摘要
本研究探讨了观察者与观察目标存在相对运动时视觉系统对目标数量特征的适应后效的皮层映射特征,并与对比度适应后效的映射规律进行比较。包括两项实验。其中,实验一要求被试在适应目标后转换注视点,考察眼跳后相同和不同视网膜区域以及相同和不同空间区域的适应后效,发现数量适应后效具有部分空间-皮层映射特性,而对比度适应后效则表现出完全的视网膜-皮层映射特征。实验二采用固定的注视点,考察目标运动后目标原位置和新位置区域的适应后效,发现数量适应后效不完全依赖于视网膜-皮层映射,它可以"追随"客体运动重新映射到新的位置,表现出基于客体映射的特征,而对比度适应后效则完全依赖于视网膜-皮层映射,不能"追随"客体移动在目标新位置重新形成映射。两项实验结果提示,相对于对比度等低级表面特征而言,数量特征对目标的描述涉及更高的加工水平,它可以与观察目标的相对运动信息进行整合,且这种整合在眼跳和非眼跳的观察条件下都可发生。
A key question in numerosity cognition is whether numerosity processing is based on quantity of items, rather than other low-level descriptions such as contrast or density. We can shed light on this question by investigating the cortical remapping features of numerosity adaptation across saccades, compared with those of low-level properties. As can be seen from previous studies, when the observer was sweeping across a stimulus, there was a spatiotopic representation of the stimulus, forming an isomorphic map in the visual cortex anchored in stable real-world coordinates. The remapping was based on transformation of retinotopic mapping of the neurons that occurred in the primary visual cortex. This transformation, however, was proposed to exist in high-level descriptions selectively by means of integrating visual properties with eye-movement information across saccades. Therefore, distinct mechanisms can be revealed if the remappings show different characteristics between numerosity and low-level properties such as contrast or density, which is helpful in supporting the statement that numerosity processing is relatively independent of primary visual cues. Object-based remapping was thought to be possible when stimuli moved without saccades. The mechanism underlying this kind of mapping is not yet clearly demonstrated. Specifically, if this remapping is due to object-file updating, then all visual properties could be remapped when objects move without saccades, despite the different processing levels of them. By contrast, if the object-based remapping is based on a similar mechanism to that with saccades, then a distinction would appear in remapping features of descriptions in different levels： only higher-level descriptions＇ aftereffects could be remapped to final positions when objects moved. Therefore, exploring remapping features when objects are moving without saccades is an effective way to study the mechanism of object-based remapping without saccades. In our study, remapping characteristics of numerosity adaptation aftereffects were investigated systematically when relative motion occurred between the target and the observing eyes, compared with those of contrast adaptation aftereffects. Two experiments were included. In Experiment 1, subjects were asked to shift their fixations to a new position after adapting to the stimulus. The adaptation effects in the same and different retinae/screen positions were compared. The numerosity and contrast adaptation were tested respectively. As a result, numerosity adaptation effects showed spatiotopic remapping features to some extent, whereas the remapping of contrast adaptation aftereffects appeared to be purely retinotopic. According to the result, we proposed that numerosity was a higher-level description of stimuli, which can be integrated with eye-moving information and built up across saccades. In Experiment 2, with a stable fixation and moving adapting targets, we determined the numerosity and contrast adaptation aftereffects in the original and final positions of targets, respectively. The results suggested that numerical adaptation aftereffects can be remapped to the final position of targets. On the contrary, contrast adaptation aftereffects could not be remapped to the final position of moved targets, showing a completely retinotopic remapping feature. The distinct results in Experiment 2 underlined further differences in numerosity and contrast processing, as well as an identical mechanism in remapping features of relatively moving objects with and without saccades. In conclusion, cortical remapping of numerosity adaptation aftereffects was shown to be not constrained to the retinotopic level in our study. With saccades, it was shown to be spatiotopic; without saccades, the numerical aftereffects could also be remapped in the final position of moving objects. On the contrary, contrast showed completely retinotopic remapping features. These results provide new evidence to support the view that numerosity is processed at higher-level rather than being completely dependent on inferring of low-level visual cues. Moreover, we propose that the information of relative motion can be integrated with higher-level properties of stimuli no matter there are saccades or not.
出处
《心理学报》
CSSCI
CSCD
北大核心
2014年第1期5-16,共12页
Acta Psychologica Sinica
基金
教育部人文社会科学研究规划基金(11YJA190025)资助
关键词
数量加工
数量适应后效
视网膜-皮层映射
空间-皮层映射
基于客体的映射
numerical processing
numerosity adaptation aftereffect
retinotopic mapping
spatiotopic remapping
object-based remapping
