Recent neurobiological studies have begun to reveal the cognitive and neural coding mechanisms that underlie declarative memory--our ability to recollect everyday events and factual knowledge. These studies indicate that the critical circuitry involves bidirectional connections between the neocortex, the parahippocampal region and the hippocampus. Each of these areas makes a unique contribution to memory processing. Widespread high-order neocortical areas provide dedicated processors for perceptual, motor or cognitive information that is influenced by other components of the system. The parahippocampal region mediates convergence of this information and extends the persistence of neocortical memory representations. The hippocampus encodes the sequences of places and events that compose episodic memories, and links them together through their common elements. Here I describe how these mechanisms work together to create and re-create fully networked representations of previous experiences and knowledge about the world.

A cortical–hippocampal system for declarative memory

The cAMP responsive element binding protein (CREB) is a nuclear protein that modulates the transcription of genes with cAMP responsive elements in their promoters. Increases in the concentration of either calcium or cAMP can trigger the phosphorylation and activation of CREB. This transcription factor is a component of intracellular signaling events that regulate a wide range of biological functions, from spermatogenesis to circadian rhythms and memory. Here we review the key features of CREB-dependent transcription, as well as the involvement of CREB in memory formation. Evidence from Aplysia, Drosophila, mice, and rats shows that CREB-dependent transcription is required for the cellular events underlying long-term but not short-term memory. While the work in Aplysia and Drosophila only involved CREB function in very simple forms of conditioning, genetic and pharmacological studies in mice and rats demonstrate that CREB is required for a variety of complex forms of memory, including spatial and social learning, thus indicating that CREB may be a universal modulator of processes required for memory formation.

Creb and memory

It is well documented that animals take risk of predation into account when making decisions about how to behave in particular situations, often trading-off risk against opportunities for mating or acquiring energy. Such an ability implies that animals have reliable information about the risk of predation at a given place and time. Chemosensory cues are an important source of such information. They reliably reveal the presence of predators (or their presence in the immediate past) and may also provide information on predator activity level and diet. In certain circumstances (e.g., in the dark, for animals in hiding) they may be the only cues available. Although a vast literature exists on the responses of prey to predator chemosensory cues (or odours), these studies are widely scattered, from marine biology to biological control, and not well known or appreciated by behavioural ecologists. In this paper, we provide an exhaustive review of this literature, primarily in tabular form. We highlight so...

The scent of death: Chemosensory assessment of predation risk by prey animals

Biochar has been heralded as an amendment to revitalize degraded soils, improve soil carbon sequestration, increase agronomic productivity, and enter into future carbon trading markets. However, scientific and economic technicalties may limit the ability of biochar to consistently deliver on these expectations. Past research has demonstrated that biochar is part of the black carbon continuum with variable properties due to the net result of production (e.g., feedstock and pyrolysis conditions) and postproduction factors (storage or activation). Therefore, biochar is not a single entity but rather spans a wide range of black carbon forms. Biochar is black carbon, but not all black carbon is biochar. Agronomic benefits arising from biochar additions to degraded soils have been emphasized, but negligible and negative agronomic effects have also been reported. Fifty percent of the reviewed studies reported yield increases after black carbon or biochar additions, with the remainder of the studies reporting alarming decreases to no significant differences. Hardwood biochar (black carbon) produced by traditional methods (kilns or soil pits) possessed the most consistent yield increases when added to soils. The universality of this conclusion requires further evaluation due to the highly skewed feedstock preferences within existing studies. With global population expanding while the amount of arable land remains limited, restoring soil quality to nonproductive soils could be key to meeting future global food production, food security, and energy supplies; biochar may play a role in this endeavor. Biochar economics are often marginally viable and are tightly tied to the assumed duration of agronomic benefits. Further research is needed to determine the conditions under which biochar can provide economic and agronomic benefits and to elucidate the fundamental mechanisms responsible for these benefits.

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Biochar: a synthesis of its agronomic impact beyond carbon sequestration.

