Conscious and unconscious processing of illusory figure: a psychophysical and electrophysiological study.

Illusory figures represent one of the most interesting phenomena of visual perception. The general purpose of these thesis was to produce more insight into the neurophysiological mechanism that correlates with the conscious and unconscious perception of the illusory figures. In the first part I provided evidences that simple reaction time (RTs) can be modulated by the presence vs absence of an illusory figure. This result, converging with previous data in the literature, indicates the ventral rather than the dorsal as the visual system controlling a simple reaction time task. In the second part electrophysiological correlates of illusory figures were studied. I provided evidence that the presence vs absence of the illusory figure correlates with a modulation of the N1 component both in a simple reaction and in a choice reaction time task. It is likely that the N1 effect depends on the support ratio of the illusory figure, but this needs supplementary investigation. In the third part I provided evidence that unconscious priming could be obtained as a result of only the processing of the Salient Region (SR) of illusory figures by preventing the illusory contours (ICs) processing via a metacontrast masking. These results indicated that the unconscious processing of the SR yields a priming effect and that a reduction of the saliency of the SR leads to a reduction of the priming effect while its complete elimination does not abolish it.