Many studies may have all along misinterpreted brain mapping data and overestimated the age of the human brain, suggests a new study that challenges current theories of brain ageing.
Previously reported changes in the ageing brain using functional magnetic resonance imaging (fMRI) may be due to vascular (or blood vessels) changes, rather than changes in neuronal activity which is associated with brain function, the findings showed.
The study suggests that older brains may be more similar to younger brains than previously thought.
A fundamental problem of fMRI is that it measures neural activity indirectly through changes in regional blood flow, the researchers pointed out.
"There is a need to refine the practice of conducting fMRI. Researchers should make use of available resting state data as a suitable alternative," said Kamen Tsvetanov from the University of Cambridge.
An alternative candidate for correction makes use of resting state fMRI measurements, which is easy to acquire in most fMRI experiments.
While this method has been difficult to validate in the past, the unique combination of an impressive data set across 335 healthy volunteers over the lifespan, allowed the team to probe the true nature of ageing effects on resting state fMRI signal amplitude.
The study found that the age differences in signal amplitude during a task are of a vascular but not of neuronal origin.
The new method can be used as a robust correction factor to control for vascular differences in fMRI studies of ageing, the study noted.
"These findings clearly show that without such correction methods, fMRI studies of the effects of age on cognition may misinterpret effect of age as a cognitive, rather than vascular, phenomena," Tsvetanov concluded.
However, Tsvetanov pointed out that "this does not mean that studies lacking 'golden standard' calibration measures, such as large scale studies, patient studies or ongoing longitudinal studies are invalid."
The study appeared in the journal Human Brain Mapping.
