MY MUCH-delayed flight from Dublin circles over a snow-covered London, waiting for a landing slot as weather teams fight to clear the Heathrow runways. From above the landscape looks eerily serene. The vivid whiteness everywhere eventually tires the eye. I find myself drifting through the clouds, as if swimming in air. There is a sensation of weightlessness that uncannily evokes a dream experienced by a lovelorn Gael Garcia Bernal in The Science of Sleep.

"You see something and you think of something else, " Michel Gondry tells me, after I belatedly reach his Mayfair hotel. He wrote and directed The Science of Sleep, and also directed the Oscar-winning Eternal Sunshine Of The Spotless Mind. Dreams are his obsession. The previous day I'd seen a preview of The Science of Sleep. I'd been thinking of what I might say to him when I dozed off on the plane.

"You rewire your brain when you do that. The fact is you're refreshing some old connections, and that's very much what's going to be in your dream. If I see an image, even if it's only a glimpse, it triggers a memory. I remember watching The Pianist and that shot of the keyboard seen from above, but just a little upside down. It reminded me of the Salvador Dali painting of the crucifixion, suspended forward.

My brain made the connection and I had a dream about the painting."

There's a similar shot in The Science of Sleep, a brilliantly unorthodox comedy peppered with snatches from Gondry's own dreams. It's a romance between a student, whose dreams constantly invade his waking life, and a neighbour - Charlotte Gainsbourg - with whom he imagines himself to be in love but is incapable of relating to in real life. It's set in Paris and filmed in the same apartment where Gondry once lived. The couple are called Stephane and Stephanie and are in many ways opposite sides of his own self, as indeed are all the characters.

"I was very depressed when I was doing this film, " he says.

"The dream in which Stephane gets married with Stephanie was a dream I had with a previous girlfriend who left me when I was filming Eternal Sunshine. It was exactly like that. I was thinking why doesn't she want to get married with me, and she was saying, 'Just ask me for Christ's sake, ask me what you want to say, ' so I'd say, 'Do you want to get married?' 'YES, ' she'd say.

And then I'd wake up and realise it was a dream. It was horrible.

I'd prefer to dream I'd killed someone. At least when I'd wake up I'd be happy I hadn't killed anyone."

Whereas other people might go to a psychiatrist to explain their dreams, Gondry's first instinct has always been to make a music video or a movie. His distinctive way of blurring perceptions - mixing live-action with charmingly primitive stopmotion animation - has made him a top director of commercials. He's worked several times with Bjork, the Chemical Brothers, Daft Punk, the Rolling Stones and the White Stripes, notably on their celebrated 'Fell In Love With A Girl' video, which depicted Jack and Meg White as animated Lego figures. Every shot had to be done by hand and it took two months to make.

What particularly intrigues Gondry is the after-life of a dream. "When you wake up you believe the dream's real for a certain amount of time, " he says.

"When you go to sleep, the analytical part of your brain is put to sleep as well. Sometimes when you wake up it's still asleep, it's slower that the rest of the brain to wake up."

Gondry has revolutionised the way dreams and memories are depicted on the screen, whether in his 2001 debut movie Human Nature, a comic parable about a scientist trying to civilise an enfant sauvage (a man raised in the wild), and most particularly Eternal Sunshine Of The Spotless Mind, an original story by Gondry - written, like Human Nature, in collaboration with Charlie Kaufman - in which Jim Carrey and Kate Winslet attempt to rejuvenate a failed romance by erasing all memory of it from their minds and starting all over again.

Gondry grew up in Versailles, outside Paris, where his father ran a music shop. "I constantly go back to a mixed-up version of it in my dreams, " he says. He'd go to sleep as a child to the sounds of his mother playing the piano downstairs. "She particularly liked Debussy and 'La Mer' with its rippling sound of the sea. My grandfather was a jazz musician and my father played jazz as well.

I was surrounded by music."

His parents gave Gondry and his elder brother Olivier - who also became a music-video director - a drum kit and bass guitar with which they formed a punk band. When he was studying graphics and animation in Paris he became a drummer for a band called Oui Oui, for which he made his first videos on 16mm.

"Our family totally went with whatever we did, however quirky. It's more important to be accepted at home than by your peers when you are really young, because that's when you build all your emotions and your opinions and your self-esteem. I'd rather be unpopular at school - not that I was, I was normal - and popular at home. You need to be free to daydream as a child. That way you learn better to communicate with the outside world."

A soft-spoken man with curly brown hair, he sits back in a leather couch and shrugs. "I'm trying to do that now with my 15year-old son, " he says. "I encourage him to dream."

He's just finished filming Be Kind Rewind with Jack Black, Mos Def, Mia Farrow and Danny Glover. It's about people working in a video rental store who accidentally erase all their stock and try to cover up by re-filming - from illustrations on the sleeves - whatever movie their sole customer wants to rent. "It comes from another of my dreams, " he says.

"There's no escaping them.

Sometimes I'm scared to fall asleep because I'm afraid where I'm going to end up. It's like I'm being drawn into a whirlpool.

One of the reasons I have a lot of insomnia is this fear of falling asleep."

'The Science of Sleep' opened on Friday