ABSTRACT This study aimed to reveal neural and behavioural correlates of masked and unmasked priming and illusion using functional Magnetic Resonance Imaging and a new line-length comparison task. A convenient sample of eight right-handed healthy graduate students participated in the study. They were all enrolled at Carleton University-University of Ottawa joint Neuroscience Program, Psychology Department. Their task was to select the longer part of a target line (always non-illusory) after a briefly presented masked or unmasked prime that was either illusory (Müller-Lyer) or non-illusory, as well as congruent or incongruent, with the target. The behavioural data indicated a clear priming effect, in the masked priming, for both illusory and non-illusory conditions (p < .05). The imaging results showed that the unmasked, compared to masked, priming significantly (p < .001) activates a brain network, mainly the parietal, temporal, and frontal cortices, mostly left dorsal Anterior Cingulate Cortex and medial Pre-Frontal Cortex. Also, the unmasked illusion significantly (p < .005) activated the left Inferior Frontal Gyros and dorsolateral medial Pre-Frontal Cortex. The fact that, in the behaviuoral results, no difference was found between the illusory and the real line conditions suggests that the illusion was as compelling as the real lines. Also, the activation of a wide brain network in unmasked compared to masked priming can be seen as a neural index of the so called conscious processes.
Buy this Article
|