Cell: A self-positioning brain circuit was found in zebrafish

In a new study, researchers from the Howard Hughes Medical Institute in the United States show that a multi-regional brain circuit allows juvenile zebrafish to track where they are, where they have been, and how they return to their original location
after displacement.
The findings shed light on how juvenile zebrafish track their position and use this to navigate
after being pushed away by currents.
The results were published in the December 22, 2022 issue of the journal Cell in the paper "A brainstem integrator for self-location memory and positional homeostasis in zebrafish.
"

Misha Ahrens, co-corresponding author of the paper and a member of the Jainelia Research Park at the Howard-Hughes Medical Institute, said, "We studied a behavior in which juvenile zebrafish must remember past displacements to accurately maintain their position in space, for example, when currents can roll them into dangerous zones
in their natural environment.
" 。 However, whether they explicitly track their position over a long time frame and use the location information in their memory to return to their earlier position --- behavior we call positional homeostasis --- unclear
.
This ability may be ethically crucial because juvenile zebrafish swim intermittently and are washed away
by currents at rest.
”

Many animals track their location
in the environment.
They use self-identifying information for many important behaviors, such as effectively returning to a safe place after visiting unknown and potentially dangerous areas, revisiting food-rich areas, and avoiding foraging in food-poor areas
.
While self-localization is characterized in hippocampal formation, how this representation arises, whether they exist in older brain regions, and by what pathways they control movement
, is unknown.

Co-corresponding author En Yang of the Howard-Hughes Medical Institute's Janelia Research Park said, "Such brain circuits have been difficult to identify because neuroscience often relies on recording from cells from pre-selected brain regions, which make up only a small fraction
of all neurons in the brain.
”

In the new study, the authors set out to identify the complete navigation circuit of juvenile zebrafish, from motion integrator to premotor center, by exhaustively imaging and analyzing
the entire brain at cellular resolution in a behavior that relies on self-localization 。 Visits to more than 100,000 neurons per juvenile zebrafish revealed previously unknown brain regions involved in self-localization, leading to the discovery of a multiregional posterior brain circuit that, through displacement memory, mediates the transition
from speed to behavior.

"Our findings shed light on the neural system of self-localization and related behavior in the vertebrate hindbrain and provide a circuit-level, representational, and control theory understanding
of its function," Ahrens said.
The system operates in a closed circuit in a dynamic environment that includes integration, self-localized neural representation, and motor control
.
These results suggest the need to consider the brain at a holistic level and unify concepts of systems neuroscience--- such as self-localization and motor control, which have often been studied
separately.
”

Image from Cell, 2022, doi:10.
1016/j.
cell.
2022.
11.
022
.

Whole-brain functional imaging reveals not only the presence of positional balance in juvenile zebrafish, but also how the brain recognizes and corrects changes
in zebrafish position.
This circuit forms memories of past displacements by integrating visual information to calculate self-positioning in the dorsal brainstem as zebrafish actively or passively change their position
.
This characterization of self-localization is read by the lower olive nucleus as a persistent position error signal, reflecting the difference between the original and current positions of
the zebrafish.
This signal is converted into a motion output so that the cumulative displacement
can be corrected within seconds.

The authors say that this multi-regional circuit has potential anatomical and functional homology in mammals and may interact with
other known self-localization representations.
In addition, the new study links self-localization and olive cerebellar motor control and establishes the vertebrate hindbrain as a neural control center
for goal-directed navigation behavior.

"Our results regarding positional memory and positional balance are consistent
with the idea that evolutionarily ancient brain regions play a central role in higher-order behavior," Ahrens said.
The idea that cognitive processes are widely distributed throughout the nervous system is consistent with evolutionary claims that complex behaviors emerge, in part by constructing new circuits on ancient brain structures that perform relevant calculations
.
Therefore, whole-brain investigation of neural activity may be critical
to determine the mechanisms of distributed cognitive function.
(Biovalley Bioon.
com)

Resources:

1.
En Yang et al.
 A brainstem integrator for self-location memory and positional homeostasis in zebrafish.
Cell, 2022, doi:10.
1016/j.
cell.
2022.
11.
022.

2.
Scientists identify neural circuit that enables self-localization in zebrafish

https://medicalxpress.
com/news/2022-12-scientists-neural-circuit-enables-self-localization.
html