Benton Christopher P, Redfern Annabelle S
School of Experimental Psychology, University of Bristol Bristol, UK.
Front Psychol. 2016 Dec 15;7:1950. doi: 10.3389/fpsyg.2016.01950. eCollection 2016.
Recent adaptation studies provide evidence for early visual areas playing a role in duration perception. One explanation for the pronounced duration compression commonly found with adaptation is that it reflects adaptation-driven stimulus-specific reduction in neural activity in early visual areas. If this level of stimulus-associated neural activity does drive duration, then we would expect a strong effect of contrast on perceived duration as electrophysiological studies shows neural activity in early visual areas to be strongly related to contrast. We employed a spatially isotropic noise stimulus where the luminance of each noise element was independently sinusoidally modulated at 4 Hz. Participants matched the perceived duration of a high (0.9) or low (0.1) contrast stimulus to a previously presented standard stimulus (600 ms, contrast = 0.3). To achieve perceptually equivalent durations, the low contrast stimulus had to be presented for longer than the high contrast stimulus. This occurred when we controlled for stimulus size and when we adjusted for individual differences in perceived temporal frequency. Further, we show that the effect cannot be explained by shifts in perceived onset and offset and is not explained by a simple contrast-driven response bias. The direction of our results is clearly consistent with the idea that level of neural activity drives duration. However, the magnitude of the effect (~10% duration difference over a 0.9-0.1 contrast reduction) is in marked contrast to the larger duration distortions that can be found with repetition suppression and the oddball effect; particularly when these may be associated with smaller differences in neural activity than that expected from our contrast difference. Taken together, these results indicate that level of stimulus-related neural activity in early visual areas is unlikely to provide a general mechanism for explaining differences in perceived duration.
近期的适应性研究为早期视觉区域在时长感知中发挥作用提供了证据。对于适应性过程中常见的显著时长压缩现象，一种解释是它反映了早期视觉区域中由适应性驱动的特定刺激的神经活动减少。如果这种与刺激相关的神经活动水平确实驱动了时长，那么我们预期对比度对感知时长会有强烈影响，因为电生理研究表明早期视觉区域的神经活动与对比度密切相关。我们采用了一种空间各向同性的噪声刺激，其中每个噪声元素的亮度以4赫兹独立地进行正弦调制。参与者将高对比度（0.9）或低对比度（0.1）刺激的感知时长与之前呈现的标准刺激（600毫秒，对比度 = 0.3）进行匹配。为了实现感知上等效的时长，低对比度刺激必须比高对比度刺激呈现更长的时间。当我们控制刺激大小时以及当我们针对个体在感知时间频率上的差异进行调整时，这种情况都会发生。此外，我们表明这种效应不能用感知起始和结束的偏移来解释，也不是由简单的对比度驱动的反应偏差所解释。我们结果的方向显然与神经活动水平驱动时长的观点一致。然而，这种效应的大小（在对比度从0.9降低到0.1的情况下，时长差异约为10%）与重复抑制和奇球效应中能发现的更大的时长扭曲形成了显著对比；特别是当这些可能与神经活动的较小差异相关，而这种差异比我们对比度差异所预期的要小。综合来看，这些结果表明早期视觉区域中与刺激相关的神经活动水平不太可能为解释感知时长差异提供一种通用机制。
