--- _id: '14821' alternative_title: - ISTA Thesis article_processing_charge: No author: - first_name: Heloisa full_name: Chiossi, Heloisa id: 2BBA502C-F248-11E8-B48F-1D18A9856A87 last_name: Chiossi citation: ama: Chiossi HSC. Adaptive hierarchical representations in the hippocampus. 2024. doi:10.15479/at:ista:14821 apa: Chiossi, H. S. C. (2024). Adaptive hierarchical representations in the hippocampus. Institute of Science and Technology Austria. https://doi.org/10.15479/at:ista:14821 chicago: Chiossi, Heloisa S. C. “Adaptive Hierarchical Representations in the Hippocampus.” Institute of Science and Technology Austria, 2024. https://doi.org/10.15479/at:ista:14821. ieee: H. S. C. Chiossi, “Adaptive hierarchical representations in the hippocampus,” Institute of Science and Technology Austria, 2024. ista: Chiossi HSC. 2024. Adaptive hierarchical representations in the hippocampus. Institute of Science and Technology Austria. mla: Chiossi, Heloisa S. C. Adaptive Hierarchical Representations in the Hippocampus. Institute of Science and Technology Austria, 2024, doi:10.15479/at:ista:14821. short: H.S.C. Chiossi, Adaptive Hierarchical Representations in the Hippocampus, Institute of Science and Technology Austria, 2024. date_created: 2024-01-16T14:25:21Z date_published: 2024-01-19T00:00:00Z date_updated: 2024-02-01T09:50:29Z day: '19' ddc: - '570' degree_awarded: PhD department: - _id: GradSch - _id: JoCs doi: 10.15479/at:ista:14821 ec_funded: 1 file: - access_level: closed checksum: d3fa3de1abd5af5204c13e9d55375615 content_type: application/vnd.openxmlformats-officedocument.wordprocessingml.document creator: hchiossi date_created: 2024-01-19T11:04:05Z date_updated: 2024-01-19T11:04:05Z file_id: '14838' file_name: PhD_Thesis_190124.docx file_size: 8656268 relation: source_file - access_level: closed checksum: 13adc8dcfb5b6b18107f89f0a98fa8bd content_type: application/pdf creator: hchiossi date_created: 2024-01-19T11:03:59Z date_updated: 2024-01-19T11:03:59Z embargo: 2025-01-19 embargo_to: open_access file_id: '14839' file_name: PhD_Thesis_190124.pdf file_size: 6567275 relation: main_file file_date_updated: 2024-01-19T11:04:05Z has_accepted_license: '1' language: - iso: eng month: '01' oa_version: Published Version page: '89' project: - _id: 2564DBCA-B435-11E9-9278-68D0E5697425 call_identifier: H2020 grant_number: '665385' name: International IST Doctoral Program publication_identifier: issn: - 2663 - 337X publication_status: published publisher: Institute of Science and Technology Austria status: public supervisor: - first_name: Jozsef L full_name: Csicsvari, Jozsef L id: 3FA14672-F248-11E8-B48F-1D18A9856A87 last_name: Csicsvari orcid: 0000-0002-5193-4036 title: Adaptive hierarchical representations in the hippocampus type: dissertation user_id: 8b945eb4-e2f2-11eb-945a-df72226e66a9 year: '2024' ... --- _id: '11932' abstract: - lang: eng 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." 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. alternative_title: - ISTA Thesis article_processing_charge: No author: - first_name: Michele full_name: Nardin, Michele id: 30BD0376-F248-11E8-B48F-1D18A9856A87 last_name: Nardin orcid: 0000-0001-8849-6570 citation: ama: Nardin M. On the encoding, transfer, and consolidation of spatial memories. 