Neuro-cognitive mechanisms of synesthetic perception

• Applicant: Professor Dr. Gregor Volberg
• Subject Area: General, Cognitive and Mathematical Psychology
• Term: from 2014 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 256575971

Synesthesia is a perceptual phenomenon where stimulation in one sensory modality induces a concurrent sensation in a different modality or feature dimension that was not objectively stimulated. A well-investigated form of synesthesia is grapheme-color-synesthesia where written numbers or letters induce a concurrent sensation of color. Current results from brain imaging and psychophysiology indicate that synesthetes compared to controls show a more pronounced neural connectivity, both between early sensory brain areas as well as between higher and lower brain areas within the visual processing stream. The results of behavioral studies moreover suggest that the synesthetic color percept depends on the available attentional resources. The color impression is stronger if a pre-cue can be used for the spatial selection of the graphemes, and it is reduced if the parietal attention system is de-activated by magnetic stimulation. Visual attention is thus an important factor for the emergence of synesthetic colors in grapheme-color-synesthesia. However, the common neural mechanisms of visual attention and synesthetic color perception are yet unknown.In this project we aim to identify the neuro-cognitive mechanisms of grapheme-color-synesthesia. Especially, we will investigate the role of visual attention for synesthetic perception. The project focuses on investigating neural connectivity between grapheme and color processing brain areas and brain areas associated with visual-spatial selection. To this end, EEG experiments as well as combined EEG and fMRI studies will be conducted. The planned experiments are novel in synesthesia research with respect to the topic and the applied techniques. Synesthesia offers the unique possibility to investigate perceptual errors in an otherwise neurologically intact population. The results of this project should therefore not only improve our understanding of synesthesia, but will also expand our knowledge on perception related to visual awareness or visual feature integration.

• DFG Programme: Research Grants
• Participating Person: Professor Dr. Mark Greenlee