Neurotensin: The Neurotransmitter That Gives Value to Memories

Neurotensin is the protagonist in the storage of memories. It plays a fundamental role in the influence that rewards and punishments have on our behavior. Therefore, control over its levels could help to treat people with maladaptive social behaviors. On the other hand, this would open up an extremely dangerous path because we'd be far more manipulable.

Written and verified by the psychologist María Vélez.

Last update: 21 December, 2022

Memory is one of the most studied cognitive processes and continues to be the one that arouses the most curiosity and interest. Knowing how we can retain so much information, or how we’re able to give value to memories is something that continues to fascinate experts and non-experts alike.

For this reason, investigations are ongoing. In this article, we’re going to talk about a study published in the journal, Nature in 2022 that delved into the neurobiology of memory. More specifically, the substances and areas that are involved in assigning a positive or negative valence to a memory.

To better understand its results and implications, we’ll examine how memory and emotions are related and the mechanisms involved.

Emotion and memory

These two basic psychological processes are related. Throughout our lives, we receive an unquantifiable amount of stimuli. These pass through certain selection filters before being retained in order for us to function properly. Therefore, our brains are responsible for choosing those with greater meaning.

It’s well known that the brain areas involved in memory (hippocampus) and emotional processing (amygdala) are closely linked. This is so that the most important experiences are retained and retrieved more quickly.

It occurs thanks to the reward and punishment mechanisms that associate experiences and stimuli with pleasant or unpleasant sensations. In turn, they encourage behaviors to either approach or avoid these experiences.

Characteristics of emotions

What makes one piece of information stand out over another is how important it’s thought to be. In other words, how intense and unpleasant/pleasant an experience is. To understand, we have to look at the characteristics that our emotions possess. At a theoretical level, they’re classified into three dimensions:

• Activation. Level of stimulation or excitement that the emotion provokes. For example, low activation when we’re feeling calm.
• Valence. Level of like or dislike, ranging from positive to negative. For instance, positive valence when we’re feeling happy.
• Dominance. Our level of control. For example, low dominance when we feel afraid.

Thus, if an experience presents us with high levels of activation and positive valence, it’ll probably activate our reward system, strengthening its memory, and somehow encouraging us to repeat the experience.

How are memories valued?

So how is it determined whether something is pleasant or not and if it has a positive or negative valence? How is a value given to what eventually becomes a memory? This same question was asked by a research group from the Salk Institute in the United States in the study we mentioned earlier. They contextualized their research in the face of three facts that had already been studied:

• When learning is associated with a positive or negative experience, the information is transmitted in different ways through the amygdala.
• In this brain region, dopamine plays a fundamental role. However, it doesn’t differentiate between positive and negative.
• Neurotensin, present in the amygdala, is involved in both reward and punishment processing and affects long-term potentiation.

Neurotensin is a 13-amino acid peptide that’s present in the brain and neuroendocrine cells. It has varied and numerous implications. Among them are the intestinal absorption of fats, the modulation of reproductive hormones, and the regulation of other neurotransmitters. These are reduced in people suffering from schizophrenia.

The study

In their study, this group of researchers selectively deleted the neurotensin gene from amygdala cells. Mice were exposed to a task in which they had to learn the association between a tone and a pleasant result (sugar solution), and another tone and a puff of air (unpleasant).

The mice were unable to learn the relationship between the tone and the pleasurable experience. That’s to say, they couldn’t assign positive valence to the relationship. On the other hand, they did learn the link between the other tone and the negative stimulus.

Therefore, the researchers discovered that neurotensin plays a fundamental role in giving value to future memories. Especially in those that are related to pleasant experiences.

Implications

Even though this study was conducted with animals, the findings have a series of important implications both at a theoretical and clinical level. On the one hand, the research helps to understand the neurobiological mechanisms of memory. Indeed, knowing the regions and neurotransmitters involved makes it easier to understand their relationship with other processes and brain areas. In addition, it provides valuable information on how information is processed and how memories are consolidated.

On a practical level, neurotensin has already been studied as a treatment for schizophrenia due to its relationship with dopamine. Further promising results have also been discovered. In fact, as neurotensin is responsible for giving value to memories, a pharmacological treatment that reduces the intensity and relevance of negative experiences could be developed. If this were the case, it would help thousands of people suffering from anxiety disorders, depression, and post-traumatic stress.

In short, science never ceases to surprise us and open up new paths toward further knowledge.