The brain uses the same pathways when we produce speech and predict sounds


In a nutshell: By comparing brain activity when individuals are making sounds, anticipating forthcoming sounds or listening to sounds passively, researchers have shown that the same pathways are involved.

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The brain uses the same pathways when we produce speech and predict sounds

To be able to respond quickly and flexibly to unexpected events in the environment, the brain must predict forthcoming sensations based on past experiences. According to a theory known as ‘predictive coding’, the brain constantly updates these predictions by comparing the actual sensory input – such as a sight, sound, smell, taste or touch – to the expected sensation. The relevant information is conveyed between different areas of the brain along specific pathways.

The pathways used in predicting sounds were not fully known, although researchers thought that they might be the same as the pathways used when producing speech.

Brain Function CoE chief investigator Marta Garrido and Lena Oestreich from the Queensland Brain Institute and Thomas Whitford from the University of New South Wales designed a three-part experiment to determine whether the same brain regions are involved in producing speech and predicting sounds.

During the ‘talk’ task, participants were recorded repeating the syllable ‘ah’ for several minutes. In the ‘cued listen’ task, they listened to their own recordings while watching a video of their vocalization waveforms, which enabled them to predict when they would hear the next ‘ah’ sound. In the ‘passive listen’ task, participants heard the same recording but did not see the video, meaning that they couldn’t predict the timing of the next sound. Throughout the whole experiment, participants’ brain activity was recorded using electroencephalography (EEG).

By comparing the EEG recordings from the three tasks, the researchers showed that the brain sends signals about predicted sounds along known pathways that are anatomically connected. Their results also agree with the predictive coding theory about the directions in which these signals are transmitted along these pathways.

Learning more about how the brain predicts sounds is important for understanding not only how we respond to external stimuli, but also conditions such as psychosis and schizophrenia, which have been linked to dysfunctional predictive abilities.

Next steps:
Using information about brain structure and activity from almost 100 people, the team plans to investigate whether the degree to which these pathways are anatomically connected is associated with how they predict forthcoming sensations.

Oestreich L. K. L., Whitford, T. J., & Garrido, M. I. (2018). Prediction of speech sounds is facilitated by a functional fronto-temporal network. Frontiers in Neural Circuits, doi: 10.3389/fncir.2018.00043

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