Chadnova Eva, Reynaud Alexandre, Clavagnier Simon, Hess Robert F
McGill Vision Research, Department of Ophthalmology, McGill University, Montreal, Quebec, Canada.
McGill Vision Research, Department of Ophthalmology, McGill University, Montreal, Quebec, Canada.
Vision Res. 2017 Nov;140:73-80. doi: 10.1016/j.visres.2017.07.014. Epub 2017 Sep 1.
Recently, psychophysical studies have shown that humans with amblyopia do have binocular function that is not normally revealed due to dominant suppressive interactions under normal viewing conditions. Here we use magnetoencephalography (MEG) combined with dichoptic visual stimulation to investigate the underlying binocular function in humans with amblyopia for stimuli that, because of their temporal properties, would be expected to bypass suppressive effects and to reveal any underlying binocular function. We recorded contrast response functions in visual cortical area V1 of amblyopes and normal observers using a steady state visually evoked responses (SSVER) protocol. We used stimuli that were frequency-tagged at 4Hz and 6Hz that allowed identification of the responses from each eye and were of a sufficiently high temporal frequency (>3Hz) to bypass suppression. To characterize binocular function, we compared dichoptic masking between the two eyes in normal and amblyopic participants as well as interocular phase differences in the two groups. We observed that the primary visual cortex responds less to the stimulation of the amblyopic eye compared to the fellow eye. The pattern of interaction in the amblyopic visual system however was not significantly different between the amblyopic and fellow eyes. However, the amblyopic suppressive interactions were lower than those observed in the binocular system of our normal observers. Furthermore, we identified an interocular processing delay of approximately 20ms in our amblyopic group. To conclude, when suppression is greatly reduced, such as the case with our stimulation above 3Hz, the amblyopic visual system exhibits a lack of binocular interactions.
最近，心理物理学研究表明，患有弱视的人确实具有双眼功能，只是在正常观察条件下，由于优势抑制性相互作用，这种功能通常不会显现出来。在此，我们使用脑磁图（MEG）结合双眼分视视觉刺激，来研究弱视患者对于某些刺激的潜在双眼功能。由于这些刺激的时间特性，预计它们会绕过抑制效应，并揭示任何潜在的双眼功能。我们使用稳态视觉诱发电位（SSVER）协议，记录了弱视患者和正常观察者视觉皮层V1区的对比度响应函数。我们使用了频率标记为4Hz和6Hz的刺激，这些刺激能够识别每只眼睛的响应，并且具有足够高的时间频率（>3Hz）以绕过抑制。为了表征双眼功能，我们比较了正常参与者和弱视参与者双眼之间的双眼分视掩蔽以及两组的眼间相位差异。我们观察到，与健眼相比，初级视觉皮层对弱视眼刺激的反应较小。然而，弱视视觉系统中的相互作用模式在弱视眼和健眼之间并没有显著差异。但是，弱视抑制性相互作用低于我们正常观察者双眼系统中观察到的相互作用。此外，我们在弱视组中确定了约20毫秒的眼间处理延迟。总之，当抑制作用大大降低时，例如我们上述3Hz以上的刺激情况，弱视视觉系统表现出缺乏双眼相互作用。
