Thread by @fMRI_guy

As a pain researcher, I'm honestly wondering what he thinks the right answer is here. Let's review some of the most important facts, shall we?
First, defining pain is a bit of an issue. You can have pain signals in the nerves without any perceived pain and vice versa. 1/7

https://twitter.com/tedcruz/status/1233131075184078851

That's why doctors say, correctly, that the best measure of pain is asking someone "how bad is your pain." It's the best method we have!
Now you might be wondering, if that's the case, how would we ever know if an infant or animal is in pain? And that is, in fact, complicated: 2/

Many non-verbal beings still show effects of pain: animals might howl and avoid the painful stimulus. But we also know that signaling behavior (e.g. howling) is connected to the social behavior of an animal: if it's solitary, it won't signal. That means you might see an animal 3/

shrug off the painful stimulus and you won't ever know if it actually "feels" any pain. And avoidance behavior? You see that even in microbes. It doesn't tell you much.

So where does this all leave us in terms of fetuses? 4/7

Well, at the very least, the following has to be there in order to perceive pain: a connection between the thalamus (the hub that relays pain signals from the body) and the somatosensory cortex (the area that registers perceived pain). Thankfully, we know when that comes in. 5/7

As you can see in this fairly recent paper from @FrontNeurosci, the relevant thalamocortical connections develop slowly over time, and are complete around the third trimester. 6/7
ncbi.nlm.nih.gov/pmc/articles/P…

So, my dearest @tedcruz, let me know when you think a fetus can feel physical pain. I can tell you what science says: that it's unlikely we'll ever get a clear answer to the question, but that, in all probability, pain perception is impossible before the third trimester. 7/7