This is exactly what happens in the brain when it uses context

From the most insignificant of decisions to life-altering choices, context is key. Context is what tells us to grab the heavy winter jacket on especially chilly mornings or pack some sunglasses while heading to the beach on a summer afternoon. It isn’t something we all consciously recognize as it happens, but the human mind is constantly using environmental information to help form choices.

Without context, life would be like trying to find your way through a pitch-black room forever. If a recently sober friend who had struggled with alcoholism in the past invited you over for a party, would you bring over a bottle of vodka? Of course not, and it’s easy to understand why given the context of your friend’s personal history. 

A new study just released by the University of Tsukuba and the National Eye Institute (NEI) has uncovered for the first time the neuronal processes responsible for humanity’s ability to instantly learn and establish context across any given situation.

In short, the study authors conclude contextual learning takes place within the brain’s basal ganglia region, facilitated by the movements of fast-spiking neurons.

“Value and reward are known to be encoded in the part of the brain called the basal ganglia,” explains Distinguished Investigator Dr. Okihide Hikosaka from the NEI. “We set out to identify the specific neuronal circuits underlying environment-based value learning.”

Somewhat ironically, these findings were not produced using human subjects. No, instead the research team looked to humanity’s closed relative in the animal kingdom: monkeys.

To start, each monkey was taught a game similar to the classic “Where’s Waldo?” books. Throughout several repeated rounds, the monkeys were shown a series of scenes and instructed to look through each one for “embedded objects” in exchange for rewards. Depending on the context of each scene, certain objects would result in larger rewards than others. Over the course of multiple repeated scenes and objects, the monkeys eventually learned (based on the context of each scene) which objects yielded the biggest rewards across each scene.

Once the monkeys had played this game for a while, they were able to almost always bring their visual attention immediately to the largest reward-offering objects and ignore other objects that resulted in smaller rewards. This held up even after researchers started switching scenes very quickly, forcing the monkeys to react quickly.

Now, it’s known that the basal ganglia brain region is responsible for motor movements, which of course includes eye movements. So, study authors theorized that a specific neuron found in the basal ganglia, called fast-spiking neurons, is responsible for contextual learning. To test their hypothesis, a drug was given to all the monkeys that blocked the input of fast-spiking neurons to various regions within the basal ganglia. Importantly, the primates were all given this drug just as they were attempting to learn new contextual associations between a fresh set of scenes and objects.

Sure enough, researchers noted that when neuronal input to the tail end of the primates’ striatums (a portion of the basal ganglia) was blocked, the monkeys could no longer learn new contextual associations regarding an object’s value based on the scene surrounding it.

It’s worth noting, however, that even while on the drug the monkeys were still able to recognize high-reward objects within scenes they had already studied. So, it seems blocking fast-spiking neurons doesn’t undo previously learned contextual understandings.

Besides the topical nature of these findings, the research team is quick to point out that their discoveries hold plenty of clinical potential as well.

“Reduced input from fast-spiking neurons has been observed in some clinical conditions,” comments study leader Dr. Jun Kunimatsu, an assistant professor at the University of Tsukuba, “including Tourette syndrome and Huntington’s disease, both of which are accompanied by deficits in skill learning that could be related to an inability to learn environment-based values.”

Many mysteries of the mind remain for humanity to uncover, but this work represents a major step forward in our collective understanding of how context is learned and processed within the brain.

The full study can be found here, published in the Proceedings of the National Academy of Sciences.