2022. doi:10.15479/at:ista:11932 apa: Nardin, M. (2022). On the encoding, transfer, and consolidation of spatial memories. Institute of Science and Technology Austria. https://doi.org/10.15479/at:ista:11932 chicago: Nardin, Michele. “On the Encoding, Transfer, and Consolidation of Spatial Memories.” Institute of Science and Technology Austria, 2022. https://doi.org/10.15479/at:ista:11932. ieee: M. Nardin, “On the encoding, transfer, and consolidation of spatial memories,” Institute of Science and Technology Austria, 2022. ista: Nardin M. 2022. On the encoding, transfer, and consolidation of spatial memories. Institute of Science and Technology Austria. mla: Nardin, Michele. On the Encoding, Transfer, and Consolidation of Spatial Memories. Institute of Science and Technology Austria, 2022, doi:10.15479/at:ista:11932. short: M. Nardin, On the Encoding, Transfer, and Consolidation of Spatial Memories, Institute of Science and Technology Austria, 2022. date_created: 2022-08-19T08:52:30Z date_published: 2022-08-19T00:00:00Z date_updated: 2023-09-05T12:02:14Z day: '19' ddc: - '573' degree_awarded: PhD department: - _id: GradSch - _id: JoCs doi: 10.15479/at:ista:11932 ec_funded: 1 file: - access_level: closed checksum: 2dbb70c74aaa3b64c1f463e943baf09c content_type: application/zip creator: mnardin date_created: 2022-08-19T16:31:34Z date_updated: 2023-06-20T22:30:04Z embargo_to: open_access file_id: '11935' file_name: Michele Nardin, Ph.D. Thesis - ISTA (1).zip file_size: 13515457 relation: source_file - access_level: open_access checksum: 0ec94035ea35a47a9f589ed168e60b48 content_type: application/pdf creator: mnardin date_created: 2022-08-22T09:43:50Z date_updated: 2023-06-20T22:30:04Z embargo: 2023-06-19 file_id: '11941' file_name: Michele_Nardin_Phd_Thesis_PDFA.pdf file_size: 9906458 relation: main_file file_date_updated: 2023-06-20T22:30:04Z has_accepted_license: '1' language: - iso: eng month: '08' oa: 1 oa_version: Published Version page: '136' project: - _id: 2564DBCA-B435-11E9-9278-68D0E5697425 call_identifier: H2020 grant_number: '665385' name: International IST Doctoral Program publication_identifier: issn: - 2663-337X publication_status: published publisher: Institute of Science and Technology Austria related_material: record: - id: '10077' relation: part_of_dissertation status: public - id: '6194' relation: part_of_dissertation status: public status: public supervisor: - first_name: Jozsef L full_name: Csicsvari, Jozsef L id: 3FA14672-F248-11E8-B48F-1D18A9856A87 last_name: Csicsvari orcid: 0000-0002-5193-4036 title: On the encoding, transfer, and consolidation of spatial memories type: dissertation user_id: 8b945eb4-e2f2-11eb-945a-df72226e66a9 year: '2022' ... --- _id: '6849' abstract: - lang: eng 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. ' acknowledged_ssus: - _id: Bio - _id: PreCl - _id: M-Shop alternative_title: - ISTA Thesis article_processing_charge: No author: - first_name: Dámaris K full_name: Rangel Guerrero, Dámaris K id: 4871BCE6-F248-11E8-B48F-1D18A9856A87 last_name: Rangel Guerrero orcid: 0000-0002-8602-4374 citation: ama: Rangel Guerrero DK. The role of CCK-interneurons in regulating hippocampal network dynamics. 2019. doi:10.15479/AT:ISTA:6849 apa: Rangel Guerrero, D. K. (2019). The role of CCK-interneurons in regulating hippocampal network dynamics. Institute of Science and Technology Austria. https://doi.org/10.15479/AT:ISTA:6849 chicago: Rangel Guerrero, Dámaris K. “The Role of CCK-Interneurons in Regulating Hippocampal Network Dynamics.” Institute of Science and Technology Austria, 2019. https://doi.org/10.15479/AT:ISTA:6849. ieee: D. K. Rangel Guerrero, “The role of CCK-interneurons in regulating hippocampal network dynamics,” Institute of Science and Technology Austria, 2019. ista: Rangel Guerrero DK. 2019. The role of CCK-interneurons in regulating hippocampal network dynamics. Institute of Science and Technology Austria. mla: Rangel Guerrero, Dámaris K. The Role of