Unconscious adapting strategies dissociate top-down from bottom-up visual object processing

Background and Aim : Although massive body of imaging studies provide neural substrate of unconscious object processing(Sterzer, Jalkanen, & Rees, 2009)(Suzuki & Noguchi, 2013), behavioral data couldn’t capture this effect in the context of unconscious priming(Moradi, Koch, & Shimojo, 2005)(I Amihai, L Deouell, 2011). To clarify variety, modality, and magnitude of conscious and unconscious priming, we used name-picture verification task and employed words and pictures as a prime stimuli using a binocular rivalry setup. We examine both level of abstraction for categorizing, i.e. basic and subordinate, to address bottom-up and top-down processing in the brain.Methods : Four categories of stimuli in two levels of abstraction, i.e. basic and subordinate level, were applied in the experiment. Both image and word version of stimuli were presented as prime, sample word, and image target in name-picture verification task. In unconscious conditions, we presented stimuli rendered invisible through binocular rivalry. Using continues flash suppression, the strength of unconscious influence in prime stimuli were increased by raising time invisibility.Results : Our results illustrate the different influence of unconscious priming on both basic and subordinate levels. The unconscious priming at the basic levels facilitates the processing of name-picture verification task by reducing the reaction times, whereas sub ordinate unconscious priming lead to negative priming influences, reflecting impairment in response time of following verification task. Interestingly, there is opposite direction of priming effect across conscious trials. This observation reveals measurable differences between conscious and unconscious processing. The laterality analyses of face image trials suggest a strong role of left hemisphere in unconscious face processing, while the right hemisphere is salient in representation of word used for priming face pictures in name-picture verification task.Conclusion : Since subordinate processing in the brain needs feedback connections, the facilitation of conscious priming of this level can be considered as an extra information which provides by prim stimulus and helps top-down signals for accurate representation. While in bottom-up basic level processing, the conscious priming information acts as an adaptor which leads to impairment of perception.

کلیدواژه ها:

unconscious priming ، binocular rivalry ، continues flash suppression ، different level of abstraction ، top down processing