Implanting false memories in a bird's brain changes its tune

Young zebra finches have had memories implanted in their brains that change the length of the notes they sing. The process involved manipulating a region of the brain that birds use to learn their song.

The zebra finch song consists of a series of short notes, or syllables. Zebra finches normally learn their song by memorising the song of their father, then slowly learning to copy it.

Todd Roberts at the University of Texas Southwestern Medical Center and his colleagues are working on understanding how memories are encoded in the brain – particularly memories that guide the development of speech and social skills.

Previous work had shown that a region of the brain in birds called HVC is important for learning songs, and disrupting its activity interferes with the ability to learn songs. This area receives input from another area called NIf, and neurons in this structure fire at the beginning and end of syllables. That suggested these neurons have a role in coding the length of syllables.

To investigate further, Roberts’s team used a technique called optogenetics to manipulate neural activity at the connections, or synapses, between NIf and HVC neurons. This involves inserting genes into neurons that allow them to be controlled by light, then using small fibreoptic cables to shine light onto the selected brain area.

Roberts’s team performed the experiments on young male zebra finches that had never been exposed to singing adults but were starting to develop their own song. The group then analysed differences in the final tune about 30 days later.

When the team used short pulses of light, the birds produced songs with short syllables. With long pulses of light, the birds produced songs with long syllables.

“We identified a pathway in the brain that if we activate, it can implant false memories for the duration of the syllables, without the bird having experience with another bird,” says Roberts.

Syllable length is just one aspect of the song that zebra finches have to learn. Other features, such as pitch and the combination of syllables into sequences, are likely to be more difficult to encode, but Roberts hopes his team will eventually be able to implant those too.

Dozens of genes involved in the vocal learning that underpins human speech show similar patterns of activity in songbirds. In light of these similarities, Roberts says the mechanisms of vocal learning in the bird brain could serve as a model for understanding how animals learn from social experiences. “We can use that information to perhaps pinpoint circuits in the brain that might be particularly affected in neurodevelopmental conditions like autism,” he says.

A previous study showed that we could implant memories in mice that made them expect to find a reward in a particular place. Applying such techniques in humans is a long way off, but some hope we will one day be able to alter memories associated with psychological trauma.