Dopamine, a Target of Parkinson’s Disease, Found to Play Key Role in Vocal Learning
Emory University researchers, investigating the role of dopamine in the regulation of vocal learning through auditory feedback, observed that reducing this neurotransmitter in a specific brain area, the basal ganglia, considerably impairs learning. The study, in songbirds called Bengalese finches, further illuminate the role of dopamine in vocal behavior, and is relevant to Parkinson’s disease, in which dopamine-containing neurons slowly die and patients often display problems with vocal control.
Skill learning, such as calibration of vocal behavior, involves sensory feedback to the brain and motor performance. Auditory feedback to fix behavioral mistakes is an essential mechanism in numerous activities, such as learning to speak, sing, or play a musical instrument. However, the neural basis of sensorimotor learning and vocal learning, in particular, remains poorly understood.
Researchers investigated the role of dopamine in the basal ganglia (a region of the forebrain involved in movement coordination and learning) of the finches, which have extremely precise singing and can modify their behavior in response to auditory feedback. These animals represent a valuable model to understand similar patterns in humans.
The team recorded each bird singing and occasionally emitted a white noise from a speaker near the birds’ cages, which the birds interpreted as an error. The researchers then measured how fast the birds changed their singing pitch to correct the mistake. They next administered a drug that lowers dopamine levels by half in an area of the basal ganglia, and again recorded the singing, observing that the birds’ ability to correct perceived mistakes was also greatly reduced. This confirmed the effect of dopamine on vocal learning driven by an auditory feedback.
“We found that their ability to correct their singing in response to the white noise also went down by about half,” the study’s lead author, Dr. Samuel Sober, said in a university press release. “They were still able to learn from the white noise ‘mistake,’ but they were significantly worse at it.”
Interestingly, no effect was observed on the quality of vocal performance or the amount of song produced.
This experiment is, according to the researchers, the first to isolate the role of dopamine in sensory-motor learning, apart from its other functions in the brain. “We don’t know if reducing the level of dopamine changes the birds’ ability to detect a vocal mistake, or whether it just affects their ability to fix mistakes once they detect them, or perhaps both,” Dr. Sober said. “Our next step is to better understand, at the cellular and molecular level, how changes in dopamine affect activity in the basal ganglia.”