How many neurons are there in the human brain? It was a question that scientists thought they had nailed – and the answer was 100bn (give or take). If you went looking you would find that figure repeated widely in the neuroscience literature and beyond.
But when a researcher in Brazil called Dr Suzana Herculano-Houzel started digging, she discovered that no one in the field could actually remember where the 100bn figure had come from – let alone how it had been arrived at. So she set about discovering the true figure (HT to the excellent Nature neuroscience podcast NeuroPod).
This involved a remarkable – and to some I suspect unsettling – piece of research. Her team took the brains of four adult men, aged 50, 51, 54 and 71, and turned them into what she describes as “brain soup”. All of the men had died of non-neurological diseases and had donated their brains for research.