[{"degree_awarded":"PhD","ddc":["612"],"article_processing_charge":"No","author":[{"orcid":"0000-0003-1727-6612","full_name":"Cumpelik, Andrea D","id":"3F158B32-F248-11E8-B48F-1D18A9856A87","first_name":"Andrea D","last_name":"Cumpelik"}],"title":"The role of prefrontal spatial coding in supporting a contextual association task","user_id":"ba8df636-2132-11f1-aed0-ed93e2281fdd","type":"dissertation","file_date_updated":"2025-09-30T22:30:02Z","OA_place":"publisher","alternative_title":["ISTA Thesis"],"date_updated":"2026-04-07T12:37:58Z","oa_version":"Published Version","oa":1,"OA_embargo":"6 months","doi":"10.15479/AT-ISTA-19456","keyword":["neuroscience","decision making","learning","cognitive flexibility","medial prefrontal cortex","hippocampus","electrophysiology"],"citation":{"ieee":"A. D. Cumpelik, “The role of prefrontal spatial coding in supporting a contextual association task,” Institute of Science and Technology Austria, 2025.","mla":"Cumpelik, Andrea D. <i>The Role of Prefrontal Spatial Coding in Supporting a Contextual Association Task</i>. Institute of Science and Technology Austria, 2025, doi:<a href=\"https://doi.org/10.15479/AT-ISTA-19456\">10.15479/AT-ISTA-19456</a>.","chicago":"Cumpelik, Andrea D. “The Role of Prefrontal Spatial Coding in Supporting a Contextual Association Task.” Institute of Science and Technology Austria, 2025. <a href=\"https://doi.org/10.15479/AT-ISTA-19456\">https://doi.org/10.15479/AT-ISTA-19456</a>.","short":"A.D. Cumpelik, The Role of Prefrontal Spatial Coding in Supporting a Contextual Association Task, Institute of Science and Technology Austria, 2025.","ista":"Cumpelik AD. 2025. The role of prefrontal spatial coding in supporting a contextual association task. Institute of Science and Technology Austria.","ama":"Cumpelik AD. The role of prefrontal spatial coding in supporting a contextual association task. 2025. doi:<a href=\"https://doi.org/10.15479/AT-ISTA-19456\">10.15479/AT-ISTA-19456</a>","apa":"Cumpelik, A. D. (2025). <i>The role of prefrontal spatial coding in supporting a contextual association task</i>. Institute of Science and Technology Austria. <a href=\"https://doi.org/10.15479/AT-ISTA-19456\">https://doi.org/10.15479/AT-ISTA-19456</a>"},"day":"18","page":"96","abstract":[{"lang":"eng","text":"Making decisions requires flexibly adapting to changing environments, a process that\r\ndepends on accurately interpreting current contingencies and integrating them with\r\npast experience. Two brain regions are particularly critical for this process, the medial\r\nprefrontal cortex (mPFC) and the hippocampus. Using contextual information from the\r\nhippocampus, the mPFC selects relevant cognitive frameworks and suppresses\r\nirrelevant ones to guide appropriate actions. Several studies have shown that some\r\nmPFC pyramidal neurons become spatially tuned when spatial information is required\r\nto guide goal-directed behavior. However, the role of prefrontal spatial representations\r\nin learning and decision making is not well understood. This work aims to characterize\r\nthe role of mPFC spatial tuning in supporting a contextual association task. Rats were\r\ntrained to learn two cue–location associations on a radial arm maze over multiple days,\r\nwhile we simultaneously recorded from dorsal CA1 of the hippocampus and the\r\nprelimbic area of the mPFC. We describe a subset of spatially tuned hippocampal and\r\nprefrontal pyramidal neurons that “flicker” between multiple spatial representations on\r\ndifferent trials, suggesting dynamic, context-dependent coding. This flickering may\r\nprovide a substrate for how the network reorganizes in response to task demands,\r\nlikely by enabling the flexible evaluation of competing representations. "}],"date_created":"2025-03-25T11:22:38Z","year":"2025","publication_identifier":{"isbn":["978-3-99078-056-5"],"issn":["2663-337X"]},"month":"02","_id":"19456","supervisor":[{"last_name":"Csicsvari","first_name":"Jozsef L","id":"3FA14672-F248-11E8-B48F-1D18A9856A87","full_name":"Csicsvari, Jozsef L","orcid":"0000-0002-5193-4036"}],"publication_status":"published","acknowledged_ssus":[{"_id":"PreCl"},{"_id":"Bio"},{"_id":"LifeSc"},{"_id":"M-Shop"}],"has_accepted_license":"1","publisher":"Institute of Science and Technology Austria","file":[{"date_updated":"2025-09-30T22:30:02Z","content_type":"application/pdf","checksum":"1c7573303d8e5f6da3eb03d59055390f","file_size":11869040,"relation":"main_file","file_name":"2025_Thesis_Cumpelik_corrections_PDFA.pdf","embargo":"2025-09-30","file_id":"19457","access_level":"open_access","creator":"acumpeli","date_created":"2025-03-25T11:07:55Z"},{"content_type":"application/vnd.openxmlformats-officedocument.wordprocessingml.document","date_updated":"2025-09-30T22:30:02Z","embargo_to":"open_access","relation":"source_file","checksum":"b93265ebd9a53f7a14100d0d48b4ff5b","file_size":20436467,"access_level":"closed","file_id":"19458","file_name":"2025_Thesis_Cumpelik_corrections.docx","date_created":"2025-03-25T11:08:05Z","creator":"acumpeli"}],"fulldoi":"https://doi.org/10.15479/AT-ISTA-19456","date_published":"2025-02-18T00:00:00Z","corr_author":"1","department":[{"_id":"GradSch"},{"_id":"JoCs"}],"language":[{"iso":"eng"}],"status":"public"},{"day":"11","page":"104","citation":{"ieee":"P. Zivadinovic, “Scale-free activity as a basis for spatial learning and memory in the brain,” Institute of Science and Technology Austria, 2025.","chicago":"Zivadinovic, Predrag. “Scale-Free Activity as a Basis for Spatial Learning and Memory in the Brain.” Institute of Science and Technology Austria, 2025. <a href=\"https://doi.org/10.15479/AT-ISTA-20777\">https://doi.org/10.15479/AT-ISTA-20777</a>.","short":"P. Zivadinovic, Scale-Free Activity as a Basis for Spatial Learning and Memory in the Brain, Institute of Science and Technology Austria, 2025.","mla":"Zivadinovic, Predrag. <i>Scale-Free Activity as a Basis for Spatial Learning and Memory in the Brain</i>. Institute of Science and Technology Austria, 2025, doi:<a href=\"https://doi.org/10.15479/AT-ISTA-20777\">10.15479/AT-ISTA-20777</a>.","ista":"Zivadinovic P. 2025. Scale-free activity as a basis for spatial learning and memory in the brain. Institute of Science and Technology Austria.","apa":"Zivadinovic, P. (2025). <i>Scale-free activity as a basis for spatial learning and memory in the brain</i>. Institute of Science and Technology Austria. <a href=\"https://doi.org/10.15479/AT-ISTA-20777\">https://doi.org/10.15479/AT-ISTA-20777</a>","ama":"Zivadinovic P. Scale-free activity as a basis for spatial learning and memory in the brain. 2025. doi:<a href=\"https://doi.org/10.15479/AT-ISTA-20777\">10.15479/AT-ISTA-20777</a>"},"doi":"10.15479/AT-ISTA-20777","project":[{"_id":"eb943429-77a9-11ec-83b8-9f471cdf5c67","name":"Functional Advantages of Critical Brain Dynamics","grant_number":"M03318"}],"oa":1,"oa_version":"Published Version","alternative_title":["ISTA Thesis"],"das_tickbox":"1","date_updated":"2026-07-24T08:14:37Z","OA_place":"publisher","file_date_updated":"2026-06-11T22:30:02Z","article_processing_charge":"No","type":"dissertation","user_id":"8b945eb4-e2f2-11eb-945a-df72226e66a9","author":[{"id":"68AA0E5A-AFDA-11E9-9994-141DE6697425","full_name":"Zivadinovic, Predrag","first_name":"Predrag","last_name":"Zivadinovic"}],"title":"Scale-free activity as a basis for spatial learning and memory in the brain","degree_awarded":"PhD","ddc":["570","539","571"],"language":[{"iso":"eng"}],"status":"public","acknowledgement":"My work has been funded through the project \"Functional Advantages of Critical Brain\r\nDynamics\" of the ISTA interdisciplinary fund and through the FWF.