Laboratory of Nachum Ulanovsky
Neural Codes for 2D and 3D Space in Bat Hippocampus and Entorhinal Cortex
Our lab focuses on elucidating the neural basis of spatial cognition, navigation, and spatial memory in the mammalian hippocampal formation – using bats as a novel animal model that we pioneered. Out study species, the Egyptian fruit bat, is a large bat species weighing ~150-180 gr, which allows the bat to carry wireless neural telemetry and neuro-logging devices, optogenetic stimulators, miniaturized GPS systems, and more – all in flight. Some of our main results in recent years include finding grid-cells in the entorhinal cortex of crawling bats, without theta oscillations – arguing against theta-based models of grid cells. We also succeeded in recording neural spiking activity in freely flying bats, using a custom neural-telemetry system, and have found that in flight, 3D hippocampal place cells had nearly spherical 3D place fields. Recordings in the bat presubiculum revealed 3D head-direction tuning in many 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 assiciated with a standard spherical coordinate system. Further, we 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. We also discovered recently a surprising optimization principle in the sonar system of Egyptian fruit bats. Additional studies included tracking of bat navigation in the wild, using tiny GPS dataloggers, which provided evidence for a 'cognitive map' on a 100-km scale in bats.
Overall, our general approach is to take advantage of the unique properties of bats – their temporally-discrete sensory system (sonar) and excellent vision, and their 3D flight abilities – in order to ask general questions in Systems Neuroscience; particularly questions that are difficult to address using rodents. 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.