Centre for Cognitive Neuroscience, University of Turku, 20014 Turku, Finland.
Neuroimage. 2010 Jun;51(2):828-34. doi: 10.1016/j.neuroimage.2010.02.042. Epub 2010 Feb 24.
A "late" period of activity in striate cortex (V1) in response to extrastriate feedback has been proposed to act as a marker of visual awareness. It is not clear, however, whether such recurrent activity is associated exclusively with aware perception or whether it is necessary also for unaware visual processing. We investigated the role of the "late" V1 activity in both aware and unaware visual motion perception. Participants were asked to make a forced-choice direction discrimination judgment on a coherently moving random-dot display and additionally rate their subjective awareness of the stimulus. Transcranial magnetic stimulation (TMS) was applied over the early visual cortex (V1/V2) either 20, 40, 60, 80, or 100 ms after motion offset. Visual awareness was impaired at an "early" (20 ms) and a "late" (60 ms) stimulation time window. Participants' forced-choice direction discrimination performance on "unaware" trials was above chance in No TMS baseline condition. Importantly, this performance was impaired by TMS over V1/V2 at the "late" time window. In a second experiment we show that the critical time window of V5/MT falls between the "early" and "late" time windows of V1/V2 activity. The results indicate that recurrent extrastriate-V1 activity is necessary for both aware and unaware perception.
有人提出，纹状皮层（V1）对外侧反馈的“晚期”活动可作为视觉意识的标志物。然而，尚不清楚这种递归活动是否仅与有意识的感知有关，或者它是否也是无意识视觉处理所必需的。我们研究了“晚期”V1 活动在有意识和无意识视觉运动感知中的作用。要求参与者对一致运动的随机点显示进行强制性方向判别判断，并对刺激的主观意识进行评分。经颅磁刺激（TMS）在运动结束后 20、40、60、80 或 100 ms 施加于早期视皮层（V1/V2）。在“早期”（20 ms）和“晚期”（60 ms）刺激时间窗中，视觉意识受损。在无 TMS 基线条件下，参与者在“无意识”试验中的强制性方向判别表现超过了机会。重要的是，V1/V2 的 TMS 会损害该表现。在第二个实验中，我们表明 V5/MT 的关键时间窗介于 V1/V2 活动的“早期”和“晚期”时间窗之间。结果表明，外侧纹状皮层-V1 的递归活动对于有意识和无意识的感知都是必需的。
