Sequential information of self-produced song is represented in the auditory areas in male Bengalese finches
Laboratory for Biolinguistics, Brain Science Institute, RIKEN, Saitama, Japan.Neuroreport (Impact Factor: 1.52). 05/2012; 23(8):488-92. DOI: 10.1097/WNR.0b013e32835375ef
Male Bengalese finches have a complex song-sequence pattern containing multiple elements. Learning and producing songs require memorization of the phonology and the sequence of elements. We tested the auditory memory of male finches for their own songs to determine whether the auditory memory included the sequence of elements. An immediate early gene ZENK is induced by auditory processing in the secondary auditory area of the caudomedial nidopallium (NCM) and the caudomedial mesopallium (CMM) in response to song presentations. Repeated presentations of the same song result in a decrease in ZENK expression in these areas, reflecting habituation to auditory processing. We examined sequential differences in auditory processing using the habituation-dishabituation method. After repeatedly presenting the male finches' own song stimulus, we changed the stimulus to a shuffled sequence of songs. If the shuffled songs induced ZENK expression, it indicated that the auditory areas had been dishabituated by the sequential differences. The shuffled songs caused intermediate ZENK expression in the NCM when compared with the expression by a conspecific new song and that by the same song. The tendency toward intermediate expression was similar in the CMM; however, a significant difference was observed between the conspecific song and shuffled songs. These results suggest that the sequential difference caused a partial dishabituation in the NCM. Thus, the auditory areas processed not only the phonology but also the sequence of songs.
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ABSTRACT: In his pioneering research on the neural mechanisms of filial imprinting, Gabriel Horn has gone a long way to fulfilling Karl Lashley's dream of finding the 'engram' or memory trace in the brain. Here we review recent research into the engram(s) of song learning in songbirds, particularly zebra finches. When juvenile songbirds learn their songs from a tutor, they form and alter a central representation of the tutor song, known as the 'template'. Secondary auditory regions in the caudal medial pallium are likely to contain the neural substrate for the representation of tutor song, but the roles of the different regions remain to be elucidated. Female zebra finches do not sing, but nevertheless form an auditory memory of their father's song, for which the neural substrate is located in the caudomedial pallium. In males that are learning their songs, there is continual interaction between the secondary auditory regions and sensorimotor regions, similar to the interaction between Broca's and Wernicke's areas in human infants acquiring speech and language. Copyright © 2014. Published by Elsevier Ltd.
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