Department of Psychology, University of York, Heslington, York, UK; Institute of Cognitive Neuroscience, University College London, London, UK.
Department of Mathematics and Computer Science, Rutgers University-Newark, Newark, NJ, USA.
Neuroimage. 2021 Apr 15;230:117780. doi: 10.1016/j.neuroimage.2021.117780. Epub 2021 Jan 24.
Even after conventional patching treatment, individuals with a history of amblyopia typically lack good stereo vision. This is often attributed to atypical suppression between the eyes, yet the specific mechanism is still unclear. Guided by computational models of binocular vision, we tested explicit predictions about how neural responses to contrast might differ in individuals with impaired binocular vision. Participants with a history of amblyopia (N = 25), and control participants with typical visual development (N = 19) took part in the study. Neural responses to different combinations of contrast in the left and right eyes, were measured using both electroencephalography (EEG) and functional magnetic resonance imaging (fMRI). Stimuli were sinusoidal gratings with a spatial frequency of 3c/deg, flickering at 4 Hz. In the fMRI experiment, we also ran population receptive field and retinotopic mapping sequences, and a phase-encoded localiser stimulus, to identify voxels in primary visual cortex (V1) sensitive to the main stimulus. Neural responses in both modalities increased monotonically with stimulus contrast. When measured with EEG, responses were attenuated in the weaker eye, consistent with a fixed tonic suppression of that eye. When measured with fMRI, a low contrast stimulus in the weaker eye substantially reduced the response to a high contrast stimulus in the stronger eye. This effect was stronger than when the stimulus-eye pairings were reversed, consistent with unbalanced dynamic suppression between the eyes. Measuring neural responses using different methods leads to different conclusions about visual differences in individuals with impaired binocular vision. Both of the atypical suppression effects may relate to binocular perceptual deficits, e.g. in stereopsis, and we anticipate that these measures could be informative for monitoring the progress of treatments aimed at recovering binocular vision.
即使经过常规的修补治疗，有弱视病史的个体通常也缺乏良好的立体视觉。这通常归因于双眼之间的异常抑制，但具体机制仍不清楚。受双眼视觉计算模型的指导，我们测试了关于神经对对比度反应可能在双眼视觉受损个体中存在差异的明确预测。参与者包括有弱视病史的个体（N=25）和具有典型视觉发育的对照组参与者（N=19）。使用脑电图（EEG）和功能磁共振成像（fMRI）测量了左眼和右眼不同对比度组合的神经反应。刺激物是空间频率为 3c/deg、以 4Hz 闪烁的正弦光栅。在 fMRI 实验中，我们还运行了群体感受野和视网膜映射序列，以及相位编码定位器刺激，以识别对主要刺激敏感的初级视觉皮层（V1）中的体素。两种模态的神经反应都随刺激对比度单调增加。当用 EEG 测量时，较弱眼的反应减弱，这与该眼的固定紧张性抑制一致。当用 fMRI 测量时，较弱眼中的低对比度刺激会显著降低较强眼中高对比度刺激的反应。这种效应比刺激眼配对反转时更强，与双眼之间的不平衡动态抑制一致。使用不同方法测量神经反应会导致对双眼视觉受损个体的视觉差异产生不同的结论。这两种异常抑制效应都可能与双眼知觉缺陷有关，例如在立体视中，我们预计这些测量结果可用于监测旨在恢复双眼视觉的治疗进展。
