Biology subjects

Robbe, D.

Publications and source records attributed to Robbe, D..

10 recordsLinked to original sources

bioRxiv2025

Lateralized foraging induces asymmetric corticostriatal plasticity in mice

With practice, animals perform reward-oriented actions faster and with less variability. The dorsal striatum (DS) plays a key role in this process, potentially through opposing changes in cortical input strength to the two main striatal projection neurons (D1- and D2-SPNs). To test this hypothesis, we trained mice in a foraging task requiring them to perform quarter-turns (QTs) in a single direction (counterclockwise, CCW) along the walls of square towers to collect drops of water. As training progressed, the number and speed of CCW QTs increased while the variability of their trajectory decreased. Whisker trimming in well-trained mice altered QTs kinematics, highlighting the role of tactile inputs in guiding these actions. Combining ex vivo patch-clamp recordings in the DS with glutamate uncaging in the barrel cortex, we mapped the cortical neurons monosynaptically connected to D1- or D2-SPNs and measured the strength of these connections in the contralateral hemispheres, relative to the turn direction. In well-trained mice, compared to naive controls, the contralateral hemisphere showed no major changes in D1- or D2-SPNs connectivity, despite increased excitation of cortical pyramidal neurons. In contrast, the ipsiversive hemisphere exhibited no change in cortical excitability but showed increased cortical connectivity and input strength to SPNs. These findings reveal an unexpected hemispheric asymmetry in corticostriatal connectivity during lateralized foraging, which may reflect a homeostatic process normalizing striatal activity across hemispheres despite unbalanced cortical input.

neuroscience↗

bioRxiv2025

The Towers Foraging Park: A Flexible Naturalistic Framework to Study Learning, Decision-Making, and Motor Control in Freely Moving Mice

Adaptive behavior depends on a variety of brain functions, such as learning, decision-making, spatial navigation and motor control, which have been studied using two main strategies. Trial-based tasks allow their mechanistic dissection but tend to generate highly stereotypical behavior, whereas open-field investigations capture naturalistic dynamics with less experimental control. To leverage the strengths of both approaches, we developed a behavioral framework which recreates dilemmas faced by animals during patch foraging. In the Tower Foraging Park (TFP), mice harvest rewards along square towers (patches) by making quarter-turns around them in a single direction (exploit) and alternating between towers (explore) as patches eventually deplete. Within a couple of sessions, naive mice performed quarter-turns in the rewarded direction with increasing vigor and reduced variability, and switched towers after short exploitation bouts. When the harvest direction was reversed, mice rapidly adapted their turning direction, with quarter-turn trajectory variability and speed becoming decoupled. Mice subjected to daily reversals adapted progressively faster, revealing meta-learning. When the next rewarding tower became harder to locate, all trained mice increased exploitation duration, although metalearners outperformed animals trained under stable contingencies. Altogether, the TFP produced behavior consistent with foraging theory and revealed new processes facilitating flexible foraging: meta-learning and the decoupling of movement variability and speed. Moreover, because the TFP accommodates diverse protocol variants, adheres to FAIR principles, and is fully compatible with modern neurophysiological techniques, it provides a promising platform for mechanistic investigations of brain functions underlying adaptive behavior while maintaining ethological validity.

animal behavior and cognition↗

bioRxiv2025

Sparse innervation and local heterogeneity in the vibrissal corticostriatal projection

