Feature selectivity within and across areas of the primate visual cortex ROWLEYDECLAN PATRICK 2020 In the visual cortex, information is represented in terms of particular structures (or “features”) within a region of the visual field at various levels of complexity. This thesis looks at the feature selectivity of single cells as well the organisation of the functional architecture in which they are embedded. Electrophysiology, as well as both wide-field and single cell calcium imaging techniques in the visual cortex of the marmoset monkey (Callithrix jacchus) is used to provide new insight into feature-based processing in visual cortex in terms of both feature selectivity and how it is mapped across the cortical surface.