This article describes background information for the symposium held at the 70th Annual meeting of the Japanese Society for Animal Psychology. The main theme of this symposium was to provide updated information on neurodevelopmental toxicity caused by environmental chemicals, through lectures by three distinguished researchers, and to discuss possible contributions and expected roles of animal psychology in toxicological studies designed to protect children's health. The Ministry of the Environment has commenced a large-scale, long-term epidemiological study entitled the “Environment and Children's Study (Eco-Chil)”, to elucidate health effects caused by chemical exposures of children including pervasive developmental disorders. Neurobehavioral assessments have been included in globally accepted guidelines for neurotoxicity and reproductive toxicity studies in rodents as effective tools for collecting experimental evidence. Findings from these experiments provide a scientific basis for the epidemiological studies, like Eco-Chil. However, currently available behavioral testing methods are insufficient for detecting neurodevelopmental effects of environmental chemicals, especially for emotionality and social aspects of behavior. Appropriate animal behavioral models are needed to advance toxicological studies further. Animal psychologists could greatly contribute to the development of these animal models and the interpretation of behavioral test results.

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Thyroid hormone plays an important role in brain development. Deficiency of thyroid hormone during perinatal critical period results in irreversible adverse effect in brain known as cretinism in human. Thyroid hormone exerts its effect mainly by binding to the thyroid hormone receptor (TR), which is a ligand-regulated transcription factor. On the other hand, perinatal exposure to several environmental chemicals such as the polychlorinated biphenyl (PCB) and polybrominated diphenyl ether (PBDE) show abnormal brain development similar to those seen in perinatal hypothyroidism. Although molecular mechanisms of such chemical action on thyroid hormone system have not yet fully been understood, recent studies have shown important clues. People may consider that such studies may directly contribute in making decisions to control such chemicals. However, the standards of academic science are sometimes inappropriate to the needs of regulatory science for making legislation for regulation of environmental chemicals. How basic researchers can involve in this issue needs to be seriously considered.

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To demonstrate the induction of the delayed central nervous toxicity by disturbing neuronal activities in the developing brain, we administered a single oral dose of ibotenic acid (one of the mushroom toxin: 1 mg/kg), a potent glutamate receptor agonist, to the pregnant female mice at the gestational day of 14.5, infant male mice at 2 weeks old and adult male mice at 11 weeks old. The deviances of anxiety-related behaviors, impairment of memory and depleted information processing capability were suggested in male mice dosed with ibotenic acid at the juvenile stage by our behavioral analysis constructed by openfield test, light and dark transition test, elevated plus-maze test, contextual and cued fear conditioning test and auditory startle response/prepulse inhibition test. The overgrowth of neural processes and impairment of synaptic distribution were detected in the hippocampus of these mice. Gene expression analysis of mouse hippocampus by percellome methods indicated that the axonal repulsion and spine formation were affected by oral intake of ibotenic acid at the juvenile stage.

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We here introduce characteristic features of the novel behavioral tests, named Flavor Map and IntelliCage, recently developed to elucidate how maternal exposure to environmental chemicals affects executive brain functions in rats and mice. Flavor Map test requires rats to learn the existence of a schema of paired-associate of flavor and location, and enables to examine the short-term memory, long-term memory and paired-associative learning ability in adult rats. We have found that maternal exposure to a low dose of dioxin causes deficit in the paired-associative memory formation. Using the IntelliCage system, we have developed our own test protocol in mice. IntelliCage is versatile in terms of accommodation of as many as 16 mice at a time to monitor and record their basic physical activities and learning function. Our protocol successfully increases the efficiency of detection of the learning behavior with minimal variations between individual mice. We found that male mice born to dioxin-administered dams develop less behavioral flexibility. We believe that these behavioral tests can be used to study the executive functions in rats and mice, in biomedical research fields not only in toxicological study but also in animal psychology.

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Hippocampal long-term potentiation (LTP), an increase in the efficacy of synaptic transmission, has been considered a powerful candidate for the physiological basis of memory. Although hippocampal LTP has been induced by high frequency electrical stimulation of the presynaptic fiber in most studies, it has been reported that pharmacological blockade of potassium ion channels also induces synaptic plasticity. Furthermore, several studies have recently used a newly developed selective blocker and opener to demonstrate that potassium ion channels play an important role in memory and learning. This article reviews studies that have shown the possible involvement of potassium ion channels in memory function and hippocampal synaptic plasticity.

