Brain cells in Parkinson's disease exhaust themselves and die prematurely, burning out like an "overheating motor", an early study suggests.
Canadian researchers say the findings might help explain why only small parts of the brain are affected in the disease.
Parkinson's is caused by a loss of nerve cells in certain areas of the brain - but why these cells are vulnerable has been a mystery.
The work appears in Current Biology.
Tremor and stiffness
An estimated 127,000 people in the UK have Parkinson's disease, which can lead to a pronounced tremor, slow movement, and stiff and inflexible muscles.
In this paper, scientists from the University of Montreal studied the disease in mice cells.
They found, unlike other similar brain cells, neurons most often involved in Parkinson's disease were complex and had many more branches.
The cells also had much higher energy requirements, producing more waste products as they met this need.
Researchers suggest it is the accumulation of these waste products that triggers cell death.
Prof Louis-Eric Trudeau said: "Like a motor constantly running at high speed, these neurons need to produce an incredible amount of energy to function.
"They appear to exhaust themselves and die prematurely."
The team hope this finding may help create better experimental models of Parkinson's and identify new treatments.
They suggest, for example, that medication could one day be developed to help reduce the energy requirement of cells or increase their energy efficiency.
Dr Arthur Roach, at the charity Parkinson's UK, said:"Out of the billions of cells in the brain, it is always the same small group that degenerate and die in Parkinson's. We don't know why only these cells are affected.
"This study provides strong support to the idea that it is the unique structure and function of these cells that makes them especially susceptible to a damaging process called oxidative stress.
"We hope that this study will rekindle interest in the approach, and even lead to new treatments based on the most up-to-date ideas about oxidative stress."