The effects of predator odors in mammalian prey species: A review of field and laboratory studies

http://static1.1.sqspcdn.com/static/f/1329369/17269716/1332457576517/phys++behav+42+119-124.pdf?token=myfVCsea24Lz6P4n3C8QQhcDzKE%3D

Carbon Disulfide: A Semiochemical Mediating Socially-Induced Diet Choice in Rats

-Recent work has demonstrated that Red-winged Blackbirds (Agelaius phoeniceus) display food preferences as a result of observational leaming. Also, individual birds learn to avoid food the ingestion of which has been paired with sickness. Such preferences or aversions depend on visual cues associated with the food. A related but unanswered question is whether observational leaming is sufficient for birds to associate visual cues with sickness. In the present experiments, Red-wings observed a conspecific consume a food paired with a color cue (CS) and toxin-induced illness (UCS). The observers were subsequently given two-choice preference tests between a food (either the food consumed by the gavaged bird or another food) paired with the CS or with another color. The birds avoided consumption of any food paired with the CS (but not of the other color) during all tests. Such results are consistent with the notion that opportunistic foragers, such as Redwings, readily learn to avoid conspicuous foods paired with aversive consequences. Moreover, the results support the notion that Batesian model-mimic systems could be maintained, at least in part, by observational learning of models and subsequent generalization of that learning to mimics. Observational learning could provide an efficient strategy to protect against the ingestion of potentially dangerous food. Received 15 July 1981, accepted 12 De-

Observational Learning of Food Aversions in Red-Winged Blackbirds (Agelaius phoeniceus)

Consumption of food by Aplodontia rufa from bowls scented with control odors, secretion from anal glands of minks ( Mustela vison ) or urine from minks, bobcats ( Felis rufus ) and coyotes ( Canis latrans ) was studied. In two-choice control tests, subjects indiscriminately consumed apple from unscented bowls and from bowls scented with urine from an unfamiliar herbivore ( Cavia porcellus ), or with butyric acid. During two-choice tests offering apple from bowls scented with secretion from anal glands of minks and from bowls scented with butyric acid, significantly less apple was consumed from bowls containing mink scent. In two-choice tests in which apple was offered from bowls scented with urine from either mink, bobcat, coyote, or domestic dog, all predator urines reduced feeding. Habituation was studied by measuring consumption of dry pellets during continuous exposure to coyote urine for 5 days. Significantly less chow was consumed from bowls scented with coyote urine than from control bowls, indicating a lack of habituation to the predator scent. We conclude that predator scents act as natural repellents. The responsiveness to scents from several sympatric predators as well as from domestic dogs suggest an innate reaction to a signal, which is common to carnivores. The utility of predator scents in the control of browsing damage by mountain beavers should be explored.

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Effects of predator odors on feeding in the mountain beaver (Aplodontia rufa)

-In the presence of food-deprived and therefore rapidly feeding Red-winged Blackbirds (Agelaius phoeniceus), pairs of nondeprived conspecifics increased their own food consumption and spillage. The effect of social facilitation appeared amplified when both pairs of birds were food-deprived. Blackbirds also showed clear differential preferences for novel foods based on observations of male conspecifics consuming and spilling novel food. Social facilitation of feeding and observational learning of differential food preferences for novel foods may help to explain the Red-winged Blackbird's tendency to locate and exploit (i.e. damage) crops during short periods when the crops are especially vulnerable. Received 30 January 1981, accepted 21 April 1981. SOCIALLY facilitated behavior such as flocking may protect birds from predators (Conner et al. 1975, Clayton 1979, Lazarus 1979) and contribute to reproductive synchrony (Roell 1978). Social facilitation may also lead to a more complete exploitation of food resources by birds through more rapid selection of new foods (Davies 1976, Traemer and Kemp 1979) or through increased food consumption (Rubenstein et al. 1977, Feare and Inglis 1979). Consumption is influenced by the feeding rates of neighboring birds in a flock, regardless of their sex, or, sometimes, their species (Fairchild et al. 1977). In addition, consumption is discriminative for most species, i.e. individuals forage selelctively and tend to choose foods that other birds in the flock are choosing (e.g. Murton 1971, Williamson and Grey 1975). Social facilitation of food selection among members of a flock may have deleterious agricultural consequences. For example, foraging based on observational learning may encourage the selective crop damage that is often produced by gregarious pests, such as Red-winged Blackbirds (Agelaius phoeniceus). Here, we report two experiments that demonstrate that: (1) Red-winged Blackbirds will increase their feeding activity in the presence of feeding conspecifics; and (2) Red-winged Blackbirds differentially select some foods as a result of observing the behaviors of other individuals. EXPERIMENT 1, SOCIAL FACILITATION OF FEEDING

Effects of Social Facilitation and Observational Learning on Feeding Behavior of the Red-Winged Blackbird (Agelaius phoeniceus)

