Lemieux Louis, Laufs Helmut, Carmichael David, Paul Joseph Suresh, Walker Matthew C, Duncan John S
Department of Clinical and Experimental Epilepsy, Institute of Neurology, University College London, Queen Square, London, UK.
Hum Brain Mapp. 2008 Mar;29(3):329-45. doi: 10.1002/hbm.20389.
Till now, most studies of the Blood Oxygen Level-Dependent (BOLD) response to interictal epileptic discharges (IED) have assumed that its time course matches closely to that of brief physiological stimuli, commonly called the canonical event-related haemodynamic response function (canonical HRF). Analyses based on that assumption have produced significant response patterns that are generally concordant with prior electroclinical data. In this work, we used a more flexible model of the event-related response, a Fourier basis set, to investigate the presence of other responses in relation to individual IED in 30 experiments in patients with focal epilepsy. We found significant responses that had a noncanonical time course in 37% of cases, compared with 40% for the conventional, canonical HRF-based approach. In two cases, the Fourier analysis suggested activations where the conventional model did not. The noncanonical activations were almost always remote from the presumed generator of epileptiform activity. In the majority of cases with noncanonical responses, the noncanonical responses in single-voxel clusters were suggestive of artifacts. We did not find evidence for IED-related noncanonical HRFs arising from areas of pathology, suggesting that the BOLD response to IED is primarily canonical. Noncanonical responses may represent a number of phenomena, including artefacts and propagated epileptiform activity.
到目前为止，大多数关于血氧水平依赖（BOLD）对发作间期癫痫放电（IED）反应的研究都假定其时间进程与短暂生理刺激的时间进程密切匹配，这种短暂生理刺激通常被称为典型事件相关血流动力学反应函数（典型HRF）。基于该假设的分析产生了与先前电临床数据总体一致的显著反应模式。在这项研究中，我们使用了一种更灵活的事件相关反应模型——傅里叶基集，来研究30例局灶性癫痫患者个体IED相关的其他反应的存在情况。我们发现，37%的病例中存在时间进程非典型的显著反应，相比之下，基于传统典型HRF方法的这一比例为40%。在两个病例中，傅里叶分析显示存在激活，而传统模型未显示。非典型激活几乎总是远离癫痫样活动的假定起源。在大多数具有非典型反应的病例中，单像素簇中的非典型反应提示为伪影。我们没有找到证据表明由病变区域产生与IED相关的非典型HRF，这表明对IED的BOLD反应主要是典型的。非典型反应可能代表多种现象，包括伪影和传播的癫痫样活动。
