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Principles underlying information flow across the entire brain of the zebrafish

Periodic Reporting for period 1 - BrainInformationFlow (Principles underlying information flow across the entire brain of the zebrafish)

Reporting period: 2020-01-01 to 2021-12-31

How information is processed and how it flows through the brain to generate motor behaviours and cognitive functions is a paramount question in neurosciences. In 1949 Donald Hebb proposed that individual neurons cooperate to form functional structures (neuronal assemblies) that communicate through phase sequences. Recent experiments support the existence of neuronal assemblies with specific funcitonal roles, but how does the information flow between these neuronal assemblies to generate phase sequences, remain elusive. For this project, we used the zebrafish larva as the experimental model in combination with light-sheet microscopy, we monitored whole-brain dynamics with single-neuron resolution while simultaneously recording free tail movements as a behavioral output. I analyzed the topology, occurrence frequency and transition probability of whole-brain assemblies and phase sequences triggered spontaneously, or by different sensory stimuli and therefore during different behavioral motives. I showed that there is a large variability of whole-brain assembly characteristics. In addition, there are almost no silent moments in the brain while increases and decreases in the number of active assemblies are more consistent with activation cascades than with sequences in which each has a temporary beginning and end. In addition, I observed global state shifts at the brain activity characterized by the shutting down of a vast majority of active assemblies at the same time that the inactive assemblies are activated. In particular, those shifts are associated with the activation of noradrenergic neurons from the locus Coeruleus (LC).

Our project addresses fundamental questions in neuroscience aiming to contribute to scientific knowledge.
The project was very challenging and high risk, as it involved the development of a light sheet microscope to monitor whole brain activity with single-neuron resolution in intact and behaving zebrafish larvae.
Despite the development of the microscopy, the analysis of the obtained high-dimensional large datasets (big data) requires the development of specific software and algorithms.

We found that there is a large variability of whole-brain assembly characteristics. In addition, there are almost no silent moments in the brain while increases and decreases in the number of active assemblies are more consistent with activation cascades than with sequences in which each has a temporary beginning and end. In addition, I observed global state shifts at the brain activity characterized by the shutting down of a vast majority of active assemblies at the same time that the inactive assemblies are activated. In particular, those shifts are associated with the activation of noradrenergic neurons from the locus Coeruleus (LC).

These results will be presented at the FENS conference in paris and the neutoethology international conference in lisbon. We are now starting to write the manuscript.
There are just a few labs in the world capable of recording the totality of neurons in an intact vertebrate animal, and none working on the ongoing spontaneous activity.
Therefore, this project represents the first study to address the spontaneous flow of information across the entire brain, to reveal the communication channels of the brain.
we developed the optics to record whole-brain activity, and the software necessary for its analysis.
We are finishing the first manuscript describing the flow of information between neuronal assemblies (phase sequences), revealing information channels in the brain.
as a fundamental project, its main aim is to build scientific knowledge.
information in the figure itself
information in the figure itself