\r\n","doi_confirm":"1","date_published":"2025-12-11T00:00:00Z","department":[{"_id":"GradSch"},{"_id":"JoCs"}],"corr_author":"1","fulldoi":"https://doi.org/10.15479/AT-ISTA-20777","has_accepted_license":"1","publication_status":"published","publisher":"Institute of Science and Technology Austria","file":[{"checksum":"aae9d1ed53f7b67f75e289c26a02b72f","file_size":8105379,"relation":"main_file","date_updated":"2026-06-11T22:30:02Z","content_type":"application/pdf","creator":"pzivadin","date_created":"2025-12-10T19:28:20Z","file_name":"2025_Zivadinovic_Predrag_PhD_thesis.pdf","embargo":"2026-06-11","access_level":"open_access","file_id":"20778"},{"creator":"pzivadin","date_created":"2025-12-10T19:28:10Z","file_name":"2025_Zivadinovic_Predrag_PhD_thesis_source.zip","access_level":"closed","file_id":"20779","file_size":8512240,"checksum":"8a08a3804ce7d9d625fdf1631113da8c","relation":"source_file","embargo_to":"open_access","date_updated":"2026-06-11T22:30:02Z","content_type":"application/zip"}],"supervisor":[{"orcid":"0000-0002-5193-4036","id":"3FA14672-F248-11E8-B48F-1D18A9856A87","full_name":"Csicsvari, Jozsef L","first_name":"Jozsef L","last_name":"Csicsvari"}],"_id":"20777","month":"12","publication_identifier":{"issn":["2663-337X"]},"date_created":"2025-12-10T19:37:41Z","abstract":[{"text":"A major challenge in neuroscience is deciphering how the brain orchestrates behavior in\r\nresponse to changes in environmental conditions. This process is characterized by several\r\nprocessing stages, from perception to the storage of important information. Information\r\nstorage is performed by a memory system implemented through complex networks of highly\r\ninterconnected neurons. The collective operational principles of neuronal networks that support\r\nformation and storage are the main topics of this thesis.\r\nTo investigate the collective dynamics of the hippocampus from the perspective of the brain\r\ncriticality hypothesis, I started by analyzing cascades of neural activity ¯ neuronal avalanches\r\n¯ that have been characterized by the absence of a typical spatial or temporal scale. Measures\r\nderived from neuronal avalanches suggested that during wakefulness the hippocampus operated\r\nfurther away from criticality than during sleep/rest. In addition, neural activity propagated\r\ndifferently in these two brain states, as indicated by different collapses of the avalanche shapes.\r\nNext, the Phenomenological Renormalization Group approach also indicated conceptually\r\nsimilar differences, through the scaling exponent of activity variance α, which was higher during\r\nsleep/rest than during awake. These results confirmed that the activity of the hippocampus\r\nexhibits signatures of criticality and that these signatures change with the state of the brain.\r\nNext, I found that memory retention was predicted by the scaling exponent of activity variance\r\nα. The exponent α measured during the sleep/rest session that followed learning correlated\r\nwith memory retention during the subsequent unrewarded testing session. Moreover, α\r\npredicted performance even when controlled for reactivation that occurs in parallel. Second, α\r\nmeasured in the sleep/rest phase that preceded learning was correlated with the learning speed.\r\nI analyzed distributions of the cells’ characteristic timescale and burstiness. The day-to-day\r\nvariability of these distributions, during sleep/rest that followed learning, correlated with the\r\nscaling exponent of activity variance α, as well as with memory retention. These findings\r\nconfirmed that variance scaling and functional heterogeneity provide behaviorally meaningful\r\nperspectives on hippocampal activity, as they are directly related to memory consolidation.\r\nI further investigated the process of memory acquisition and consolidation between the\r\nhippocampus CA1 and the mEC. During learning, CA1 cells shifted their firing field towards\r\nthe goals, while mEC cells remained mostly stable, shifting their firing fields towards the goals\r\nduring sleep/rest that followed learning. This shift during sleep/rest was supported by the\r\nreactivation process, which occurred in two ways, synchronously with CA1 (during SWRs) and\r\nindependently of the hippocampal SWRs. Both types of reactivation predicted subsequent\r\nmemory retention, as well as the amount of goal-related remapping. Again, the day-to-day\r\nvariability of the distribution of the cell timescales correlated with the goal-related remapping,\r\nin CA1 during the learning session and in mEC during sleep/rest. These results suggest that\r\nin spatial navigation tasks, the functional responsibilities of CA1 and mEC change between\r\nlearning and sleep/rest and that their function benefits from increased functional heterogeneity\r\namong cells.\r\n","lang":"eng"}],"year":"2025"},{"supplementarymaterial":"no","fulldoi":"https://doi.org/10.15479/at:ista:17346","language":[{"iso":"eng"}],"status":"public","date_published":"2024-07-31T00:00:00Z","doi_confirm":"1","department":[{"_id":"GradSch"},{"_id":"JoCs"}],"corr_author":"1","publication_identifier":{"issn":["2663-337X"]},"abstract":[{"lang":"eng","text":"Acquiring, retaining, and retrieving information over a wide range of timescales are crucial\r\nfunctions of the brain. The successful processing of memories affects many aspects of our\r\nlives and enables us and many other organisms to operate in a complex environment and\r\nto interact with it. In this context, the hippocampus and functionally connected brain\r\nareas, such as the prefrontal cortex, are central and have been subject to intensive research\r\nin the past decades. Storage of memories is believed to rely on distributed neural activity\r\nwithin these neural circuits. Additionally, neural memory traces of recent experience are\r\nreinstated during periods of rest or sleep. These reactivations are thought to play an\r\noutstanding role in the consolidation of memories and potentially facilitate the transfer of\r\ninformation from the hippocampus to cortical areas for long-term storage and integration\r\ninto existing knowledge.\r\nHowever, there is growing evidence that memory-related neural representations in the\r\nhippocampus are not as stable as initially thought and that they change even in the\r\nabsence of learning. It has been suggested that these changes reflect the accumulation of\r\nexperience, but the influence of interspersed consolidation periods has not been considered.\r\nPrevious studies have analyzed consolidation periods by detecting activity that strongly\r\nresembled neural activity during the acquisition of memory. Besides being often limited\r\nto only non-rapid eye movement (NREM) sleep, the used approaches were not capable of\r\ntracking changes in neural representations over extended temporal periods. More fluid\r\nrepresentations do not only challenge our understanding of how information is stored, but\r\nthey also affect the transfer of information between brain areas during the consolidation\r\nprocess.