Biology subjects

Ciocchi, S.

Publications and source records attributed to Ciocchi, S..

3 recordsLinked to original sources

bioRxiv2023

Hippocampal networks support reinforcement learning in partially observable environments

Mastering navigation in environments with limited visibility is crucial for survival. Although the hippocam-pus has been associated with goal-oriented navigation, its role in real-world behaviour remains unclear. To investigate this, we combined deep reinforcement learning (RL) modelling with behavioural and neural data analysis. First, we trained RL agents in partially observable environments using egocentric and allocentric tasks. We show that agents equipped with recurrent hippocampal circuitry, but not purely feedforward networks, learned the tasks in line with animal behaviour. Next, using dimensionality reduction, our agents predicted reward, strategy, and temporal rep-resentations, which we validated experimentally using hippocampal recordings. Moreover, hippocampal RL agents predicted state-specific trajectories, mirroring empirical findings. In contrast, agents trained in fully observable en-vironments failed to capture experimental observations. Finally, we show that hippocampal-like RL agents demon-strated improved generalisation across novel task conditions. In summary, our findings suggest an important role of hippocampal networks in facilitating reinforcement learning in naturalistic environments.

neuroscience↗

bioRxiv2023

Hippocampal contextualization of social rewards

Acquiring and exploiting memories of rewarding experiences is critical for survival. The spatial environment in which a rewarding stimulus is encountered regulates memory retrieval. The ventral hippocampus (vH) has been implicated in contextual memories involving rewarding stimuli such as food, social cues or drugs. Yet, the spatial representations and circuits underlying contextual memories of socially rewarding stimuli are poorly understood. Here, using in vivo electrophysiological recordings during a social reward contextual conditioning paradigm in mice, we showed that vH neurons discriminate between contexts with neutral or acquired social reward value and exhibit a preferential remapping of their place fields to the context previously paired with social reward cues. The formation of context-discriminating vH neurons following learning was contingent upon the presence of salient reinforcers. Moreover, vH neurons showed different contextual representations during retrieval of social reward and fear contextual memories, suggesting different vH circuits underlie positively and negatively valenced contextual memories. Finally, optogenetic inhibition of locus coeruleus (LC) projections in the vH selectively disrupted social reward contextual memory by impairing vH contextual representations. Collectively, our findings reveal that the vH integrates contextual and social reward information, with memory encoding of these representations supported by input from the LC.

neuroscience↗

bioRxiv2022

Dynamic firing patterns of ventral hippocampal neurons govern anxiety-dependent behaviour and predict the extent of exploration of an anxiogenic location

The ventral hippocampus (vH) plays a crucial role in anxiety-related behaviour and vH neurons increase their firing when animals explore anxiogenic environments. However, if and how such neuronal activity induces or restricts the exploration of an anxiogenic location remains unexplained. Here, we developed a novel behavioural paradigm to motivate rats to explore an anxiogenic area. Rats ran along an elevated linear maze with protective sidewalls, which were subsequently removed in parts of the track to introduce an anxiogenic location. We recorded neuronal action potentials during task performance and found that vH neurons exhibited remapping of activity, overrepresenting anxiogenic locations. Direction-dependent firing was homogenised by the anxiogenic experience. We further showed that the activity of vH neurons predicted the extent of exploration of the anxiogenic location. Our data suggest that anxiety-related firing does not solely depend on the exploration of anxiogenic environments, but also on intentions to explore them.

neuroscience↗