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Vocalizations of common marmoset (Callithrix jacchus) were examined under experimental situations related to fear or anxiety. When marmosets were isolated in an unfamiliar environment, they frequently vocalized "tsik-egg" calls, which were the combination calls of 'tsik' followed by several 'egg'. Tsik-egg calls were also observed after treatment with the anxiogenic drug FG-7142 (20mg/kg, sc). In contrast, when marmosets were exposed to predatory stimuli as fear-evoking situations, they frequently vocalized tsik solo calls as well as tsik-egg calls. These results suggest that marmosets dissociate the vocalization of tsik-egg and tsik calls under conditions related to fear/anxiety; tsik-egg solo vocalizations were emitted under anxiety-related conditions (e.g., isolation and anxiogenic drug treatment), whereas a mixed vocalization of tsik-egg and tsik was emitted when confronted with fear-provoking stimuli (i.e., threatening predatory stimuli). Tsik-egg call with/without tsik can be used as a specific vocal index of fear/anxiety in marmosets, which allows us to understand the neural mechanism of negative emotions in primate., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Although left-right (L-R) asymmetry is a fundamental feature of higher-order brain function, little is known about how asymmetry defects of the brain affect animal behavior. Previously, we identified structural and functional asymmetries in the circuitry of the mouse hippocampus resulting from the asymmetrical distribution of NMDA receptor GluR ε2 (NR2B) subunits. We further examined the ε2 asymmetry in the inversus viscerum (iv) mouse, which has randomized laterality of internal organs, and found that the iv mouse hippocampus exhibits right isomerism (bilateral right-sidedness) in the synaptic distribution of the ε2 subunit, irrespective of the laterality of visceral organs. To investigate the effects of hippocampal laterality defects on higher-order brain functions, we examined the capacity of reference and working memories of iv mice using a dry maze and a delayed nonmatching-to-position (DNMTP) task, respectively. The iv mice improved dry maze performance more slowly than control mice during acquisition, whereas the asymptotic level of performance was similar between the two groups. In the DNMTP task, the iv mice showed poorer accuracy than control mice as the retention interval became longer. These results suggest that the L-R asymmetry of hippocampal circuitry is critical for the acquisition of reference memory and the retention of working memory.