Jansma Johan Martijn, van Raalten Tamar R, Boessen Ruud, Neggers Sebastiaan F W, Jacobs Richard H A H, Kahn René S, Ramsey Nick F
Department of Neurology and Neurosurgery, Rudolf Magnus Institute of Neuroscience, University Medical Centre Utrecht, Utrecht, The Netherlands.
Department of Neurology and Neurosurgery, Rudolf Magnus Institute of Neuroscience, University Medical Centre Utrecht, Utrecht, The Netherlands ; Department of Child- and Adolescent Psychiatry, Rudolf Magnus Institute of Neuroscience, University Medical Centre Utrecht, Utrecht, The Netherlands.
PLoS One. 2013 Dec 20;8(12):e80256. doi: 10.1371/journal.pone.0080256. eCollection 2013.
Cognitive tasks that do not change the required response for a stimulus over time ('consistent mapping') show dramatically improved performance after relative short periods of practice. This improvement is associated with reduced brain activity in a large network of brain regions, including left prefrontal and parietal cortex. The present study used fMRI-guided repetitive transcranial magnetic stimulation (rTMS), which has been shown to reduce processing efficacy, to examine if the reduced activity in these regions also reflects reduced involvement, or possibly increased efficiency.
First, subjects performed runs of a Sternberg task in the scanner with novel or practiced target-sets. This data was used to identify individual sites for left prefrontal and parietal peak brain activity, as well as to examine the change in activity related to practice. Outside of the scanner, real and sham rTMS was applied at left prefrontal and parietal cortex to examine their involvement novel and practiced conditions.
Prefrontal as well as parietal rTMS significantly reduced target accuracy for novel targets. Prefrontal, but not parietal, rTMS interference was significantly lower for practiced than novel target-sets. rTMS did not affect non-target accuracy, or reaction time in any condition.
These results show that task practice in a consistent environment reduces involvement of the prefrontal cortex. Our findings suggest that prefrontal cortex is predominantly involved in target maintenance and comparison, as rTMS interference was only detectable for targets. Findings support process switching hypotheses that propose that practice creates the possibility to select a response without the need to compare with target items. Our results also support the notion that practice allows for redistribution of limited maintenance resources.
随着时间推移，对刺激的所需反应不变的认知任务（“一致映射”）在经过相对较短时间的练习后，表现会显著提高。这种提高与包括左前额叶和顶叶皮质在内的大脑区域大网络中的大脑活动减少有关。本研究使用功能性磁共振成像引导的重复经颅磁刺激（rTMS），已证明其可降低处理效率，以检验这些区域活动的减少是否也反映了参与度降低，或者可能是效率提高。
首先，受试者在扫描仪中对新的或已练习的目标集进行斯滕伯格任务测试。这些数据用于确定左前额叶和顶叶大脑活动峰值的个体部位，并检验与练习相关的活动变化。在扫描仪外，对左前额叶和顶叶皮质施加真实和 sham rTMS，以检验它们在新的和已练习条件下的参与情况。
前额叶以及顶叶rTMS显著降低了新目标的目标准确性。对于已练习的目标集，前额叶rTMS干扰显著低于新目标集，但顶叶rTMS干扰无此差异。rTMS在任何条件下均未影响非目标准确性或反应时间。
这些结果表明，在一致环境中的任务练习会降低前额叶皮质的参与度。我们的研究结果表明，前额叶皮质主要参与目标维持和比较，因为rTMS干扰仅在目标上可检测到。研究结果支持过程转换假说，该假说提出练习创造了无需与目标项目比较即可选择反应的可能性。我们的结果还支持这样一种观点，即练习允许有限维持资源重新分配。
