Is déjà vu a real memory event you could learn to trigger?

We sometimes get the feeling of having been here before. It fades fast, leaving nothing to point to, no earlier scene, just a strong certainty you have experienced this moment already. Is it a memory glitch, a near-match firing without its source? Or a real glimpse into the future? And can it be reproduced on demand?

open-question·neuroscience·memory