Unconscious priming requires early visual cortex at specific temporal phases of processing.

Area of Science:

• Neuroscience
• Cognitive Psychology
• Visual Perception

Background:

• Unconscious priming effects are well-documented, but the neural basis, particularly the role of early visual cortex (V1/V2), remains unclear.
• Previous research suggests V1/V2 is crucial for conscious visual perception.

Purpose of the Study:

• To investigate whether early visual cortex (V1/V2) is necessary for unconscious shape priming.
• To determine the temporal dynamics of V1/V2 involvement in both conscious and unconscious visual processing.

Main Methods:

• Transcranial Magnetic Stimulation (TMS) was used to temporarily disrupt V1/V2 activity.
• TMS was applied at varying temporal intervals relative to prime and target stimuli.
• Participants' responses were recorded to assess conscious perception and unconscious priming effects.

Main Results:

• Conscious perception of shapes was abolished when V1/V2 was stimulated by TMS.
• Unconscious shape priming occurred at an intermediate temporal interval even when V1/V2 was suppressed.
• Both conscious perception and unconscious priming at later stages (65-125 msec) were abolished by V1/V2 disruption.

Conclusions:

• Early visual cortex (V1/V2) is not essential for unconscious priming at all processing stages.
• Feedback processing appears critical for unconscious priming, suggesting it's not solely sufficient for conscious vision.
• The findings differentiate the neural requirements for conscious versus unconscious visual processing.