Department of Neurobiology, Weizmann Institute of Science, Rehovot 76100, Israel.
Neuroimage. 2012 Aug 15;62(2):1163-9. doi: 10.1016/j.neuroimage.2012.01.002. Epub 2012 Jan 8.
The introduction of functional brain imaging based on BOLD-fMRI, twenty years ago, has revolutionized the field of human brain research. However, right from its inception it became clear that the BOLD signal suffers from a serious limitation--it reflects the averaged activity of large neuronal populations and hence can not, on its own, index the functional properties of individual neurons. The method of fMR-adaptation (also termed repetition suppression) was developed to circumvent this problem and use the BOLD signal to assess functional specializations at the individual neuron level. The approach is based on the tendency of cortical neurons to reduce their activity upon stimulus repetition. By examining the sensitivity of the adaptation effect to stimulus manipulation, insight can be gained about the invariant and selective properties of neuronal networks. It has been argued that the adaptation effect occurs at the level of synaptic inputs--and hence may be mislocalized. However, it is critical to consider the adaptation effect in the context of the cortical network architecture. This cortical anatomical organization, dominated by short range intrinsic connections, ensures that the fMR-adaptation largely reflects the response profile of the neurons located within the imaged voxel proper.
二十年前，基于血氧水平依赖（BOLD）功能磁共振成像（fMRI）的脑功能成像技术的引入彻底改变了人类大脑研究领域。然而，从一开始就很清楚，BOLD 信号存在一个严重的局限性——它反映的是大神经元群体的平均活动，因此不能单独作为单个神经元功能特性的指标。fMRI 适应（也称为重复抑制）方法的发展是为了克服这个问题，并利用 BOLD 信号来评估个体神经元水平的功能专业化。该方法基于皮质神经元在刺激重复时活动减少的趋势。通过检查适应效应对刺激处理的敏感性，可以深入了解神经元网络的不变性和选择性特性。有人认为，适应效应发生在突触输入水平——因此可能定位错误。然而，在考虑皮质网络结构的背景下，适应效应至关重要。这种以短程内在连接为主导的皮质解剖组织确保了 fMRI 适应主要反映了成像体素内的神经元的反应特征。
