NIF-LIM-44, InRad, FMUSP, Universidade de São Paulo, Brazil.
Hum Brain Mapp. 2012 Feb;33(2):334-48. doi: 10.1002/hbm.21214. Epub 2011 Mar 9.
The extraction of information about neural activity timing from BOLD signal is a challenging task as the shape of the BOLD curve does not directly reflect the temporal characteristics of electrical activity of neurons. In this work, we introduce the concept of neural processing time (NPT) as a parameter of the biophysical model of the hemodynamic response function (HRF). Through this new concept we aim to infer more accurately the duration of neuronal response from the highly nonlinear BOLD effect. The face validity and applicability of the concept of NPT are evaluated through simulations and analysis of experimental time series. The results of both simulation and application were compared with summary measures of HRF shape. The experiment that was analyzed consisted of a decision-making paradigm with simultaneous emotional distracters. We hypothesize that the NPT in primary sensory areas, like the fusiform gyrus, is approximately the stimulus presentation duration. On the other hand, in areas related to processing of an emotional distracter, the NPT should depend on the experimental condition. As predicted, the NPT in fusiform gyrus is close to the stimulus duration and the NPT in dorsal anterior cingulate gyrus depends on the presence of an emotional distracter. Interestingly, the NPT in right but not left dorsal lateral prefrontal cortex depends on the stimulus emotional content. The summary measures of HRF obtained by a standard approach did not detect the variations observed in the NPT.
从 BOLD 信号中提取神经活动时间信息是一项具有挑战性的任务，因为 BOLD 曲线的形状并不直接反映神经元电活动的时间特征。在这项工作中，我们引入了神经处理时间（NPT）的概念，作为血液动力学响应函数（HRF）的生物物理模型的参数。通过这个新概念，我们旨在从高度非线性的 BOLD 效应中更准确地推断神经元反应的持续时间。通过模拟和实验时间序列的分析，评估了 NPT 概念的表面有效性和适用性。模拟和应用的结果都与 HRF 形状的综合指标进行了比较。分析的实验由一个具有同时呈现的情绪干扰物的决策范式组成。我们假设初级感觉区域（如梭状回）中的 NPT 大约与刺激呈现持续时间相当。另一方面，在与情绪干扰物处理相关的区域中，NPT 应该取决于实验条件。正如所预测的，梭状回中的 NPT 接近刺激持续时间，而背侧前扣带皮层中的 NPT 取决于情绪干扰物的存在。有趣的是，右背外侧前额叶皮层中的 NPT 取决于刺激的情绪内容，而左背外侧前额叶皮层中的 NPT 则不取决于刺激的情绪内容。通过标准方法获得的 HRF 综合指标没有检测到 NPT 中观察到的变化。
