Simultaneous activity in V1 and IPS is critical for conscious but not unconscious visual perception M Koivisto1, M Lähteenmäki1, V Kaasinen2, H Railo1 |
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1Department of Psychology, University of Turku, Finland |
| Conscious visual perception is known to rely on feedforward and recurrent activity along the ventral stream from V1 to temporal cortex, but the timing and contribution of parietal cortex on conscious and unconscious vision have remained poorly understood. Here, we studied the role of intraparietal sulcus (IPS) and V1 in conscious and unconscious processing by interfering with their functioning with transcranial magnetic stimulation (TMS) applied 30, 60, 90, or 120 ms after stimulus-onset. The observers (n = 13) made binary forced-choice decisions concerning the orientation (shape task) or color (color task) of the metacontrast masked target. After each trial, the participants rated their level of conscious stimulus perception. In the shape task, TMS of V1 impaired conscious shape perception at 60, 90, and 120 ms and unconscious performance at 90 ms. TMS of IPS impaired conscious shape perception at 90 ms. TMS did not affect performance on the color task. The results suggest that simultaneous activity in V1 and IPS around 90 ms is necessary for visual awareness of shape but not for unconscious perception. The overlapping activity periods of IPS and V1 may reflect recurrent interaction between parietal cortex and V1 in conscious perception. |
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