[{"doi":"10.15479/AT:ISTA:18991","date_published":"2025-02-04T00:00:00Z","OA_place":"repository","corr_author":"1","has_accepted_license":"1","oa_version":"Published Version","ddc":["570"],"tmp":{"short":"CC BY-NC-ND (4.0)","name":"Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)","legal_code_url":"https://creativecommons.org/licenses/by-nc-nd/4.0/legalcode","image":"/images/cc_by_nc_nd.png"},"oa":1,"month":"02","contributor":[{"first_name":"Michele","orcid":"0000-0001-8849-6570","contributor_type":"researcher","id":"30BD0376-F248-11E8-B48F-1D18A9856A87","last_name":"Nardin"},{"orcid":"0000-0002-6699-1455","first_name":"Gašper","last_name":"Tkačik","contributor_type":"supervisor","id":"3D494DCA-F248-11E8-B48F-1D18A9856A87"},{"orcid":"0000-0002-5193-4036","first_name":"Jozsef L","last_name":"Csicsvari","contributor_type":"supervisor","id":"3FA14672-F248-11E8-B48F-1D18A9856A87"}],"article_processing_charge":"No","title":"Research data for the publication \"Learning reshapes the hippocampal representation hierarchy\"","keyword":["hippocampus","electrophysiology","behavior"],"acknowledged_ssus":[{"_id":"PreCl"},{"_id":"M-Shop"}],"related_material":{"record":[{"relation":"used_in_publication","id":"19453","status":"public"}]},"type":"research_data","year":"2025","date_updated":"2026-05-06T13:12:00Z","file":[{"file_name":"Chiossi_etal_2025_PNAS_data.zip","date_updated":"2025-02-04T10:16:52Z","success":1,"date_created":"2025-02-04T10:16:52Z","access_level":"open_access","checksum":"04d761ed42e8879abffde04a560409ce","file_size":769383201,"file_id":"18992","relation":"main_file","creator":"hchiossi","content_type":"application/zip"},{"creator":"hchiossi","content_type":"text/plain","relation":"main_file","file_size":3215,"file_id":"18993","checksum":"50602931dcd33e4f009ed46af11335f3","access_level":"open_access","date_created":"2025-02-04T10:18:33Z","date_updated":"2025-02-04T10:18:33Z","success":1,"file_name":"readme.txt"}],"fulldoi":"https://doi.org/10.15479/AT:ISTA:18991","date_created":"2025-02-04T10:36:18Z","status":"public","file_date_updated":"2025-02-04T10:18:33Z","day":"04","author":[{"full_name":"Chiossi, Heloisa","id":"2BBA502C-F248-11E8-B48F-1D18A9856A87","last_name":"Chiossi","first_name":"Heloisa","orcid":"0009-0004-2973-278X"}],"abstract":[{"text":"Research data for the article \"Learning reshapes the hippocampal representation hierarchy\" from Chiossi et al. (PNAS, 2025). The data includes hippocampal CA1 unit activity and behaviour tracking of 5 Long Evans rats during the learning of an associative memory task. Detailed information can be found in the 'readme.txt' file.","lang":"eng"}],"OA_type":"gold","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","publisher":"Institute of Science and Technology Austria","citation":{"ieee":"H. S. C. Chiossi, “Research data for the publication ‘Learning reshapes the hippocampal representation hierarchy.’” Institute of Science and Technology Austria, 2025.","mla":"Chiossi, Heloisa S. C. <i>Research Data for the Publication “Learning Reshapes the Hippocampal Representation Hierarchy.”</i> Institute of Science and Technology Austria, 2025, doi:<a href=\"https://doi.org/10.15479/AT:ISTA:18991\">10.15479/AT:ISTA:18991</a>.","ama":"Chiossi HSC. Research data for the publication “Learning reshapes the hippocampal representation hierarchy.” 2025. doi:<a href=\"https://doi.org/10.15479/AT:ISTA:18991\">10.15479/AT:ISTA:18991</a>","short":"H.S.C. Chiossi, (2025).","apa":"Chiossi, H. S. C. (2025). Research data for the publication “Learning reshapes the hippocampal representation hierarchy.” Institute of Science and Technology Austria. <a href=\"https://doi.org/10.15479/AT:ISTA:18991\">https://doi.org/10.15479/AT:ISTA:18991</a>","ista":"Chiossi HSC. 2025. Research data for the publication ‘Learning reshapes the hippocampal representation hierarchy’, Institute of Science and Technology Austria, <a href=\"https://doi.org/10.15479/AT:ISTA:18991\">10.15479/AT:ISTA:18991</a>.","chicago":"Chiossi, Heloisa S. C. “Research Data for the Publication ‘Learning Reshapes the Hippocampal Representation Hierarchy.’” Institute of Science and Technology Austria, 2025. <a href=\"https://doi.org/10.15479/AT:ISTA:18991\">https://doi.org/10.15479/AT:ISTA:18991</a>."