A brainstem integrator for self-location memory and positional homeostasis in zebrafish

Area of Science:

• Neuroscience
• Comparative Biology
• Animal Behavior

Background:

• Animals track self-location by integrating movement, with positional representations known in the mammalian hippocampus.
• It remains unclear if ancient brain regions represent self-location or how self-motion integrates to control locomotion.

Purpose of the Study:

• To investigate positional representations in ancient brain regions.
• To understand how integrated self-motion generates positional memory.
• To identify the neural pathways controlling locomotion based on self-location.

Main Methods:

• Utilized a head-fixed, fictive-swimming larval zebrafish model in a virtual reality setup.
• Exposed zebrafish to involuntary spatial displacements and monitored their responses.
• Employed whole-brain functional imaging, optogenetics, and lesion studies.

Main Results:

• Zebrafish tracked involuntary displacements and initiated corrective swimming to return to previous locations, demonstrating "positional homeostasis."
• A hindbrain network, including the medulla and inferior olive, was identified as crucial for storing location memory and generating error signals.
• Optogenetic stimulation of medullary integrator cells induced displacement-memory behavior, while ablation abolished corrective swimming.

Conclusions:

• A multiregional hindbrain circuit in vertebrates integrates self-motion and stores self-location to control locomotor behavior.
• This circuit provides a fundamental mechanism for spatial navigation and orientation in ancient vertebrate brains.
• The findings reveal a conserved neural basis for self-location tracking and corrective behaviors across vertebrates.