Stimulation of the caudate nucleus causes an overestimation of negative aspects

Finding suggests that such stimulus leads to a misinterpretation of the cost/benefit ratio

Patients with anxiety, depression or OCD tend to place more emphasis on potential negative consequences than positive ones when faced with difficult decisions, often leading to irrational decisions or even inability to react.

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A negative attitude towards life confuses the ability to judge and, therefore, influences each decision in a negative way. This is particularly evident in the case of so-called attraction/repulsion conflicts, which are generally resolved by weighing the pros and cons of one choice against the other. American neuroscientists recently made an interesting discovery, published in Neuron magazine. In their work, they studied the behavior of laboratory animals confronted with an attraction/repulsion situation. A reward consisting of a juice was associated with an unpleasant stimulus, a breath of air on the snout.

In the first set of tests, the relationship between the reward (attraction) and the repellent stimulus was found to be variable. The animals made different decisions about whether or not to accept the risk. For some, the reward was high enough to compensate for the unpleasant breath of the air. In the second phase, however, the experiments were repeated after stimulation of the caudate nucleus. This large area of the basal ganglia is linked to the limbic system, which plays an important role in regulating emotions and mood. The researchers found that the cost-benefit analysis distorted after the caudate nucleus was stimulated. The animals began to refuse the reward. The risk, first accepted, was avoided after the stimulation. The effect of this stimulation remained unchanged until the next day and therefore slowly disappeared. Stimulation seems to lead animals to attach more importance to unpleasant sensations than to rewards.

The authors conclude by writing that they do not want to reduce the problem to a mechanistic or neuroanatomical level, but rather add an additional dimension for a better understanding of the phenomenon. Many people cannot recognize and abandon irrational or dysfunctional thoughts as such. Patients with Obsessive Compulsive Disorder (OCD), for example, engage in ritual behavior to avoid the alleged negative stimulus. Similarly, patients with depression tend to focus only on the negative aspects of a situation.

The researchers hope to be able to develop, if possible, a therapy based also on the results of this work.

Sources: 
1. Dr. S. Christoph “Wissenschaftler
beschreiben neurophysiologisches Korrelat von Pessimismus”. www.esanum.de
2. Amemori, K.-I., Amemori, S., Gibson, D. J. & Graybiel, A. M. Striatal Microstimulation Induces Persistent and Repetitive Negative Decision-Making Predicted by Striatal Beta-Band Oscillation. 
Neuron (2018). doi:10.1016/j.neuron.2018.07.022

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