Biology subjects

Doeller, C.

Publications and source records attributed to Doeller, C..

5 recordsLinked to original sources

bioRxiv2023

Mental maps without vision: Neural signatures of cognitive maps based on haptic input in the hippocampal formation

The human hippocampus is the key region for forming cognitive maps of our environment. Such a map can support spatial navigation. It is unclear whether this area is similarly involved when an environment is explored with our haptic sense. In this study, we investigated the neural representation of distances on a tactile map in the hippocampal formation, in visually impaired and sighted persons. To this end, 47 participants (22 persons with a visual impairment, PVIs, and 25 sighted controls) performed a navigation task where they learned a tactile city-like map including five item locations. We combined magnetic resonance imaging with adaptation analysis to assess representation of distances between item locations in the hippocampus and entorhinal cortex. Additionally, we assessed cognitive map formation on a behavioural level. We also looked at functional connectivity between navigation-related areas during a subsequent resting-state block. Our data reveal across all participants that the left entorhinal cortex represents distances between locations on a tactile map. Here, we provide the first evidence that maps in the hippocampal formation is preserved when an environment is presented in a non-visual modality. The results also suggest that both PVIs and sighted persons constructed accurate cognitive maps of the tactile environment on a behavioural level. However, early PVIs showed lower performance compared to late PVIs, suggesting an advantage of visual experience. Additionally, we reveal functional connectivity between areas that were involved in the navigation task during a subsequent resting-state block. This might suggest either visual imagination of stimuli during the preceding tasks, or cognitive processes related to our spatial navigation task, which possibly involve replay of stimulus-specific activity.

neuroscience↗

bioRxiv2023

Causal role of the angular gyrus in insight-driven memory reconfiguration

Maintaining an accurate model of the world relies on our ability to update memory representations in light of new information. Previous research on the integration of new information into memory mainly focused on the hippocampus. Here, we hypothesized that the angular gyrus, known to be involved in episodic memory and imagination, plays a pivotal role in the insight-driven reconfiguration of memory representations. To test this hypothesis, participants received continuous theta burst stimulation (cTBS) over the left angular gyrus or sham stimulation before gaining insight into the relationship between previously separate life-like animated events in a narrative-insight task. During this task, participants also underwent EEG recording and their memory for linked and non-linked events was assessed shortly thereafter. Our results show that cTBS to the angular gyrus decreased memory for the linking events and reduced the memory advantage for linked relative to non-linked events. At the neural level, cTBS targeting the angular gyrus reduced centro-temporal coupling with frontal regions and abolished insight-induced neural representational changes for events linked via imagination, indicating impaired memory reconfiguration. Further, the cTBS group showed representational changes for non-linked events that resembled the patterns observed in the sham group for the linked events, suggesting failed pruning of the narrative in memory. Together, our findings demonstrate a causal role of the left angular gyrus in insight-related memory reconfigurations.

neuroscience↗

bioRxiv2023

Integration of Euclidean and path distances in hippocampal maps

The hippocampus is a key region for forming mental maps of our environment. These maps represent spatial information such as distances between landmarks. A cognitive map can allow for flexible inference of spatial relationships that have never been directly experienced before. Previous work has shown that the human hippocampus encodes distances between locations, but it is unclear how Euclidean and path distances are distinguished. In this study, participants performed an object-location task in a virtual environment. We combined functional magnetic resonance imaging with representational similarity analysis to test how Euclidean and path distances are represented in the hippocampus. We observe that hippocampal neural pattern similarity for objects scales with Euclidean as well as path distance between object locations, suggesting that the hippocampus integrates both types of distances. One key characteristic of cognitive maps is their adaptive and flexible nature. We therefore subsequently modified path distances between objects using roadblocks in the environment. We found that hippocampal pattern similarity between objects adapted as a function of these changes in path distance, selectively in egocentric navigators but not in allocentric navigators Taken together, our study supports the idea that the hippocampus creates integrative and flexible cognitive maps.

neuroscience↗

bioRxiv2023

Mental search of concepts is supported by egocentric vector representations and restructured grid maps

The human hippocampal-entorhinal system is known to represent both spatial locations and abstract concepts in memory in the form of allocentric cognitive maps. Using fMRI, we show that the human parietal cortex evokes complementary egocentric-like vector representations in conceptual spaces during goal-directed mental search, akin to those observable during physical navigation to determine where a goal is located relative to oneself. Concurrently, grid-like representations, a neural signature of allocentric cognitive maps in entorhinal, prefrontal, and parietal cortices, are restructured as a function of conceptual goal proximity, akin to rodent grid cells firing around reward locations during spatial exploration. These brain mechanisms might support flexible and parallel readout of where target conceptual information is stored in memory, capitalizing on complementary reference frames.

neuroscience↗

bioRxiv2021

Hippocampal reconfiguration of events in mnemonic networks

It is widely assumed that episodic memories are not stored in isolation but rather in dynamic event networks. However, the mechanisms of the underlying dynamic of these representations, in particular how such networks are updated, remain elusive. In this study, we investigated the reconfiguration of events into event networks in the hippocampus by presenting new events that could update either one of two competing narratives. During the first session, participants viewed four animated movies, each representing a distinct narrative; two distinct narratives from the Jones family and two distinct narratives from the Smith family. During the second session, we re-exposed participants to snapshots of these narratives along with snapshots of new events from one of the two families, allowing updating of the acquired event networks of that family. Our findings show that the hippocampus integrated new events that relate to the old family, and then integrated these new events with the corresponding old events. Furthermore, hippocampal representations of the events within a narrative became better integrated after updating. Our results shed new light on the neural mechanisms underlying flexible mnemonic updating with realistic events and further advance our understanding of the structured reconfiguration of event networks in memory.

neuroscience↗