By Juliette Mutheu
An amazing learning period occurs during the early lives of both humans and song birds. This period unfortunately disappears early in life and finding more about it could explain why learning a different language, or how to play a musical instrument when you are an adult, can at times feel like a mammoth task.
Infants can easily learn to make an audio sound from their exposure to them. The neurons in the infant’s brain are still flexible and are at a critical time period, the so-called neural plasticity period, during which neuronal circuit can be shaped according to what the baby hears.
Dr. Yoko Yazaki-Sugiyama, who joined OIST in August 2011 as the Principal Investigator of the Neuronal Mechanism for Critical Period Unit says, “We have been able to understand the existence of the ‘critical period’ in bird song learning, specifically in zebra finches whose neural system is well understood.” Song birds are also the only animals that learn vocals in a similar way to humans.
At an early age, up to around six weeks, a young zebra finch hears its father’s song and memorizes this. The young birds later start singing by themselves and attempt to vocally mimic their memorized father’s song. Ability to memorize and mimic the father’s song depends on bird’s age and auditory experiences. Older zebra finches exposed to a new song were less likely to learn and vocalize the new tune.
Similarly, in humans, learning a language depends on our auditory experiences. Correctly pronouncing words of different languages depends on our exposure to this pronunciation at a young age. As we get older, it is often difficult to hear, mimic, and correctly pronounce the words.
Understanding how experience shapes neuronal circuit during the early development stage and what triggers this critical period to close is important in unraveling why it is difficult to learn new things when we are older. Dr. Yazaki-Sugiyama further adds, “If we can understand this, we could, for example, aid learning a new language at an older age, or facilitate physical rehabilitation after injury by reactivating these neural mechanisms.