Biology subjects

Ulanovsky, N.

Publications and source records attributed to Ulanovsky, N..

4 recordsLinked to original sources

bioRxiv2026

Multi-scale place fields provide a predictive basis for hierarchical control

Hippocampal place cells typically exhibit unimodal spatial selectivity in small enclosures, but express multiple, irregularly spaced fields in environments of naturalistic scale. However, existing predictive-map theories of the hippocampus do not scale well to large environments and do not account for these heterogeneous place field characteristics. Here, we introduce the factorised hierarchical successor representation (fHSR), a predictive map that supports hierarchical control using subgoal-directed subroutines. We show that the fHSR allows efficient generalisation across tasks, scaling favourably with environmental size, and it reproduces key statistical and topological characteristics of multi-scale CA1 place cell activity in rats and bats. Analyses of experimental data further confirmed a novel prediction of the fHSR: population firing rates exhibit spatial periodicity with a characteristic wavelength independent of environmental size. These results identify the integration of hierarchical control and predictive representations as a normative principle that unifies efficient navigation with the spatial organisation of hippocampal activity.

neuroscience↗

bioRxiv2021

Spatial coding in the hippocampus of flying owls

The elucidation of spatial coding in the hippocampus requires exploring diverse animal species. While robust place-cells are found in the mammalian hippocampus, much less is known about spatial coding in the hippocampus of birds - and nothing is known about avian spatial representation during flight. Here we used a wireless-electrophysiology system to record single neurons in the hippocampus and related pallial structures from freely flying barn owls (Tyto alba) - a central-place nocturnal predator species with excellent navigational abilities. The owls 3D position was monitored while it flew back and forth between two perches. We found place cells - neurons that robustly represented the owls location during flight, and its flight-direction - as well as neurons that coded the owls perching position between flights. Spatial coding was invariant to changes in lighting conditions and to the position of a salient object in the room. Place cells were found in the anterior hippocampus and in the adjacent posterior hyperpallium apicale, and to a much lesser extent in the visual Wulst (visual-cortex homologue). The finding of place-cells in flying owls suggests commonalities in spatial coding across a variety of species - including rodents, bats and owls.

neuroscience↗

bioRxiv2020

Head-Direction Coding in the Hippocampal Formation of Birds

Birds strongly rely on spatial memory and navigation. Therefore, it is of utmost interest to reveal how space is represented in the avian brain. Here we used tetrodes to record neurons from the hippocampal formation of Japanese quails - a ground-dwelling species - while the quails roamed a 1x1-meter arena (>2,100 neurons from 23 birds). Whereas spatially-modulated cells (place-cells, border-cells, etc.) were generally not encountered, the firing-rate of 12% of the neurons was unimodally and significantly modulated by the head-azimuth - i.e. these were head-direction cells (HD cells). Typically, HD cells were maximally active at one preferred-direction and minimally at the opposite null-direction, with preferred-directions spanning all 360{degrees}. The HD tuning was relatively broad (mean width [~]130{degrees}), independent of the animals position and speed, and was stable during the recording-session. Similarly to findings in rodents, the HD tuning usually rotated with the rotation of a salient visual cue in the arena. These findings support the existence of an allocentric head-direction representation in the quail hippocampal formation, and provide the first demonstration of head-direction cells in birds.

neuroscience↗

bioRxiv2019

Dynamic control of cortical head-direction signal by angular velocity

The sense of direction requires accurate tracking of head direction at different turning-velocities, yet it remains unclear how this is achieved in the mammalian brain. Here we recorded head-direction cells in bat dorsal presubiculum and found that, surprisingly, the head-direction signal in this cortical region was dynamically controlled by angular velocity. In most neurons, a sharp head-direction tuning emerged at some angular velocity, but was absent at other velocities - resulting in a 4-fold increase in head-direction cell abundance. The head-direction tuning changed as a function of angular velocity primarily via a redistribution of spikes between the neurons preferred and null directions - while keeping the average firing-rate constant. These results could not be explained by existing ring-attractor models of the head-direction system. We propose a novel recurrent network model that accounts for the observed dynamics of head-direction cells. This model predicts that the new classes of cells we found can improve the sensitivity of the head-direction system to directional sensory cues, and support angular-velocity integration.

neuroscience↗