Laboratory of Nachum Ulanovsky

Research interests

Neural Codes for Natural Behaviors in the Bat Hippocampal Formation

Our lab investigates the neural basis of natural behaviors. We aim to uncover general principles of mammalian brain function, by capitalizing on the unique behaviors of bats – a novel animal model that we pioneered.  Our general approach is to utilize some of the advantages that bats afford – their temporally-discrete sensory system (sonar) and excellent vision, their 3D flight, fast movement, and their high sociality – in order to ask general questions in Systems Neuroscience, Behavioral Neuroscience, and Neuroethology; particularly questions that are difficult to address in rodents.  We focus on two types of behaviors: (1) Spatial behaviors: navigation, spatial cognition, and spatial learning & memory; and (2) Social behaviors: including social memory.  To pursue these questions, we develop world-unique Neurotechnologies – in particular, we develop tiny wireless-electrophysiology devices (neural loggers), weighing only a few grams, which enable recording from the bat's brain during natural behaviors, including flight, navigation, and social interactions with multiple individuals. These loggers include also many on-board behavioral sensors, such as ultrasonic microphone, motion sensor, altimeter, and GPS – allowing asking unique experimental questions in freely behaving, unrestrained animals. Our study species, Egyptian fruit bats, are excellent navigators and highly-social mammals – making them a great model organism for behavioral neuroscience, learning & memory, and social neuroscience. They are also large bats, weighing ~150-180 gr – allowing them to fly freely while carrying our neural-loggers.  Our long-term vision is to develop a "Natural Neuroscience" approach for studying the neural basis of behavior – tapping into the animal's natural behaviors in complex, large-scale, naturalistic settings – while not compromising on rigorous experimental control. We firmly believe that pursuing such an approach will lead to novel and surprising insights about the Brain.

Some of our main results in recent years included: the finding that in flight, 3D hippocampal place cells have nearly spherical 3D place fields.  Recordings in the bat presubiculum revealed 3D head-direction cells, which could serve as a 3D compass; and surprisingly, this compass followed a toroidal coordinate system – providing an interesting biological solution to the discontinuity and non-commutativity problems associated with a standard spherical coordinate system.  Recordings in entorhinal cortex of flying bats reveled 3D grid cells that exhibited fixed local distances between firing-fields, but no global hexagonal lattice – arguing against many of the prevailing theories on the function of grid cells, which rely on lattice-like periodicity.  We also discovered a new population of neurons in the hippocampus that are tuned to the egocentric direction and distance to navigational goals - a vectorial representation of spatial goals, which could provide a neural mechanism for goal-directed navigation.  In two studies (one and two) we showed nonoscillatory phase-coding in bat place-cells and grid-cells, without any theta oscillations – suggesting that phase-coding, but not oscillations, is conserved across species.  Behavioral studies included the discovery of a surprising optimization principle in the sonar system of Egyptian fruit bats; and outdoor research where we tracked bat navigation in the wild, using tiny GPS dataloggers – which provided evidence for a 'cognitive map' on a 100-km scale in bats.  Recently we constructed a huge behavioral setup – a 200-meter long tunnel – and found that in bats flying in a very large environment, hippocampal CA1 neurons exhibit a surprising neural code for space – a multifield multiscale code – where the fields of the same neuron differed up to 20-fold in size; theoretical analysis showed that this multiscale code reduced dramatically the decoding-errors. We also got interested in the neural basis of social behaviors, and discovered a population of hippocampal neurons that represent the spatial position of a conspecific bat, in allocentric coordinates ; these "social place-cells" may underlie social-spatial cognition in bats and other mammals. In pairs of bats flying in the long tunnel, hippocampal neurons exhibited extreme dynamism of the neural code – rapidly switching between coding position when flying alone, to jointly coding position x distance when encountering another bat.