\r\nFor this thesis, I investigated the evolution of memory-related activity during sleep\r\nperiods expected to be involved in consolidation in the hippocampus and between the\r\nhippocampus and prefrontal cortex. I found that reactivated activity in the hippocampus\r\ngradually transformed during prolonged periods of sleep and inactivity. In the beginning,\r\nneural activity strongly resembled acquisition activity, whereas, with the progression of\r\ntime, it became more similar to the subsequent recall activity. NREM periods drove\r\nthis process, while rapid-eye movement (REM) periods showed a resetting effect. This\r\nreactivation drift was due to firing rate changes of a subset of cells and mirrored the\r\nrepresentational changes from the acquisition to the recall. A stable subset of cells\r\nwithstood the drift and maintained their activity. Therefore, my results indicate that\r\nmemory-related representations undergo spontaneous modifications during consolidation\r\nperiods and that these changes are predictive of representational drift.\r\nFurthermore, I found that the amount of change in the neural activity during subsequent\r\nsleep periods was biased by prior behavioral performance. Observed changes in the\r\nhippocampus and the prefrontal cortex were synchronized and increased after poor\r\nperformance, highlighting a potential role in the exchange of information. Low-variance\r\nvii\r\nperiods with distinct, more stable activity from a subset of cells significantly contributed\r\nto the heightened synchrony between both areas. Hence, interleaved phases of more stable\r\nneural activity could facilitate the information transfer between brain areas.\r\nIn conclusion, my investigations underline the fluidity of memory-related representations\r\nand assign a prominent role to sleep reactivation periods in their evolution. In addition, I\r\nidentified a potential mechanism of stable activity phases that might facilitate the synchronization across hippocampal-prefrontal activity despite ongoing changes. Reconciling\r\nand integrating findings from both spontaneous and behaviorally-related representational\r\nchanges in functionally related brain areas will help to broaden our understanding of how\r\nknowledge is stored, maintained, updated, and transferred between brain areas."}],"date_created":"2024-07-29T15:08:42Z","year":"2024","publication_status":"published","has_accepted_license":"1","file":[{"content_type":"application/pdf","date_updated":"2025-01-31T23:30:03Z","relation":"main_file","file_size":12920169,"checksum":"12c76297cc27449da80c60d79127770d","access_level":"open_access","file_id":"17359","embargo":"2025-01-31","file_name":"PhD_Thesis_Lars_Bollmann.pdf","date_created":"2024-07-31T18:37:19Z","creator":"lbollman"},{"creator":"lbollman","date_created":"2024-07-31T18:38:39Z","file_name":"Latex_source.zip","access_level":"closed","file_id":"17360","file_size":27568807,"checksum":"19a0265079dec8038830ad6e35c5106e","relation":"source_file","embargo_to":"open_access","date_updated":"2025-01-31T23:30:03Z","content_type":"application/zip"}],"publisher":"Institute of Science and Technology Austria","_id":"17346","month":"07","supervisor":[{"orcid":"0000-0002-5193-4036","last_name":"Csicsvari","first_name":"Jozsef L","full_name":"Csicsvari, Jozsef L","id":"3FA14672-F248-11E8-B48F-1D18A9856A87"}],"doi":"10.15479/at:ista:17346","keyword":["Memory","Hippocampus","Consolidation"],"oa":1,"day":"31","page":"103","citation":{"ieee":"L. Bollmann, “Stability and change in the memory system during rest,” Institute of Science and Technology Austria, 2024.","chicago":"Bollmann, Lars. “Stability and Change in the Memory System during Rest.” Institute of Science and Technology Austria, 2024. <a href=\"https://doi.org/10.15479/at:ista:17346\">https://doi.org/10.15479/at:ista:17346</a>.","short":"L. Bollmann, Stability and Change in the Memory System during Rest, Institute of Science and Technology Austria, 2024.","mla":"Bollmann, Lars. <i>Stability and Change in the Memory System during Rest</i>. Institute of Science and Technology Austria, 2024, doi:<a href=\"https://doi.org/10.15479/at:ista:17346\">10.15479/at:ista:17346</a>.","ista":"Bollmann L. 2024. Stability and change in the memory system during rest. Institute of Science and Technology Austria.","apa":"Bollmann, L. (2024). <i>Stability and change in the memory system during rest</i>. Institute of Science and Technology Austria. <a href=\"https://doi.org/10.15479/at:ista:17346\">https://doi.org/10.15479/at:ista:17346</a>","ama":"Bollmann L. Stability and change in the memory system during rest. 2024. doi:<a href=\"https://doi.org/10.15479/at:ista:17346\">10.15479/at:ista:17346</a>"},"article_processing_charge":"No","author":[{"last_name":"Bollmann","first_name":"Lars","full_name":"Bollmann, Lars","id":"47AD3038-F248-11E8-B48F-1D18A9856A87"}],"title":"Stability and change in the memory system during rest","user_id":"317138e5-6ab7-11ef-aa6d-ffef3953e345","type":"dissertation","degree_awarded":"PhD","ddc":["573"],"date_updated":"2026-10-02T11:26:02Z","das_tickbox":"0","alternative_title":["ISTA Thesis"],"oa_version":"Published Version","researchdata_availability":"no","file_date_updated":"2025-01-31T23:30:03Z","OA_place":"publisher"},{"status":"public","language":[{"iso":"eng"}],"corr_author":"1","department":[{"_id":"GradSch"},{"_id":"JoCs"}],"doi_confirm":"1","date_published":"2024-01-19T00:00:00Z","supplementarymaterial":"no","fulldoi":"https://doi.org/10.15479/at:ista:14821","ec_funded":1,"file":[{"file_id":"14838","access_level":"closed","file_name":"PhD_Thesis_190124.docx","date_created":"2024-01-19T11:04:05Z","creator":"hchiossi","content_type":"application/vnd.openxmlformats-officedocument.wordprocessingml.document","date_updated":"2025-01-19T23:30:04Z","embargo_to":"open_access","relation":"source_file","checksum":"d3fa3de1abd5af5204c13e9d55375615","file_size":8656268},{"embargo":"2025-01-19","file_name":"PhD_Thesis_190124.pdf","access_level":"open_access","file_id":"14839","creator":"hchiossi","date_created":"2024-01-19T11:03:59Z","date_updated":"2025-01-19T23:30:04Z","content_type":"application/pdf","file_size":6567275,"checksum":"13adc8dcfb5b6b18107f89f0a98fa8bd","relation":"main_file"}],"publisher":"Institute of Science and Technology Austria","publication_status":"published","has_accepted_license":"1","_id":"14821","month":"01","supervisor":[{"orcid":"0000-0002-5193-4036","first_name":"Jozsef L","last_name":"Csicsvari","full_name":"Csicsvari, Jozsef L","id":"3FA14672-F248-11E8-B48F-1D18A9856A87"}],"publication_identifier":{"issn":["2663-337X"]},"year":"2024","abstract":[{"text":"The hippocampus is central to memory formation, storage and retrieval over many\r\ntimescales. Neurons in this brain area are highly selective to spatial position as well as to many\r\nother variables of the environment. It is believed that the selectivity patterns of hippocampal\r\nneurons reflect the structure of tasks an animal performs. However, especially at timescales\r\nlonger than a few minutes or hours it is not fully known how these representations evolve, nor\r\nhow they map to behaviour in the process. In this thesis, I monitored the evolution of\r\nhippocampal representations in a novel spatial-associative memory task for rats. Reward\r\nlocations were associated with global sensory cues (i.e. context); animals had to remember the\r\nassociations and dig for food in those locations only. I used in vivo electrophysiology to record\r\nthe activity of the hippocampus dorsal CA1 neurons during the learning period of a few days.