---
_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
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date_created: 2024-01-19T11:04:05Z
date_updated: 2024-01-19T11:04:05Z
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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
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date_created: 2022-08-22T09:43:50Z
date_updated: 2023-06-20T22:30:04Z
embargo: 2023-06-19
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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: '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
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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'
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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: '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
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file_name: Thesis_Damaris_Rangel_source.docx
file_size: 18253100
relation: source_file
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checksum: 59c73be40eeaa1c4db24067270151555
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date_created: 2019-09-09T13:09:52Z
date_updated: 2020-09-11T22:30:04Z
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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: '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
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last_name: Csicsvari
orcid: 0000-0002-5193-4036
title: Reactivation content is important for consolidation of spatial memory
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name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
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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
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supervisor:
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title: Reactivation of the hippocampal cognitive map in goal-directed spatial tasks
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...