Category-Selective Attention Modulates Unconscious Processing

The classic theory of attention controlling and automated processing suggested that the unconscious process is an automated and independent process without any attention or other cognitive activities involved. In recent years, a growing number of studies have found that the conscious process and unconscious process could not be completely separated. The latest view find that the unconscious processing is not a exactly automated, bottom-up or stimulus-driven process, but a process influenced by the top-down attention, the impact of the task settings, and expectations. Consciousness control process can also affect the unconscious perception process., Based on the existing knowledge and experience, brain could form a kind of expectation to the upcoming input visual stimulation, as a result, the brain tried to match the bottom-up input processing visual stimuli with the expectation. There are some experimental evidence to support these views, but there have no direct evidence to prove how the conscious processing affects the unconscious processing. This study attempts to provide some physiological evidence in this aspect.In an fMRI experiment of our team, the results showed that category-selective attention modulated unconscious face/tool processes in the middle occipital gyrus. In the processes of unconscious faces, activation in the middle occipital gyrus decreased under the face-selective attention compared with tool-selective attention. In the primary visual cortex. C1is caused by the stimulation is the earliest ERP(event-related brain potential) components. The conscious stimuli can induce greater P1and N1wave with the attention condition, and visual spatial attention can adjusted the lateral-striate cortex activity of the brain. Therefore, in this study, we use the ERP tools to explore C1, P1and N1activated by the subliminal pictures, and whether and how these waves could affected by the top-down class attention.In the present study, we use an improved "stimulation-target" experimental paradigm (a conscious word cue followed by a unconscious image) to detect the modulation effect to the unconscious processing. The clue word could cause a top-down attention process, and the attention could select the following stimulus. This experiment was a2*2repeated factors measurements, and these two factors were clue words and unconscious pictures. The clue word were "face" and "tool", followed by subliminal a face picture or a tool picture. And then we contrast the two levels of face condition(face word with a face picture, face word with a tool picture), we got a top-down modulation effect to the uncouscious process:in the early visual cortex (occipital and parietal-occipital cortex), the C1wave elicited by the valid cue is different from the Cl elicited by the invalid cue. In the tool condition, we got the same result with the face condition. And in the face and tool condition, there is the consistent tendency:the Cl wave triggered by the invalid cue was larger than than the Cl triggered by the valid cue, while the other three components PI, Nl and P2waves showed no difference between the valid cue and the invalid cue. The visual EEG ingredients P1, N1and P2waves were sensitive to the characteristics of the visual stimulus. The occipital P1wave is related to the attention, and it could be enhanced by the unilateral attention. The N1and P2were sensitive to the orientation and location of the stimulus, and the P2was affected by attention to different kind of stimulus characteristics. Otherwise, in this study, the three components showed no difference in the the two conditions. Maybe it is because the picture stimulus is unconscious in our study, and this lead to a low-level process in the brain. So, the C1wave of the early visual cortex the top-down effect wave, and it reflects the selective attention adjusting the unconscious process.These results reveal that the unconscious process is not a fully automated, bottom-up or stimulus-driven process, but but a process influenced by the top-down attention. This indicates that, the selective attention could adjust the uncouscious process in the early visual cortex.This kind process of the brain has great significant for us to adapt to the environment. When a new timuli gets into our attention, the brain would generate some top-down signal and expectation to the lower level nerual activity. So it could adjust our lower level of processing to the stimulus appropriately, and this makes our perceiving process reasonable and more easier. In fact, the awareness process is unconscious, and this top-down process can also occur in the subliminal stimuli process. This cognitive process can decide whether the stimulation line with our expectations quickly. If they meet the expectations of the brain, the the more advanced cortex of brain would process the stimuli. Otherwise, the brain would issue a correction command to adjust the processing timely to made processing of the stimulus efficiently.