The density and overlap of cortical axons in the dorsolateral striatum (DLS) have suggested that striatal neurons integrate widespread information from cortical regions that are functionally related. However, in vivo, DLS neuronal responses to sensory stimuli have shown unexpectedly high selectivity, raising questions about the actual degree of input convergence of functional corticostriatal projection on individual striatal cells. Here, we investigated this question by focusing on the projections from different whisker cortical columns, as they overlap in the striatum and are co-active during behavior. Using ex vivo patch-clamp recordings in the DLS and glutamate uncaging for focal stimulations in the barrel cortex, we were able to map the location of presynaptic neurons to individual striatal projection neurons (SPNs). We found that each SPN was innervated by cells located in a small number of whisker cortical columns scattered across the barrel field in the slice. Connectivity of single SPNs with cortical neurons was thus highly discontinuous horizontally, despite the presence of more potential connections. Moreover, connectivity patterns were specific to each cell, with neighboring SPNs sharing few common clusters of presynaptic cells in the cortex. Despite this sparse and distinct innervation of individual SPNs, the projection was topographically organized at the population level. Finally, we found similar innervation patterns for D1- and D2-type SPNs, but observed differences in synaptic strength in their connections with certain cortical layers, notably the associative layer 2/3. Our results suggest that the high convergence of somatosensory inputs to the striatum, enabled by diffuse and overlapping cortical innervation, is accomplished through sparse yet complementary connectivity to individual SPNs.

neuroscience↗

bioRxiv2024

Running, Fast and Slow: The Dorsal Striatum Sets the Cost of Movement During Foraging

Humans and other animals adjust when and how fast they execute goal-directed actions according to expected costs and benefits. Yet, the behavioral principles and brain regions underlying adaptive vigor control remain poorly understood. Here, we developed a self-paced foraging task in which rats must run across a motorized treadmill to collect rewards, allowing separate manipulation of benefit (reward delivery probability) and cost (effort). Throughout the foraging sessions, run timing and speed jointly reflected the rats idiosyncratic urgency to obtain rewards. In contrast, when the cost of crossing the treadmill increased, rats ran faster to maintain a high reward rate while run timing remained stable. Consistent with distinct mechanisms for adapting to costs or benefits, dorsal striatum lesions primarily limited running speed under effortful conditions, whereas ventral striatum lesions reduced rewardseeking urgency at session onset. Together, these findings suggest that vigor is modulated by costs and benefits through distinct striatal circuits.

neuroscience↗

bioRxiv2020

Maternal phylogenetic relationships and genetic variation among rare similar phenotype donkey breeds

Maternal inheritance is an indispensable aspect in donkey rare breed population biodiversity management and breeding programs. It is a challenge to characterize breeds genetic inheritance using morphology and historical records, we study mtDNA, to overcome those limitations. The mitochondrial DNA (mtDNA) sequencing is a highly informative system to investigate maternal lineages and breed linkage such as molecular evolution and phylogenetic relationships. Martina Franca, Ragusano, Pantesco and Catalonian donkey mtDNA sequencing analyses were used to study intraspecific genetic diversity and population structure, and to reconstruct phylogenetic relations among these geographically isolated breeds.A wide lost in variability among all breeds emerged. In this scenario, the primeval haplotypes, higher haplogroups variability and larger number of maternal lineages are preserved in Martina Franca and Ragusano. Accordingly, a putative pivotal role in the phyletic relationship is likely for such breeds.Given the level of endangerment undergone by these breeds, some actions are necessary to ensure their longtime survival and conservation. Improving the reproduction and management of existing populations, clarifying their historic interactions by studying the genetic status of their populations, extending and improving monitoring maternal lineages represent valid options.View Full Text

zoology↗

bioRxiv2020

The dorsal striatum sets the sensitivity to effort

The dorsal striatum (dS) has been implicated in storing and retrieving procedural memories and controlling movement kinematics (e.g., speed). Since procedural memories are expressed through movements, the exact nature of the dS function has proven difficult to delineate. Here we challenged rats in complementary tasks designed to alleviate this performance confound. Surprisingly, dS lesions spared task-specific procedural memories but altered the kinematics of their expression in motor routines. Further behavioral analyses combined with simulations in the optimal control framework indicated that these alterations reflected an increased sensitivity to effort with preserved reward-seeking and ability to modulate movement speed. By setting the sensitivity to effort, the dS contributes to the optimization of the energy invested into voluntary movements. Such an elementary function of the dS might explain its implication in both procedural decisions and the control of movement speed.

