https://aeon.co/essays/nostalgia-doesnt-need-real-memories-an-imagined-past-works-as-well
A more tractable version of this second reading was championed by Charles Zwingman's medical analysis of nostalgia in 1960, according to which what the subject wants is for gratifying features from past experiences to be reinstated in the present, presumably because the current situation lacks them. Although a person might feel nostalgia about a childhood friendship, her longing would actually be satisfied not by travelling back in time but by improving her current relationships. There are two advantages to this approach. First, it helps to understand nostalgia's particular instantation of Gorgias' paradox: the nostalgic individual wrongly attributes the desirable features of the object to an unrecoverable event, when in reality those features can be dissociated from it and reattached to a current condition. Second, this approach can help to understand recent findings suggesting that nostalgia can be motivational, and can increase optimism, creativity and pro-social behaviours.
Neuroscience tells us that, when we imagine, we redeploy much of the same neural mechanisms that we would have employed had we actually engaged in the simulated action. When we imagine biking, we engage much of the same brain regions we'd have engaged had we actually been biking.
Coined by the Swiss physician Johannes Hofer in 1688, 'nostalgia' referred to a medical condition - homesickness - characterised by an incapacitating longing for one's motherland. Hover favoured the term because it combined two essential features of the illness: the desire to return home (nostos) and the pain (algos) of being unable to do so. Nostalgia's symptomatology was imprecise - it included rumination, melancholia, insomnia, anxiety and lack of appetite - and was thought to affect primarily soldiers and sailors. Physicians also disagreed about its cause. Hofer thought that nostalgia was caused by nerve vibrations where traces of ideas of the motherland 'still cling', whereas others, noticing that is was found predominantly among Swiss soldiers fighting at lower altitudes, proposed instead that nostalgia was caused by changes in atmospheric pressure, or eardrum damage from the clanging of Swiss cowbells. Once nostalgia was identified among soldiers from various nationalities, the idea that it was geographically specific was abandoned.
Indeed, feeling nostalgic for a time one didn't actually live through appears to be a common phenomenon if all the chatrooms, Facebook pages and websites dedicated to it are anything to go by. In fact, a new word has been coined to capture this precise variant of nostalgia – anemoia, defined by the Urban Dictionary and the Dictionary of Obscure Sorrows as 'nostalgia for a time you've never known'.
Although memory and imagination are usually thought of as different, a number of critical findings in the past three decades have challenged this view. In 1985, the psychologist Endel Tulving in Toronto observed that his amnesiac patient 'N N' not only had difficulty remembering his past: he also had trouble imagining possible future events. This led Tulving to suggest that remembering the past and imagining the future were two processes of a single system for mental time-travel. Further support for this hypothesis came in the early 2000s, as a number of scientific studies confirmed that both remembering the past and imagining the future engage the brain's so-called 'default network'. But in the past decade, it has become clear that the brain's default network supports mental simulations of other hypothetical events too, such as episodes that could have occured in one's past but didn't, atemporal routine activities (eg, brushing teeth), mind-wandering, spatial navigation, imagining other people's thoughts (mentalising) and narrative comprehension, among others. As a result, researchers now think that what unifies this common neural network isn't just mental time-travel, but rather a more general kind of psychological process characterised by being self-relevant, socially significant and episodically, dynamically imaginative.