Leaving the Memories … Or Not: What is the Psychology Behind Nostalgia?

“Congrats!” One of the most common expressions many people hear during their graduation symbolizes both a time of joy and moving forward but also provides one with the opportunity to reflect on a meaningful experience. The feeling of wanting to return to a prized memory is known as nostalgia—a feeling that many people have experienced before. While its scientific mechanisms are still being discovered, it is one of the most puzzling emotions, and its psychology can indicate a lot about the human brain. 

Nostalgia can be defined as the sentimental yearning for a return to a past period or moment in time that has ended, and it is facilitated by  memories of those events and experiences. A memory is the means by which the brain is able to process and store information. There are three main types of memories: sensory, short-term, and long-term. Sensory memory is the information collected daily by the five senses: sight, hearing, touch, taste, and smell. Sensory memory is only stored for a short period of time and is remembered in high detail, due to its short length. Short-term memory is information stored for a short period of time, ranging from a couple of seconds to minutes. This memory is also very high detail, and it is often readily available. However, long-term memory is the information stored for up to many years. 

Nostalgia is intricately intertwined with the brain’s memory pathways, since it is the longing for a sensory, short-term, or even long-term memory. A similarity between a present and past event can trigger this feeling. A scent that is similar to a home-cooked meal or a music genre that is similar to a very popular, memorable one are both examples of what can induce nostalgia. The mechanisms that occur in the brain as a result of the feeling of nostalgia are not as unknown as the true psychology behind the feeling. Nostalgia stimulates metabolic activity and blood flow into various regions of the brain. These regions include the midbrain, frontal, limbic, and paralimbic areas of the brain. For example, listening to nostalgic music can stimulate more activity in regions such as the inferior frontal gyrus, cerebellum, and insula in comparison to when this feeling is not present. 

The stimulation of these other parts of the brain are linked to the reward system, activated when nostalgia is experienced. The reward centers of the brain include the hippocampus, ventral tegmental area, and the ventral striatum. A systematic review led by Ziyan Yang and published in the National Library of Medicine describes the patterns in brain activity that are associated with nostalgia. This systematic review encompasses the methods by which nostalgia is rooted in autobiographical memory. Nostalgia relies on the recalling of one’s past, including meaningful episodes and experiences. One of the most important aspects of this publication regards the multivariate pattern analysis (MVPA), a type of algorithm that involves more than one brain region. MVPA allows for scientists to observe the changes and decode the patterns within many specific parts of the brain simultaneously, allowing for the distinction between nostalgia and similar emotions. A study involved participants watching emotional movies and later imagining situations in which they would feel the same emotions they felt during those movies. A classifier—a machine learning tool that recognizes patterns—was trained on the participants’ brain activity during the movie to learn the different neural signatures (distinctive pattern of brain activity) associated with each emotion. The significance of this study is that it demonstrates how basic emotions—such as anger, sadness, joy, etc—have distinct and consistent neural patterns that MVPA could recognize. While this study focuses on basic emotions, it opens the possibility for future research of MVPA to distinguish between nostalgia and its neural signatures in comparison to basic emotions.  

One of the future paths in researching nostalgia and its psychology involves the multivariate approach. Traditional neuroimaging involves the identification of regions that are linked to nostalgia, such as the medial prefrontal cortex or the anterior cingulate cortex (ACC). However, such traditional methods can’t identify the main reason why these specific regions are stimulated. Namely, the ACC is involved in emotional regulation and cognitive control, but studying and observing the ACC won’t give scientists a comprehensive understanding of nostalgia pathways. In her systematic review, Yang put an emphasis on the need to understand nostalgia by analyzing the specific component processes, such as emotional regulation, associated instead of the respective regions. 

As previously described, MVPA allows for the observation of many constituents of the brain at once. MVPA can be used to analyze the activation patterns among these different regions to predict subjective experiences of nostalgia. This is similar to the mechanisms of studies that predict fear ratings based on brain activity. Piecing together observations from these various regions in the brain allows for a holistic analysis of the psychology behind nostalgia.      

When reliving memories or past experiences, these emotions may feel satisfying and comforting. However, multivariate analysis is still developing an understanding of the processes behind emotional responses to memory. The next time you experience nostalgia, remember that these memories and feelings are more complex than you think!