neuroscience↗

bioRxiv2019

The Embodied Nature of Well-Timed Behavior

How animals adapt their movements to take advantage of behaviorally-relevant time intervals is not well understood, especially in the supra-second timescale. It has been proposed that motor timing depends on the emergence of self-sustained dynamics across ensembles of neurons. Alternatively, evidence from operant conditioning suggests that animals can develop motor routines to adapt their behavior to fixed temporal constraints. But it is unclear whether animals can accurately time their behavior without the help of motor routines. To address this issue, we used a task in which rats, freely moving on a motorized treadmill, could obtain a reward if they approached it after a fixed interval. Most animals took advantage of the treadmill length and its moving direction to develop, by trial-and-error, a unique motor routine whose execution resulted in the precise timing of their reward approaches. Noticeably, when proficient animals occasionally failed to follow this routine, the timing of their reward approaches was systematically poor. In a second step, we trained naive animals in modified versions of the task specifically designed to prevent the development of this motor strategy. Compared to rats trained in the first protocol, these animals never reached a comparable level of timing accuracy. We conclude that motor timing critically depends on the ability of animals to develop motor routines adapted to the structure of their environment. Our work also suggests that self-sustained neuronal activity alone may not be sufficient to support motor timing, at least in the supra-second timescale.

animal behavior and cognition↗

bioRxiv2018

Response outcomes gate the impact of expectations on perceptual decisions

Perceptual decisions are not only determined by current sensory information but are also influenced by recent experience. Can the magnitude of expectation-based decision biases be flexibly modulated based on the outcome of previous decisions? We trained rats in several two-alternative forced choice auditory tasks, where the probability to repeat the previous stimulus category was varied in blocks of trials. All rats capitalized on the serial correlations of the stimulus sequence by consistently exploiting a transition bias: a tendency to repeat or alternate their previous response using an internal trial-by-trial estimate of the sequence repeating probability. Surprisingly, this expectation bias was null in trials immediately following an error. The internal estimate however was not reset and it became effective again causing a bias after the next correct response. This ability to rapidly activate and inactivate the bias was captured by a non-linear generative model of rat behavior, whereby a reward-driven modulatory signal gated the use of the latent estimate of the environment statistics on the current decision. These results demonstrate that rats use behavioral outcomes to flexibly modulate how expectations derived from the recent history influence their decisions.

neuroscience↗

bioRxiv2018

Dynamic Control of Hippocampal Spatial Coding Resolution by Local Visual Cues

The ability to flexibly navigate an environment relies on a hippocampal-dependent internal cognitive map. Explored space can be internally mapped at different spatial resolutions. However, whether hippocampal spatial coding resolution can be dynamically controlled within and between environments is unknown. In this work we recorded the firing of hippocampal principal cells in mice navigating virtual reality environments, which differed by the presence of local visual cues (virtual 3D objects). Objects improved spatial coding resolution globally with a higher proportion of place cells, smaller place fields, increased spatial selectivity and stability. Spatial coding resolution was notably enhanced locally near objects and could be rapidly tuned by their manipulations. In the presence of objects, place cells also displayed improved theta phase precession and theta timescale spike coordination. These results suggest that local visual cues can rapidly tune the resolution of the hippocampal mapping system within and between environments.

neuroscience↗

bioRxiv2017

A minority-ruled population coding of kinematics in the striatum

The structure of population activity in the dorsolateral striatum during the performance of motor sequences has not been characterized and it is unclear if striatal ensembles encode (predict) kinematic parameters defining how sequences are executed. Here we analyzed hundreds of striatal spike trains from naive and trained rats performing a running sequence. We found that the population response was composed of a diversity of phasic modulations covering the entire sequence. The accuracy of kinematics encoding by single neurons was around chance level but improved when neuronal ensembles were considered. The distribution of single-neuron contributions to ensemble encoding was highly skewed with a minority of neurons responsible for most of the encoding accuracy. Importantly, running speed ensemble encoding improved after learning. We propose that during motor learning, striatal ensembles adjust their task representation by tuning the activity of a minority of neurons to the kinematic parameters most relevant to motor performance.

neuroscience↗