Verified by 
In Jonathan Carroll’s novel The Ghost in Love, the residents of an apartment building suddenly find themselves able to return to the most special moment in their lives. These ranged from sitting across the table from a high-school boyfriend on their three-month anniversary or playing in the back yard with a long-dead sister, to staring into a blue sky and anticipating an upcoming trip to the beach with a new bride. The residents relive their special moments with such vivid intensity that they literally begin to fade out of the chronological present as they become more and more deeply enmeshed with their remembered past. While the physical universe outside of Carroll’s books doesn’t permit such reality exchanges, most of us can identify with the magnetic appeal that such special memories offer.
A recent MIT study with mice provides a neurological basis for this appeal. The researchers placed male mice in a cage with female mice for a period of time to create “happy memories,” then removed them from the female companionship and transferred them to a stressful environment for 10 days. Not surprisingly, the lonely, stressed-out male mice exhibited signs of depression (loss of interest in food, helplessness, etc.). Through a method called optogenetics—genetic engineering of neurons to make them fire in response to light—neurons that had activated in the presence of the female mice were reactivated to trigger a happy memory of that time. After these neurons triggered memories twice daily for a period of five days, the mice rapidly lost their symptoms of depression and returned to normal.
During the same period, researchers placed another group of depressed male mice back in the company of female mice twice a day. The prior happy memory of their encounter had not been triggered in these mice. Interestingly, they showed no improvement in their symptoms. As with the characters in Carroll’s novel, the mice responded more powerfully to the memory of a past pleasant experience than they did to the prospect of present and future pleasure.
Now, the mice’s apparent preference for a memory of past pleasure over the actuality of a new pleasure does not suggest that remembering happy times poses a risk to one’s experience of the present: The nostalgic mice did not physically fade out of the present for a perpetual return to the past, as Carroll’s characters do. Their strong positive reaction to the happy memories does, however, suggest a potential therapeutic value of nostalgia in the prevention and treatment of depression. Remembering our happy past, in other words, may better equip us to deal with the stressful present.
So the next time you find your mind wandering back to the good old days, indulge yourself. You’re not escaping reality; you’re preparing for it.
