Biology subjects

Kobelt, M.

Publications and source records attributed to Kobelt, M..

5 recordsLinked to original sources

bioRxiv2025

Task-relevant cognitive maps in episodic memory

Adaptive behavior requires stimuli to be processed in a way that meets the requirements of the current task. This is especially relevant for natural concepts that comprise a multitude of representational formats. The medial temporal lobe (MTL) has been proposed to support such flexibility by organizing stimuli within relational representational spaces serving as cognitive maps. However, while various studies investigated the formation of novel cognitive maps based on abstract features, it remains unclear how our vast existing conceptual knowledge is recruited into task-relevant representational spaces and whether these spaces influence the formation of novel episodic memories. Here we show that neural representations of natural concepts in the MTL and neocortex are embedded in low-dimensional representational spaces of task-relevant features that flexibly reorganize when task demands change. Crucially, hippocampal pattern similarity reflects task-relevant, but not task-irrelevant conceptual feature dimensions of the same set of natural concepts, indicating context-dependent reconfiguration of representational spaces. Euclidean distances within and across these spaces predicted subsequent memory confidence for individual items, suggesting a putative metric of task-dependent neural distinctiveness for the formation of memory traces. Finally, we dissociate task- and stimulus-dependent formats in neocortex, demonstrating complementary representations of natural stimuli that differentially contribute to memory formation. Our findings suggest that relational coding of task-relevant features in the MTL may serve as an index of representational distinctiveness that contributes to the formation of novel episodic memories and integrate MTL accounts based on spatial coding and episodic memory.

neuroscience↗

bioRxiv2024

Distinct representational properties of cues and contexts shape fear learning and extinction

When we learn that something is dangerous, a fear memory is formed. However, this memory is not fixed and can be updated through new experiences, such as learning that the threat is no longer present. This process of updating, known as extinction or reversal learning, is highly dependent on the context in which it occurs. How the brain represents cues, contexts, and their changing threat value remains a major question. Here, we used functional magnetic resonance imaging and a novel fear learning paradigm to track the neural representations of stimuli across fear acquisition, reversal, and test phases. We found that initial fear learning creates generalized neural representations for all threatening cues in the brains fear network. During reversal learning, when threat contingencies switched for some of the cues, two distinct representational strategies were observed. On the one hand, we still identified generalized patterns for currently threatening cues, whereas on the other hand, we observed highly stable representations of individual cues (i.e., item-specific) that changed their valence, particularly in the precuneus and prefrontal cortex. Furthermore, we observed that the brain represents contexts more distinctly during reversal learning. Furthermore, additional exploratory analyses showed that the degree of this context specificity in the prefrontal cortex predicted the subsequent return of fear, providing a potential neural mechanism for fear renewal. Our findings reveal that the brain uses a flexible combination of generalized and specific representations to adapt to a changing world, shedding new light on the mechanisms that support cognitive flexibility and the treatment of anxiety disorders via exposure therapy.

neuroscience↗

bioRxiv2023

Age differences in neural distinctiveness during memory retrieval versus reinstatement

Robust evidence points to mnemonic deficits in older adults related to dedifferentiated, i.e., less distinct, neural responses during memory encoding. However, less is known about retrieval-related dedifferentiation and its role in age-related memory decline. In this study, younger and older adults were scanned both while incidentally learning face and house stimuli and while completing a surprise recognition memory test. Using pattern similarity searchlight analyses, we looked for indicators of neural dedifferentiation during retrieval and asked whether this might explain interindividual differences in memory performance. Our findings revealed age-related reductions in neural distinctiveness during memory retrieval as well as in encoding-retrieval reinstatement in visual processing regions. We further demonstrated that the degree to which patterns elicited during encoding were reinstated during retrieval tracked variability in memory performance better than retrieval-related distinctiveness only. All in all, we contribute to meager existing evidence for age-related neural dedifferentiation during memory retrieval. We propose that the recognition task (as opposed to a cued recall task) may have revealed impairment in perceptual processing in older adults, leading to particularly widespread age differences in neural distinctiveness. We additionally provide support for the idea that well-defined reactivation of encoding patterns plays a major role in successful memory retrieval.

neuroscience↗

bioRxiv2021

Age-related declines in neural selectivity manifest differentially during encoding and recognition

The authors have withdrawn the preprint due to two errors in the analyses: The first error was a failure to account for three dummy volumes (TR = 2s) collected at the beginning of each experimental run. The second error was a coding error related to the definition of the category-selective clusters. Since correcting for these errors drastically altered the results and conclusions of this paper, the authors have withdrawn the preprint and retracted the published paper (https://doi.org/10.1016/j.neurobiolaging.2021.12.001). A report comparing original and corrected results can be found on https://osf.io/7n3mz/. If you have any questions please contact the corresponding author (sander@mpib-berlin.mpg.de).

neuroscience↗

bioRxiv2020

Tracking age differences in neural distinctiveness across representational levels

The authors have withdrawn the preprint due to two errors in the analyses: The first error was a failure to account for three dummy volumes (TR = 2s) collected at the beginning of each experimental run. The second error was a coding error related to the definition of the category-selective clusters. Since correcting for these errors drastically altered the results and conclusions of this paper, the authors have withdrawn the preprint and retracted the published paper. More information as well as a report comparing original and corrected results can be found on https://osf.io/t8dpv/. If you have any questions please contact the corresponding author (sander@mpib-berlin.mpg.de).

neuroscience↗