Mechanisms of hemispheric lateralization: How do left- and right-hemispheric regions of the core system of face perception differ functionally?
General, Cognitive and Mathematical Psychology
Cognitive, Systems and Behavioural Neurobiology
Final Report Abstract
The human brain consists of two halves. Structurally, both halves of the brain are similar at first glance, but functionally they are completely different (“hemispheric lateralisation”). For example, the left hemisphere of the brain is responsible for language in most people, while the right hemisphere is responsible for spatial attention. In the project, we investigated the lateralisation of the face processing system in more detail. In the first study, we used functional magnetic resonance imaging (fMRI) on a large cohort of healthy volunteers (n~100) to investigate the hemisphere dominance of face processing in the so-called core system of face processing, consisting of occipital face area (OFA), fusiform face area (FFA) and the face-sensitive part of the posterior superior temporal sulcus (pSTS). Unexpectedly, the fMRI activation pattern for all three regions was found to be right-lateralized only in the group mean. In contrast, at the individual level, a clear right-hemispheric dominance could only be found in half of the subjects. The fMRI activation pattern is thus less lateralized than previously assumed. A methodological challenge in the analyses was the identification of the individual regions. Classical face processing tasks are not fully suitable for all subjects to clearly separate the areas that are anatomically close to each other and to assign them to specific regions. Also unexpectedly, the interhemispheric information transfer during the processing of the faces, represented by a Dynamic Causal Modelling (DCM) analysis, was significantly lower than previously described. One possible reason could be that in previous DCM studies, unlike in the current study, the faces were in the hemifield, which led to an artificial enhancement of interhemispheric transfer. In the second study, hemispheric lateralization was investigated for face detection, an early face processing process. For this purpose, a so-called illusory face detection task was used, in which only noise stimuli were shown, but the subjects were told beforehand that a face was hidden on average in every second stimulus. When the subjects supposedly recognized a face, this, just like the processing of real faces, led to an activation of the core system. Interestingly, however, the lateralization of the OFA was significantly more left-lateralized. There was also a coupling of the core system with the bilateral orbitofrontal cortex and the lateral prefrontal cortex. However, no hemispheric differences in the coupling pattern were found. In the third study, the role of the OFA was further investigated using transcranial magnetic stimulation (TMS). Here we were able to extend previous findings to the extent that we were able to show that not only the right, but also the left OFA takes over specific functions in the discrimination of facial components (e.g. eyes).
Publications
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Illusory face detection in pure noise images: The role of interindividual variability in fMRI activation patterns. PLOS ONE, 14(1), e0209310.
Zimmermann, Kristin M.; Stratil, Ann-Sophie; Thome, Ina; Sommer, Jens & Jansen, Andreas
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“I Spy with my Little Eye, Something that is a Face…”: A Brain Network for Illusory Face Detection. Cerebral Cortex, 32(1), 137-157.
Thome, Ina; Hohmann, Daniela M.; Zimmermann, Kristin M.; Smith, Marie L.; Kessler, Roman & Jansen, Andreas
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Let's face it: The lateralization of the face perception network as measured with fMRI is not clearly right dominant. NeuroImage, 263, 119587.
Thome, Ina; García, Alanis José C.; Volk, Jannika; Vogelbacher, Christoph; Steinsträter, Olaf & Jansen, Andreas