CCK-Interneurons in Regulating Hippocampal Network Dynamics. Institute of Science and Technology Austria, 2019, doi:10.15479/AT:ISTA:6849. short: D.K. Rangel Guerrero, The Role of CCK-Interneurons in Regulating Hippocampal Network Dynamics, Institute of Science and Technology Austria, 2019. date_created: 2019-09-06T06:54:16Z date_published: 2019-09-09T00:00:00Z date_updated: 2023-09-19T10:01:12Z day: '09' ddc: - '570' degree_awarded: PhD department: - _id: JoCs doi: 10.15479/AT:ISTA:6849 file: - access_level: closed checksum: 244dc4f74dbfc94f414156092298831f content_type: application/vnd.openxmlformats-officedocument.wordprocessingml.document creator: drangel date_created: 2019-09-09T13:09:45Z date_updated: 2021-02-10T23:30:09Z embargo_to: open_access file_id: '6865' file_name: Thesis_Damaris_Rangel_source.docx file_size: 18253100 relation: source_file - access_level: open_access checksum: 59c73be40eeaa1c4db24067270151555 content_type: application/pdf creator: drangel date_created: 2019-09-09T13:09:52Z date_updated: 2020-09-11T22:30:04Z embargo: 2020-09-10 file_id: '6866' file_name: Thesis_Damaris_Rangel_pdfa.pdf file_size: 2160109 relation: main_file request_a_copy: 0 file_date_updated: 2021-02-10T23:30:09Z has_accepted_license: '1' language: - iso: eng month: '09' oa: 1 oa_version: Published Version page: '97' publication_identifier: isbn: - '9783990780039' issn: - 2663-337X publication_status: published publisher: Institute of Science and Technology Austria related_material: record: - id: '5914' relation: part_of_dissertation status: public status: public supervisor: - first_name: Jozsef L full_name: Csicsvari, Jozsef L id: 3FA14672-F248-11E8-B48F-1D18A9856A87 last_name: Csicsvari orcid: 0000-0002-5193-4036 title: The role of CCK-interneurons in regulating hippocampal network dynamics type: dissertation user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1 year: '2019' ... --- _id: '6825' abstract: - lang: eng 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. " alternative_title: - ISTA Thesis article_processing_charge: No author: - first_name: Karola full_name: Käfer, Karola id: 2DAA49AA-F248-11E8-B48F-1D18A9856A87 last_name: Käfer citation: ama: Käfer K. The hippocampus and medial prefrontal cortex during flexible behavior. 2019. doi:10.15479/AT:ISTA:6825 apa: Käfer, K. (2019). The hippocampus and medial prefrontal cortex during flexible behavior. Institute of Science and Technology Austria. https://doi.org/10.15479/AT:ISTA:6825 chicago: Käfer, Karola. “The Hippocampus and Medial Prefrontal Cortex during Flexible Behavior.” Institute of Science and Technology Austria, 2019. https://doi.org/10.15479/AT:ISTA:6825. ieee: K. Käfer, “The hippocampus and medial prefrontal cortex during flexible behavior,” Institute of Science and Technology Austria, 2019. ista: Käfer K. 2019. The hippocampus and medial prefrontal cortex during flexible behavior. Institute of Science and Technology Austria. mla: Käfer, Karola. The Hippocampus and Medial Prefrontal Cortex during Flexible Behavior. Institute of Science and Technology Austria, 2019, doi:10.15479/AT:ISTA:6825. short: K. Käfer, The Hippocampus and Medial Prefrontal Cortex during Flexible Behavior, Institute of Science and Technology Austria, 2019. date_created: 2019-08-21T15:00:57Z date_published: 2019-08-24T00:00:00Z date_updated: 2023-09-07T13:01:42Z day: '24' ddc: - '570' degree_awarded: PhD department: - _id: JoCs doi: 10.15479/AT:ISTA:6825 file: - access_level: open_access checksum: 2664420e332a33338568f4f3bfc59287 content_type: application/pdf creator: kkaefer date_created: 2019-09-03T08:07:13Z date_updated: 2020-09-06T22:30:03Z