The importance of hemispheric representations in face recognition

During natural viewing, we typically fixate on the centre of faces. Due to the organisation of the human visual system, this results in the left and right halves of a face projecting to contralateral brain hemispheres. Previous research has highlighted that the effectiveness of face recognition relies upon the integration of facial information into a holistic representation. To form this, the initially divided hemispheric representations must be united. However, previous face recognition models have overlooked how facial information is represented and integrated between hemispheres. This thesis employed behavioural and neuroimaging experiments which addressed critical gaps in understanding to develop a novel framework which incorporated the effects of natural viewing in face recognition. In Chapter 2 behavioural and fMRI measures were used to determine if there was a bias for face halves projecting to their typical hemispheres. Typical projections elicited superior recognition of familiar faces, and larger responses in face-selective, but not early visual, regions, showing the importance of natural viewing experience to face recognition. In Chapter 3, a series of behavioural experiments assessed if left and right face halves elicited a composite face effect (CFE) – a well-established marker of holistic integration. A reliable CFE indicated that hemispheric representations were holisticallyintegrated during recognition. Chapter 4 examined the neural correlates of this integrative processduring natural viewing using fMRI. Interhemispheric connectivity between face-selective regions wasconsistently stronger than intrahemispheric connectivity. This bias was absent in early visual regions,indicating the specificity of interhemispheric communication to higher-level perception. The findingspresented in this thesis have been used to modify existing neural models of face recognition toincorporate the role of visual experience and the importance of interhemispheric communication inthe binding of visual information. Together, these results underscore the importance of natural viewingpatterns in the perception and recognition of familiar faces.