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An Easily Compatible Eye-tracking System for Freely-moving Small Animals

Abstract

Measuring eye movement is a fundamental approach in cognitive science as it provides a variety of insightful parameters that reflect brain states such as visual attention and emotions. Combining eye-tracking with multimodal neural recordings or manipulation techniques is beneficial for understanding the neural substrates of cognitive function. Many commercially-available and custom-built systems have been widely applied to awake, head-fixed small animals. However, the existing eye-tracking systems used in freely-moving animals are still limited in terms of their compatibility with other devices and of the algorithm used to detect eye movements. Here, we report a novel system that integrates a general-purpose, easily compatible eye-tracking hardware with a robust eye feature-detection algorithm. With ultra-light hardware and a detachable design, the system allows for more implants to be added to the animal’s exposed head and has a precise synchronization module to coordinate with other neural implants. Moreover, we systematically compared the performance of existing commonly-used pupil-detection approaches, and demonstrated that the proposed adaptive pupil feature-detection algorithm allows the analysis of more complex and dynamic eye-tracking data in free-moving animals. Synchronized eye-tracking and electroencephalogram recordings, as well as algorithm validation under five noise conditions, suggested that our system is flexibly adaptable and can be combined with a wide range of neural manipulation and recording technologies.

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Acknowledgements

We thank Dr. Feng Wang for her comments on our manuscript and providing the animals. This work was supported in part by the National Key R&D Program of China (2021ZD0203902 and 2018YFA0701403), the Key Area R&D Program of Guangdong Province (2018B030338001 and 2018B030331001), the National Natural Science Foundation of China (31500861, 31630031, 91732304, and 31930047), the Chang Jiang Scholars Program and the Ten Thousand Talent Program, the International Big Science Program Cultivating Project of the Chinese Academy of Science (CAS) (172644KYS820170004), the Strategic Priority Research Program of the CAS (XDB32030100), the Youth Innovation Promotion Association of the CAS (2017413), Shenzhen Government Basic Research Grants (JCYJ20170411140807570, JCYJ20170413164535041), the Science, Technology and Innovation Commission of Shenzhen Municipality (JCYJ20160429185235132), a Helmholtz-CAS joint research grant (GJHZ1508), the Guangdong Provincial Key Laboratory of Brain Connectome and Behavior (2017B030301017), the Guangdong Special Support Program, the Key Laboratory of the CAS (2019DP173024), the Shenzhen Key Science and Technology Infrastructure Planning Project (ZDKJ20190204002).

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Huang, K., Yang, Q., Han, Y. et al. An Easily Compatible Eye-tracking System for Freely-moving Small Animals. Neurosci. Bull. 38, 661–676 (2022). https://doi.org/10.1007/s12264-022-00834-9

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  • DOI: https://doi.org/10.1007/s12264-022-00834-9

Keywords

  • Eye-tracking
  • Freely-moving
  • Head-mounted device
  • Pupil detection
  • Adaptive Kalman filter