Biology subjects

Sauer, J.-F.

Publications and source records attributed to Sauer, J.-F..

6 recordsLinked to original sources

bioRxiv2026

Generalized prefrontal task-progress sequences efficiently encode task structure

The medial prefrontal cortex (mPFC) occupies a central role in executive function including decision-making, rule learning and cognitive flexibility. Here, we investigated how mPFC populations represent the animal's progression along sequential task stages. Freely moving mice performed an odour-guided two-choice task requiring sensory sampling, action selection, navigation, and reward collection. Population activity in the mPFC formed sequences that evolved through cue sampling, movement towards the reward sites, and reward-related epochs. These sequences exhibited a shared temporal organization across trial types, pointing to a generalized encoding of task progress by prefrontal neurons. Artificial neural networks trained on the same task developed task-progress sequences, and experimentally disrupting task-progress tuning in these networks impaired learning efficiency. Our results indicate that mPFC activity organizes behavioural episodes along correlated trajectories and suggest that task-progress tuning offers an efficient solution for the encoding of task space during multi-stage behaviour.

neuroscience↗

bioRxiv2025

Formation of Task Representations and Replay in Mouse Medial Prefrontal Cortex

The medial prefrontal cortex (mPFC) is thought to support cognitive flexibility by forming and maintaining generalized representations of abstract tasks. The formation of these representations as well as their relation to preexisting representations of contextual or spatial information is incompletely understood. In this study, we analyzed longitudinal 1-photon calcium recordings in mice performing an olfaction-guided spatial memory task over an eight-week period that included habituation, training, and sleep epochs. Our results reveal that, while a minority of neurons initially conveyed significant information about the behavior of the animal, the bulk of task-related activity only emerged after the animals reached proficient performance. Although goal arm information is robustly represented at both the single-cell and network levels both during learning and in task proficient mice, it undergoes significant remapping throughout the learning process. Additionally, we identified the establishment of recurring sequences during learning and their replay at reward locations, with no evidence of them existing during odor sampling phase, during sleep or before training. Conversely, during odor sampling, information about odor identity is robustly available in the rate coactivation patterns, even before animals reached task proficiency. These findings suggest that the mPFC predominantly establishes generalized task representations de novo during learning, relying only minimally on preexisting spatial representations and that sub-second neural sequences in the mPFC are more likely involved in evaluating behavioral outcomes rather than planning future actions.

neuroscience↗

bioRxiv2025

Coordinated representational drift supports stable place coding in hippocampal CA1

The phenomenon of representational drift (i.e., changing neuronal tuning during repeated exposure to the same stimuli), is a fundamental paradox in neuroscience that raises the question how stable behaviour can emerge from unstable neural representations. Place cells in CA1 of the hippocampus are crucial for spatial navigation and memories1 but show gradual changes in their preferred firing location over time when exposed to the same environment2-9. This drift occurs despite the fact that the animal maintains the ability to navigate and to perform spatial tasks, suggesting a complex relationship between neural activity and behaviour. Here, we show that while the spatial tuning functions of individual CA1 neurons drift over time, stable space coding prevails at the population level: Representational drift is not random but can be described as a translation and rotation in population state space, which preserves the internal geometry of population activity over time. Compensating for the coordinated translation and rotation allows for drift correction and a recovery of spatial tuning on future days. Moreover, the preserved internal geometry stabilises downstream readout under noisy conditions. We propose that the conserved population geometry might serve as a mechanism by which downstream reader networks achieve effective drift correction and, thus, ameliorate the readout of stable information.

neuroscience↗

bioRxiv2021

Disrupted-in-Schizophrenia-1 is required for proper pyramidal cell-interneuron communication and network dynamics in the prefrontal cortex.

We interrogated prefrontal circuit function in mice lacking Disrupted-in-schizophrenia-1 (Disc1-mutant mice), a risk factor for psychiatric disorders. Single-unit recordings in awake mice revealed reduced average firing rates of fast-spiking interneurons (INTs), including optogenetically identified parvalbumin-positive cells, and a lower proportion of INTs phase-coupled to ongoing gamma oscillations. Moreover, we observed decreased spike transmission efficacy at local pyramidal cell (PYR)-INT connections in vivo, suggesting a reduced excitatory effect of local glutamatergic inputs as a potential mechanism of lower INT rates. On the network level, impaired INT function resulted in altered activation of PYR assemblies: While assembly activations were observed equally often, the expression strength of individual assembly patterns was significantly higher in Disc1-mutant mice. Our data thus reveal a role of Disc1 in shaping the properties of prefrontal assembly patterns by setting prefrontal INT responsiveness to glutamatergic drive.

neuroscience↗

bioRxiv2021

Phase-specific pooling of sparse assembly activity by respiration-related brain oscillations

Nasal breathing affects cognitive functions, but it has remained largely unclear how respiration-driven inputs shape information processing in neuronal circuits. Current theories emphasize the role of neuronal assemblies, coalitions of transiently active pyramidal cells, as the core unit of cortical network computations. Here, we show that respiration-related oscillations (RROs) directly pace the activation of neuronal assemblies in the medial prefrontal cortex (mPFC) of mice. Neuronal assemblies are more efficiently entrained than single neurons and activate preferentially during the descending phase of RROs. At the same time, overlap between individual assemblies is minimized during descending RRO due to the efficient recruitment of GABAergic neurons by assemblies. Our results thus suggest the RROs support cortical operations by defining time windows of enhanced yet segregated assembly activity.

neuroscience↗

bioRxiv2021

Topographically organized representation of space and context in the medial prefrontal cortex

Spatial tuning of neocortical pyramidal cells has been observed in diverse cortical regions and is thought to rely primarily on input from the hippocampal formation. Despite the well-studied hippocampal place code, many properties of the neocortical spatial tuning system are still insufficiently understood. In particular, it has remained unclear how the topography of direct anatomical connections from hippocampus to neocortex affects spatial tuning depth, and whether the dynamics of spatial coding in the hippocampal output region CA1 such as remapping in novel environments is transmitted to the neocortex. Using mice navigating through virtual environments we addressed these questions in the mouse medial prefrontal cortex, which receives direct input from the hippocampus. We find a rapidly emerging prefrontal representation of space in the absence of task rules, which discriminates familiar from novel environments and is reinstated upon re-exposure to the same familiar environment. Topographical analysis revealed a dorso-ventral gradient in the representation of the own position, which runs opposite to the innervation density of hippocampal inputs. Jointly, these results reveal a dynamically emerging and topographically organized prefrontal place code during spontaneous locomotion. Significance StatementThe neocortex is composed of areas with specialized function (e.g. sensory vs. associational). Despite this functional diversity, emerging evidences suggest that the encoding of space might be a universal feature of cortical circuits. Here, we identified a gradient of spatial tuning depth along the dorso-ventral axis. A complex topography of spatial tuning properties might support a division of labor among medial prefrontal cortical subnetworks to support local circuit computation relevant for the execution of context-dependent behavioral outcomes.

neuroscience↗