She had suffered skull fractures and a brain injury and was taken to John Radcliffe Hospital in Oxford where she died six days later.

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Several years ago, therefore, Robin Dunbar, an anthropologist who now works at Oxford University, concluded that the cognitive power of the brain limits the size of the social network that an individual of any given species can develop.

ECONOMIST: Even online, the neocortex is the limit

Dr Roi Cohen Kadosh, study author from the department of experimental psychology at the University of Oxford, said the noise stimulation group showed improvements in cognitive and brain functions compared with the control group.

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In March, Oxford University researchers pinpointed variations of a gene that controls dopamine, a brain chemical associated with feelings of pleasure, as playing a key role in smoking addiction.

BBC: NEWS | Health | Faulty genes feed nicotine habit