptic and postsynaptic activity would lead to an increase in synaptic weight. The relative phase of presynaptic vs. postsynapatic activity that would effect an increase in synaptic weight was a parameter of the modification rule. When this parameter was zero, synaptic modification conformed to the standard Hebbian type. With a value of 180 deg, or the reverse-Hebb condition, negative correlation between presynaptic and postsynaptic activity led to increased synaptic weight. It was found that a synaptic modification rule of the reverse-Hebb type not only optimized the cortical representation, and associated the representations from the two eyes, but was quite stable with respect to retaining the optimized state for long periods of learning.

The influence of auditory and visual experience on the phonotactic behavior of the cricket,Gryllus bimaculatus

Female crickets lacking experience with phonotaxis to conspecific calling song respond to trains of continuously repeated sound pulses (trill), whereas experienced females do not. In the present study such inexperienced crickets were tested for their responsiveness to trills of pulse repetition periods from 30 to 70 ms on a Y- shaped maze. Stimulation with a repetition period of 30 ms led to unexpectedly low phonotactic and exploratory activity. Initial stimulation with trills of 30- ms repetition period drastically reduced the responsiveness of inexperienced animals to conspecific calling song and other attractive stimuli. Effects of visual stimulation on the phonotactic behavior of female crickets are demonstrated. Threatening visual stimuli changed the behavior of experienced animals to a state that resembles that of inexperienced animals. The relevance of these observations is discussed with respect to the development of the auditory pattern recognition mechanism in crickets.