Part memoir, part medical mystery, it is an unusual, provocative and cerebral book that is already creating waves in the literary and scientific realms. A longtime sufferer of migraine and mirror touch synaesthesia, an extreme form of empathy, Hustvedt is no stranger to what she calls her 'neurological oddities'.

She recalls years ago when her left arm jerked upward and slammed her into the wall, a precursor to a migraine that lasted almost a year. Her acclaimed fiction too, has long been coloured by an inquiry into the nature of mind and body. But the convulsions were something new.

'In some ways [the book] was born of a need for mastery,' she says. 'It was that sense of if you can't cure yourself then you can at least try to understand it, and I wrote it as it happened. So there was a sense of immediacy about the story that was kind of fun.'

By the end of her book she is still the shaking woman, with no cure in sight. But her search for a diagnosis doubles as an erudite philosophical inquiry into the nature of the relationship between psychiatry and neurology, and how these disciplines have evolved in the past two centuries.

Hustvedt is relentless in her interrogation of accepted thought in both science and philosophy. She deploys theories and individual stories from the past and present, and raises fundamental questions about the relationship between mind and body, as well as the nature of perception across the various disciplines.

Was her condition epilepsy, or was it hysteria, as it would have been diagnosed in a previous century, or conversion disorder? Where does the conscious 'I' begin and end? How, exactly, do we remember?

Hustvedt has often talked about her obsession with the worlds of neurology, psychiatry and psychotherapy, and jokes that even her author husband, Paul Auster, 'has often told me that I read too much'. But her fascination intensified while researching her 2008 novel, Sorrows of An American, when she studied pharmacology and attended monthly lectures on brain science at New York Psychoanalytic Institute.

She also took on the voluntary role of teaching writing to patients at New York's Payne Whitney Psychiatric Institute and says 'part of both my pleasure in and reason for writing the book was that I desperately wanted to point out how a lot of the received knowledge about all of this is bunk. Genes are not everything, learning is not everything, all of this interacts to make something so complicated that no single model, not from neuroscience, not from neurology, not from psychiatry, not from psychoanalysis, not from the arts, not from anywhere can really embrace (it). And part of what drove me to write it is that we really live in 'expert' culture, which means that people know more and more about less and less.'

But that 'expert' culture, it seems, is taking heed of this shaking woman. Since the book's release in Germany and Britain, she has garnered invitations to speak at prestigious expert gatherings, including the Sigmund Freud Foundation in Vienna where she is to present the annual Freud lecture in May next year. What she wants most to change is the inclusion of personal narrative into medical diagnosis. 'You have the DSM [Diagnostic Statistical Manual of mental disorders, produced by the American Psychiatric Association) which essentially isolates symptoms so that a psychiatrist can look at a person - often for not very long - and make a list of symptoms, give them a diagnosis then assign drugs to the diagnosis,' she says.

'But what I found working in a hospital was that all these people had a deep need to tell, and to be treated as human beings, not as diagnostic categories.'

The overwhelming human need for narrative is a recurring theme in conversation with Hustvedt. 'We all necessarily tell ourselves stories about our own lives and those stories don't remain the same, they shift over time. But we do cling to these narratives and I think we need them, and in a very real way, we are creating them. Memory is not a fixed business. We give everything meaning and so the way you perceive your illness is vital to how you live with it.

'There are ways to live with things that aren't often talked about within the culture, because illness has become the enemy. And I think at a certain point with my migraines, and now also with this seizure story, I have written it in such a way that it's easier for me to live with.'

Hustvedt also emanates a palpable sense of joy. She credits this largely to a newfound sense of intellectual agility. 'I think it is this sense now, in my deepening middle age, that I can really dance. I get a huge kick out of ideas and reading, but when I was in college and reading all kind of wonderful writers, I just didn't have a mind that was agile enough, and I felt a kind of sinking depression all through graduate school. That liberating sense of being able to leap and dance is, of course, a product of reading. It is a product of reading and thinking and maybe sensibility. It's not a product of some essential or natural gift.'

But whatever has or hasn't shaped her intellectual skills, Hustvedt vows: 'I'm just not going to take a single day, or a single thought for granted.' In fact, the 55-year-old author and essayist has completed a new novel due for release next spring titled The Summer Without Men, and she has also been commissioned to write a series of essays.

Then there is her ever growing list of speaking engagements. Indeed, Hustvedt admits that the trajectory of her career, which took on a life of its own after the success of her 2003 novel, What I Loved, has astonished her. 'It's kind of curious that it's worked out. I feel both pleased and a little amazed.'

She first dreamed of becoming a writer aged 13. But it was not until she completed her PhD in English at Columbia University that she felt her work worthy of publication. Her first book of poems was published the year after her marriage to Auster, and the enchanted memory of her first book sale - 'to a stranger' - has never left her.

'Whenever I'm feeling lousy I just say to myself, Siri, strangers are buying your books, just get back to it because that's what this is about. This is a magical business,' she adds. 'Magical.'