On a sun-parched patch of land in Rehovot, Israel, two neuroscientists peer into the darkness of a 200-metre-long tunnel of their own design. The fabric panels of the snaking structure shimmer in the heat, while, inside, a study subject is navigating its dim length. Finally, out of the blackness bursts a bat, which executes a mid-air backflip to land upside down, hanging at the tunnel’s entrance.

Nachum Ulanovsky, the study leader, looks affectionately at the creature as his graduate student offers it a piece of banana — a reward for the valuable data it has just added to their latest study of how brains navigate.

The vast majority of experiments probing navigation in the brain have been done in the confines of labs, using earthbound rats and mice. Ulanovsky broke with the convention. He constructed the flight tunnel on a disused plot on the grounds of the Weizmann Institute of Science — the first of several planned arenas — because he wanted to find out how a mammalian brain navigates a more natural environment. In particular, he wanted to know how brains deal with a third dimension.

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