Does the same sound mean the same thing in every situation?

Neuroscientists commonly learn how the brain processes communication by playing recorded vocalizations to an animal. But hearing someone’s voice played through a speaker isn’t the same thing as actually having a conversation with them.

Does the brain treat them as equivalent?

We recorded the same individual neurons in marmoset prefrontal cortex while the animals heard the same type of vocal signal under three conditions: restrained, freely moving, and freely moving while participating in an interactive vocal exchange.

It generally didn’t. A neuron’s response to a call in one behavioral context poorly predicted how that same neuron would respond to the same kind of call in another. Across the population, neural activity identified the behavioral context with greater than 90% accuracy, and the natural communication condition was especially distinct.

During communication, the state of prefrontal cortex before another animal called also helped predict whether the marmoset would subsequently answer.

Many neurological and neuropsychiatric disorders affect social communication, including autism spectrum disorder, schizophrenia, and brain injuries that disrupt frontal systems. The clinical difficulty is that communication problems often emerge most clearly during real interactions—when a person must interpret who is speaking, what has already happened, and when and how to respond—not when isolated sounds are presented in a laboratory test.

By showing that the same vocal signal can be represented differently depending on the behavioral context, this work provides a framework for developing more realistic ways to study social-communication dysfunction. Ultimately, understanding the neural mechanisms that support interactive communication may help identify which components of this system are altered in disease and provide more behaviorally meaningful measures for evaluating dysfunction and recovery.