Franklin Michael S, Jonides John
Department of Psychology, University of California at Santa Barbara, Santa Barbara, CA 93106-9660, USA.
J Cogn Neurosci. 2009 Nov;21(11):2114-20. doi: 10.1162/jocn.2008.21181.
The role of the intraparietal sulcus (IPS) in the representation of numerical magnitude is well established. Recently, there has also been speculation that the IPS is involved in the representation of ordinal information as well. These claims, however, overlook the fact that all neuroimaging paradigms in which participants make judgments about either magnitude and/or order result in a behavioral distance effect (i.e., the comparison is easier when the stimuli span a greater distance). This leaves open two possibilities: It may be that activation of the IPS is due to the mechanism that yields distance effects, or it may be that the IPS is involved in the representation of information about both magnitude and order. The current study used fMRI to compare a magnitude task in which participants show distance effects to an order-judgment task that yields reverse-distance effects. The results reveal activation of the IPS for both the magnitude and order tasks that is based on participants' strategies as opposed to the actual distance between the numbers. This leads to the conclusion that the IPS represents a mental number line, and that accessing this line can lead to distance effects when participants compare magnitudes and to reverse-distance effects when participants check for order.
顶内沟（IPS）在数字大小表征中的作用已得到充分证实。最近，也有人推测IPS也参与序数信息的表征。然而，这些说法忽略了一个事实，即所有让参与者对大小和/或顺序进行判断的神经成像范式都会产生行为距离效应（即，当刺激之间的跨度更大时，比较更容易）。这留下了两种可能性：可能是IPS的激活是由于产生距离效应的机制，或者可能是IPS参与了大小和顺序信息的表征。当前的研究使用功能磁共振成像（fMRI）来比较一个参与者表现出距离效应的大小任务和一个产生反向距离效应的顺序判断任务。结果显示，IPS在大小和顺序任务中均有激活，这种激活基于参与者的策略，而非数字之间的实际距离。这得出一个结论，即IPS代表一条心理数字线，并且当参与者比较大小时，访问这条线会导致距离效应，而当参与者检查顺序时，会导致反向距离效应。