},"acknowledgement":"Thanks to Rebecca Morse for performing one of the experiments under H.S.C.C. supervision and Jago Wallenschus for technical support, especially with maze design.","_id":"18991","department":[{"_id":"GradSch"},{"_id":"JoCs"},{"_id":"GaTk"}]},{"date_updated":"2026-05-06T13:12:01Z","publication_status":"published","publication_identifier":{"issn":["0027-8424"],"eissn":["1091-6490"]},"publication":"Proceedings of the National Academy of Sciences","date_created":"2025-03-25T07:38:35Z","fulldoi":"https://doi.org/10.1073/pnas.2417025122","file":[{"access_level":"open_access","file_size":1553502,"file_id":"19454","checksum":"1217207c254553154faa065964990988","date_updated":"2025-03-25T07:49:04Z","success":1,"file_name":"2025_PNAS_Chiossi.pdf","date_created":"2025-03-25T07:49:04Z","content_type":"application/pdf","creator":"dernst","relation":"main_file"}],"type":"journal_article","year":"2025","related_material":{"record":[{"status":"public","id":"18991","relation":"research_data"}],"link":[{"url":"https://github.com/hchiossi/hpc-hierarchy","relation":"software"}]},"volume":122,"isi":1,"intvolume":"       122","article_processing_charge":"Yes (in subscription journal)","title":"Learning reshapes the hippocampal representation hierarchy","oa":1,"month":"03","corr_author":"1","has_accepted_license":"1","oa_version":"Published Version","article_type":"original","tmp":{"short":"CC BY-NC-ND (4.0)","name":"Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)","legal_code_url":"https://creativecommons.org/licenses/by-nc-nd/4.0/legalcode","image":"/images/cc_by_nc_nd.png"},"pmid":1,"ddc":["570"],"quality_controlled":"1","doi":"10.1073/pnas.2417025122","APC_amount":"3317,75 EUR","date_published":"2025-03-10T00:00:00Z","OA_place":"publisher","citation":{"chicago":"Chiossi, Heloisa S. C., Michele Nardin, Gašper Tkačik, and Jozsef L Csicsvari. “Learning Reshapes the Hippocampal Representation Hierarchy.” <i>Proceedings of the National Academy of Sciences</i>. National Academy of Sciences, 2025. <a href=\"https://doi.org/10.1073/pnas.2417025122\">https://doi.org/10.1073/pnas.2417025122</a>.","ista":"Chiossi HSC, Nardin M, Tkačik G, Csicsvari JL. 2025. Learning reshapes the hippocampal representation hierarchy. Proceedings of the National Academy of Sciences. 122(11), e2417025122.","short":"H.S.C. Chiossi, M. Nardin, G. Tkačik, J.L. Csicsvari, Proceedings of the National Academy of Sciences 122 (2025).","apa":"Chiossi, H. S. C., Nardin, M., Tkačik, G., &#38; Csicsvari, J. L. (2025). Learning reshapes the hippocampal representation hierarchy. <i>Proceedings of the National Academy of Sciences</i>. National Academy of Sciences. <a href=\"https://doi.org/10.1073/pnas.2417025122\">https://doi.org/10.1073/pnas.2417025122</a>","ama":"Chiossi HSC, Nardin M, Tkačik G, Csicsvari JL. Learning reshapes the hippocampal representation hierarchy. <i>Proceedings of the National Academy of Sciences</i>. 2025;122(11). doi:<a href=\"https://doi.org/10.1073/pnas.2417025122\">10.1073/pnas.2417025122</a>","mla":"Chiossi, Heloisa S. C., et al. “Learning Reshapes the Hippocampal Representation Hierarchy.” <i>Proceedings of the National Academy of Sciences</i>, vol. 122, no. 11, e2417025122, National Academy of Sciences, 2025, doi:<a href=\"https://doi.org/10.1073/pnas.2417025122\">10.1073/pnas.2417025122</a>.","ieee":"H. S. C. Chiossi, M. Nardin, G. Tkačik, and J. L. Csicsvari, “Learning reshapes the hippocampal representation hierarchy,” <i>Proceedings of the National Academy of Sciences</i>, vol. 122, no. 11. National Academy of Sciences, 2025."},"acknowledgement":"We would like to thank Rebecca Morse for performing the recordings in one of the animals under the supervision of H.S.C.C., Jago Wallenschus for the technical support, especially with maze design, Wiktor Mlynarski for the advice and discussions and Andrea Cumpelik for suggestions during the writing. M.N. was supported by the Howard Hughes Medical Institute. H.S.C.C. received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 665385.","department":[{"_id":"GaTk"},{"_id":"JoCs"}],"_id":"19453","scopus_import":"1","publisher":"National Academy of Sciences","issue":"11","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","article_number":"e2417025122","ec_funded":1,"external_id":{"isi":["001459499500001"],"pmid":["40063792"]},"abstract":[{"lang":"eng","text":"A key feature of biological and artificial neural networks is the progressive refinement of their neural representations with experience. In neuroscience, this fact has inspired several recent studies in sensory and motor systems. However, less is known about how higher associational cortical areas, such as the hippocampus, modify representations throughout the learning of complex tasks. Here, we focus on associative learning, a process that requires forming a connection between the representations of different variables for appropriate behavioral response. We