Centre de Neurosciences Système et Cognition, Institut de Recherche en Sciences Psychologiques, Université catholique de Louvain, Louvain-la-Neuve, Belgium.
Neuroimage. 2010 Oct 1;52(4):1677-86. doi: 10.1016/j.neuroimage.2010.04.254. Epub 2010 May 8.
In humans, areas around the intraparietal sulcus (IPS) have been found to play a crucial role in coding nonsymbolic numerosities (i.e., number of elements in a collection). In the parietal cortex of monkeys, some populations of neurons were found to respond selectively to sequentially- or simultaneously-presented numerosities, whereas other populations showed similar activation in both modes of presentation. However, whether such mode-dependent and -independent representations of numerosity also exist in humans is still unknown. Here, we used fMRI to identify the areas involved in numerosity processing while participants classified linear arrays of dots (simultaneous stimuli) or flashed dot sequences (sequential stimuli). The processing of simultaneous numerosities induced activations bilaterally in several areas of the IPS, whereas activations during the processing of sequential numerosities were restricted to the right hemisphere. A conjunction analysis showed that only the right IPS and precentral gyrus showed overlapping activations during the judgement of sequential and simultaneous stimuli. Voxelwise correlations confirmed the highly similar pattern of activation found in these regions during both tasks. This pattern was weaker or absent in mode-dependent regions, like the right inferior frontal cortex and the lateral occipital complex. Finally, a close look at the right IPS revealed an anterior-to-posterior gradient of activation with selective activation for sequential and simultaneous stimuli in the anterior and posterior areas, respectively, and overlapping activations in-between. This study provides the first direct evidence that, in humans, the right IPS contains both mode-dependent and mode-independent representations of numerosity.
在人类中，顶内沟（IPS）周围的区域被发现对非符号数量（即集合中元素的数量）编码起着至关重要的作用。在猴子的顶叶皮层中，发现一些神经元群体对顺序或同时呈现的数量有选择性反应，而其他群体在两种呈现模式下表现出相似的激活。然而，数量的这种模式依赖和独立的表示是否也存在于人类中仍然未知。在这里，我们使用 fMRI 来确定在参与者对线性点数组（同时刺激）或闪烁点序列（顺序刺激）进行分类时涉及数量处理的区域。同时数量的处理在 IPS 的几个双侧区域引起激活，而顺序数量的处理激活仅限于右半球。联合分析表明，只有右 IPS 和中央前回在顺序和同时刺激的判断过程中表现出重叠的激活。体素水平的相关性证实了这两个任务中这些区域的激活模式高度相似。这种模式在模式依赖区域（如右侧额下回和外侧枕叶复合体）较弱或不存在。最后，仔细观察右 IPS 发现，激活存在从前向后的梯度，分别在前后区域对顺序和同时刺激有选择性激活，而在两者之间存在重叠激活。这项研究提供了第一个直接证据，表明在人类中，右 IPS 包含数量的模式依赖和独立表示。
