Libertus Melissa E, Brannon Elizabeth M, Pelphrey Kevin A
Department of Psychology and Neuroscience, Duke University, Durham, NC 27708, USA.
Neuroimage. 2009 Feb 15;44(4):1404-14. doi: 10.1016/j.neuroimage.2008.10.027. Epub 2008 Nov 5.
Neuroimaging studies have identified a common network of brain regions involving the prefrontal and parietal cortices across a variety of working memory (WM) tasks. However, previous studies have also reported category-specific dissociations of activation within this network. In this study, we investigated the development of category-specific activation in a WM task with digits, letters, and faces. Eight-year-old children and adults performed a 2-back WM task while their brain activity was measured using functional magnetic resonance imaging (fMRI). Overall, children were significantly slower and less accurate than adults on all three WM conditions (digits, letters, and faces); however, within each age group, behavioral performance across the three conditions was very similar. FMRI results revealed category-specific activation in adults but not children in the intraparietal sulcus for the digit condition. Likewise, during the letter condition, category-specific activation was observed in adults but not children in the left occipital-temporal cortex. In contrast, children and adults showed highly similar brain-activity patterns in the lateral fusiform gyri when solving the 2-back WM task with face stimuli. Our results suggest that 8-year-old children do not yet engage the typical brain regions that have been associated with abstract or semantic processing of numerical symbols and letters when these processes are task-irrelevant and the primary task is demanding. Nevertheless, brain activity in letter-responsive areas predicted children's spelling performance underscoring the relationship between abstract processing of letters and linguistic abilities. Lastly, behavioral performance on the WM task was predictive of math and language abilities highlighting the connection between WM and other cognitive abilities in development.
神经影像学研究已经确定了一个涉及前额叶和顶叶皮质的常见脑区网络，该网络参与了各种工作记忆（WM）任务。然而，先前的研究也报告了该网络内激活的类别特异性分离。在本研究中，我们调查了在涉及数字、字母和面孔的WM任务中类别特异性激活的发展情况。8岁儿童和成年人执行了一个2-back WM任务，同时使用功能磁共振成像（fMRI）测量他们的大脑活动。总体而言，在所有三种WM条件（数字、字母和面孔）下，儿童的速度明显比成年人慢，准确性也更低；然而，在每个年龄组中，三种条件下的行为表现非常相似。fMRI结果显示，在数字条件下，成年人的顶内沟存在类别特异性激活，而儿童则没有。同样，在字母条件下，成年人的左侧枕颞叶皮质观察到类别特异性激活，而儿童没有。相比之下，在使用面孔刺激解决2-back WM任务时，儿童和成年人在外侧梭状回显示出高度相似的脑活动模式。我们的结果表明，当这些过程与任务无关且主要任务要求较高时，8岁儿童尚未激活与数字符号和字母的抽象或语义处理相关的典型脑区。尽管如此，字母反应区域的脑活动预测了儿童的拼写表现，强调了字母抽象处理与语言能力之间的关系。最后，WM任务的行为表现预测了数学和语言能力，突出了WM与发育中其他认知能力之间的联系。
