According to a new study led by Lund University scientist Stanley Heinze, a network of compass and speed neurons in the bee brain integrates every detail of changes in direction and distance covered on outbound journeys, and enables the insect to return directly home.
Brain of the sweat bee Megalopta genalis (body length: 1-2 cm). Highlight/inset shows compass regions. Abbreviations: CBL – lower division of the central body, CBU – upper division of the central body, LBU – lateral bulb, MBU – medial bulb, NO – noduli, PB – protocerebral bridge. Scale bars – 200 μm. Image credit: A. Narendra / Stone et al, doi: 10.1016/j.cub.2017.08.052.
Bees use their vision to navigate, but until now little was known about what happens inside their brains — which are smaller than a grain of rice — as they perform this task.
“Polarized-light-based compass neurons and optic-flow-based speed-encoding neurons are located in a part of the bee brain called the central complex,” the study authors explained.
“We found this region plays a pivotal role in controlling the navigation system — known as path integration or ‘dead reckoning’ — which is used by many animals, including bees, ants and humans.”
“These cells are used to add up all elements of the outbound journey, creating a memory that bees use to fly home by the most direct route.”
Dr. Heinze and colleagues unraveled the complex workings of the system by studying the brains of tropical nocturnal bees Megalopta genalis.
They monitored nerve function by attaching tiny electrodes to bees’ heads as the insects were shown virtual reality simulations of what they see when flying forward or rotating.
Their results, together with microscope studies of how the nerve cells are connected, were used to develop a detailed computer model of the bee’s brain.
The model was tested on a simulated bee and on a robot.
“The most exciting part of this research was when computer modeling of the ‘spaghetti’ of connections between nerve cells revealed the elegant principle by which bees keep track of their position and steer back home,” said co-author Professor Barbara Webb, from the University of Edinburgh in the UK.
“Understanding such a complex behavior at the level of single neurons is an important step forward for the science of brain function.”
The study is published in the journal Current Biology.
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Thomas Stone et al. An Anatomically Constrained Model for Path Integration in the Bee Brain. Current Biology, published online October 5, 2017; doi: 10.1016/j.cub.2017.08.052