\r\nI report here a novel and simple method to classify behaviour performance to account\r\nfor individual variability in learning speed and spurious performance unrelated to true task rule\r\nlearning. Using this classification I was then able to investigate neural responses on different\r\nstages of learning matched across animals. On the first day of learning, I observed a fast\r\nformation of single-cell selectivity to task variables which remained stable over days. I also\r\nobserved that reward tuning was not a single process but dependent on task-related cognitive\r\nload. At the population level, a linear decoding approach revealed a hierarchy in the\r\nrepresentation of task variables that changed with learning. In the high-dimensional space of\r\npopulation activity, the representation of contexts was specific to each position in the maze, and\r\ncould thus be better decoded if the position was known. The decoding of position did not improve\r\nwith knowledge of other variables. As learning progressed, the hippocampal code underwent a\r\nreorganisation of high-variance directions in population activity, identified by principal\r\ncomponent analysis. I found that dominant dimensions started carrying increasing amounts of\r\ninformation about task context specifically at those positions where it mattered for task\r\nperformance. When I contrasted this with variables less relevant to task performance (e.g.\r\nmovement direction), I did not observe differences in decoding quality over positions nor a\r\nreduction of dimensionality with learning.\r\nOverall, the largest changes in CA1 neural response with task learning happened in a\r\nmatter of a few trials; over days, changes undetectable in single-cell statistics were responsible\r\nfor re-structuring the hierarchy of neural representations at the population level; these changes\r\nwere task-specific and reflected different stages of learning. This indicates that complex task\r\nlearning may involve different magnitudes of response modulation in CA1, which happen at\r\nspecific time scales linked to behaviour.","lang":"eng"}],"date_created":"2024-01-16T14:25:21Z","page":"89","day":"19","citation":{"chicago":"Chiossi, Heloisa S. C. “Adaptive Hierarchical Representations in the Hippocampus.” Institute of Science and Technology Austria, 2024. <a href=\"https://doi.org/10.15479/at:ista:14821\">https://doi.org/10.15479/at:ista:14821</a>.","short":"H.S.C. Chiossi, Adaptive Hierarchical Representations in the Hippocampus, Institute of Science and Technology Austria, 2024.","mla":"Chiossi, Heloisa S. C. <i>Adaptive Hierarchical Representations in the Hippocampus</i>. Institute of Science and Technology Austria, 2024, doi:<a href=\"https://doi.org/10.15479/at:ista:14821\">10.15479/at:ista:14821</a>.","ieee":"H. S. C. Chiossi, “Adaptive hierarchical representations in the hippocampus,” Institute of Science and Technology Austria, 2024.","apa":"Chiossi, H. S. C. (2024). <i>Adaptive hierarchical representations in the hippocampus</i>. Institute of Science and Technology Austria. <a href=\"https://doi.org/10.15479/at:ista:14821\">https://doi.org/10.15479/at:ista:14821</a>","ama":"Chiossi HSC. Adaptive hierarchical representations in the hippocampus. 2024. doi:<a href=\"https://doi.org/10.15479/at:ista:14821\">10.15479/at:ista:14821</a>","ista":"Chiossi HSC. 2024. Adaptive hierarchical representations in the hippocampus. Institute of Science and Technology Austria."},"project":[{"grant_number":"665385","name":"International IST Doctoral Program","call_identifier":"H2020","_id":"2564DBCA-B435-11E9-9278-68D0E5697425"}],"doi":"10.15479/at:ista:14821","oa":1,"das_tickbox":"0","oa_version":"Published Version","alternative_title":["ISTA Thesis"],"date_updated":"2026-10-02T11:26:27Z","file_date_updated":"2025-01-19T23:30:04Z","OA_place":"publisher","researchdata_availability":"no","title":"Adaptive hierarchical representations in the hippocampus","author":[{"orcid":"0009-0004-2973-278X","id":"2BBA502C-F248-11E8-B48F-1D18A9856A87","full_name":"Chiossi, Heloisa","first_name":"Heloisa","last_name":"Chiossi"}],"type":"dissertation","user_id":"317138e5-6ab7-11ef-aa6d-ffef3953e345","article_processing_charge":"No","ddc":["570"],"degree_awarded":"PhD"},{"day":"19","page":"136","citation":{"ama":"Nardin M. On the encoding, transfer, and consolidation of spatial memories. 2022. doi:<a href=\"https://doi.org/10.15479/at:ista:11932\">10.15479/at:ista:11932</a>","apa":"Nardin, M. (2022). <i>On the encoding, transfer, and consolidation of spatial memories</i>. Institute of Science and Technology Austria. <a href=\"https://doi.org/10.15479/at:ista:11932\">https://doi.org/10.15479/at:ista:11932</a>","ista":"Nardin M. 2022. On the encoding, transfer, and consolidation of spatial memories. Institute of Science and Technology Austria.","mla":"Nardin, Michele. <i>On the Encoding, Transfer, and Consolidation of Spatial Memories</i>. Institute of Science and Technology Austria, 2022, doi:<a href=\"https://doi.org/10.15479/at:ista:11932\">10.15479/at:ista:11932</a>.","chicago":"Nardin, Michele. “On the Encoding, Transfer, and Consolidation of Spatial Memories.” Institute of Science and Technology Austria, 2022. <a href=\"https://doi.org/10.15479/at:ista:11932\">https://doi.org/10.15479/at:ista:11932</a>.","short":"M. Nardin, On the Encoding, Transfer, and Consolidation of Spatial Memories, Institute of Science and Technology Austria, 2022.","ieee":"M. Nardin, “On the encoding, transfer, and consolidation of spatial memories,” Institute of Science and Technology Austria, 2022."},"doi":"10.15479/at:ista:11932","project":[{"name":"International IST Doctoral Program","grant_number":"665385","call_identifier":"H2020","_id":"2564DBCA-B435-11E9-9278-68D0E5697425"}],"oa":1,"oa_version":"Published Version","date_updated":"2026-07-06T12:47:25Z","alternative_title":["ISTA Thesis"],"related_material":{"record":[{"status":"public","relation":"part_of_dissertation","id":"6194"},{"status":"public","id":"10077","relation":"part_of_dissertation"}]},"file_date_updated":"2023-06-20T22:30:04Z","OA_place":"publisher","article_processing_charge":"No","title":"On the encoding, transfer, and consolidation of spatial memories","author":[{"orcid":"0000-0001-8849-6570","first_name":"Michele","last_name":"Nardin","id":"30BD0376-F248-11E8-B48F-1D18A9856A87","full_name":"Nardin, Michele"}],"user_id":"ba8df636-2132-11f1-aed0-ed93e2281fdd","type":"dissertation","degree_awarded":"PhD","ddc":["573"],"language":[{"iso":"eng"}],"status":"public","date_published":"2022-08-19T00:00:00Z","acknowledgement":"I acknowledge the support from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie Grant Agreement No. 665385.","department":[{"_id":"GradSch"},{"_id":"JoCs"}],"corr_author":"1","ec_funded":1,"fulldoi":"https://doi.org/10.15479/at:ista:11932","publication_status":"published","has_accepted_license":"1","file":[{"relation":"source_file","embargo_to":"open_access","file_size":13515457,"checksum":"2dbb70c74aaa3b64c1f463e943baf09c","content_type":"application/zip","date_updated":"2023-06-20T22:30:04Z","date_created":"2022-08-19T16:31:34Z","creator":"mnardin","file_id":"11935","access_level":"closed","file_name":"Michele Nardin, Ph.D. Thesis - ISTA (1).zip"},{"file_size":9906458,"checksum":"0ec94035ea35a47a9f589ed168e60b48","relation":"main_file","date_updated":"2023-06-20T22:30:04Z","content_type":"application/pdf","creator":"mnardin","date_created":"2022-08-22T09:43:50Z","embargo":"2023-06-19","file_name":"Michele_Nardin_Phd_Thesis_PDFA.pdf","file_id":"11941","access_level":"open_access"}],"publisher":"Institute of Science and Technology Austria","month":"08","_id":"11932","supervisor":[{"id":"3FA14672-F248-11E8-B48F-1D18A9856A87","full_name":"Csicsvari, Jozsef L","first_name":"Jozsef L","last_name":"Csicsvari","orcid":"0000-0002-5193-4036"}],"publication_identifier":{"issn":["2663-337X"]},"abstract":[{"text":"The ability to form and retrieve memories is central to survival. In mammals, the hippocampus\r\nis a brain region essential to the acquisition and consolidation of new memories. It is also\r\ninvolved in keeping track of one’s position in space and aids navigation. Although this\r\nspace-memory has been a source of contradiction, evidence supports the view that the role of\r\nthe hippocampus in navigation is memory, thanks to the formation of cognitive maps. First\r\nintroduced by Tolman in 1948, cognitive maps are generally used to organize experiences in\r\nmemory; however, the detailed mechanisms by which these maps are formed and stored are not\r\nyet agreed upon. Some influential theories describe this process as involving three fundamental\r\nsteps: initial encoding by the hippocampus, interactions between the hippocampus and other\r\ncortical areas, and long-term extra-hippocampal consolidation. In this thesis, I will show how\r\nthe investigation of cognitive maps of space helped to shed light on each of these three memory\r\nprocesses.