Is your morning coffee half empty? Do you feel it’s always darkest before it goes pitch black?
Have you ever wondered why you, like each of us here, is such a pessimist – apart from, y’know, the fact everything inevitably goes horribly wrong all the time?
Well, now scientists think they may have figured the out answer. Keyword: may. You never know with these eggheads.
There are, we’re told, c-shaped nubs buried within each hemisphere of the brain called the caudate nuclei. A group of neuro-boffins at the Massachusetts Institute of Technology in America found that when these were stimulated in a pair of macaque monkeys, it caused them to make more pessimistic decisions.
“We feel we were seeing a proxy for anxiety, or depression, or some mix of the two,” said MIT Prof Ann Graybiel, a senior author of the study, which was published on Thursday in the journal Neuron. She believes it’s an important result because: “These psychiatric problems are still so very difficult to treat for many individuals suffering from them.”
In one experiment, the team tempted the monkeys with a reward of fruit juice. Some of the macaques were offered the sweet liquid if they accepted receiving an annoying puff of air to the face. The others were offered a small amount of juice unconditionally.
If the amount of juice offered in the first choice is large enough, the reward outweighs the sacrifice, and the monkeys willingly undergo the uncomfortable sensation of air blown in its face. However, if it’s not quite worth it, the monkeys will choose the second option.
Shocking state of current affairs
In a second round of experiments, the researchers stimulated the primates’ caudate nucleus with an electric current. The result: they no longer accepted the blast of air even though the same amount of juice was being offered as before. The behaviour continued for a while after the stimulation stopped, before eventually subsiding.
“This state we’ve mimicked has an overestimation of cost relative to benefit,” Graybiel explained. The researchers believe that activating the caudate nucleus drove the animals to focus more on the negative consequences of the reward, and made them more apathetic about the value of the juice.
(The act of sticking electric probes in their noggins might also have induced a few negative thoughts, never mind the caudate nuclei, but what do we know?)
Caudate nuclei are linked to limbic system in brain, an area responsible for regulating emotions and mood. The researchers believe that it could be a contributing factor to anxiety, depression or obsessive compulsive disorder by somehow disrupting dopamine levels in the brain.
“There must be many circuits involved,” she said. “But apparently we are so delicately balanced that just throwing the system off a little bit can rapidly change behavior.”
They are now working with psychiatrists at the McLean hospital in Boston to see if patients suffering from those disorders display any abnormal activity in their caudate nuclei when making decisions.
As for Reg hacks and likeminded readers: simply stop stimulating your caudate nuclei. Now you can enjoy your weekend. ®