embargo: 2020-09-05 file_id: '6846' file_name: Thesis_Kaefer_PDFA.pdf file_size: 3205202 relation: main_file request_a_copy: 0 - access_level: closed checksum: 9a154eab6f07aa590a3d2651dc0d926a content_type: application/zip creator: kkaefer date_created: 2019-09-03T08:07:17Z date_updated: 2020-09-15T22:30:05Z embargo_to: open_access file_id: '6847' file_name: Thesis_Kaefer.zip file_size: 2506835 relation: main_file file_date_updated: 2020-09-15T22:30:05Z has_accepted_license: '1' language: - iso: eng month: '08' oa: 1 oa_version: Published Version page: '89' publication_identifier: issn: - 2663-337X publication_status: published publisher: Institute of Science and Technology Austria related_material: record: - id: '5949' relation: part_of_dissertation status: public status: public supervisor: - first_name: Jozsef L full_name: Csicsvari, Jozsef L id: 3FA14672-F248-11E8-B48F-1D18A9856A87 last_name: Csicsvari orcid: 0000-0002-5193-4036 title: The hippocampus and medial prefrontal cortex during flexible behavior type: dissertation user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1 year: '2019' ... --- _id: '48' abstract: - lang: eng 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. ' alternative_title: - ISTA Thesis article_processing_charge: No author: - first_name: Igor full_name: Gridchyn, Igor id: 4B60654C-F248-11E8-B48F-1D18A9856A87 last_name: Gridchyn orcid: 0000-0002-1807-1929 citation: ama: Gridchyn I. Reactivation content is important for consolidation of spatial memory. 2018. doi:10.15479/AT:ISTA:th_1042 apa: Gridchyn, I. (2018). Reactivation content is important for consolidation of spatial memory. Institute of Science and Technology Austria. https://doi.org/10.15479/AT:ISTA:th_1042 chicago: Gridchyn, Igor. “Reactivation Content Is Important for Consolidation of Spatial Memory.” Institute of Science and Technology Austria, 2018. https://doi.org/10.15479/AT:ISTA:th_1042. ieee: I. Gridchyn, “Reactivation content is important for consolidation of spatial memory,” Institute of Science and Technology Austria, 2018. ista: Gridchyn I. 2018. Reactivation content is important for consolidation of spatial memory. Institute of Science and Technology Austria. mla: Gridchyn, Igor. Reactivation Content Is Important for Consolidation of Spatial Memory. Institute of Science and Technology Austria, 2018, doi:10.15479/AT:ISTA:th_1042. short: I. Gridchyn, Reactivation Content Is Important for Consolidation of Spatial Memory, Institute of Science and Technology Austria, 2018. date_created: 2018-12-11T11:44:21Z date_published: 2018-08-27T00:00:00Z date_updated: 2023-09-07T12:42:44Z day: '27' ddc: - '573' degree_awarded: PhD department: - _id: JoCs doi: 10.15479/AT:ISTA:th_1042 file: - access_level: closed checksum: 7db4415e435590fa33542c7b0a0321d7 content_type: application/vnd.openxmlformats-officedocument.wordprocessingml.document creator: dernst date_created: 2019-04-08T13:36:01Z date_updated: 2021-02-11T23:30:22Z embargo_to: open_access file_id: '6236' file_name: 2018_Thesis_Gridchyn_source.docx file_size: 7666687 relation: source_file - access_level: open_access checksum: f96f3fe8979f7b1e6db6acaca962b10c content_type: application/pdf creator: dernst date_created: 2019-04-08T13:36:01Z date_updated: 2021-02-11T11:17:18Z embargo: 2019-08-29 file_id: '6237' file_name: 2018_Thesis_Gridchyn.pdf file_size: 6034153 relation: main_file file_date_updated: 2021-02-11T23:30:22Z has_accepted_license: '1' language: - iso: eng month: '08' oa: 1 oa_version: Published Version page: '104' publication_identifier: issn: - 2663-337X publication_status: published publisher: Institute