Positions-Merkmal Interaktionen in der visuellen Objektverarbeitung
Kognitive und systemische Humanneurowissenschaften
Zusammenfassung der Projektergebnisse
The research conducted during this fellowship found evidence for feature-location interactions in visual perception. For instance, human observers are better at recognising eyes and mouths when they appear in the upper and lower visual field, respectively. This is true for individuating eyes and mouths from different faces, as well as for discriminating normal facial features from features that have been manipulated to look grotesque. It is further true for populations showing different types of gaze behaviour towards faces, namely healthy controls and participants with autism spectrum disorders. The size of these location dependent effects is considerable and suggests they play an important role in established illusions in face perception (‘face inversion effect' and ‘Thatcher illusion'). To investigate the neural basis of these effects, we used a novel analysis method in functional neuroimaging to probe response properties of neural populations in an area of the brain known to be important for face perception: the occipital face area. This study showed that neural populations in this area preferably respond to stimuli appearing at a given part of the visual field and showing a given part of a face. They further show that these neural populations cluster along the cortical surface according to their visual field and face part preferences. However, neural ‘tuning’ for face parts and spatial location are only weakly correlated. It therefore remains unclear whether these neural tuning properties alone can account for the perceptual effects described above. A further study showed that the feature of object size is perceived differently at different parts of the visual field. A ring of constant physical size appears smaller when it is shown in the periphery than when looked at directly. Furthermore, different observers show idiosyncratic biases in size perception across visual field quadrants. For instance, some observers may perceive objects shown in the upper right as smaller than stimuli shown in the lower left, while for others this contingency might be reversed. We conducted a neuroimaging experiment showing that these individual biases in perception are linked to functional properties of the individual brain. Observers who see a stimulus at smaller at a given visual field location show coarser spatial tuning for this location in their primary visual cortex. This result is predicted by a simple computational model of size perception, which holds that object size is computed from edge-induced activations in primary visual cortex.
Projektbezogene Publikationen (Auswahl)
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(2018) Feature-location effects in the Thatcher illusion. Journal of vision 18 (4) 16
Haas, Benjamin de; Schwarzkopf, D. Samuel
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(2016). Cortical idiosyncrasies predict the perception of object size. Nature communications, 7:12110
Moutsiana, C., de Haas, B., Papageorgiou, A., Van Dijk, J. A., Balraj, A., Greenwood, J. A., & Schwarzkopf, D. S.
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(2016). Perception and Processing of Faces in the Human Brain Is Tuned to Typical Feature Locations. Journal of Neuroscience, 36(36), 9289-9302
de Haas, B., Schwarzkopf, D. S., Alvarez, I., Lawson, R. P., Henriksson, L., Kriegeskorte, N., & Rees, G.
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(2017). Face-Part Tuning in the Occipital Face Area. Perception 46(10), 1235-1236
de Haas, B., Sereno, M. I., & Schwarzkopf, D. S.
