Thursday, April 30, 2020

In findings published last month in the journal Current Biology, neuroscientists from the Netherlands Institute for Neuroscience examined harm aversion in laboratory rats for conspecifics — rats not wanting to hurt other members of the same species — and reported which region of the brain was crucial for it. Wikinews caught up with Dr Christian Keysers and Dr Valeria Gazzola, two of the authors who contributed to the paper.

For the experiment, the rats were put in a container with two levers. The rats were trained to develop a preference for one of the two levers: each delivering one pellet of sucrose. One of the two levers was harder to press.

After developing a preference, the preferred lever was wired to deliver a shock to another rat in a neighbouring compartment, while delivering a single pellet of sucrose. The study showed the actor rat, which pressed the lever tend to switch the lever to avoid shocking the other rat. The rat receiving the shock was called a victim rat.

Aversion of harm to fellow rats was reported to be equal in both male and female rats. If the actor rats were previously exposed to the shocks, their degree of harm aversion for others was heightened, the study revealed.

The investigation reported the rats avoided pressing the preferred lever to shock another rat, even if that lever delivered two sucrose pellets and the no-harm lever delivered only one. However, this was not the case when the rats were given three pellets by the shock lever. Most of the actor rats did not switch when they received three pellets pressing the lever, which also delivered an electric shock. Dr Gazzola called it a “tipping point” and said it was a “cost-benefit” function.

The study also revealed the importance of the anterior cingulate cortex (ACC) region of the rat’s brain for harm aversion. The scientists tested harm aversion for conspecifics in the rodents after deactivating the ACC using muscimol. Muscimol was injected in the rats belonging to the test group, while saline water was injected to rats in the control group. The observations showed without the active ACC due to muscimol, the active rats in the test group were no longer averse to harming the victim rats, but degree of harm aversion did not drop in the control group rats.