Ah yes, I remember it well

No film afforded me more pleasure or food for thought in 2000 than Memento. And no theatre piece afforded me more pleasure or food for thought in 1999 than Mnemonic. It perhaps is no accident that these two works (Christopher Nolan's dazzling reverse-chronology film and Theatre de Complicite's profound synaptic-sizzle of a drama) grapple with the phenomenon of memory. The tricky processes and the human significance of memory - whether on individual level (as in "recovered memories" of childhood abuse) or the collective (post-totalitarian public inquests, say) are preoccupying artists as never before.

No film afforded me more pleasure or food for thought in 2000 than Memento. And no theatre piece afforded me more pleasure or food for thought in 1999 than Mnemonic. It perhaps is no accident that these two works (Christopher Nolan's dazzling reverse-chronology film and Theatre de Complicite's profound synaptic-sizzle of a drama) grapple with the phenomenon of memory. The tricky processes and the human significance of memory - whether on individual level (as in "recovered memories" of childhood abuse) or the collective (post-totalitarian public inquests, say) are preoccupying artists as never before.

Next month, Simon McBurney and company will revive Mnemonic at the National Theatre and later this month, there's a transfer from the Cottesloe to the Olivier for Di Trevis's sold-out stage adaptation of Harold Pinter's never-filmed screenplay of the greatest novel on the subject: Proust's A la Recherche du Temps Perdu. The conjunction of the two invites a consideration of how drama has attempted to convey this crucial aspect of consciousness.

In a large proportion of memory-plays an autobiographical narrator revisits scenes from childhood. His or her past is as objectively "there" to be dropped in on as Madame Tussaud's or the National Gallery. An equivalent falsity in movies is the supposedly subjective flashback where the retrieval of history is so comprehensive and unimpeded that it actually contains information the "rememberer" is in no position to access. The fact that remembering is a complex negotiation involving what we recall from the past, believe about the present, and fearfully or desiringly anticipate of the future is largely evaded in such works.

The idea of the central figure in a memory piece as some kind of solicitous, curatorial time-traveller was brilliantly demolished in Peter Nichols's 1971 play, Forget-Me-Not Lane where the dynamic nature of recollection and the truth that it takes place in a psychological present tense are vibrantly demonstrated. The title of John Buchan's autobiography is Memory, Hold the Door, but this sounds an unrealistically genteel activity compared to what happens in Forget-Me-Not Lane where memories of the author's wartime adolescence and of a household dominated by his overbearing autodidactic salesman father (welcomed back at weekends about as warmly as if he'd been the Luftwaffe) bucket rudely through the stylised line-up of doors on the semi-circular set.

As the various resummoned characters mutinously chip back at the middle-aged Nichols-surrogate ("We are part of your mental landscape for ever, ducky") or appeal over his head to the audience, the vaudeville velocity of the piece gives the lie to any conviction that we can control our recollections or that they are unshaped by present needs. The year before had seen the premiere of John Mortimer's A Voyage Round My Father, another autobiographical memory-play about a dominating patriarch. But while it's a vivid, funny and touching portrait of this blind, Bard-quoting lawyer, the earlier play adopts a safely conventional approach to the on-going drama of remembering.

Mnemonic and the stage version of Remembrance of Things Past both understand that one method of communicating the behaviour of memory is to create a parallel activity for the audience to experience. The Proust play has the tougher task here since the cumulative rhythms of voluntary and involuntary recollection and the stereoscopic nature of seeing into the past are far easier to substantiate in a 3,500-page first-person novel than they are in just under three hours of stage time. The results at the National are only patchily successful. The incisive surgery and the abrupt suggestiveness of the original screenplay get muffled. But bravely avoiding the easy, banal option of having an author-presenter, the Pinter/Trevis Remembrance plunges you straight into a dream-like flurry of motifs (the vital, triggering trip on the paving stones; the ringing of the garden-gate bell at Combray etc), so that, instructively, you seem to be living inside Marcel's memory before either he or you can climactically unlock the significance of these impressions for his life and his art.

Mnemonic recruits the audience as collaborators in a more head-on manner. It begins with a kind of mass séance. After filling you in on the latest research on the workings of memory, Simon McBurney, acting here as a cross between a stand-up comic and a philosopher-hypnotist, invites the audience to don the blindfolds and hold the single leaves provided in little plastic bags. He then invites you to concentrate on ever more distant and misty moments from your past (New Year's Day, 1999; your first day at school etc) and then on the receding vistas of ancestry which, viewed far back enough, relate everyone in the theatre to each other. He encourages you to feel the leaf, imagining that its veins are the complex lines of heritage ending in the stalk which is you.

This prelude ushers you into a wondrous piece which imitates brain function in itself being like a sizzle of connections across the collective synapses as it takes you on two detective trails into the past. One follows the forensic and ethical debate surrounding the real-life 1991 discovery in the Austrian Alps of the ice-preserved naked body of a Neolithic man from 5,200 years ago. Paralleling this, in a blizzard of synchronicities, is the hunt across present-day Eastern Europe and the history of the 20th century undertaken by a young woman who has discovered that the father she never met may still be alive. In the no-man's-land between is her insomniac boyfriend, played by McBurney. He furnishes the piece with its central image of a naked man lying on his left side - now the ice-man, now the boyfriend. Our moral duty to the past and its memory, our obligation not to treat it as a tourist attraction are movingly illustrated at the end in a tumbling-through-time choreographed sequence where the rotating cast take it in turns to assume the pose of (and identify with) the mummified naked ice-man.

"I just feel that if I don't have a past, I can't live in the present," reveals the questing girl in Mnemonic. What, though, if her grasp of her life-story were incomplete not because of the politics of the time, but through neurological disorder? It's this problem which is excellently dramatised in the movie Memento and in Peter Brook's 1998 theatre piece, Je Suis Un Phenomene. Memento must be the first movie about a revenger (here of a raped, murdered wife) who can only glory in his bloody vengeance for a matter of seconds because he has lost his short-term memory. The protagonist is an insurance investigator and what the reverse chronology of the movie brilliantly achieves is the ironic, gradually unfolding suspicion that the loss of short-term memory can be a semi-willed insurance policy as well as brain damage. A series of overlapping flashbacks each offer us a more complete view of this man's history. And for once, the "objectivity" of the flashback convention feels both legitimate artistically and morally creepy because we repeatedly have access to his immediate past which our hero's brain crucially denies him.

Je Suis Un Phenomene, by contrast, focuses on the real-life case of a person, the Russian memory man, Solomon Shereshevsky, whose problem was that he could remember everything but had little power to make the abstractions from experience on which "intelligence" depends. There was a humanely unreductive sense of awe and mystery in Brook's multi-media evocation of this figure's inner world: the video monitors flashing up the multiplicity of synaesthetic associations involving colour, shape and taste that enabled him to recite uncomprehendingly a long passage from The Divine Comedy. The protagonist of Memento would, perhaps too readily, agree with the head of a memory-enhancement institute in Saul Bellow's Bellarosa Connection who claims that "Memory is life". To be unable to forget anything, though, would be close to a living hell.