Changing Taste Perception with Optogenetics

Hey everyone! My summer of research in Ann Arbor has come to an end and it’s been an awesome experience. It’s been a busy 10 weeks of making daily improvements to my rig, resoldering the flyPAD, collecting data, and presenting what I found to others. The original goal of this project was to see if altering taste perception was possible by activating taste neurons with light – a new technique called optogenetics. To test this I stimulated channelrhodopsin in the neurons of fruit flies’ which give them a sweet taste response.

If you missed it, my first post: Optogenetics with the flyPAD, and my second post: The Taste Preferences of Fruit Flies

The FlyPAD setup in its full glory

Naturally, fruit flies prefer eating sugary as opposed to unsweet foods, similar to humans. This was the case when I offered them banana, a sweet fruit, and avocado, broccoli, and brussels sprouts, the unsweet alternatives. The flies always preferred banana over anything else. However, when Arduinos were programmed to pulse red light at the flies the same instant they sipped the unsweet foods, their gr5a neurons were activated, tricking them into thinking that what they were eating was sweet. The data is shown below, as bar graphs of the average number of sips and of sip % to see how food choice preference changed.

As we see here, the flies naturally prefer banana over avocado

But this preference switched when stimulation of channelrhodopsin activated their sweet tasting (gr5a) neuron

Flies, naturally, REALLY prefer banana over broccoli

The star preference we saw earlier disappeared, and the flies ate some of both foods: more of the newly sweet tasting broccoli and less of the banana.

Again, we see that banana wins the prize naturally.

And again, with stimulation, we see the sweet and the non-sweet options begin to level out

So, changing the subjective perception of taste is possible, as we could make a fly’s least preferred food become their absolute favorite! These findings show that subjective perception is alterable, but also that optogenetics is a neuroscience technique which can be done with little, affordable equipment.

If I end up continuing work on this project, I am interested to see how long the altered preference of the flies can persist. Anecdotally, I’ve seen that when the LED lights stop working there are some flies which continue to visit the unsweet food which they were tricked into tasting sweet. This wasn’t within the scope of my summer research, but I suspect that doing experiments on this would be interesting as it could reveal how powerful optogenetics is by creating a change in food choice preference that persists once stimulation trials have stopped.

After finding these results I compiled them into a poster which I recently presented at an UROP (undergraduate research opportunity program) symposium at the University of Michigan. It was fun explaining my summer’s work to the public and other researchers. Got a ribbon for it too!

Call me “Blue Ribbon”

A close up of my poster!

Aside from collecting data in the lab, I also had the chance to showcase my project with TED for their upcoming series of episodes focussed on the Backyard Brains’ research fellows’ projects. I was able to conduct experiments for them and give step by step walkthroughs of how they are carried out. Stay tuned on their posts coming around this fall to catch our episodes!

Getting filmed

Huge thanks to Greg for mentoring me this summer and introducing me to the world of Neuroscience research in the coolest way possible with BYB.

Thank you so much to Backyard Brains for giving me this amazing opportunity and to all the research fellows who made it a really fun summer!