Not being able to sleep at night could be costing our mind dearly, as researchers have observed difference in brain function of people saying they have insomnia and those enjoying a full night`s sleep.

According to researchers at the University of California, San Diego, the poor sleepers struggled in focussing part of their brain during memory tests. Other experts said the brain`s wiring may actually be affecting perceptions of sleep quality, the BBC reported.

The findings, published in the journal Sleep, have shown how people with insomnia not just struggle to sleep at night, but it also has consequences for them during the day in terms of delayed reaction times and memory.

The study compared 25 people who said they had insomnia with as many describing themselves as good sleepers. MRI brain scans were carried out while they performed increasingly challenging memory tests.

Sean Drummond, one of the researchers, said: "We found that insomnia subjects did not properly turn on brain regions critical to a working memory task and did not turn off `mind-wandering` brain regions irrelevant to the task.

"This data helps us understand that people with insomnia not only have trouble sleeping at night, but their brains are not functioning as efficiently during the day."