Kumano Hironori, Uka Takanori
Department of Neurophysiology, Graduate School of Medicine, Juntendo University, Bunkyo, Tokyo, Japan.
Department of Neurophysiology, Graduate School of Medicine, Juntendo University, Bunkyo, Tokyo, Japan
J Neurophysiol. 2014 Aug 1;112(3):620-30. doi: 10.1152/jn.00639.2013. Epub 2014 May 14.
Observers have difficulty identifying a target in their peripheral vision in the presence of surrounding stimuli. Although hypotheses addressing this phenomenon have been proposed, such as the integration of stimuli and surround suppression in the higher-order visual cortex, no direct comparisons of the psychophysical and neuronal sensitivities have been performed. Here we measured the performance of monkeys with a variant of the direction discrimination task using a center/surround bipartite random-dot stimulus while simultaneously recording from isolated neurons from the middle temporal visual area (MT). The psychophysical threshold increased with the addition of a task-irrelevant noise annulus that surrounded the task-relevant motion stimuli. The neuronal threshold of MT neurons also increased at a spatial scale similar to the psychophysical threshold. This suggests that the impaired ability in our task resulted from impairment in the MT area. Importantly, reduced neuronal performance was due to both a reduced response to preferred motion and an enhanced response to nonpreferred motion. These observations suggest that impairment caused by surrounding noise results from interactions between stimuli and noise and not from a reduction in the response of visual neurons.
在存在周围刺激的情况下，观察者很难在其周边视觉中识别目标。尽管已经提出了一些解释这一现象的假设，比如高阶视觉皮层中刺激的整合和周边抑制，但尚未对心理物理学和神经元敏感性进行直接比较。在这里，我们使用中心/周边二分随机点刺激，通过方向辨别任务的变体来测量猴子的表现，同时从颞中视觉区域（MT）分离出的神经元进行记录。随着围绕任务相关运动刺激添加一个与任务无关的噪声环，心理物理学阈值增加。MT神经元的神经元阈值也在与心理物理学阈值相似的空间尺度上增加。这表明我们任务中的能力受损是由MT区域的损伤导致的。重要的是，神经元表现的降低是由于对偏好运动的反应减少以及对非偏好运动的反应增强。这些观察结果表明，周围噪声引起的损伤是由刺激和噪声之间的相互作用导致的，而不是视觉神经元反应的降低。
