Cappelletti Marinella, Barth Hilary, Fregni Felipe, Spelke Elizabeth S, Pascual-Leone Alvaro
Center for Non-Invasive Brain Stimulation, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02215, USA.
Exp Brain Res. 2007 Jun;179(4):631-42. doi: 10.1007/s00221-006-0820-0. Epub 2007 Jan 11.
It has been widely argued that the intraparietal sulcus (IPS) is involved in tasks that evoke representations of numerical magnitude, among other cognitive functions. However, the causal role of this parietal region in processing symbolic and non-symbolic numerosity has not been established. The current study used repetitive Transcranial Magnetic Stimulation (rTMS) to the left and right IPS to investigate the effects of temporary deactivations of these regions on the capacity to represent symbolic (Arabic numbers) and non-symbolic (arrays of dots) numerosities. We found that comparisons of both symbolic and non-symbolic numerosities were impaired after rTMS to the left IPS but enhanced by rTMS to the right IPS. A signature effect of numerical distance was also found: greater impairment (or lesser facilitation) when comparing numerosities of similar magnitude. The reverse pattern of impairment and enhancement was found in a control task that required judging an analogue stimulus property (ellipse orientation) but no numerosity judgements. No rTMS effects for the numerosity tasks were found when stimulating an area adjacent but distinct from the IPS, the left and right angular gyrus. These data suggest that left IPS is critical for processing symbolic and non-symbolic numerosity; this processing may thus depend on common neural mechanisms, which are distinct from mechanisms supporting the processing of analogue stimulus properties.
人们普遍认为，顶内沟（IPS）参与了引发数字大小表征的任务以及其他认知功能。然而，这个顶叶区域在处理符号性和非符号性数字数量方面的因果作用尚未确定。当前的研究使用重复经颅磁刺激（rTMS）作用于左右IPS，以研究这些区域的暂时失活对表征符号性（阿拉伯数字）和非符号性（点阵列）数字数量能力的影响。我们发现，对左IPS进行rTMS后，符号性和非符号性数字数量的比较均受损，但对右IPS进行rTMS则增强了这种比较。还发现了数字距离的标志性效应：比较相似大小的数字数量时，损伤更大（或促进作用更小）。在一项需要判断模拟刺激属性（椭圆方向）但无需数字数量判断的对照任务中，发现了相反的损伤和增强模式。当刺激与IPS相邻但不同的区域，即左右角回时，未发现对数字数量任务的rTMS效应。这些数据表明，左IPS对于处理符号性和非符号性数字数量至关重要；因此，这种处理可能依赖于共同的神经机制，这些机制与支持模拟刺激属性处理的机制不同。
