Mechanisms of hemispheric lateralization: How do left- and right-hemispheric regions of the core system of face perception differ functionally?

• Applicant: Professor Dr. Andreas Jansen
• Subject Area: Human Cognitive and Systems Neuroscience ; General, Cognitive and Mathematical Psychology ; Cognitive, Systems and Behavioural Neurobiology
• Term: from 2018 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 401160617

Face perception relies on computations carried out in face-selective cortical areas. These areas have been intensively studied for two decades. This work has been guided by an influential neural model suggested by Haxby and colleagues in 2000 (“Haxby-model”). This model proposes that face perception is mediated by a distributed, typically right-lateralized neural network. The network is divided into a “core system” and an “extended system”. The core system is comprised of brain regions in the occipitotemporal cortex: the fusiform face area (FFA), the occipital face area (OFA), and the posterior superior temporal sulcus (pSTS). The extended system is comprised of regions that are not specifically dedicated face processing, but are associated with the extraction of additional information from faces, e.g., emotions, biographical information, attractiveness. Despite its indisputable ability to describe important aspects of face processing on the neural systems level, the Haxby-model has a fundamental limitation. Its focus is on the posterior-anterior hierarchy of the face-processing network and neglects aspects of functional lateralization. Apart from the early visual areas (V1 and V2) that have identical functions (but for the left and right halves of the visual field, respectively), it is unlikely that also the neural face processing mechanisms are the same in the left and right hemisphere. In particular in terms of neural resource usage, such duplicated processing would seem puzzling. Also the coupling between core and extended system is likely to be different for the left and right hemisphere.In the present project, we aim to further investigate how the left- and right-hemispheric homologues of the core system of face perceptions differ with regard to their functional roles. For that, we will apply two approaches. In a first approach, we will use network models to test the hypothesis that the right hemisphere is more specialized to process a holistic representation of the face, whereas the left hemisphere relies more on a feature-detection strategy. We expect that the interhemispheric transfer between left and right OFA and/or left and right FFA is associated with the face processing style. The transfer from the left to the right hemisphere is, for instance, hypothesized to be increased when a holistic processing strategy is demanded (e.g., by task instructions) and face stimuli are presented in the right visual hemifield (work package 1). In a second approach, we will investigate how left- and right-hemispheric brain areas of the core system of face processing are coupled to the extended system. We aim to clarify whether the coupling patterns of both hemispheres are similar or not (work packages 2 and 3).

• DFG Programme: Research Grants