It’s like trying to sing Sinatra’s “My Way” while someone is playing heavy metal in the background. Rather than hearing just their own voice, the birds hear something different, and the mismatch causes them to alter the pitch, timing and sequence of syllables in their songs. “We're excited about the work because it suggests that burst firing may be especially important for driving long-lasting changes in vocal sequences and may be one mechanism that can be targeted to restore normal vocal sequences,” said Mimi Kao, assistant professor of biology at Tufts University and corresponding author of the study.Įarlier studies have evoked changes in song patterns not with a drug but by interrupting the auditory feedback by playing back white noise or a different song sequence. Once the new song patterns are learned in the parts of their brain that control vocal motor activity, LMAN firing is no longer needed to drive them. The changes in song patterns were observed to accumulate gradually over several days during infusion and can persist for weeks after treatment is stopped. The treatment used to induce LMAN to fire its neurons was a simple infusion of a drug, bicuculline methiodide (BMI), that acts on specific neuron receptors and ion channels. Typical frequency of stuttering in humans can occur in 4 – 8% of syllables. Stuttering in syllable transitions can increase from 0.1% before treatment to as much as 13.6%.
When the LMAN is stimulated to fire its neurons in short rapid bursts, the birds start to “improvise” by varying the sequence of notes and tweeting a series of repetitions that share many similarities to stuttering in humans, including partial syllable repeats and abnormal pauses mid-sequence, followed by continuation to the next normal syllable after the repetition. The part of the brain that appears to be linked to birdsong “re-tweeting” of syllables is the lateral magnocellular nucleus of the anterior nidopallium, or LMAN. In a study published today in Current Biology, the researchers were able to observe that a simple, reversible pharmacological treatment in zebra finches can stimulate rapid firing in a part of the brain that leads to large variations in their song patterns, including the stuttering of short sequences of notes or syllables. The cause of stuttering has long been a mystery, but researchers at Tufts University are beginning to unlock its causes and a strategy to develop potential treatments using a very curious model system – songbirds. President Biden himself struggled with stuttering as a child and has largely overcome it with speech therapy. Speech problems such as stammering or stuttering plague millions of people worldwide, including 3 million Americans. Cell, Molecular & Developmental Biology.