Researchers Read Mouse Thoughts by Analyzing Facial Movements

A recent study conducted at the Champalimaud Foundation in Portugal demonstrates that the subtle movements of a mouse’s face can reflect its problem-solving strategies, pushing forward our understanding of how observable behavior links to hidden mental processes. Published in Nature Neuroscience, the team reports that machine learning can uncover the strategies animals use to solve puzzles simply by analyzing video footage, suggesting a non-invasive approach to studying brain function that may also prompt new discussions about mental privacy.

The team challenged mice with a task where they had to identify which of two water spouts dispensed a sugary reward, requiring them to develop decision-making strategies as the location of the reward switched. “We knew that mice can solve this task using different strategies, and we could identify which strategy they were using according to their behaviour,” explained first author Fanny Cazettes. Interestingly, recordings of neural activity revealed that all problem-solving strategies were simultaneously present in the mice’s brains, not just the one they used at any given moment.

Taking the next step, the researchers investigated whether these overlapping strategies could also be detected in the animals’ facial movements. By tracking facial expressions while monitoring brain activity, and utilizing machine learning algorithms to analyze the data, the scientists found that the mice’s faces were just as informative in revealing their strategies as neural recordings themselves. According to principal investigator Zachary Mainen, “We can get as much information about what the mouse was ‘thinking’ as we could from recording the activity of dozens of neurons.”

Notably, the study also uncovered that similar facial patterns represented the same strategies across different mice. According to co-author Davide Reato, “This suggests that the reflection of specific patterns of thought at the level of facial movement might be stereotyped, much like emotions.”

The research opens the door to less invasive approaches for probing brain states, with applications in understanding health and disease. However, by showing that seemingly ordinary video recordings can reveal detailed mental processes, the study’s authors urge consideration of regulations to safeguard mental privacy. “Videos are not just records of behaviour–they can also provide a detailed window into brain activity,” concludes co-author Alfonso Renart.