Fascinating article on how learned fearful aversions in mice are passed down to offspring mice by epigenetic mechanisms

[Hip]

The big idea: can you inherit memories from your ancestors?

This fascinating article details how a fearful aversion learned by mice can be passed down to offspring mice.

Mice, who normally love eating cherries, were presented with the smell of cherries, and then given mild electric shocks. The mice quickly associated the cherry scent with an adverse outcome, and they learnt to freeze in anticipation each time they got a waft of cherries.

The researchers then found that this learned aversion to the smell of cherries was passed down along two generations of mice: the offspring of the offspring of these mice were also highly fearful of the smell of cherries, even though they had not been trained to have any fear of cherries.

 

[Florida Guy]

Very interesting and bound to be controversial. It doesn't seem to work in humans. The experiment will have to be redone a number of times before scientists are convinced. It reminds me of a few years ago some researchers said they had created fusion energy on a tabletop. For a while some scientists said yes it works but eventually it was found not to be true. Big claims require big proof

If we hated every food one of our ancestors hated, we might not eat anything at all

Another flaw in the experiment is the fact the next generations had no contact with cherries at all. It was a brand new smell and might have put them off. My bunny I had a while back was used to eating food from a certain bag for a long time. When the new bag came in, it was the same brand and everything but the silly creature would not eat it. It smelled different somehow. I mixed a bit of the old food with the new and eventually it ate the new food too.

 

[Rufous McKinney]

It doesn't seem to work in humans.

Why do you say that?

 

[Florida Guy]

Why do you say that?

Because we have seen many examples of children having different tastes than their parents or grandparents. Sometimes the parent will encourage children to eat a certain item but the kids might not like it. And vice versa, kids might like things their parents didn't like.

I've never heard about this before and if it were a thing, it seems we would have heard about it long ago.

 

[wabi-sabi]

have seen many examples of children having different tastes than their parents or grandparents.

Maybe because people are smarter than mice.

 

[linusbert]

Because we have seen many examples of children having different tastes than their parents or grandparents. Sometimes the parent will encourage children to eat a certain item but the kids might not like it. And vice versa, kids might like things their parents didn't like.

kids do not like bitter tastes. and love sweets. there must be a reason for that.
but if this has to do anything with this epigenetics? idk

Maybe because people are smarter than mice.

i would bet my money on the mice

 

[Florida Guy]

What they should have done is after they did that experiment they should have done it again but this time test mice that have never seen cherries nor have ever been shocked. I believe the mice would react very cautiously to the new odor. If they react the same as the mice whose grandparents were shocked, that disproves their conclusion

Animals are very cautious when they come in contact with something new in their environment. Particularly mice because they are prey for many larger animals. They are also very cautious when a new food source is found. A lot of things are toxic, they prefer to eat the usual things they always eat. So when they smell cherries, which they had not seen before, they are not going to run around trying to find and eat the cherries like mice that are used to cherries. The odor could mean a predator is near or it could be something poisonous. It will take a lot of testing before they will eat or respond positively to the smell

Like I said, my bunny did that when the food I offered seemed a tiny bit different that what she was used to. She wanted the exact same thing and it took a little while to get used to the new stuff

But its a cool story

 

[kushami]

It’s important to note that this study was about inducing a fear response, not a dislike for a certain food. The researchers could have shown the mice a particular colour, played a distinctive sound, or exposed them to a non-food smell in conjunction with the electric shock.

I imagine they chose a food because animals need to be able to identify poisonous foods, and they thought that would be easier to imprint a new fear on them because evolutionarily this would be a capacity that they already had.

And when the next generation of mice were exposed to the smell of cherries, they exhibited a fear response, not just a disinclination to eat cherries (although of course it follows that they wouldn’t eat something they were frightened of because they wouldn’t go near it).

So this wasn’t about inheriting likes or dislikes for a certain food, it was about inheriting a fear of a certain stimulus.

 

[Florida Guy]

So this wasn’t about inheriting likes or dislikes for a certain food, it was about inheriting a fear of a certain stimulus.

@kushami, that is most certainly true but its just another way of saying they responded negatively to the odor of cherry. What is a fear response? It would be to freeze up at first so the predator, if there was one, would not see them. What is the response to a new and possibly dangerous new stimuli? The very same, they pause, they are not afraid like they would be if they smelled a cat but a new odor means be careful until you identify it

So, mice who were used to eating cherries respond positively to the scent while mice who had never encountered such an odor reacted cautiously. Mice who had been shocked after the cherry odor also acted cautiously and were probably frightened since a shock might be coming. How do you tell the difference between caution in response to an unknown new stimulus and a fear response? They apparently conflated the two, mice freezing in fear and mice pausing to assess what the new odor might be

This experiment had no controls at all. It was not a real scientific study, more like a high school science fair project. One group of mice acted similarly to another group so they must be both afraid of cherries. That is a leap of faith, not a scientific conclusion based on the evidence. They should have tested normal mice to see how they react to a novel stimulus in their environment. Not doing so leaves a glaring hole in the results

Again, when I disagree with something, it is not at all a criticism of who brought it up. We need to find interesting anomalies like this and while much of what we find turns out to not work or may have a false conclusion, that is part of the scientific process. People who got better, who made a full level or more improvement were mostly people who tried a number of things. The first few they tried may not have helped but they kept going and found something that did. While this was not a possible treatment for cfs, it was interesting and if true, would have been a revolution in the field

 

[Vlad83]

The big idea: can you inherit memories from your ancestors?

This fascinating article details how a fearful aversion learned by mice can be passed down to offspring mice.

Mice, who normally love eating cherries, were presented with the smell of cherries, and then given mild electric shocks. The mice quickly associated the cherry scent with an adverse outcome, and they learnt to freeze in anticipation each time they got a waft of cherries.

The researchers then found that this learned aversion to the smell of cherries was passed down along two generations of mice: the offspring of the offspring of these mice were also highly fearful of the smell of cherries, even though they had not been trained to have any fear of cherries.

I read the article and found it quite fascinating. This makes sense evolutionary. We humans can teach our children to fear and avoid snakes, for example, but how would mice do that with no books or visual aids? If the offspring did not have that information passed to them somehow, hey would have fewer chances of survival.

The genetic modification they observed is wild. Does it suggest that learned experiences can actually transfer to the germline DNA sequence?

 

[Vlad83]

The genetic modification they observed is wild. Does it suggest that learned experiences can actually transfer to the germline DNA sequence?

Or through DNA methylation..

 

[wabi-sabi]

how would mice do that with no books

I have yet to hear of anyone training a dog to read, but they seem able to learn lots of other amazing things.

 

[hapl808]

i would bet my money on the mice

No mouse has ever tried to convince be that a theorized biopsychosocial model of medicine is, on its own, an explanation for all the things they don't understand.

 

[hapl808]

this point, the scientists took up the experiment again. Could the acquired association of a shock with the sweet smell possibly have been transmitted to the third generation? It had. The grandpups were highly fearful of and more sensitive to the smell of cherries. How had this happened? The team discovered that the DNA in the grandfather mouse’s sperm had changed shape. This in turn changed the way the neuronal circuit was laid down in his pups and their pups, rerouting some nerve cells from the nose away from the pleasure and reward circuits and connecting them to the amygdala, which is involved in fear.

It's interesting, but I think the nuance is not that specific fearful aversions are passed down (eg. the smell of cherries), but that general changes occur in the DNA. So maybe the mice are just less adventurous. I think this occurs in humans, too - but not in any specific ways that we can understand. The child of someone exposed to severe trauma might be more likely to have negative effects. I think that's a reasonable hypothesis, although far from proven.