Yazdani Partow, Serrano-Pedraza Ignacio, Whittaker Roger G, Trevelyan Andrew, Read Jenny C A
J Vis. 2015;15(13):21. doi: 10.1167/15.13.21.
Psychophysical surround suppression is believed to reflect inhibitory neuronal mechanisms in visual cortex. In recent years, two psychophysical measures of surround suppression have been much studied: (i) duration thresholds on a motion-discrimination task (which are worse for larger than for smaller stimuli) and (ii) contrast thresholds on a contrast-detection task (which are worse when grating stimuli are surrounded by a stimulus of the same orientation than when they are presented in isolation or surrounded by a stimulus of orthogonal orientation). Changes in both metrics have been linked to several different human conditions, including aging, differences in intelligence, and clinical disorders such as schizophrenia, depression, and autism. However, the exact nature of the neuronal correlate underlying these phenomena remains unclear. Here, we use an individual-differences approach to test the hypothesis that both measures reflect the same property of the visual system, e.g., the strength of GABA-ergic inhibition across visual cortex. Under this hypothesis we would expect the two measures to be significantly positively correlated across individuals. In fact, they are not significantly correlated. In addition, we replicate the previously reported correlation between age and motion-discrimination surround suppression, but find no correlation between age and contrast-detection surround suppression. We conclude that the two forms of psychophysical surround suppression arise independently from different cortical mechanisms.
心理物理学外周抑制被认为反映了视觉皮层中的抑制性神经元机制。近年来，人们对两种心理物理学外周抑制测量方法进行了大量研究：（i）运动辨别任务中的持续时间阈值（较大刺激的持续时间阈值比小刺激的更差）和（ii）对比度检测任务中的对比度阈值（当光栅刺激被相同方向的刺激包围时，对比度阈值比单独呈现或被正交方向的刺激包围时更差）。这两种指标的变化都与几种不同的人类状况有关，包括衰老、智力差异以及精神分裂症、抑郁症和自闭症等临床疾病。然而，这些现象背后神经元相关性的确切性质仍不清楚。在这里，我们采用个体差异方法来检验这一假设，即这两种测量方法反映了视觉系统的相同特性，例如整个视觉皮层中γ-氨基丁酸能抑制的强度。在这一假设下，我们预计这两种测量方法在个体间会显著正相关。事实上，它们并没有显著相关性。此外，我们重复了之前报道的年龄与运动辨别外周抑制之间的相关性，但未发现年龄与对比度检测外周抑制之间的相关性。我们得出结论，这两种形式的心理物理学外周抑制独立地源于不同的皮层机制。
