Key brain areas light up when rats help other rats they know
If you heard a cry for help, most likely you’d investigate and try to lend a hand to whoever had called. And if you were a rat, you’d likely do the same thing: we reported here on the eLife Podcast about 5 years ago on the observation that rats will release other rats caught in traps - even ones they don’t know - that look like they do. Now the same team that made that observation have gone a step further and identified the brain regions that are activated when the animals perform these Good Samaritan acts. Speaking with Chris Smith, Inbal Ben-Ami Bartal is at Tel-Aviv University…
Inbal - Rats tend to have kind of a bad rep, but they're really social creatures and they care a lot if they see a member of their own social group in distress. And what we find is that rats will learn to open a little restrainer, that's like a little trap, and release a cage mate or another rat from their own social group that is trapped inside. So we use this behaviour to look at what happens in the brain of these rats. What we do is actually measure which neurons were active while rats were performing this helping behaviour. And we compare that to another group that they don't care so much about. And we see the very same areas that are seen in humans that respond to other people's distress, active in rats that see a trapped rat in distress. Now, the interesting thing is that all the rats activated these brain regions, regardless of whether they actually help the trapped rat or not. But what does really predict whether rats will help or not is whether they activate a different network in the brain, which is a reward network in the brain.
Chris - Do you know what lies upstream of activating that reward centre then? Is it familiarity? This is my social group activate the reward centre, and that's the gatekeeper on whether you choose to act on this empathy signal? Or is something else then dictating what actually your behaviour is?
Inbal - That is kind of the million dollar question, isn't it Chris? We are really interested in understanding how the brain categorizes social identity of others and how that categorization determines the decisions that we make. And so what we see in this study is we see a very interesting network that connects these two systems, the empathy network in the brain and the reward network in the brain. And from the results that we find in this paper, there is an important link between these two networks that is important for helping behaviour. So in other words, when I see someone that I care about, then I act with more empathy towards that individual, and I am more motivated to help that individual in distress.
Chris - How do you know though that they're not getting that reward surge because they've helped the person, individual member of their social group that they care about, and actually the reward signal is coming downstream of the outcome, which is: "I helped them. And now I feel good about myself"?
Inbal - First of all, we still don't know all the answers, but we have a little hint that that is the case because we see that when areas in the empathy network are active in these rats, specifically a connection from the empathy network to the reward network, the more active this connection is the more likely rats are to help the trapped rats. And when we record live neuronal activity from these rats, as they're circling around a strapped individual, we see that the rewards network is active whenever the free rat is approaching the trapped rat, even before they learn to help.
Chris - So it's almost like they're anticipating how good they will feel if they help. And if that answer is big enough, because they are familiar with that social group that they're going to help, they want to do it. They're motivated to want to help.
Inbal - It's definitely possible that there is some anticipation of rewards, but since in the beginning, they don't even know that they can open the door and help, there could be another element that's involved here, an element of this motivational aspects of wanting to approach an individual that we care about when they are in distress. This very strong drive to approach with a prosocial intention is part of what we think is an evolutionarily ancient mechanism that evolved in across social species and mammalian species that had to take care of their offspring in order for the offspring to survive. So we, as mammals, developed this very strong urge to approach someone that we care about that is in distress and what we see in the reward and motivation network in the brain that is activated in these situations can be reflective of this drive to approach.
Chris - Can you mimic that effect? So if you take two rats that wouldn't normally help each other, can you inject that signal into the would-be helper to create the kind of mental effect as though they want to help, so they do?
Inbal - That is absolutely what we're working on right now in the lab. We're really interested in understanding how we can cause a shift in prosocial motivation in these rats, by stimulating those same areas. Environmentally, we can cause this shift in prosocial motivation. So in our previous eLife publication, we showed that if rats are housed for two weeks with a member of the other social group, not only do they begin to help that rat, but they know they also help strangers from the other group. And what we're trying to do now is to identify what changes in the brains of these rats while they're living together those two weeks. And can we artificially simulate that environment and cause rats to actually just really care about a rat from the other social group, even though they have no familiarity with the social group?