Stimulating the Caudate Nucleus: Why the Glass May Seem Half Empty to You

November 2, 2018


Have you ever felt like your judgement was being clouded by pessimism? Have you ever wondered why you focus on the downside of a situation rather than the upside? Well, researchers at MIT have recently found that stimulating a region of the brain known as the caudate nucleus, likely has an impact on your mood and the decisions that you make.

The caudate nucleus is located deep in the brain on both the right and left hemispheres. It is known to play a significant role in storing and processing memories but in recent years, it has been connected to emotional decision-making. Previously, a neural circuit was found to affect a type of decision-making known as approach-avoidance conflict. Approach-avoidance conflict is described as an element of stress where a situation/goal may seem appealing and unappealing at the same time. Therefore, there are both positive and negative feelings involved which ultimately becomes a conflict for a person making a decision.


With approach-avoidance conflict in mind, researchers at MIT decided to run a test on animals. They stimulated the animal’s caudate nucleus with a compact electrical current and the animals were then given juice as their reward along with a puff of air to the face, acting as the negative stimuli. It is important to note that the ratio between the positive reward (juice) and the negative stimuli (puff of air) was different in each trial and the animals were given the opportunity to choose whether to accept the reward or not.

If the reward is seen as good enough to outweigh the negative stimuli, then the animals will accept the reward. However, if the ratio is too low and the reward is not seen as high enough, the animals will reject it. This is known as the cost-benefit calculation which was skewed once the researchers had stimulated the animals’ caudate nucleus. The animals avoided combinations that would have previously been accepted and this avoidance remained after the stimulation was terminated. The results imply that the value of the reward (juice) decreased and the cost of the unwanted stimuli (puff of air) was heavily focused on.


The researchers also discovered that the brainwave activity, specifically the beta frequency, changed within the caudate nucleus once decision-making patterns altered. Ultimately, electrical activity in the beta frequency may help indicate whether a patient will respond well to a drug treatment or not.

Though this is a big discovery, the next step is to see if the same effect will occur in humans. While the caudate nucleus is connected to the limbic system (system which plays a role in mood regulation) a lot more research needs to be done in order to confirm the caudate nucleus’ complete function.