Adaptive changes in visual cortex following prolonged contrast reduction
Adaptive changes in visual cortex following prolonged contrast reduction
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DOI：
10.1167/9.2.20
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发表时间：
2009-01-01
影响因子：
1.8
通讯作者：
He, Sheng
中科院分区：
文献类型：
--
作者：
Kwon, MiYoung;Legge, Gordon E.;He, Sheng
视网膜图像对比度的长期降低如何影响视觉对比度编码？最近的证据表明，某些形式的长期视觉剥夺会导致成人视觉通路的代偿性知觉和神经变化。尚未确定对比度适应引起的变化是否最好被描述为“对比度增益”或“响应增益”。我们提出了预测适应长期对比度降低应导致响应增益的理论依据。为了检验这一假设，视力正常的受试者通过降低对比度的护目镜观察周围环境，进行了四个小时的适应。在适应期间，受试者进行正常的日常活动。在适应之前和之后获得了受试者在皮质区域 V1 和 V2 的对比辨别阈值和 fMRI BOLD 反应。适应后，我们观察到 V1 和 V2 中对比度辨别阈值显着下降，而 BOLD 响应显着增加。观察到的适应效应的眼间转移表明适应具有皮质起源。这些结果揭示了成人视觉皮层的一种新的适应性，即在刺激对比范围缩小的情况下对对比反应增益的调整，这与反应增益机制是一致的。这种适应似乎是补偿性的，使得对于低视网膜图像对比度提高了对比度编码的精度。
How does prolonged reduction in retinal-image contrast affect visual-contrast coding? Recent evidence indicates that some forms of long-term visual deprivation result in compensatory perceptual and neural changes in the adult visual pathway. It has not been established whether changes due to contrast adaptation are best characterized as "contrast gain" or "response gain." We present a theoretical rationale for predicting that adaptation to long-term contrast reduction should result in response gain. To test this hypothesis, normally sighted subjects adapted for four hours by viewing their environment through contrast-reducing goggles. During the adaptation period, the subjects went about their usual daily activities. Subjects' contrast-discrimination thresholds and fMRI BOLD responses in cortical areas V1 and V2 were obtained before and after adaptation. Following adaptation, we observed a significant decrease in contrast-discrimination thresholds, and significant increase in BOLD responses in V1 and V2. The observed interocular transfer of the adaptation effect suggests that the adaptation has a cortical origin. These results reveal a new kind of adaptability of the adult visual cortex, an adjustment in the gain of the contrast-response in the presence of a reduced range of stimulus contrasts, which is consistent with a response-gain mechanism. The adaptation appears to be compensatory, such that the precision of contrast coding is improved for low retinal-image contrasts.