The sleep of bees. So human

So different, yet so alike. Through pollination, bees play an important role in the ecosystem, affecting the life cycle of plants, biodiversity and agricultural production. Their presence goes hand in hand with human activity. Now, a study at the University of Trento suggests an even deeper connection. What happens in the brains of these insects during sleep turns out to be not so different from what occurs in the human brain when we sleep. In other words, sleep appears to carry the same "signature" at the neuronal level.

These findings are detailed in the article "Neuronal correlates of sleep in honey bees", now published in the journal Neural Networks.

Albrecht Haase is the principal investigator of this study, which was partly funded by Brain Network Dynamics (BRANDY), a strategic initiative of the University of Trento. The research team included Sebastian Moguilner, Ettore Tiraboschi, Giacomo Fantoni, Heather Strelevitz, Hamid Soleimani, Luca Del Torre, and Uri Hasson. They are all members of the Center for Mind/Brain Sciences (CIMeC) at the University of Trento, where Haase directs the Neurophysics laboratory, in collaboration with the Department of Physics, and Hasson leads the Integration and Information group. The study drew on the diverse expertise of an interdisciplinary team of neuroscientists, neurobiologists, computational neuroscientists, bioinformaticians and physicists.

"For the first time, we have observed what happens in the brain of sleeping honey bees and we have identified neuronal network states which are signatures of sleep," Haase comments.

"The science of sleep has evolved considerably over the years, with research groups from all over the world striving to reveal the evolutionary origins and cognitive functions of sleep. Until now, however, the mechanisms of sleep in invertebrates at the neuronal level have remained largely unknown. Our study explores this new territory and offers the first imaging study to analyse sleep in insects at the neuronal network level," he says.

The researchers combined optical brain imaging, machine learning analysis and computational neural modelling to study how sleep influences the neural networks responsible for sensory perception, particularly the antennal lobes, which are the primary olfactory centres of bees. Data were collected automatically during the night, when bees naturally enter their sleep phase.

The bees’ body movements were monitored with a front-facing camera, while their brain activity was simultaneously recorded with a two-photon microscope. By analysing the calcium concentration in neurons, scientists were able to detect neuronal activity both during sleep and wakefulness.

"We have shown that, in resting states, the brain networks of bees switch to a synchronised and reduced information processing mode, similar to what happens in mammals. Using computational simulations of the brain, we identified how the neural network and its connections change during sleep. The model shows that changing a single parameter, the synaptic coupling between neurons, caused the brain to no longer optimise the decoding of odour signals. This reduction of olfactory perception is consistent with what typically occurs during sleep, also in humans."

Will your findings influence future research in this field?

"This work is important for basic neuroscience, but it also contributes to research on the global concern for pollinator health. Honey bees are a key species, with a profound impact on ecosystem stability, biodiversity and agricultural productivity because of their role in pollination. By revealing how sleep modulates their sensory information processing, these methods can help to understand how environmental stress, pesticides and climate change can affect the sleep of bees and therefore their behaviour, cognition and survival."

The results of this study at the University of Trento may therefore inspire further research into the function of sleep in bees. "During sleep, for example, bees consolidate the memory that allows them to build a cognitive map that they use to navigate to food sources."

In the future, the study could also provide new approaches in human neuroscience. "Honey bees offer the opportunity to study sleep at the level of individual neurons, which is impossible in humans. The parallels we have identified between bee and human sleep could open up new directions for research into memory consolidation and sleep disorders in humans."