RT @biorxiv_evobio: Evolution of a central dopamine circuit underlies adaptation of light-evoked sensorimotor response in the blind cavefis….

Together, this system shows how evolution has enacted itself on a functional circuit, revealing insight into this fundamental question. Moreover, this is a unique model that can be used to now address fundamental questions in the evolution of neural circuits. 15/15 fin.

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Whether these light-tuned neurons represent a novel cell type, or whether an existing cell type has changed its functional properties remains unclear, though the system is well poised to address the question. 14/15.

Our model is that the pineal controls light fluctuations in both forms and hindbrain motor neurons, fed by a dopaminergic motor circuit, drive photokinesis. We show that neurons in the hypothalamus have changed their tuning properties to drive photokinesis during light. 13/15

Our hypothesis is that this circuit has emerged to keep cavefish in the darkness where they thrive, while mining surface fish in lit conditions where their vision gives them an advantage. 12/15.

We then used the brain atlas to define the neuronal identity of these neurons. These neurons mapped to a set of DA neurons. To test these cells, we used pharmacological antagonists, and laser-mediated ablations of these cells, and found that photokinesis was dysregulated. 11/15

We then used transgenic Astyanax expressing GCaMP pan-neuronally (elavl3:H2B-GCaMP6s) and examined neural activity during light transitions. We found that in surface fish, most clusters tended to be dark-tuned, but in cavefish, a subset of these clusters are light-tuned. 10/15

Using whole-brain phosoERK mapping, we found a region of the brain that was active during dark exposure in surface fish and became active in cavefish during light exposure. The area mapped to a region containing the anterior hypothalamus (PT). 9/15

The simplistic circuit to explain this behavior has three nodes: light sensing, motor output, and something that integrates the info. We think the pineal is sensing illumination in both forms. Question is: what part of the brain integrates this info? 8/15

In this study, we looked at this behavior. We find that both forms have a photokinesis, but that the valence is reversed. Surface fish become hyperactive in darkness, presumably light-searching, but cavefish become active in light, presumably a dark-searching behavior. 7/15

But what about behavior? Photokinesis is a well-established phenomenon in fish. When a larva is transitioned from a lit background to darkness, the fish becomes hyperactive. This hyperactivity is thought to be a light-searching behavior (credit Luchtenburg et al, 2019). 6/15

Several years ago, work with @AlexCarlKeene and @SumbreLab revealed that despite the loss of eyes, cavefish still showed neural activity in the optic tectum when exposed to changes in light. 5/15.

The blind cavefish, Astyanax, could address this question. The system has eyed surface fish and at least 30 populations of cavefish. Over the years we have brought this system into the genetic era and have shown a number of behaviors that differ between surface and cavefish. 4/15

It seems like this is an easy question to address, but the lack of a suitable model, amendable to genetic assessment, that has a change to a known behaviorally relevant circuit is a significant impediment to addressing this question. 3/15.

A recent perspective piece was just published, which highlighted that while our understanding of neural circuits function is detailed, less is known about how these circuits evolve. 2/15.

We are really excited that this paper is finally out. Special shout out to @KozolRobert (now at St. Johns) for spearheading this work. This was a fun collaboration with @AlexCarlKeene and @JohannaKowalko Labs. Thread. 1/15.

Kicking off #Cavefish24 with @AlexCarlKeene @NicolasRohner, @JohannaKowalko and Wes Warren at #BOcean resort

Sitting on a packed @united flight with no AC. Flight attendants let us know maintenance is coming to turn on the AC, but we're waiting on pilots. Take off was 5 minutes ago. #fail.

RT @NicolasRohner: 📢 Our latest in-depth review on #cavefish genetics is LIVE in @TrendsGenetics. A huge shoutout to our brilliant grad stu….

Transgenic #Astyanax are changing the way we study evolution of the brain and emergence of adaptive behaviors.