\r\nThe first study included in this thesis deals with the initial encoding of spatial memories in\r\nthe hippocampus. Much is known about encoding at the level of single cells, but less about\r\ntheir co-activity or joint contribution to the encoding of novel spatial information. I will\r\ndescribe the structure of an interaction network that allows for efficient encoding of noisy\r\nspatial information during the first exploration of a novel environment.\r\nThe second study describes the interactions between the hippocampus and the prefrontal\r\ncortex (PFC), two areas directly and indirectly connected. It is known that the PFC, in concert\r\nwith the hippocampus, is involved in various processes, including memory storage and spatial\r\nnavigation. Nonetheless, the detailed mechanisms by which PFC receives information from the\r\nhippocampus are not clear. I will show how a transient improvement in theta phase locking of\r\nPFC cells enables interactions of cell pairs across the two regions.\r\nThe third study describes the learning of behaviorally-relevant spatial locations in the hippocampus and the medial entorhinal cortex. I will show how the accumulation of firing around\r\ngoal locations, a correlate of learning, can shed light on the transition from short- to long-term\r\nspatial memories and the speed of consolidation in different brain areas.\r\nThe studies included in this thesis represent the main scientific contributions of my Ph.D. They\r\ninvolve statistical analyses and models of neural responses of cells in different brain areas of\r\nrats executing spatial tasks. I will conclude the thesis by discussing the impact of the findings\r\non principles of memory formation and retention, including the mechanisms, the speed, and\r\nthe duration of these processes.","lang":"eng"}],"date_created":"2022-08-19T08:52:30Z","year":"2022"},{"corr_author":"1","department":[{"_id":"JoCs"},{"_id":"GradSch"}],"date_published":"2019-08-24T00:00:00Z","status":"public","language":[{"iso":"eng"}],"fulldoi":"https://doi.org/10.15479/AT:ISTA:6825","supervisor":[{"orcid":"0000-0002-5193-4036","last_name":"Csicsvari","first_name":"Jozsef L","full_name":"Csicsvari, Jozsef L","id":"3FA14672-F248-11E8-B48F-1D18A9856A87"}],"month":"08","_id":"6825","publisher":"Institute of Science and Technology Austria","file":[{"content_type":"application/pdf","date_updated":"2020-09-06T22:30:03Z","relation":"main_file","file_size":3205202,"checksum":"2664420e332a33338568f4f3bfc59287","request_a_copy":0,"access_level":"open_access","file_id":"6846","embargo":"2020-09-05","file_name":"Thesis_Kaefer_PDFA.pdf","date_created":"2019-09-03T08:07:13Z","creator":"kkaefer"},{"date_updated":"2024-04-10T22:30:48Z","content_type":"application/zip","checksum":"9a154eab6f07aa590a3d2651dc0d926a","file_size":2506835,"embargo_to":"open_access","relation":"source_file","file_name":"Thesis_Kaefer.zip","file_id":"6847","access_level":"closed","creator":"kkaefer","date_created":"2019-09-03T08:07:17Z"}],"has_accepted_license":"1","publication_status":"published","year":"2019","date_created":"2019-08-21T15:00:57Z","abstract":[{"text":"The solving of complex tasks requires the functions of more than one brain area and their interaction. Whilst spatial navigation and memory is dependent on the hippocampus, flexible behavior relies on the medial prefrontal cortex (mPFC). To further examine the roles of the hippocampus and mPFC, we recorded their neural activity during a task that depends on both of these brain regions.\r\nWith tetrodes, we recorded the extracellular activity of dorsal hippocampal CA1 (HPC) and mPFC neurons in Long-Evans rats performing a rule-switching task on the plus-maze. The plus-maze task had a spatial component since it required navigation along one of the two start arms and at the maze center a choice between one of the two goal arms. Which goal contained a reward depended on the rule currently in place. After an uncued rule change the animal had to abandon the old strategy and switch to the new rule, testing cognitive flexibility. Investigating the coordination of activity between the HPC and mPFC allows determination during which task stages their interaction is required. Additionally, comparing neural activity patterns in these two brain regions allows delineation of the specialized functions of the HPC and mPFC in this task. We analyzed neural activity in the HPC and mPFC in terms of oscillatory interactions, rule coding and replay.\r\nWe found that theta coherence between the HPC and mPFC is increased at the center and goals of the maze, both when the rule was stable or has changed. Similar results were found for locking of HPC and mPFC neurons to HPC theta oscillations. However, no differences in HPC-mPFC theta coordination were observed between the spatially- and cue-guided rule. Phase locking of HPC and mPFC neurons to HPC gamma oscillations was not modulated by\r\nmaze position or rule type. We found that the HPC coded for the two different rules with cofiring relationships between\r\ncell pairs. However, we could not find conclusive evidence for rule coding in the mPFC. Spatially-selective firing in the mPFC generalized between the two start and two goal arms. With Bayesian positional decoding, we found that the mPFC reactivated non-local positions during awake immobility periods. Replay of these non-local positions could represent entire behavioral trajectories resembling trajectory replay of the HPC. Furthermore, mPFC\r\ntrajectory-replay at the goal positively correlated with rule-switching performance. \r\nFinally, HPC and mPFC trajectory replay occurred independently of each other. These results show that the mPFC can replay ordered patterns of activity during awake immobility, possibly underlying its role in flexible behavior. ","lang":"eng"}],"publication_identifier":{"issn":["2663-337X"]},"citation":{"mla":"Käfer, Karola. <i>The Hippocampus and Medial Prefrontal Cortex during Flexible Behavior</i>. Institute of Science and Technology Austria, 2019, doi:<a href=\"https://doi.org/10.15479/AT:ISTA:6825\">10.15479/AT:ISTA:6825</a>.","short":"K. Käfer, The Hippocampus and Medial Prefrontal Cortex during Flexible Behavior, Institute of Science and Technology Austria, 2019.","chicago":"Käfer, Karola. “The Hippocampus and Medial Prefrontal Cortex during Flexible Behavior.” Institute of Science and Technology Austria, 2019. <a href=\"https://doi.org/10.15479/AT:ISTA:6825\">https://doi.org/10.15479/AT:ISTA:6825</a>.","ieee":"K. Käfer, “The hippocampus and medial prefrontal cortex during flexible behavior,” Institute of Science and Technology Austria, 2019.","ama":"Käfer K. The hippocampus and medial prefrontal cortex during flexible behavior. 