Emir Uzay E, Bayraktaroglu Zubeyir, Ozturk Cengizhan, Ademoglu Ahmet, Demiralp Tamer
Bogazici University, Biomedical Engineering Institute, 34342 Bebek, Istanbul, Turkey.
Neurosci Lett. 2008 May 9;436(2):185-8. doi: 10.1016/j.neulet.2008.03.021. Epub 2008 Mar 13.
The dependency of positive BOLD (PBOLD) and post-stimulus undershoot (PSU) on the temporal frequency of visual stimulation was investigated using stimulation frequencies between 1 and 44 Hz. The PBOLD peak at 8 Hz in primary visual cortex was in line with previous neuroimaging studies. In addition to the 8 Hz peak, secondary peaks were observed for stimulation frequencies at 16 and 24 Hz. These additional local peaks were contrary to earlier fMRI studies which reported either a decrease or a plateau for frequencies above 8 Hz but in line with electrophysiological results obtained in animal local field potential (LFP) measurements and human steady-state visual evoked potential (SSVEP) recordings. Our results also indicate that the dependency of PSU amplitude on stimulus frequency deviates from that of PBOLD. Although their amplitudes were correlated within the 1-13 Hz range, they changed independently at stimulation frequencies between 13 and 44 Hz. The different dependency profiles of PBOLD and PSU to stimulation frequency points to different underlying neurovascular mechanisms responsible for the generation of these BOLD transients with regard to their relation to inhibitory and excitatory neuronal activity.
使用1至44赫兹之间的刺激频率，研究了正性BOLD（PBOLD）和刺激后负波（PSU）对视觉刺激时间频率的依赖性。初级视觉皮层中8赫兹时的PBOLD峰值与先前的神经影像学研究结果一致。除了8赫兹的峰值外，在16和24赫兹的刺激频率下还观察到了次级峰值。这些额外的局部峰值与早期的功能磁共振成像研究结果相反，早期研究报告称频率高于8赫兹时信号会降低或趋于平稳，但与在动物局部场电位（LFP）测量和人类稳态视觉诱发电位（SSVEP）记录中获得的电生理结果一致。我们的结果还表明，PSU振幅对刺激频率的依赖性与PBOLD不同。虽然它们的振幅在1至13赫兹范围内相关，但在13至44赫兹的刺激频率下它们独立变化。PBOLD和PSU对刺激频率的不同依赖性特征表明，就其与抑制性和兴奋性神经元活动的关系而言，产生这些BOLD瞬变的潜在神经血管机制不同。
