Contributor:

Burnat, Kalina (1971- ) : Supervisor

Publisher:

Nencki Institute of Experimental Biology PAS

Place of publishing:

Warsaw

Description:

165 pages : illustrations ; 30 cm ; Bibliography ; Summary in Polish

Degree name:

PhD in Biological Sciences

Degree discipline :

Biological Sciences

Degree grantor:

Nencki Institute of Experimental Biology PAS ; degree obtained 10.10.2025

Type of object:

Thesis

Abstract:

In the cortical representation of the visual field, receptive fields (RFs) form a gradient from small sizes in the center to the largest at the periphery. Center and peripheral cortical representation of the visual field differs functionally, center being engaged in sharp vision, whereas periphery in motion and attention. In this thesis I aim to analyze brain activity using functional MRI (fMRI) after visual field loss. The thesis is divided into two studies: first is devoted to the analysis of the receptive field (RF) adaptation in primary (V1), secondary (V2), and third (V3) cortical visual areas by population RF (pRF) mapping, second describes motion-based acuity by measuring individual thresholds and establishing whole-brain activations. We gathered two large groups of patients with long-term photoreceptors degeneration: Stargardt (STGD) with loss of the central retina and Retinitis Pigmentosa (RP) with loss in the peripheral retina. We also modelled peripheral vision loss in healthy participants by transiently limiting the visual field bilaterally to 10 degrees. In the first study, we found in V1, that the pRF size increased bilaterally in RP and controls in limited vision, as compared to the controls in full vision. In STDG, we found a clear separation between dorsal and ventral pRF responses, with pRF size increasing significantly only in the dorsal subdivision of V1. The response in V2 and V3 differed depending on the nature of the loss. Both controls in limited vision and RP patients showed a decrease in pRF size in V2 and V3. On the contrary, in STGD, we observed an increase in pRF size, not only in V1, but also in V2 and V3. Interestingly, in the STGD patients, this increase of pRF sizes was predominantly occurring within the dorsal subdivision of the visual cortex. In the second study, fMRI results indicated distinct functional impairments in RP patients that differed from transient loss of peripheral vision in controls in limited vision. RP patients exhibited higher thresholds for motion-acuity tasks in negative contrast and fast velocity conditions. RP patients when tested in fMRI using the same motion-acuity test, showed significantly lower activations within the cortical representation of the peripheral visual field in V1-3, in line with the behavioral response to the fast velocity in negative contrast stimuli, likely reflecting peripheral vision loss. Outside the visual cortices, we also found higher responses of putamen and dorsal anterior cingulate cortex for the RP patients, likely pointing to a faster adaptation to new stimuli for long-term loss of vision compared to transient loss of vision in controls. Results described in the thesis provides further insight into the interplay between visual field loss and cortical reorganization, emphasizing the role of dorsal subdivisions in compensatory adaptations. The findings extend the understanding of visual system plasticity and possibly direct potential therapeutic approaches for STGD and RP treatments.

Detailed Resource Type:

PhD Dissertations

Resource Identifier:

oai:rcin.org.pl:246168

Source:

IBD PAN, call no. 20807

Language:

eng

Language of abstract:

pol

Rights:

Rights Reserved - Free Access

Terms of use:

Copyright-protected material. May be used within the limits of statutory user freedoms

Copyright holder:

Publication made available with the written permission of the author

Digitizing institution:

Nencki Institute of Experimental Biology of the Polish Academy of Sciences

Original in:

Library of the Nencki Institute of Experimental Biology PAS

Access:

Open