2019. doi:<a href=\"https://doi.org/10.15479/AT:ISTA:6825\">10.15479/AT:ISTA:6825</a>","apa":"Käfer, K. (2019). <i>The hippocampus and medial prefrontal cortex during flexible behavior</i>. Institute of Science and Technology Austria. <a href=\"https://doi.org/10.15479/AT:ISTA:6825\">https://doi.org/10.15479/AT:ISTA:6825</a>","ista":"Käfer K. 2019. The hippocampus and medial prefrontal cortex during flexible behavior. Institute of Science and Technology Austria."},"page":"89","day":"24","oa":1,"doi":"10.15479/AT:ISTA:6825","OA_place":"publisher","file_date_updated":"2024-04-10T22:30:48Z","related_material":{"record":[{"status":"public","relation":"part_of_dissertation","id":"5949"}]},"alternative_title":["ISTA Thesis"],"date_updated":"2026-04-08T13:56:14Z","oa_version":"Published Version","ddc":["570"],"degree_awarded":"PhD","type":"dissertation","user_id":"ba8df636-2132-11f1-aed0-ed93e2281fdd","title":"The hippocampus and medial prefrontal cortex during flexible behavior","author":[{"full_name":"Käfer, Karola","id":"2DAA49AA-F248-11E8-B48F-1D18A9856A87","last_name":"Käfer","first_name":"Karola"}],"article_processing_charge":"No"},{"publisher":"Institute of Science and Technology Austria","file":[{"file_name":"Thesis_Damaris_Rangel_source.docx","file_id":"6865","access_level":"closed","creator":"drangel","date_created":"2019-09-09T13:09:45Z","date_updated":"2021-02-10T23:30:09Z","content_type":"application/vnd.openxmlformats-officedocument.wordprocessingml.document","file_size":18253100,"checksum":"244dc4f74dbfc94f414156092298831f","relation":"source_file","embargo_to":"open_access"},{"date_updated":"2020-09-11T22:30:04Z","content_type":"application/pdf","checksum":"59c73be40eeaa1c4db24067270151555","file_size":2160109,"relation":"main_file","file_name":"Thesis_Damaris_Rangel_pdfa.pdf","embargo":"2020-09-10","file_id":"6866","access_level":"open_access","request_a_copy":0,"creator":"drangel","date_created":"2019-09-09T13:09:52Z"}],"publication_status":"published","acknowledged_ssus":[{"_id":"Bio"},{"_id":"PreCl"},{"_id":"M-Shop"}],"has_accepted_license":"1","_id":"6849","month":"09","supervisor":[{"first_name":"Jozsef L","last_name":"Csicsvari","id":"3FA14672-F248-11E8-B48F-1D18A9856A87","full_name":"Csicsvari, Jozsef L","orcid":"0000-0002-5193-4036"}],"publication_identifier":{"isbn":["978-3-99078-003-9"],"issn":["2663-337X"]},"year":"2019","abstract":[{"text":"Brain function is mediated by complex dynamical interactions between excitatory and inhibitory cell types. The Cholecystokinin-expressing inhibitory cells (CCK-interneurons) are one of the least studied types, despite being suspected to play important roles in cognitive processes. We studied the network effects of optogenetic silencing of CCK-interneurons in the CA1 hippocampal area during exploration and sleep states. The cell firing pattern in response to light pulses allowed us to classify the recorded neurons in 5 classes, including disinhibited and non-responsive pyramidal cell and interneurons, and the inhibited interneurons corresponding to the CCK group. The light application, which inhibited the activity of CCK interneurons triggered wider changes in the firing dynamics of cells. We observed rate changes (i.e. remapping) of pyramidal cells during the exploration session in which the light was applied relative to the previous control session that was not restricted neither in time nor space to the light delivery. Also, the disinhibited pyramidal cells had higher increase in bursting than in single spike firing rate as a result of CCK silencing. In addition, the firing activity patterns during exploratory periods were more weakly reactivated in sleep for those periods in which CCK-interneuron were silenced than in the unaffected periods. Furthermore, light pulses during sleep disrupted the reactivation of recent waking patterns. Hence, silencing CCK neurons during exploration suppressed the reactivation of waking firing patterns in sleep and CCK interneuron activity was also required during sleep for the normal reactivation of waking patterns. These findings demonstrate the involvement of CCK cells in reactivation-related memory consolidation. An important part of our analysis was to test the relationship of the identified CCKinterneurons to brain oscillations. Our findings showed that these cells exhibited different oscillatory behaviour during anaesthesia and natural waking and sleep conditions. We showed that: 1) Contrary to the past studies performed under anaesthesia, the identified CCKinterneurons fired on the descending portion of the theta phase in waking exploration. 2) CCKinterneuron preferred phases around the trough of gamma oscillations. 3) Contrary to anaesthesia conditions, the average firing rate of the CCK-interneurons increased around the peak activity of the sharp-wave ripple (SWR) events in natural sleep, which is congruent with new reports about their functional connectivity. We also found that light driven CCK-interneuron silencing altered the dynamics on the CA1 network oscillatory activity: 1) Pyramidal cells negatively shifted their preferred theta phases when the light was applied, while interneurons responses were less consistent. 2) As a population, pyramidal cells negatively shifted their preferred activity during gamma oscillations, albeit we did not find gamma modulation differences related to the light application when pyramidal cells were subdivided into the disinhibited and unaffected groups. 3) During the peak of SWR events, all but the CCK-interneurons had a reduction in their relative firing rate change during the light application as compared to the change observed at SWR initiation. Finally, regarding to the place field activity of the recorded pyramidal neurons, we showed that the disinhibited pyramidal cells had reduced place field similarity, coherence and spatial information, but only during the light application. The mechanisms behind such observed behaviours might involve eCB signalling and plastic changes in CCK-interneuron synapses. In conclusion, the observed changes related to the light-mediated silencing of CCKinterneurons have unravelled characteristics of this interneuron subpopulation that might change the understanding not only of their particular network interactions, but also of the current theories about the emergence of certain cognitive processes such as place coding needed for navigation or hippocampus-dependent memory consolidation. ","lang":"eng"}],"date_created":"2019-09-06T06:54:16Z","status":"public","language":[{"iso":"eng"}],"corr_author":"1","department":[{"_id":"JoCs"},{"_id":"GradSch"}],"date_published":"2019-09-09T00:00:00Z","doi_confirm":"1","fulldoi":"https://doi.org/10.15479/AT:ISTA:6849","oa_version":"Published Version","date_updated":"2026-09-03T06:40:36Z","alternative_title":["ISTA Thesis"],"file_date_updated":"2021-02-10T23:30:09Z","OA_place":"publisher","related_material":{"record":[{"status":"public","id":"5914","relation":"part_of_dissertation"}]},"author":[{"orcid":"0000-0002-8602-4374","full_name":"Rangel Guerrero, Dámaris K","id":"4871BCE6-F248-11E8-B48F-1D18A9856A87","first_name":"Dámaris K","last_name":"Rangel Guerrero"}],"title":"The role of CCK-interneurons in regulating hippocampal network dynamics","user_id":"8b945eb4-e2f2-11eb-945a-df72226e66a9","type":"dissertation","article_processing_charge":"No","ddc":["570"],"degree_awarded":"PhD","page":"97","day":"09","citation":{"ieee":"D. K. Rangel Guerrero, “The role of CCK-interneurons in regulating hippocampal network dynamics,” Institute of Science and Technology Austria, 2019.","chicago":"Rangel Guerrero, Dámaris K. “The Role of CCK-Interneurons in Regulating Hippocampal Network Dynamics.” Institute of Science and Technology Austria, 2019. <a href=\"https://doi.org/10.15479/AT:ISTA:6849\">https://doi.org/10.15479/AT:ISTA:6849</a>.","short":"D.K. Rangel Guerrero, The Role of CCK-Interneurons in Regulating Hippocampal Network Dynamics, Institute of Science and Technology Austria, 2019.","mla":"Rangel Guerrero, Dámaris K. <i>The Role of CCK-Interneurons in Regulating Hippocampal Network Dynamics</i>. Institute of Science and Technology Austria, 2019, doi:<a href=\"https://doi.org/10.15479/AT:ISTA:6849\">10.15479/AT:ISTA:6849</a>.","ista":"Rangel Guerrero DK. 2019. The role of CCK-interneurons in regulating hippocampal network dynamics. Institute of Science and Technology Austria.","apa":"Rangel Guerrero, D. K. (2019). <i>The role of CCK-interneurons in regulating hippocampal network dynamics</i>. Institute of Science and Technology Austria. <a href=\"https://doi.org/10.15479/AT:ISTA:6849\">https://doi.org/10.15479/AT:ISTA:6849</a>","ama":"Rangel Guerrero DK. The role of CCK-interneurons in regulating hippocampal network dynamics. 