PhD ceremony Mr. K.V. Haak: Computational neuroimaging of visual field loss

PhD ceremony: Mr. K.V. Haak, 12.45 uur, Academiegebouw, Broerstraat 5, Groningen

Dissertation: Computational neuroimaging of visual field loss

Promotor(s): prof. J.M.M. Hooymans

Faculty: Medical Sciences

Eye diseases such as macular degeneration damage the retina of the eye, often causing blindness. When the retina is partly damaged in both eyes, parts of the visual areas in the brain are no longer stimulated. This raises the important question of how the visual brain areas will respond: will they remain unchanged, or reorganize themselves to cope better with the new situation?

Using fMRI techniques, it was shown that the human visual brain areas are actually much more stable than generally assumed. Signs of reorganization in the presence of retinal damage were not found, and the effects previously interpreted as reorganization can also be seen in healthy individuals. This thesis also discusses the issue that, although some studies conclude that visual brain areas exhibit large-scale reorganization, the data can often be explained without having to refer to reorganization. This point is further illustrated in a case study, in which the visual brain areas of a patient with only one cerebral hemisphere are discussed. Finally, a new fMRI data-analysis is described. This new method is expected to become important for future studies investigating the (re)organization of visual brain areas. Our finding that the visual areas of the brain do not reorganize themselves is good news for individuals with retinal damage: when in the future restoration of the retina becomes possible, it is probably not necessary to undo reorganization in the brain to restore sight.