Visual Illusions and Synaesthesia
Illusory percept opens the possibility to investigate perceptual processes. E.g., during the waterfall illusion (motion after effect) we perceive a movement while a stable stimulus is presented. Motion induced blindness, on the other hand, will lead to the disappearance of a salient stimulus due to a second, moving stimulus. An interesting case is synaesthesia. Grapheme-color synaesthetes perceive color when reading certain letters or digits while they have no color percept for other graphemes. Synaesthetic color perception is automatic, involuntary, idiosyncratic (stable over time), hereditary and has a prevalence of about 4%.
Illusionary perception is fascinating; however, it is also well suited for exploring the neuronal states of the brain underlying perception and at the same time dissociate it from brain activity that deals with the processing of the specific sensory input that would normally lead to this kind of perception.
Händel B, Jensen, O. (2014). Spontaneous local alpha oscillations predict motion-induced blindness. European Journal of Neuroscience, 40 (9), 3371-3379.
van Leeuwen TM, Hagoort P, Händel B. (2013) Real color captures attention and overrides spatial cues in grapheme-color synesthetes but not in controls. Neuropsychologia, 51 (10), 1802-1813.
Tikhonov A*, Händel B*, Haarmeier T, Lutzenberger W, Thier P. (2007) Gamma oscillations underlying the visual motion after-effect. Neuroimage, 38: 708-719.