2019. doi:<a href=\"https://doi.org/10.15479/AT:ISTA:6849\">10.15479/AT:ISTA:6849</a>"},"doi":"10.15479/AT:ISTA:6849","oa":1},{"oa_version":"Published Version","alternative_title":["ISTA Thesis"],"date_updated":"2026-04-08T14:13:15Z","OA_place":"publisher","file_date_updated":"2021-02-11T23:30:22Z","article_processing_charge":"No","type":"dissertation","user_id":"ba8df636-2132-11f1-aed0-ed93e2281fdd","author":[{"orcid":"0000-0002-1807-1929","full_name":"Gridchyn, Igor","id":"4B60654C-F248-11E8-B48F-1D18A9856A87","last_name":"Gridchyn","first_name":"Igor"}],"title":"Reactivation content is important for consolidation of spatial memory","degree_awarded":"PhD","ddc":["573"],"day":"27","page":"104","citation":{"ama":"Gridchyn I. Reactivation content is important for consolidation of spatial memory. 2018. doi:<a href=\"https://doi.org/10.15479/AT:ISTA:th_1042\">10.15479/AT:ISTA:th_1042</a>","apa":"Gridchyn, I. (2018). <i>Reactivation content is important for consolidation of spatial memory</i>. Institute of Science and Technology Austria. <a href=\"https://doi.org/10.15479/AT:ISTA:th_1042\">https://doi.org/10.15479/AT:ISTA:th_1042</a>","ista":"Gridchyn I. 2018. Reactivation content is important for consolidation of spatial memory. Institute of Science and Technology Austria.","mla":"Gridchyn, Igor. <i>Reactivation Content Is Important for Consolidation of Spatial Memory</i>. Institute of Science and Technology Austria, 2018, doi:<a href=\"https://doi.org/10.15479/AT:ISTA:th_1042\">10.15479/AT:ISTA:th_1042</a>.","chicago":"Gridchyn, Igor. “Reactivation Content Is Important for Consolidation of Spatial Memory.” Institute of Science and Technology Austria, 2018. <a href=\"https://doi.org/10.15479/AT:ISTA:th_1042\">https://doi.org/10.15479/AT:ISTA:th_1042</a>.","short":"I. Gridchyn, Reactivation Content Is Important for Consolidation of Spatial Memory, Institute of Science and Technology Austria, 2018.","ieee":"I. Gridchyn, “Reactivation content is important for consolidation of spatial memory,” Institute of Science and Technology Austria, 2018."},"doi":"10.15479/AT:ISTA:th_1042","oa":1,"has_accepted_license":"1","publication_status":"published","publisher":"Institute of Science and Technology Austria","file":[{"date_created":"2019-04-08T13:36:01Z","creator":"dernst","file_id":"6236","access_level":"closed","file_name":"2018_Thesis_Gridchyn_source.docx","relation":"source_file","embargo_to":"open_access","file_size":7666687,"checksum":"7db4415e435590fa33542c7b0a0321d7","content_type":"application/vnd.openxmlformats-officedocument.wordprocessingml.document","date_updated":"2021-02-11T23:30:22Z"},{"creator":"dernst","date_created":"2019-04-08T13:36:01Z","file_name":"2018_Thesis_Gridchyn.pdf","embargo":"2019-08-29","access_level":"open_access","file_id":"6237","checksum":"f96f3fe8979f7b1e6db6acaca962b10c","file_size":6034153,"relation":"main_file","date_updated":"2021-02-11T11:17:18Z","content_type":"application/pdf"}],"supervisor":[{"id":"3FA14672-F248-11E8-B48F-1D18A9856A87","full_name":"Csicsvari, Jozsef L","last_name":"Csicsvari","first_name":"Jozsef L","orcid":"0000-0002-5193-4036"}],"_id":"48","month":"08","publication_identifier":{"issn":["2663-337X"]},"date_created":"2018-12-11T11:44:21Z","abstract":[{"text":"The hippocampus is a key brain region for spatial memory and navigation and is needed at all stages of memory, including encoding, consolidation, and recall. Hippocampal place cells selectively discharge at specific locations of the environment to form a cognitive map of the space. During the rest period and sleep following spatial navigation and/or learning, the waking activity of the place cells is reactivated within high synchrony events. This reactivation is thought to be important for memory consolidation and stabilization of the spatial representations. The aim of my thesis was to directly test whether the reactivation content encoded in firing patterns of place cells is important for consolidation of spatial memories. In particular, I aimed to test whether, in cases when multiple spatial memory traces are acquired during learning, the specific disruption of the reactivation of a subset of these memories leads to the selective disruption of the corresponding memory traces or through memory interference the other learned memories are disrupted as well. In this thesis, using a modified cheeseboard paradigm and a closed-loop recording setup with feedback optogenetic stimulation, I examined how the disruption of the reactivation of specific spiking patterns affects consolidation of the corresponding memory traces. To obtain multiple distinctive memories, animals had to perform a spatial task in two distinct cheeseboard environments and the reactivation of spiking patterns associated with one of the environments (target) was disrupted after learning during four hours rest period using a real-time decoding method. This real-time decoding method was capable of selectively affecting the firing rates and cofiring correlations of the target environment-encoding cells. The selective disruption led to behavioural impairment in the memory tests after the rest periods in the target environment but not in the other undisrupted control environment. In addition, the map of the target environment was less stable in the impaired memory tests compared to the learning session before than the map of the control environment. However, when the animal relearned the task, the same map recurred in the target environment that was present during learning before the disruption. Altogether my work demonstrated that the reactivation content is important: assembly-related disruption of reactivation can lead to a selective memory impairment and deficiency in map stability. These findings indeed suggest that reactivated assembly patterns reflect processes associated with the consolidation of memory traces. ","lang":"eng"}],"pubrep_id":"1042","year":"2018","publist_id":"8006","language":[{"iso":"eng"}],"status":"public","date_published":"2018-08-27T00:00:00Z","corr_author":"1","department":[{"_id":"JoCs"}],"tmp":{"name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","short":"CC BY (4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode","image":"/images/cc_by.png"},"fulldoi":"https://doi.org/10.15479/AT:ISTA:th_1042"},{"file_date_updated":"2020-07-14T12:48:12Z","OA_place":"publisher","related_material":{"record":[{"status":"public","relation":"part_of_dissertation","id":"5828"}]},"alternative_title":["ISTA