Nemani Ajay K, Atkinson Ian C, Thulborn Keith R
Center for Magnetic Resonance Research, University of Illinois at Chicago, Chicago, IL 60612, USA.
Neuroimage. 2009 Oct 1;47(4):1417-24. doi: 10.1016/j.neuroimage.2009.05.018. Epub 2009 May 14.
Conventional functional magnetic resonance imaging using blood oxygenation level dependent contrast requires signal averaging and statistical methods to detect activation. Signal averaging implicitly assumes that brain activation in response to a stimulus is reproducible on the scale of the imaging voxel. This assumption is examined in the absence of averaging by analyzing individual trials of individual voxels that approach the size of the functional unit, the cortical column, in the human primary visual cortex. In the absence of spatial and temporal averaging, even highly active voxels demonstrate inconsistent activation to the same repeated stimulus despite consistent behavioral responses. This observation implies a variable selection of suitable cortical columns from a population of available functional units to produce consistent perception of the stimulus. The implication of this observation for neuroplasticity and behavioral consistency at the level of functional units is discussed.
使用基于血氧水平依赖对比的传统功能磁共振成像需要信号平均和统计方法来检测激活。信号平均隐含地假设，在成像体素尺度上，对刺激的大脑激活是可重复的。通过分析接近人类初级视觉皮层功能单元（即皮质柱）大小的单个体素的单个试验，在不进行平均的情况下检验了这一假设。在没有空间和时间平均的情况下，即使是高度活跃的体素，尽管行为反应一致，但对相同的重复刺激也表现出不一致的激活。这一观察结果意味着从一群可用的功能单元中可变地选择合适的皮质柱，以产生对刺激的一致感知。讨论了这一观察结果对功能单元水平上神经可塑性和行为一致性的影响。