trained rats in a space-context associative task and monitored hippocampal neural activity throughout the entire learning period, over several days. This allowed us to assess changes in the representations of context, movement direction, and position, as well as their relationship to behavior. We identified a hierarchical representational structure in the encoding of these three task variables that was preserved throughout learning. Nevertheless, we also observed changes at the lower levels of the hierarchy where context was encoded. These changes were local in neural activity space and restricted to physical positions where context identification was necessary for correct decision-making, supporting better context decoding and contextual code compression. Our results demonstrate that the hippocampal code not only accommodates hierarchical relationships between different variables but also enables efficient learning through minimal changes in neural activity space. Beyond the hippocampus, our work reveals a representation learning mechanism that might be implemented in other biological and artificial networks performing similar tasks."}],"OA_type":"hybrid","file_date_updated":"2025-03-25T07:49:04Z","day":"10","language":[{"iso":"eng"}],"author":[{"orcid":"0009-0004-2973-278X","first_name":"Heloisa","last_name":"Chiossi","id":"2BBA502C-F248-11E8-B48F-1D18A9856A87","full_name":"Chiossi, Heloisa"},{"id":"30BD0376-F248-11E8-B48F-1D18A9856A87","full_name":"Nardin, Michele","last_name":"Nardin","first_name":"Michele","orcid":"0000-0001-8849-6570"},{"id":"3D494DCA-F248-11E8-B48F-1D18A9856A87","full_name":"Tkačik, Gašper","last_name":"Tkačik","orcid":"0000-0002-6699-1455","first_name":"Gašper"},{"orcid":"0000-0002-5193-4036","first_name":"Jozsef L","id":"3FA14672-F248-11E8-B48F-1D18A9856A87","full_name":"Csicsvari, Jozsef L","last_name":"Csicsvari"}],"status":"public","project":[{"grant_number":"665385","name":"International IST Doctoral Program","_id":"2564DBCA-B435-11E9-9278-68D0E5697425","call_identifier":"H2020"}]},{"citation":{"ista":"Chiossi HSC. 2024. Adaptive hierarchical representations in the hippocampus. Institute of Science and Technology Austria.","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>.","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.","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>","short":"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>"},"degree_awarded":"PhD","_id":"14821","department":[{"_id":"GradSch"},{"_id":"JoCs"}],"publisher":"Institute of Science and Technology Austria","user_id":"ba8df636-2132-11f1-aed0-ed93e2281fdd","ec_funded":1,"alternative_title":["ISTA Thesis"],"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"}],"day":"19","file_date_updated":"2025-01-19T23:30:04Z","author":[{"first_name":"Heloisa","orcid":"0009-0004-2973-278X","last_name":"Chiossi","full_name":"Chiossi, Heloisa","id":"2BBA502C-F248-11E8-B48F-1D18A9856A87"}],"language":[{"iso":"eng"}],"project":[{"call_identifier":"H2020","name":"International IST Doctoral Program","_id":"2564DBCA-B435-11E9-9278-68D0E5697425","grant_number":"665385"}],"status":"public","date_updated":"2026-04-07T13:21:56Z","file":[{"access_level":"closed","file_size":8656268,"file_id":"14838","checksum":"d3fa3de1abd5af5204c13e9d55375615","date_updated":"2025-01-19T23:30:04Z","file_name":"PhD_Thesis_190124.docx","embargo_to":"open_access","date_created":"2024-01-19T11:04:05Z","content_type":"application/vnd.openxmlformats-officedocument.wordprocessingml.document","creator":"hchiossi","relation":"source_file"},{"content_type":"application/pdf","creator":"hchiossi","relation":"main_file","access_level":"open_access","embargo":"2025-01-19","file_id":"14839","file_size":6567275,"checksum":"13adc8dcfb5b6b18107f89f0a98fa8bd","date_updated":"2025-01-19T23:30:04Z","file_name":"PhD_Thesis_190124.pdf","date_created":"2024-01-19T11:03:59Z"}],"fulldoi":"https://doi.org/10.15479/at:ista:14821","date_created":"2024-01-16T14:25:21Z","publication_status":"published","publication_identifier":{"issn":["2663-337X"]},"year":"2024","type":"dissertation","article_processing_charge":"No","title":"Adaptive hierarchical representations in the hippocampus","supervisor":[{"full_name":"Csicsvari, Jozsef L","id":"3FA14672-F248-11E8-B48F-1D18A9856A87","last_name":"Csicsvari","orcid":"0000-0002-5193-4036","first_name":"Jozsef L"}],"oa":1,"month":"01","page":"89","has_accepted_license":"1","corr_author":"1","ddc":["570"],"oa_version":"Published Version","doi":"10.15479/at:ista:14821","OA_place":"publisher","date_published":"2024-01-19T00:00:00Z"}]