Thesis"],"oa_version":"Published Version","date_updated":"2026-06-18T18:56:25Z","ddc":["571"],"degree_awarded":"PhD","title":"Reactivation of the hippocampal cognitive map in goal-directed spatial tasks","author":[{"id":"310349D0-F248-11E8-B48F-1D18A9856A87","full_name":"Xu, Haibing","first_name":"Haibing","last_name":"Xu"}],"user_id":"ba8df636-2132-11f1-aed0-ed93e2281fdd","type":"dissertation","article_processing_charge":"No","citation":{"ieee":"H. Xu, “Reactivation of the hippocampal cognitive map in goal-directed spatial tasks,” Institute of Science and Technology Austria, 2017.","chicago":"Xu, Haibing. “Reactivation of the Hippocampal Cognitive Map in Goal-Directed Spatial Tasks.” Institute of Science and Technology Austria, 2017. <a href=\"https://doi.org/10.15479/AT:ISTA:th_858\">https://doi.org/10.15479/AT:ISTA:th_858</a>.","short":"H. Xu, Reactivation of the Hippocampal Cognitive Map in Goal-Directed Spatial Tasks, Institute of Science and Technology Austria, 2017.","mla":"Xu, Haibing. <i>Reactivation of the Hippocampal Cognitive Map in Goal-Directed Spatial Tasks</i>. Institute of Science and Technology Austria, 2017, doi:<a href=\"https://doi.org/10.15479/AT:ISTA:th_858\">10.15479/AT:ISTA:th_858</a>.","ista":"Xu H. 2017. Reactivation of the hippocampal cognitive map in goal-directed spatial tasks. Institute of Science and Technology Austria.","apa":"Xu, H. (2017). <i>Reactivation of the hippocampal cognitive map in goal-directed spatial tasks</i>. Institute of Science and Technology Austria. <a href=\"https://doi.org/10.15479/AT:ISTA:th_858\">https://doi.org/10.15479/AT:ISTA:th_858</a>","ama":"Xu H. Reactivation of the hippocampal cognitive map in goal-directed spatial tasks. 2017. doi:<a href=\"https://doi.org/10.15479/AT:ISTA:th_858\">10.15479/AT:ISTA:th_858</a>"},"page":"93","day":"23","oa":1,"doi":"10.15479/AT:ISTA:th_858","month":"08","_id":"837","supervisor":[{"orcid":"0000-0002-5193-4036","first_name":"Jozsef L","last_name":"Csicsvari","id":"3FA14672-F248-11E8-B48F-1D18A9856A87","full_name":"Csicsvari, Jozsef L"}],"file":[{"relation":"source_file","file_size":3589490,"checksum":"f11925fbbce31e495124b6bc4f10573c","content_type":"application/vnd.openxmlformats-officedocument.wordprocessingml.document","date_updated":"2020-07-14T12:48:12Z","date_created":"2019-04-05T08:59:51Z","creator":"dernst","access_level":"closed","file_id":"6213","file_name":"2017_Xu_Haibing_Thesis_Source.docx"},{"creator":"dernst","date_created":"2019-04-05T08:59:51Z","file_name":"2017_Xu_Thesis_IST.pdf","access_level":"open_access","file_id":"6214","file_size":11668613,"checksum":"ffb10749a537d615fab1ef0937ccb157","relation":"main_file","date_updated":"2020-07-14T12:48:12Z","content_type":"application/pdf"}],"publisher":"Institute of Science and Technology Austria","publication_status":"published","has_accepted_license":"1","year":"2017","pubrep_id":"858","abstract":[{"text":"The hippocampus is a key brain region for memory and notably for spatial memory, and is needed for both spatial working and reference memories. Hippocampal place cells selectively discharge in specific locations of the environment to form mnemonic represen tations of space. Several behavioral protocols have been designed to test spatial memory which requires the experimental subject to utilize working memory and reference memory. However, less is known about how these memory traces are presented in the hippo campus, especially considering tasks that require both spatial working and long -term reference memory demand. The aim of my thesis was to elucidate how spatial working memory, reference memory, and the combination of both are represented in the hippocampus. In this thesis, using a radial eight -arm maze, I examined how the combined demand on these memories influenced place cell assemblies while reference memories were partially updated by changing some of the reward- arms. This was contrasted with task varian ts requiring working or reference memories only. Reference memory update led to gradual place field shifts towards the rewards on the switched arms. Cells developed enhanced firing in passes between newly -rewarded arms as compared to those containing an unchanged reward. The working memory task did not show such gradual changes. Place assemblies on occasions replayed trajectories of the maze; at decision points the next arm choice was preferentially replayed in tasks needing reference memory while in the pure working memory task the previously visited arm was replayed. Hence trajectory replay only reflected the decision of the animal in tasks needing reference memory update. At the reward locations, in all three tasks outbound trajectories of the current arm were preferentially replayed, showing the animals’ next path to the center. At reward locations trajectories were replayed preferentially in reverse temporal order. Moreover, in the center reverse replay was seen in the working memory task but in the other tasks forward replay was seen. Hence, the direction of reactivation was determined by the goal locations so that part of the trajectory which was closer to the goal was reactivated later in an HSE while places further away from the goal were reactivated earlier. Altogether my work demonstrated that reference memory update triggers several levels of reorganization of the hippocampal cognitive map which are not seen in simpler working memory demand s. Moreover, hippocampus is likely to be involved in spatial decisions through reactivating planned trajectories when reference memory recall is required for such a decision. ","lang":"eng"}],"date_created":"2018-12-11T11:48:46Z","publication_identifier":{"issn":["2663-337X"]},"department":[{"_id":"JoCs"}],"corr_author":"1","date_published":"2017-08-23T00:00:00Z","acknowledgement":"I am very grateful for the opportunity I have had as a graduate student to explore and incredibly interesting branch of neuroscience, and for the people who made it possible. Firstly, I would like to offer my thanks to my supervisor Professor Jozsef Csicsvari for his great support, guidance and patience offered over the years. The door to his office was always open whenever I had questions. I have learned a lot from him about carefully designing experiments, asking interesting questions and how to integrate results into a broader picture. I also express my gratitude to the remarkable post- doc , Dr. Joseph O’Neill. He is a gre at scientific role model who is always willing to teach , and advice and talk through problems with his full attention. Many thanks to my wonderful “office mates” over the years and their support and encouragement, Alice Avernhe, Philipp Schönenberger, Desiree Dickerson, Karel Blahna, Charlotte Boccara, Igor Gridchyn, Peter Baracskay, Krisztián Kovács, Dámaris Rangel, Karola Käfer and Federico Stella. They were the ones in the lab for the many useful discussions about science and for making the laboratory such a nice and friendly place to work in. A special thank goes to Michael LoBianco and Jago Wallenschus for wonderful technical support. I would also like to thank Professor Peter Jonas and Professor David M Bannerman for being my qualifying exam and thesi s committee members despite their busy schedule. I am also very thankful to IST Austria for their support all throughout my PhD. ","status":"public","language":[{"iso":"eng"}],"publist_id":"6811","fulldoi":"https://doi.org/10.15479/AT:ISTA:th_858","tmp":{"name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","short":"CC BY (4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode","image":"/images/cc_by.png"}}]