# Complexity in speech and music listening via neural manifold flows

## TL;DR

This study uses a new method to show that listening to speech and music engages the brain in more complex ways than rest, with speech being more complex than music.

## Contribution

The study introduces the Manifold Density Flow (MDF) method to quantify brain complexity during speech and music perception.

## Key findings

- Speech and music listening induce higher neural complexity than resting states.
- Speech listening leads to greater complexity than music listening.
- The MDF method effectively captures cognitive task-induced brain dynamics.

## Abstract

Understanding the complex neural mechanisms underlying speech and music perception remains a multifaceted challenge. In this study, we investigated neural dynamics using human intracranial recordings. Employing a novel approach based on low-dimensional reduction techniques, the Manifold Density Flow (MDF), we quantified the complexity of brain dynamics during naturalistic speech and music listening and during resting state. Our results reveal higher complexity in patterns of interdependence between different brain regions during speech and music listening compared with rest, suggesting that the cognitive demands of speech and music listening drive the brain dynamics toward states not observed during rest. Moreover, speech listening has more complexity than music, highlighting the nuanced differences in cognitive demands between these two auditory domains. Additionally, we validated the efficacy of the MDF method through experimentation on a toy model and compared its effectiveness in capturing the complexity of brain dynamics induced by cognitive tasks with another established technique in the literature. Overall, our findings provide a new method to quantify the complexity of brain activity by studying its temporal evolution on a low-dimensional manifold, suggesting insights that are invisible to traditional methodologies in the contexts of speech and music perception.

Understanding how the human brain processes speech and music is a fascinating and complex challenge. Our study explores how brain activity changes when people listen to naturalistic speech compared to when they listen to music or when they are at rest. We found that both speech and music engage the brain in more complex patterns of activity than rest, with speech leading to even greater complexity. To achieve this, we used a novel method to study the brain's activity in a simplified, low-dimensional space, representing the dynamical evolution of brain activity across different regions. This approach highlights the demands placed on brain function during the perception of speech and music, providing new insights into how we process these auditory experiences.