Ances B M, Greenberg J H, Detre J A
Department of Neurology, University of Pennsylvania, Philadelphia 19104, USA.
J Cereb Blood Flow Metab. 2000 Feb;20(2):290-7. doi: 10.1097/00004647-200002000-00010.
In functional neuroimaging studies, the hemodynamic response to functional activation is used as a surrogate marker for neuronal activity, typically in response to task paradigms that use periodic stimuli. With use of a model system of electrical forepaw stimulation in rats (n = 14) with laser-Doppler (LD) monitoring of cerebral blood flow (CBF) changes in the somatosensory cortex, the effects of variations in the interstimulus interval (ISI) on the hemodynamic response to periodic stimuli were examined. A characteristic peak flow response was seen for 4-second stimuli and a peak and plateau response were seen for all 8-second stimuli regardless of ISI. However, both the amplitude of the LD(CBF) response and the integrated response were significantly reduced for shorter ISIs, whereas the baseline flow was not altered. Somatosensory evoked potential responses were also recorded in some rats (n = 8) and remained unchanged for the various ISIs for a particular stimulus duration. These results suggest that the decrease in the LD(CBF) responses observed with shorter ISIs likely represents a refractoriness of the hemodynamic response and not neuronal function. These results may have important implications for the optimization and interpretation of functional activation paradigms that use periodic stimuli.
在功能神经影像学研究中，对功能激活的血流动力学反应被用作神经元活动的替代标志物，通常是针对使用周期性刺激的任务范式。利用大鼠（n = 14）前爪电刺激模型系统，并通过激光多普勒（LD）监测体感皮层的脑血流量（CBF）变化，研究了刺激间隔（ISI）变化对周期性刺激血流动力学反应的影响。对于4秒的刺激，观察到特征性的峰值血流反应；对于所有8秒的刺激，无论ISI如何，均观察到峰值和平原反应。然而，对于较短的ISI，LD（CBF）反应的幅度和综合反应均显著降低，而基线血流未改变。在一些大鼠（n = 8）中也记录了体感诱发电位反应，对于特定刺激持续时间的各种ISI，该反应保持不变。这些结果表明，较短ISI时观察到的LD（CBF）反应降低可能代表血流动力学反应的不应期，而非神经元功能。这些结果可能对使用周期性刺激的功能激活范式的优化和解释具有重要意义。
