Brain drain: scientists look at why mental exertion triggers exhaustion

Prolonged mental activity leads to buildup of potentially toxic neurotransmitter in brain, study finds

It's a familiar feeling on a Friday evening. After finishing a gruelling day's work, you finally agree with friends on where to meet for a night out.

But by the time you have figured out what to wear and where you left your keys, a night on the sofa begins to sound more appealing than one on the tiles.