First author

Vocal communication is a dynamic process that involves both speaking and hearing. The auditory system must continuously distinguish between external sounds and feedback from one's own voice. Steven Eliades, a recent MD–PhD graduate of Johns Hopkins University School of Medicine in Baltimore, Maryland, and his advisor Xiaoqin Wang monitored marmoset vocalizations, and report that suppression of some neurons in the auditory cortex during vocalization enhances the neurons' sensitivity to self-generated sounds (see page 1102). Eliades explains the potential link between auditory processing and speech-related disorders.

How did this work evolve?

This whole project came about by accident. Several years ago, we were monitoring neurons in marmosets as part of a simple auditory experiment. We noticed that when we heard a monkey vocalize, the neuron we were monitoring stopped firing. We created conditions that altered what the animal heard while vocalizing in real time. We show that auditory cortex neurons that are suppressed — that is, fire less often — during vocalization are most sensitive to one's own vocal feedback. This suggests that these neurons are responsible for self-monitoring.

What were the biggest challenges of working with marmosets?

They aren't very vocal when alone under typical experimental conditions. Through trial and error, we created a way to get high-quality sound recordings of the vocalizations of free-roaming marmosets. Other major challenges were adapting an implantable electrode for use in small monkeys such as marmosets, and making sure the monkeys didn't climb on or chew through the implant wires.

What insight did you gain from this work?

I realized how little we understand of how hearing and speech interact. Disruptions in this process may be more of a clinical problem than is currently appreciated.

What types of disorder might this shed light on?

Some 50-year-old theories suggest that a malfunction in auditory processing may underlie stuttering. This work suggests that some stutterers might be unable to self-monitor because their auditory system does not process feedback information correctly. Initial data also suggest that a difficulty faced by patients with Parkinson's disease — who tend to speak too softly, limiting their ability to carry on conversations — may be a self-monitoring problem.