As
London taxi drivers in training are busy learning how to navigate the
city’s thousands of streets and places of interest over a period of
years, the experience actually changes the very structure of their
brains, according to a report published online on Dec. 8 in Current Biology, a Cell Press publication.
The
findings add to evidence that learning changes the adult brain and
should come as encouraging news for life-long learning and also
rehabilitation after brain injury, says Eleanor Maguire of University
College London.
Becoming
a licensed London taxi driver is no easy feat. Trainees must acquire
what’s known as “the Knowledge,” learning 25,000 streets and their very
complicated layout as well as 20,000 landmarks. The learning process
generally takes three to four years, culminating in a series of exams
that only about half of trainees ultimately pass.
Maguire’s
earlier studies of London taxi drivers showed that they have more gray
matter in the back part of a brain structure called the hippocampus
compared to non-taxi drivers, and less in the front. The hippocampus
plays important roles in memory and spatial navigation. Those studies
suggested that the brain might have changed in order to accommodate an
internal “map” of London.
In
the new study, Maguire and colleague Katherine Woollett directly
examined this idea by following a group of trainee taxi drivers and
non-taxi driver controls, capturing images of their brain structure over
time and testing their memory.
At
the start, study participants showed no differences in either brain
structure or memory. Three to four years later, it was another story:
the researchers found an increase in gray matter in the back part of the
hippocampus of those trainees who qualified as taxi drivers. Changes
were not observed in those trainees who failed to qualify, or in the
non-taxi driver controls.
“The
human brain remains ‘plastic’ even in adult life, allowing it to adapt
when we learn new tasks,” says Maguire. “By following the trainee taxi
drivers over time as they acquired—or failed to acquire—’the Knowledge,’
we have seen directly and within individuals how the structure of the
hippocampus can change with external stimulation.”
Woollett
and Maguire speculate that the findings may reflect an increase in the
rate at which new neurons are generated and survive when faced with a
significant cognitive challenge, noting that the hippocampus is one of
the few brain areas where the birth of new neurons is known to occur.
Successful training might also strengthen the connections between
existing neurons.
It
remains less clear whether those who succeeded at becoming taxi drivers
had some inherent advantage over those who did not, Maguire adds.
“Could it be that those who qualified are genetically predisposed
towards having a more adaptable, ‘plastic’ hippocampus? This leaves the
perennial question of ‘nature versus nurture’ still open.”
Acquiring “the Knowledge” of London’s Layout Drives Structural Brain Changes