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Recent behavioural studies in corvids (i.e. crows and jays) have demonstrated their sophisticated cognitive abilities such as mental-time travel, theory-of-mind-like ability, reasoning, and tool manufacture and use. These abilities are thought as a case of cognitive convergence which has been evolutionary driven by the social complexity common between corvids and primates. However, ‘complexity’ of the social life of corvids has been less understood. Here I review the social ecology of crows and jays with focusing on the social relationships and inter-individual interactions. Particular attentions are paid to affiliative relationships, including social bonds and friendships, and cooperation styles as the foundation of the conflict management which should evolutionarily work as a socio-ecological demand for cognitive-processing power of corvids.

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Planning, or an internal process of making decisions about one's future behavior, appears advantageous not only for humans but also for non-human species. In fact, recent studies have shown that many non-human primates as well as some avian species may be endowed with planning capacities. Those animals are suggested to plan in order to meet not only present but also future needs, as opposed to the Bischof-Köhler hypothesis. Testing planning in a wider variety of species using various setups would be required to uncover phylogenetic and ecological factors that may have facilitated evolution of planning. In particular, it is important to examine planning abilities by using general learning tasks instead of species-specific situations such as tool-use and food-caching. After reviewing evidence on planning by non-human animals, we introduce recent findings about planning by pigeons in operant tasks including computerized navigation and maze tasks. Planning capacities may be shared across species from wider-ranging taxa than have been assumed. Metacognition of planning would serve as one of the most important topics for the future quest.

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Turn alternation is the tendency of an organism during a single trial to turn in the opposite direction to a previous forced turn. It has been shown that this phenomenon depends on feedback from proprioceptive cues derived from prior response. Turn alternation has been studied mainly in invertebrates. An early explanation of invertebrate turn alternation was based on Hull's concept of reactive inhibition (Hull, 1943). However, more recent studies focus on the bilaterally asymmetrical leg movements (BALM) hypothesis which emphasizes activity differences between the right and left legs (Hughes, 1985). Additionally, many studies have shown variables that can modify turn alternation. The most commonly investigated are pre- and post- forced turn distances, the number of forced turns, and the angle of a forced turn. Although there are many studies which have investigated these variables, some of the results are conflicting because these studies tested different species with varying experimental designs. Further studies which control the experimental designs are needed to gain a further understanding of the nature of turn alternation.

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Two experiments investigated the processing of global and local information by pigeons. In Experiment 1, pigeons were trained to discriminate four hierarchical stimuli composed of two letters at global level and two other letters at local level. Color frames predicted the level to be tested in the subsequent two-alternative forced-choice test. The pigeons learned to discriminate the global/local compound stimuli and then showed successful transfer to the stimuli composed of novel letters that were irrelevant to the subsequent test. In Experiment 2, new pigeons were trained with the stimuli that had relevant letters only at one level. The local-relevant and global-relevant stimuli appeared in alternating daily sessions, so that the daily context allowed attention to be directed to the appropriate level. Performances on probe trials for the familiar training stimuli and novel global/local compound stimuli were compared under the context-consistent and context-inconsistent conditions. The tests revealed a cognitive precedence for local information of the compound stimuli.

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In studies assessing sustained attention, performance is often characterized by a decline in function over time. This response pattern, termed the vigilance decrement, is sensitive to manipulations affecting task difficulty, and reversal with nicotine. The choice reaction time task (CRTT) has been described as a test of sustained attention in rats. However, studies describing vigilance decrements and effects of nicotine in this task are scarce. We manipulated the CRTT to determine under which conditions a replicable vigilance decrement could be observed, and sought to determine whether this change was sensitive to nicotine administration. In the ten rats, dose-responses were then derived for nicotine (0.01-0.3 mg/kg). Decreasing the presentation rate of stimulus by prolonging the inter-trial intervals resulted in a decline in the performance speed and increase in omission errors. Nicotine administration reversed the performance decrement. These results serve to validate further the CRTT as a measure of sustained attention.

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