Neuroscientists at the University of Massachusetts Amherst have shown in new research that dopamine plays a key role in how songbirds learn complex sounds.
Published in Journal of Neurosciences, the finding that dopamine boosts plasticity in the auditory pallium of zebra finches lays new foundations for advancing understanding of the functions of this neurotransmitter in an area of the brain that encodes complex stimuli.
“People associate dopamine with reward and pleasure,” says lead author Matheus Macedo-Lima, who conducted the research in lead author Luke Remage-Healey’s lab as a doctor. student of the postgraduate program in Neuroscience and Behavior at UMass Amherst. “It’s a well-known concept that dopamine is involved in learning. But knowledge about dopamine in areas related to sensory processing in the brain is limited. We wanted to understand whether dopamine played a role in learning this brain region. we are or changes with sounds. “
The study of vocal learning in songbirds provides information on how spoken language is learned, adds Remage-Healey, a behavioral neuroscientist, professor of psychological and brain sciences. “It’s not just the songbird that poses this strategy of uniting sounds and signifying the use of dopamine. Here’s something parallel that interests us, as humans.”
The research team conducted a series of in vitro and in vivo experiments, analyzing neurons under the microscope and in the brains of living birds watching videos and listening to sounds. Ultimately, the scientists obtained anatomical, behavioral, and physiological evidence to support their hypothesis about the role of dopamine.
Using antibodies, the researchers proved it dopamine receptors they are present in many types of neurons in the auditory brain of songbirds ¬- can be inhibitory or excitatory and can also contain an enzyme that produces estrogen. “Dr. Remage-Healey’s research has shown that in the auditory brain of songbirds of both sexes, neurons produce estrogen in social situations, such as when we hear a song of birds or see another bird. We believe that dopamine and estrogens could work together in the sound learning process, but this work focused on dopamine because there were still so many things we didn’t know about how dopamine affected the brains of songbirds, ”explains Macedo-Lima, now an associate. postdoctoral fellowship at the University of Maryland.
Macedo-Lima developed a test, similar to Pavlov’s well-known dog experiment, in which birds were alone in a room and presented with a random sound immediately followed by a silent video of other birds. “We wanted to focus on the association between a meaningless sound (a tone) and what’s relevant to the behavior, which is another bird in the video,” he says.
The researchers examined the auditory brain regions of birds after this sound-video pairing, using a known genetic marker that is expressed when a neuron goes through changes or plasticity. “We found this increase very interesting in this gene expression in the left hemisphere, the ventral part of the auditory region, in neurons that express the dopamine receptor, which reflects the learning process and parallels human brain lateralization for speech learning, ”says Macedo-Lima.
To show the effect of dopamine on basic signaling of neurons, the researchers used a whole-cell patch clamping technique, monitoring and measuring the currents the neurons received. They found in a dish that dopamine activation decreases inhibition and increases arousal.
“This modulator is tuning the system in a way that lowers the stop signals and increases the go signals,” explains Remage-Healey. “This is a simple but powerful control mechanism of how animals potentially encode sound. It is a neurochemical lever that can change the way stimuli are recorded and transmitted in this part of the brain.”
The team investigated without pain the brain living bird cells. “What happened when we administered dopamine was exactly what we predicted from cell-wide data,” says Macedo-Lima. “We saw that inhibitory neurons fired less when we administered the dopamine agonist, while excitatory neurons fired more.”
The same effect occurred when the birdsong of other songbirds was played: excitatory neurons responded more and inhibitory neurons responded less when dopamine activation occurred. “We were happy to replicate what we saw on a plate in a live animal listening to relevant real sounds,” says Macedo-Lima.
Dopamine activation also made them neurons unable to adapt to new songs presented to the animal, which strongly corroborates the hypothesis of the role of dopamine in sensory learning. “We currently don’t know how dopamine affects sensory learning in most animals,” says Macedo-Lima, “but this research gives many clues as to how this mechanism might work among vertebrates who need to learn complex sounds, such as humans. “.
Matheus Macedo-Lima et al, activation of the dopamine D1 receptor boosts the plasticity of the hearing bird’s auditory pallor, The Journal of Neuroscience (2021). DOI: 10.1523 / JNEUROSCI.2823-20.2021
University of Massachusetts Amherst
Citation: Research Identifies Role of Dopamine in Brain Plasticity of Singing Birds (2021, July 2) Retrieved July 2, 2021 at https://medicalxpress.com/news/2021-07-role-dopamine-songbird -brain-plasticity.html
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