Department of Psychology, University of California at Berkeley, Berkeley, California 94110, USA.
J Neurosci. 2012 Oct 31;32(44):15458-66. doi: 10.1523/JNEUROSCI.0627-12.2012.
The prefrontal cortex (PFC) is proposed to be the source of top-down signals that can modulate extrastriate visual processing in accordance with behavioral goals, yet little direct causal evidence for this hypothesis exists. Using theta burst transcranial magnetic stimulation, we disrupted PFC function in human participants before performing a working memory task during fMRI scanning. PFC disruption decreased the tuning of extrastriate cortex responses, coinciding with decrements in working memory performance. We also found that activity in the homologous PFC region in the nonstimulated hemisphere predicted performance following disruption. Specifically, those participants with greater homologous PFC activity and greater connectivity between this region and extrastriate cortex were the most resistant to PFC disruption. These findings provide evidence for a compensatory mechanism following insults to the brain, and insight into the dynamic nature of top-down signals originating from the PFC.
前额叶皮层（PFC）被认为是自上而下的信号源，这些信号可以根据行为目标来调节外纹状视觉处理，然而，这个假设几乎没有直接的因果证据。使用 theta 爆发经颅磁刺激，我们在人类参与者执行 fMRI 扫描期间的工作记忆任务之前，破坏了 PFC 功能。PFC 的破坏降低了外纹状皮层反应的调谐，与工作记忆表现的下降相一致。我们还发现，在刺激半球的同源 PFC 区域的活动预测了破坏后的表现。具体来说，那些具有更大的同源 PFC 活动和该区域与外纹状皮层之间更大连通性的参与者对 PFC 破坏的抵抗力最强。这些发现为大脑受到损伤后的补偿机制提供了证据，并深入了解了源自 PFC 的自上而下信号的动态性质。
