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It is something all good map readers have long suspected - sat-navs dull the mind.

A study found the brain is less active when we blindly follow directions than when we try to work out the route ourselves, causing regions thought to be key to navigation to become particularly quiet.

The finding, which will be seized upon by those who have been ridiculed for refusing to abandon their 'old-fashioned' road maps and A-Zs, comes from a University College London study into how we navigate.

A study found the brain is less active when we blindly follow directions such as from a sat-nav (pictured) than when we try to work out the route ourselves, causing regions thought to be key to navigation to become particularly quiet

The researchers began by taking a group of healthy men and women to Soho in central London and giving them a thorough tour of the warren of bustling streets and the shops, bars and cafes in them.

A detailed exam followed and confirmed that they had got to know the area well.

A day later, the volunteers' brains were scanned as they watched films of the streets they had walked around.

Sometimes they were asked to navigate to a particular destination. Other times, they were shown the destination and then given directions to follow.

The scans showed that two brain areas light up when navigating.

The first is active at the start of a journey and seems to compute the distance as a crow flies.

The second, neighbouring area, then calculates the distance as we weave and wind our way along the route, with detours and junctions sparking flurries of activity.

Interestingly, when the volunteers simply followed instructions, similar to using a sat nav, the two brain regions abandoned their calculations.

Researcher Dr Hugo Spiers said: 'What happens to the brain when using the sat-nav is that these areas stop tracking.

In an experiment, people were asked to navigate to a particular destination and when they manually had to find a location (illustrated by map reading) scans showed that two brain areas light up

'There is absolutely no interest in the distance to the goal.'

The brain in general was also much less active. However, Dr Spiers says this isn't necessarily a bad thing, as it frees up the mind to concentrate on other tasks.

It is thought that the two navigation hubs may simply work better in those who have a good sense of direction.

And despite the long-standing joke about women being worse at navigating and map-reading than men, the study didn't find any differences between the sexes. The topic will be the subject of 'intensive' further research.

The scans revealed two brain areas light up when navigating. The first is active at the start of a journey and computes the distance as a crow flies. The second area calculates the distance as people weave along the route, with detours and junctions sparking flurries of activity. A stock image of an MRI scan is pictured

The research, detailed in the journal Current Biology, could help shed light on dementia.

Alzheimer's patients often become disorientated and the two brain regions identified – the entorhinal cortex and the hippocampus – are among the first to be attacked by the disease.

Dr John Williams, of the Wellcome Trust, which funded the research, said: 'These results provide some explanation as to why such patients struggle to find their way and become lost.

'Combining these findings with clinical work could enable medical benefits in the future.'