Prof Dirk De Ridder has a hands-on relationship with southern brains, as both a neurosurgeon and Neurological Foundation professor of neurosurgery at the University of Otago. He talks to David Loughrey about phantoms, how brains create God, and the relative nature of morality.
To stare inside the human brain is also to look right back out.
For deep within that strange and complex organ are the circuits that process how we see ourselves and the world around us.
It is, Prof De Ridder says, the source of the concepts humans hold above all others - our morality, our sense of self, and our sense of God; or lack thereof.
It is also a home of tumours, of illnesses such as food, drug and alcohol addiction, and phantom pains and noises.
And its study raises all sorts of philosophical questions.
Those are questions Prof De Ridder began asking as a teenager, ironically motivated in part by his Catholic education.
Prof De Ridder is a man befitting his academic and surgical roles, with a grey-white shock of hair, a Belgian accent, and occasional quirks of word order.
A leading Belgian neurosurgeon and brain researcher, he was appointed the inaugural professor of neurosurgery in 2012, to lead New Zealand's first academic neurosurgery unit.
He spends half his time as a Dunedin Hospital neurosurgeon.
From age 13 he became ''very interested in philosophy and art''.
That involved trying to understand issues like ''what life's about, what love's about, what's important in life, what's not important in life.''
''That was because I went to a Catholic school where that was part of the training.
''In the fifth year of high school, year 12 here, I had a teacher who wasn't following the normal course whatsoever.
The teacher of Greek and Latin would deviate from what was normally supposed to be taught, adding poetry, philosophy and even music.
''He was an extremely engaging and very motivating teacher.''
After a year as an exchange student in the United States, he started medical school in Belgium.
''In medical school I was really attracted to the brain.
''The way I looked at it, it controlled everything, and probably also controlled my former interests of art and philosophy - everything I was interested in at the time.
''I wanted to understand what is beauty, how does the brain create beauty, how does the brain create religion, how does the brain create phantom percepts?''
From private practice as a neurosurgeon, he moved to more research-based roles, and in interest in neuromodulation.
''If we understand how the brain works, we can use magnetic or electrical stimuli to change the working of the brain.''
His work focused on tinnitus and ''phantom pain'' such as the pain patients where an amputated limb had been.
He moved to Dunedin after being appointed in 2012, as the city had ''a good neuroscience department'' he could collaborate with, to develop new ways of modulating the brain.
''Being a surgeon, my interest is, of course, to insert electrodes in the brain to treat diseases.''
The idea, in the case of alcohol addiction, was to try to reduce the overactivity in the network in the brain that controlled craving - the drive to drink.
''This craving is in the same area, whether it's for alcohol, or for food, or for sex, or for gaming.''
Two patients had received implants so far, one in Belgium, which had been ''very successful''.
In the second, a procedure done in Dunedin about three weeks ago to treat alcohol addiction, ''we're still looking for the perfect stimulation parameters in order to suppress it''.
The study of the brain, and in particular its ability to throw up phantom pain and conditions such as tinnitus, leads to questions of human perception of concepts such as morality and God.
If electrodes can change one aspect of the brain, what could they do to another?
''I went to a Catholic school, but I'm not religious whatsoever,'' Prof De Ridder says.
''I have no particular bias towards or against it, which I think is very important.''
''When I started thinking about religion, from an evolutionary point of view it makes sense that people would resort to religion.
''Once people became aware of themselves, they also automatically became aware of others.
''To the network in the brain that deals with understanding of the self and the other, you add one or two areas, then another couple, then the network becomes bigger and bigger though evolution.
''Then you have the social brain - the social brain automatically leads to non-religious morality.''
An example of that was when you had two tribes in an area, and one tribe developed a ''morality'' gene that meant members would not kill each other, but collaborate.
''Then that tribe will become more powerful than the one next door, because the one group says we won't kill each other, we will only kill the others.
''They will kill other clans, meaning the morality gene will develop.''
The problem was morality ruled what people should do or not do, but there was no external referee.
''It's like playing a rugby game without a referee.
''You need a referee to say how far you can go.
''That's why after the development in evolution, religion came about.''
There is also, Prof De Ridder says, evidence from within the brain that can explain aspects of religious experience.
That relates to what he calls ''phantom percepts''.
An example is Horatio Nelson, the 18th-century naval officer who lost his arm in battle.
Nelson, like many who lose a hand, could still feel his fingers.
He used that as an argument to argue for a God who could be felt but not seen.
Prof De Ridder sees it another way.
''So what if we can perceive God because it is a phantom, ultimately of the non-self, the other?''When people lost some of their hearing, after a rock concert for instance, the lost frequencies were
filled in by the brain as a ringing in the ears.
''This filling-in is the same for phantom pain.
''If you read religious texts, prophets who wanted to get in contact with God, they went to the desert for a long time, they went where there were no stimuli whatsoever.
''So if there are no social stimuli, the brain starts creating them.
''The brain itself creates consciousness, or a belief in God, or a belief God doesn't exist, by all these different brain cells; they have to be connected in a very specific way in order to generate a feeling of me, a feeling of God, a feeling that God doesn't exist.
''That also means for me that everything is very relative, and there is nothing that is absolute, from a brain point of view.
''Even morality.''
Prof De Ridder says morality is just what brain circuits tell us to be: but these are modifiable.
''And so there is no absolute morality.
''By studying the brain and seeing how it adapts to the environment, it has taught me that there is nothing which is absolute, nothing which is dogmatic, that everything is just depending on how the environment changes, and that's the only thing your brain picks up; changes in the environment.''
That ''probably has made me a lot more open-minded I would say, less dogmatic''.
But if morality is relative, an evolutionary trick of the brain, where does that leave us?
''Morality is extremely important, because if you live with a lot of people in a certain space there have to be rules, so that it becomes livable.
''Even if I disagree with some of those moral rules, you have to accept that there are rules.''