-Red-winged Blackbirds (Agelaius phoeniceus) can acquire food preferences and aversions merely by observing conspecifics. In Experiment 1, red-wings were trained to prefer or avoid food paired with yellow, as conspecifics watched. After training, all birds were given two-choice tests between food paired with yellow or green for 12 days. Trainers were tested in visual isolation, whereas watchers were tested either in visual isolation or in visual contact with birds who had observed the opposite behavior during training. Food aversions were more resistant to extinction than food preferences (P < 0.05), and, among watchers, social cues facilitated avoidance (P < 0.05). In Experiment 2, red-wings were trained to avoid food paired with yellow, as Common Grackles (Quiscalus quiscula) and red-wings watched, or vice versa, and then two-choice tests were given between yellow and green. Both grackles and red-wings exhibited observational learning, regardless of the training species (P's < 0.05). Social interactions among avian predators may influence how predator abundance affects the Batesian model-mimic complex. We speculate that avoidance learning, which occurs when a predator observes the ingestion of a model, is stronger than preference learning, which occurs when a mimic is ingested. Relatively few models would be needed for the model-mimic complex to operate successfully, and the number of mimics could exceed the number of models without jeopardizing the mimetic advantage. Received 4 November 1983, accepted 12 March 1984. RED-WINGED Blackbirds (Agelaius phoeniceus) can learn food preferences and aversions by observing conspecifics feed and without necessarily ingesting food themselves (Mason and Reidinger 1981, 1982a). Such observational learning is guided by the visual characteristics of the food (Mason and Reidinger 1983a), although tactile and gustatory stimuli, as well as the long-term consequences of ingestion, may become important. Such findings are consistent with results obtained from other species (Klopfer 1959, Duecker 1976). Regarding preferences, Common Chaffinches (Fringilla coelebs), for example, are more likely to commence feeding and to sample new foods when exposed to conspecifics doing so (Rubenstein et al. 1977). White Wagtails (Motacilla alba) and Tennessee Warblers (Vermivora peregrina) behave in a similar fashion (Davies 1976, Tramer and Kemp 1979), and European Starlings (Sturnus vulgaris) may increase feed' The third author is assigned to the Monell Chemical Senses Center from the U.S. Fish and Wildlife Service, Denver Wildlife Research Center, Section of Supporting Sciences, Building 16, Federal Center, Lakewood, Colorado 80225 USA. ing efficiency while minimizing energy expenditure through social feeding (Hamilton and Gilbert 1969). This social feeding is discriminative, and individuals in the flock tend to choose foods that other birds in the flock are choosing (Murton 1974, Williamson and Grey 1975). Regarding aversions, many insectivorous species learn to avoid visual stimuli associated with prey whose ingestion has sickened them (e.g. Brower 1958a, b, c; Duncan and Sheppard 1965; Wickler 1968; Morell and Turner 1970; Rettenmeyer 1970). Some investigators have suggested that observational avoidance learning may also have implications for Batesian mimicry (e.g. Alcock 1969a, b), a phenomenon in which predators learn to avoid noxious prey by developing conditioned aversions (Mason et al. 1982) and generalize this learning to mimics of the unpalatable items. One such implication is that predator pressure on prey, at least in some instances, may not increase linearly with the number of predators. Instead, social interactions among predators may ultimately determine how predator abundance affects the Batesian complex (Avery 1983). An unanswered question relevant to this issue is 796 The Auk 101: 796-803. October 1984 This content downloaded from 157.55.39.163 on Wed, 21 Sep 2016 05:51:28 UTC All use subject to http://about.jstor.org/terms October 1984] Blackbird Observational Learning 797 the strength (i.e. resistance to extinction) of observationally learned aversions in comparison with similarly acquired preferences. Avian predators are likely to observe attacks by conspecifics on both models and mimics, and, in some cases, observed attacks on mimics should exceed observed attacks on models, because mimics are more numerous (Brower 1960). In the former case, the observer should learn approach, or preference, but, in the latter instance, learned avoidance, or aversion, should accrue. In Experiment 1, we assessed which sort of observational experience would exert greater control over behavior.

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J. Russell Mason

Papers

Carbon Disulfide: A Semiochemical Mediating Socially-Induced Diet Choice in Rats

Observational Learning of Food Aversions in Red-Winged Blackbirds (Agelaius phoeniceus)

Effects of predator odors on feeding in the mountain beaver (Aplodontia rufa)

Effects of Social Facilitation and Observational Learning on Feeding Behavior of the Red-Winged Blackbird (Agelaius phoeniceus)

Comparative assessment of food preferences and aversions acquired by blackbirds via observational learning