of Science and Technology Austria publist_id: '8006' pubrep_id: '1042' status: public supervisor: - first_name: Jozsef L full_name: Csicsvari, Jozsef L id: 3FA14672-F248-11E8-B48F-1D18A9856A87 last_name: Csicsvari orcid: 0000-0002-5193-4036 title: Reactivation content is important for consolidation of spatial memory tmp: image: /images/cc_by.png legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0) short: CC BY (4.0) type: dissertation user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1 year: '2018' ... --- _id: '837' abstract: - lang: eng 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. ' 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. ' alternative_title: - ISTA Thesis article_processing_charge: No author: - first_name: Haibing full_name: Xu, Haibing id: 310349D0-F248-11E8-B48F-1D18A9856A87 last_name: Xu citation: ama: Xu H. Reactivation of the hippocampal cognitive map in goal-directed spatial tasks. 2017. doi:10.15479/AT:ISTA:th_858 apa: Xu, H. (2017). Reactivation of the hippocampal cognitive map in goal-directed spatial tasks. Institute of Science and Technology Austria. https://doi.org/10.15479/AT:ISTA:th_858 chicago: Xu, Haibing. “Reactivation of the Hippocampal Cognitive Map in Goal-Directed Spatial Tasks.” Institute of Science and Technology Austria, 2017. https://doi.org/10.15479/AT:ISTA:th_858. ieee: H. Xu, “Reactivation of the hippocampal cognitive map in goal-directed spatial tasks,” Institute of Science and Technology Austria, 2017. ista: Xu H. 2017. Reactivation of the hippocampal cognitive map in goal-directed spatial tasks. Institute of Science and Technology Austria. mla: Xu, Haibing. Reactivation of the Hippocampal Cognitive Map in Goal-Directed Spatial Tasks. Institute of Science and Technology Austria, 2017, doi:10.15479/AT:ISTA:th_858. short: H. Xu, Reactivation of the Hippocampal Cognitive Map in Goal-Directed Spatial Tasks, Institute of Science and Technology Austria, 2017. date_created: 2018-12-11T11:48:46Z date_published: 2017-08-23T00:00:00Z date_updated: 2023-09-07T12:06:38Z day: '23' ddc: - '571' degree_awarded: PhD department: - _id: JoCs doi: 10.15479/AT:ISTA:th_858 file: - access_level: closed checksum: f11925fbbce31e495124b6bc4f10573c content_type: application/vnd.openxmlformats-officedocument.wordprocessingml.document creator: dernst date_created: 2019-04-05T08:59:51Z date_updated: 2020-07-14T12:48:12Z file_id: '6213' file_name: 2017_Xu_Haibing_Thesis_Source.docx file_size: 3589490 relation: source_file - access_level: open_access checksum: ffb10749a537d615fab1ef0937ccb157 content_type: application/pdf creator: dernst date_created: 2019-04-05T08:59:51Z date_updated: 2020-07-14T12:48:12Z file_id: '6214' file_name: 2017_Xu_Thesis_IST.pdf file_size: 11668613 relation: main_file file_date_updated: 2020-07-14T12:48:12Z has_accepted_license: '1' language: - iso: eng month: '08' oa: 1 oa_version: Published Version page: '93' publication_identifier: issn: - 2663-337X publication_status: published publisher: Institute of Science and Technology Austria publist_id: '6811' pubrep_id: '858' related_material: record: - id: '5828' relation: part_of_dissertation status: public status: public supervisor: - first_name: Jozsef L full_name: Csicsvari, Jozsef L id: 3FA14672-F248-11E8-B48F-1D18A9856A87 last_name: Csicsvari orcid: 0000-0002-5193-4036 title: Reactivation of the hippocampal cognitive map in goal-directed spatial tasks tmp: image: /images/cc_by.png legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0) short: CC BY (4.0) type: dissertation user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1 year: '2017' ...