Jenni Ogden takes the skull down from the top shelf in her library and pokes at its brain.
"It was under here they operated," she gestures, lifting a wrinkled, folded wedge and pointing to a piece shaped like a seahorse, called the hippocampus. The brain has two. Lose them and you lose your memory.
Ogden, a neuropsychologist, places the life-size model on a table and talks about the most studied patient in medical history, a cheerful American who throughout his adult life was known by the initials "H.M." to protect his identity.
His full name was Henry Gustav Molaison. His fame rests on an operation he had as a 27-year-old, when two holes were bored with a hand-drill through his forehead so a surgeon could suck out bits of his brain. In a risky operation, Henry lost most of his hippocampus on both sides of his brain, along with another blob of grey matter called the amygdala, which is thought to be linked to emotion and aggression.
That surgery, in 1953, designed to eliminate dreadful epilectic seizures that had made Henry's life a misery, had a tragic consequence. It left him without a memory - from that day until he died, at 82, in 2008.
Henry, says Ogden, could not remember what he was doing five minutes beforehand, he could not recall where he lived nor who cared for him, the day or the week or the fact he had a birthday the day before. He could recite some distant events from his childhood and early teens, but the rest was a blank sheet. Yet Henry was happy, generous and giving, and willingly took part in 50 years of tests - which he had no clue had had ever occurred. He lived, unable to store or retrieve new experiences, in the permanent present moment.
Remarkably, the operation that wiped out Henry's past was a milestone in neuroscience in that it led to a far deeper understanding of memory. Until his surgery - during which he remained awake - scientists believed memory was a function of the larger brain. The excavation beneath Henry's skull by Dr William Scoville turned that view on its head as the operation revealed that nearly all of our ability to hold or dig into past experiences was localised in the material taken away on the operating table.
Ogden was one of the few neuroscientists granted access to Henry, whose privacy was guarded by Suzanne Corkin at the Massachusetts Institute of Technology in Boston. Corkin, who became Henry's guardian when his parents died, led the massive research programme on "H.M." and gave Ogden, who had a year-long fellowship at the prestigious US university, the green light to study her patient at close quarters.
Eventually the New Zealand scientist wrote about Henry, but more about his personality than the research about memory processes and the brain mass that gives rise to remembering.
"He had a soul, he had a personality," remarked Ogden, recalling that she never found him angry or niggly, despite the frustrations of not knowing much about the here and now. Perhaps, she observes: "If you've got no memory it's hard to be angry, because you can't remember what to be angry about." Henry's personality was apparently similar to his father's, and that good humour and placid nature may have been at the core of Henry's identity.
Now retired from the University of Auckland, where she ran the postgraduate clinical psychology programme, Ogden has written about Henry and 14 other patients in Trouble In Mind, an absorbing and accessible account of people with brain disorders. Besides H.M., we meet Julian, who as a result of a tumour "misplaced his body", brain-damaged motorcyclist Michael who lost the ability to know what he was looking at, and Kate, who as a teenager had the left side of her brain removed to stop seizures but still enjoyed a fulfilling life.
"Half a brain will do the job," Kate told Ogden.
Henry is the only individual actually identified in the book and that, explains Ogden, is because the famous amnesiac became a public figure in death. Not only is H.M. named, but he appears, bespectacled and smiling, on the dedication page of her book.
The black and white picture was taken - against all MIT protocols and much to the horror of Professor Corkin - by the author during one of their sessions and caused a brief stir. "What on earth have you done?" a shocked Corkin asked Ogden. "No one is allowed to take pictures." A chastised Ogden duely gave her supervisor prints and negatives from her "Box Brownie". But she also kept one and, when the famous patient died, a desperate Corkin called her New Zealand colleague in the hope that one image remained. It did, and Ogden's illicit photograph was suddenly in hot demand.
Ogden, now 65, lives with her husband John on Great Barrier Island. They share a towering A-frame house and live, like everyone else on the Barrier, off the grid. Power comes from solar panels or sometimes in winter from a generator. A small, lively woman with infectious good-humour, Ogden welcomes the Weekend Herald with toast made from newly baked bread and a fresh pot of coffee. Though retired, the couple are far from idle. Ogden occasionally blogs about neuropsychology and has written three works of fiction with - naturally - psychological themes.
Born in Ashburton, Ogden initially studied to be a vet but stumbled over a paper during her studies at Massey. She turned to psychology and found her calling. Many of the patients who fill her book she found at Auckland Hospital, where as a young neuropsychologist she virtually had the ward to herself.
"I was lucky in that respect," she said.
It was there she found Janet, a bright, middle-aged woman whose brain ignored the left side of her world. Her disorder, called hemineglect, was caused by a malignant tumour. Ogden describes a poignant test she conducted with Janet, when she drew a circle on her right cheek and a large black cross on the left.
Asked what she saw in the bathroom mirror, Janet only registered the circle, calling it ridiculous.
"Is there anything else that looks ridiculous?" asked Ogden. "No. Isn't that enough?" responded the testy patient. Janet is one of the sadder cases in Ogden's book. Sent for surgery, doctors removed much of her tumour. Radiotherapy followed, before her carers devised rehabilitation to awaken her left side. A ribbon was tied to her left wrist and she was encouraged to look for it as she reached the right-hand side of reading material. Her tumour returned and her condition worsened until she died, four years after her diagnosis.
Ogden remembers her as a brave woman, who despite living on borrowed time, readily agreed to be part of a research project into the mysteries of her disorder.
On a brighter note, the author relates her encounters with Mike, the "mind-blind motorcyclist". As a young man, Mike had a dreadful bike smash. He lost an arm and nearly his life. He also suffered a head injury which rendered him blind. Ogden met him four years after the accident, called by a therapist who told her: "He seems to be getting his sight back but he still can't see."
She had struck gold. Michael had visual object agnosia, a disorder which left him unable to identify the object he was seeing through his admittedly tunnel vision. Shown a bicycle, he could see and name lines, circles, triangles and squares but his brain could not assemble the pieces into a bike. He had a second disorder, prosopagnosia, or an inability to recognise faces. He never recognised his mother after his accident, though she saw him most days, nor could he pick his own face from photographs.
Ogden says she had a long and rewarding relationship with Michael, even though his brain damage remained unchanged and his neuropsychological problems persisted.
She says she was careful to put boundaries around the connection to avoid the risk of Michael becoming a "professional subject".
"They [brain-injured patients] are often sitting around bored shitless. Of course they want to please," laughed Ogden.
Approaching 50, Michael remains a bright, upbeat man, reports Ogden, having spent half his life unable to visually recognise his family or the world beyond. For Ogden, the joy of having worked with Michael came from the sense that despite his minimal recovery from his head injury he managed to make the most of his life.
He told her: "I can see a little, but can conceive of all."
• Trouble In Mind by Jenni Ogden (Scribe RRP $37)