Scientists will open a new frontier today in their understanding of one of life's most basic processes: pain. A research unit will, within tight ethical limits, shock, heat and poke people in an attempt to understand how the human body produces that hurting feeling.

Given that most people feel pain of some kind nearly every day, scientists are surprisingly still in the dark about how the process works. The new multimillion pound pain clinical research hub at King's College hospital in London will use state-of-the-art imaging techniques to look inside the brains and nervous systems of people suffering from pain. The aim is to discover fresh ways to measure pain and work out the effectiveness of current treatments.

Scientists will not just study the pain associated with trapping fingers in a door, a bee sting or a sharp poke in the ribs, all of which are defence mechanisms crucial for survival.

The ultimate goal at the unit, a planned five-year collaboration between King's College hospital, King's College London and the pharmaceutical company Pfizer, is to understand chronic pain.

"The area we're looking at is when the pain becomes pathological," said Magdi Hanna, director of pain services at King's College hospital and clinical director of the research centre.

"The pain has no function itself other than leading to other problems. When you have chronic pain from diabetes, that doesn't defend you at all. Or pain as a result of shingles, that doesn't defend you from anything."

A forthcoming study in the European Journal of Pain estimates that about one in seven people in the UK suffers from some sort of chronic pain.

"Patients in chronic pain at the moment are really having a raw deal both from facilities available across the country and the availability of medicines and treatments," Dr Hanna said. "More than 60% of people in chronic pain are not treated. Generally, the wider medical population do not recognise the symptoms of chronic pain and the seriousness as much as they should."

Chronic pain not only affects quality of life but also has various physiological effects. "Our immune response suffers when we have chronic pain, our defence mechanism suffers, our cardiovascular system suffers, control of our blood pressure becomes more poor, our heart functions less well," said Dr Hanna.

The unit will use everything from basic sensory equipment to test response to various stimuli to functional magnetic resonance imaging to look at what is happening in the brain in real time when a person is feeling pain.

"The only thing we know at the moment is that we think there is a special area that responds to painful stimuli - this is what we call the pain matrix," Dr Hanna said. The pain matrix includes areas such as the amygdala, the brain's alarm bell for danger, and the frontal cortex, the seat of the brain's higher cognitive functions. In addition, the relay station at the centre of the brain, the thalamus, lights up. As does the insula, the part of our brains responsible for recognising pain and disgust. But exactly how each bit of this complex system is activated in response to a painful event is a mystery.

Another task for the research team is to make pain easier for scientists to measure. "Until now, we've only ever had people's subjective measures of pain," said Steve Williams, head of imaging sciences at the institute of psychiatry at King's College London. "We don't know whether one person's ouch is equivalent to the next person's ouch, as we've never had an objective way of measuring it."

"If the pain is very mild, then how much nerve electricity occurs? We can measure that," Dr Hanna said. "And how much brain response as a result of that? We can start grading that a little bit more objectively than available with the tools we have now."

Having a more objective guide would allow doctors to fine-tune doses of drugs more accurately. The longer-term results of the research unit's work will, it is hoped, lead to new treatments.

"We will be finding a target either within the peripheral nervous system or the brain itself," said Dr Hanna. "At the moment, most of the drugs are like blanket drugs, they don't have very great activity in the site of action."

Using data from the research, scientists will be able to target drugs to specific areas of the brain or spinal cord through which they know that the pain signals travel. "If you have pain as a result of diabetes or shingles, then you can target individual components of that pain process, rather than just giving blanket painkillers," Dr Hanna said.

Prof Williams said there was scope for trying to understand some of the more esoteric mysteries that result from pain.

"Chronic pain patients seem to be suffering a greater rate of brain tissue loss than healthy volunteers," he said. "Whether they're self-medicating with alcohol or whatever, we don't know. We want to have a look at whether ongoing pain is detrimental to cognition."