Surround modulation and texture segregation in macaque V1 and V4 studied with two-photon Calcium imaging

Bibliographic Details
Main Author: Zhao, Xingnan
Publication Date: 2023
Language: cmn
Source: Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)
Download full: https://hdl.handle.net/10316/116921
Summary: Documentos apresentados no âmbito do reconhecimento de graus e diplomas estrangeiros
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spelling Surround modulation and texture segregation in macaque V1 and V4 studied with two-photon Calcium imagingSurround modulationTexture segregationTwo-photon calcium imagingAwake macaquesV1 & V4Neuronal population codingDocumentos apresentados no âmbito do reconhecimento de graus e diplomas estrangeirosNeuronal responses to stimuli presented in the classical receptive field (CRF) are modulated by stimuli surrounding the CRF. Surround modulation improves the feature selectivity throughout the visual system. It has been interpreted as the neural substrates for various visual phenomena, such as perceptual pop-out and figure-ground segregation. Existing electrophysiological studies mainly focus on surround modulation in neurons best tuned to the center stimulus orientation, but the modulation effect can be more robustly and accurately characterized when neurons tuned to all orientations are considered as a population. This Ph.D. thesis research used the two-photon calcium imaging technique to investigate the surround modulation of V1 neuronal population responses (Study I) and the roles of V1 and V4 in texture-based figure-ground segregation (Study II). Two-photon calcium imaging could record the responses of thousands of neurons simultaneously. The large datasets allowed descriptive summaries of neuronal responses with sufficient statistical power. Furthermore, the analysis of neuronal population responses could also reveal stimulus-related features existing only at the level of the population and not apparent at the level of individual neurons. Study I investigated surround modulation in macaque V1 from a population perspective using two-photon calcium imaging. Previous electrode recordings reveal that surround modulation is mostly orientation-specific, as neuronal responses are more suppressed by isooriented surrounds than cross-oriented surrounds. Our results demonstrated that changes in neuronal responses and trial-by-trial response variability both contribute to iso-surround suppression and cross-surround de-suppression. More critically, we found that iso and cross surround modulation might initiate separate processes by comparing population orientation tuning functions. Iso-surrounds produce significant orientation-untuned suppression to neurons tuned to all orientations and lesser suppression to neurons tuned to the center stimulus orientation. Meanwhile, cross-surrounds mainly reduce orientation-untuned suppression by scaling up all neurons’ responses, accompanied by a push-pull effect that suppresses responses to cross-surrounds per se. As quantified by a population gain-control model, these results indicate that iso-surround suppression is predominantly orientation-untuned, offset by cross surrounds, as the orientation discontinuity may boost all neurons’ responses. Further, the lesser target orientation-tuned suppression, which is itself unaffected by surround orientation changes, may reflect nonlinear response changes in center orientation-tuned neurons due to surround modulation. Therefore, previous observations of orientation-tuned surround modulation may actually reflect the net effect of separate and mostly orientation-untuned surround influences. Study II investigated the roles of V1 and V4 in texture-based figure-ground segregation from a population perspective in awake macaques. Our results indicated that V1 neurons responded to the figure-ground border more strongly than to the figure or background regardless of their orientation preferences, suggesting possible orientation discontinuity detection, but less likely figure-ground segregation. In contrast, V4 neurons responded significantly stronger to the figure than to the background, though with a very small effect size. We thus examined whether the roles of V1 and V4 neurons in figure-ground texture segregation could be better understood in terms of the changes in population response patterns. Specifically, linear SVM was trained to decode figure-ground textures using PCA-transformed