Zhang Gong-Liang, Li Hao, Song Yan, Yu Cong
J Vis. 2015;15(10):8. doi: 10.1167/15.10.8.
The brain site of perceptual learning has been frequently debated. Recent psychophysical evidence for complete learning transfer to new retinal locations and orientations/directions suggests that perceptual learning may mainly occur in high-level brain areas. Contradictorily, ERP C1 changes associated with perceptual learning are cited as evidence for training-induced plasticity in the early visual cortex. However, C1 can be top-down modulated, which suggests the possibility that C1 changes may result from top-down modulation of the early visual cortex by high-level perceptual learning. To single out the potential top-down impact, we trained observers with a peripheral orientation discrimination task and measured C1 changes at an untrained diagonal quadrant location where learning transfer was previously known to be significant. Our assumption was that any C1 changes at this untrained location would indicate top-down modulation of the early visual cortex, rather than plasticity in the early visual cortex. The expected learning transfer was indeed accompanied with significant C1 changes. Moreover, C1 changes were absent in an untrained shape discrimination task with the same stimuli. We conclude that ERP C1 can be top-down modulated in a task-specific manner by high-level perceptual learning, so that C1 changes may not necessarily indicate plasticity in the early visual cortex. Moreover, learning transfer and associated C1 changes may indicate that learning-based top-down modulation can be remapped to early visual cortical neurons at untrained locations to enable learning transfer.
感知学习的脑区位置一直备受争议。最近有心理物理学证据表明,学习可完全转移至新的视网膜位置及方向,这表明感知学习可能主要发生在大脑高级区域。与之矛盾的是,与感知学习相关的ERP C1变化被视为早期视觉皮层训练诱导可塑性的证据。然而,C1可被自上而下调节,这表明C1变化可能是由高级感知学习对早期视觉皮层的自上而下调节所致。为了找出潜在的自上而下的影响,我们让观察者进行周边方向辨别任务训练,并在一个未训练的对角象限位置测量C1变化,此前已知该位置学习转移显著。我们的假设是,在这个未训练位置的任何C1变化都将表明早期视觉皮层的自上而下调节,而非早期视觉皮层的可塑性。预期的学习转移确实伴随着显著的C1变化。此外,在使用相同刺激的未训练形状辨别任务中未出现C1变化。我们得出结论,ERP C1可被高级感知学习以任务特定的方式自上而下调节,因此C1变化不一定表明早期视觉皮层的可塑性。此外,学习转移及相关的C1变化可能表明基于学习的自上而下调节可重新映射到未训练位置的早期视觉皮层神经元,以实现学习转移。