Thread by @RibeiroCarlitos

Excited to share our latest work - we use pan-neuronal 2 photon imaging to dissect how the #brain integrates multiple internal states to guide #food #choice! Fantastic work by @Dahaniel who took on this challenging project almost solo! #drosophila biorxiv.org/content/10.110… 1/21

We wanted to know what changes in the brain when animals #crave #foods. How do different internal states interact to change neuronal processing of #food #taste to alter feeding decisions? And can we use neurogenetics to identify causal brain regions driving food choice? 2/21

We had shown that when flies are protein deprived they increase their preference for protein-rich food like yeast. Food taste is key when deciding what to eat. But does the metabolic state alter taste processing and how do internal states change decisions? 3/21

Furthermore, after mating females anticipatorily develop protein cravings to ensure that they do not run out of proteins while producing eggs. We know that reproductive state is set in the brain by a dedicated neuronal circuit. But what happens there? 4/21

How internal states alter sensorimotor processing to change behavior and how multiple internal states are integrated to influence a specific decision are fundamental questions in #neuroscience. 5/21

Most likely internal states shape brain processing at large scale. @Dahaniel therefore decided to take a bold approach and do pan-neuronal volumetric two-photon calcium imaging across the ventral brain of #drosophila in different internal states tasting different foods. 6/21

But there was a problem. The SEZ which is where taste information goes in and feeding motor outputs go out is poorly characterized and one easily gets lost there. So we needed a map! 7/21

To compare data between flies at different internal states, we aligned all data to the same template brain and used group level ICA to functionally parcellate this #brain region. In short we did a functional SEZ atlas which recapitulates most known structures. 8/21

We found that depriving flies of protein, selectively changed how protein (yeast) taste is processed across a large fraction of the SEZ (~50%). Strikingly this was not the case for sucrose. Protein state therefore widely but selectively changes food taste processing. 9/21

But how can this explain why flies eat more protein when protein deprived? Turns out that one of the most striking effects we observed was in motor neurons. In protein deprived flies motor neurons get activated much more rapidly than in fully fed flies. 10/21

In contrast to metabolic state, reproductive state only affected the motor neuron regions! While in virgins sensory regions strongly react to metabolic state changes, motor neuron region activity is strongly gated by mating. Activity there is boosted by mating state. 11/21

While both internal states act very differently on how taste is processed by the brain they both get integrated at the level of the motor neuron output to synergistically boost protein appetite in a predictive manner! This blew our mind! 12/21

But what is the functional relevance of the changes we see in the SEZ upon changes in internal states? We decided to focus on a SEZ region which we named “#borboleta”. Borboleta means butterfly in Portuguese. 13/21

The activity induced by yeast taste but not sucrose taste was strongly modulated by metabolic state. This suggested that this region is a key integration center where food taste is integrated with internal state information. 14/21

A challenge of whole brain studies is going to the functional level and testing if the modulations are functionally relevant. @Dahaniel built a pipeline to bridge the SEZ atlas to the Braincode atlas @strawlab allowing us to pick Gal4 lines labeling the borboleta region. 15/21

We selected Gal4 lines labeling different parts of the borboleta region and used them to drive activity in the borboleta neurons in fully fed females. And amazingly we could induce protein appetite! No effect on sucrose feeding! 16/21

This strongly suggests that the borboleta region is indeed able to influence protein feeding in a metabolic state dependent way. We also use the flyPAD system to extract more cool functional details about what the borboleta region does. Check it out! 17/21

So, we are excited because we think that this paper provides some important answers to some fundamental questions in #neuroscience. Especially about what internal states do, how they get integrated, and how they shape decision making. 18/21

We also provide a map for the SEZ which is one of the enigmatic regions in the #Drosophila #brain which we hope can be used by other people interested in this important brain region with similarities to vertebrate brainstem. 19/21

And finally, we think that pan-neuronal volumetric calcium imaging is a very cool technique to look at what internal states do in the brain and we now provide a path to test effects functionally using the amazing tools in the fly world. 20/21

Thank you everyone in the @RibeiroLab and @Neuro_CF, especially @GoldschmidtDe for your help and encouragement! It has been a fun ride! 21/21 @CraigWeekend