neural responses in V1 and V4. V1 neurons decoded figure-ground border with considerably higher efficiency (requiring a few principal components) than V4 neurons, while V4 neurons were more efficient in figure-ground segregation. Moreover, V4 neurons tuned to different orientations contributed nearly equally to figure-ground segregation, as did orientationuntuned V4 neurons. These results indicate that V1 neurons are mainly responsible for border detection, and in addition provide rudimentary figure-ground information, which can be linearly read out and efficiently represented by downstream V4 neurons for segregation. In summary, the population data in this thesis provide new insights into neuronal surround modulation and neural correlates of texture-based figure-ground segregation. In future research, we look forward to investigating the coding fidelity of V1 neurons in awake macaques by quantifying the perceptual threshold of orientation discrimination estimated from large neural ensembles, and analyzing how surround modulation affects coding fidelity.2023-06doctoral thesisinfo:eu-repo/semantics/publishedVersionhttps://hdl.handle.net/10316/116921https://hdl.handle.net/10316/116921cmnZhao, Xingnaninfo:eu-repo/semantics/openAccessreponame:Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)instname:FCCN, serviços digitais da FCT – Fundação para a Ciência e a Tecnologiainstacron:RCAAP2024-11-07T09:41:33Zoai:estudogeral.uc.pt:10316/116921Portal AgregadorONGhttps://www.rcaap.pt/oai/openaireinfo@rcaap.ptopendoar:https://opendoar.ac.uk/repository/71602025-05-29T06:10:35.037455Repositórios Científicos de Acesso Aberto de Portugal (RCAAP) - FCCN, serviços digitais da FCT – Fundação para a Ciência e a Tecnologiafalse
dc.title.none.fl_str_mv Surround modulation and texture segregation in macaque V1 and V4 studied with two-photon Calcium imaging
title Surround modulation and texture segregation in macaque V1 and V4 studied with two-photon Calcium imaging
spellingShingle Surround modulation and texture segregation in macaque V1 and V4 studied with two-photon Calcium imaging
Zhao, Xingnan
Surround modulation
Texture segregation
Two-photon calcium imaging
Awake macaques
V1 & V4
Neuronal population coding
title_short Surround modulation and texture segregation in macaque V1 and V4 studied with two-photon Calcium imaging
title_full Surround modulation and texture segregation in macaque V1 and V4 studied with two-photon Calcium imaging
title_fullStr Surround modulation and texture segregation in macaque V1 and V4 studied with two-photon Calcium imaging
title_full_unstemmed Surround modulation and texture segregation in macaque V1 and V4 studied with two-photon Calcium imaging
title_sort Surround modulation and texture segregation in macaque V1 and V4 studied with two-photon Calcium imaging
author Zhao, Xingnan
author_facet Zhao, Xingnan
author_role author
dc.contributor.author.fl_str_mv Zhao, Xingnan
dc.subject.por.fl_str_mv Surround modulation
Texture segregation
Two-photon calcium imaging
Awake macaques
V1 & V4
Neuronal population coding
topic Surround modulation
Texture segregation
Two-photon calcium imaging
Awake macaques
V1 & V4
Neuronal population coding
description Documentos apresentados no âmbito do reconhecimento de graus e diplomas estrangeiros
publishDate 2023
dc.date.none.fl_str_mv 2023-06
dc.type.driver.fl_str_mv doctoral thesis
dc.type.status.fl_str_mv info:eu-repo/semantics/publishedVersion
status_str publishedVersion
dc.identifier.uri.fl_str_mv https://hdl.handle.net/10316/116921
https://hdl.handle.net/10316/116921
url https://hdl.handle.net/10316/116921
dc.language.iso.fl_str_mv cmn
language cmn
dc.rights.driver.fl_str_mv info:eu-repo/semantics/openAccess
eu_rights_str_mv openAccess
dc.source.none.fl_str_mv reponame:Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)
instname:FCCN, serviços digitais da FCT – Fundação para a Ciência e a Tecnologia
instacron:RCAAP
instname_str FCCN, serviços digitais da FCT – Fundação para a Ciência e a Tecnologia
instacron_str RCAAP
institution RCAAP
reponame_str Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)
collection Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)
repository.name.fl_str_mv Repositórios Científicos de Acesso Aberto de Portugal (RCAAP) - FCCN, serviços digitais da FCT – Fundação para a Ciência e a Tecnologia
repository.mail.fl_str_mv info@rcaap.pt
_version_ 1833602602871291904

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