Dopamine Drives Cultural Transmission of Song Learning in Zebra Finches
Cultural transmission has been a defining feature of human civilization. However, it is not unique to the human lineage. In fact, it can be also found in birds. For example, an important instance of cultural transmission in songbirds is song learning through imitation. Studies done over the years have shown that songbirds can culturally transmit complex songs across generations.
Zebra finches, for instance, are not born with an innate ability to chirp their own songs. They learn songs from adult or tutor birds, just like we humans learn speech from adults in society. It has been known that social communication is critical to successful imitation. Indeed, experiments have shown that juvenile zebra finches do not learn from the playback of recorded songs. However, what makes the social interaction imperative in song imitation has remained a puzzle.
A study led by Assistant Professor Masashi Tanaka from Waseda University, Japan has now answered this question. It is a substance called dopamine, known to be related to reward sensing and addiction, that is secreted in zebra finches’ brains to trigger song imitation. In their work, state-of-the-art technologies enabled visualization of dopamine in the brain under a microscope in awake, freely-behaving zebra finches.
When juvenile zebra finches were interacting with a singing tutor, dopamine was secreted in a motor-related brain area called the high vocal center (HVC), which controls singing. Blocking off dopamine in the HVC hindered song imitation, yet left their ability to sing intact. It appeared that dopamine is required to form a memory of the tutor song and initiate song imitation.
In contrast, when juvenile zebra finches were exposed to the playback of recorded songs, dopamine was not secreted in the HVC. Experiments showed that only social interaction with a live, singing tutor could efficiently secrete dopamine in the HVC. Strikingly, however, boosting dopamine in the HVC enabled juvenile birds to imitate even from the playback of recorded songs. Therefore, zebra finches can learn songs by virtue of dopamine, a fact that supports a close link between imitation and social communication.
Songbirds are interesting animals that transmit unique songs across generations similar to human culture. Future studies on songbirds could lead to a deeper understanding of our imitation ability and the basis for complex cultures and civilizations in human society.
Link to the original journal article:
https://www.nature.com/articles/s41586-018-0636-7
About the author
Dr. Masashi Tanaka is an Assistant Professor at Waseda University in Japan. In 2013, he received his Ph.D. in Psychology from The University of Tokyo, Japan. He served at the Department of Neurobiology at Duke University, USA, where he was a postdoctoral associate from 2013 – 2018. His research interests lie in transmission of complex, cultural behaviors in songbirds and humans.
