Karnup S V
Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Russia.
Zh Vyssh Nerv Deiat Im I P Pavlova. 2004 Jan-Feb;54(1):32-43.
The hippocampal rhythms observed in vivo are the result of a complex interplay between cellular and synaptic properties within the hippocampus, and extra-hippocampal tonic as well as periodic inputs. For the stable rhythm to occur, the hippocampal circuitry should have the potential to oscillate at the specific frequencies. The in vitro studies revealed multiple mechanisms supporting the generation of the theta rhythm, which is the main operational mode of the hippocampus. In the hippocampus and related structures cellular membranes can oscillate at theta rhythm when they are depolarized to near-threshold membrane potentials; membranes are also adjusted to resonate with the external signal applied at theta frequency. Synaptically connected hippocampal network alone can generate theta rhythm when a necessary tonic excitation is provided. Finally, rhythmic inputs in theta range from the septum and entorhinal cortex have a propensity to synchronize oscillations in the whole hippocampal formation and associated structures to operate in a unified mode of activity. Based on the results obtained in slices and slice cultures, the present review shows this multilevel hierarchy, which serves to guarantee easy occurrence and reliable maintenance of the theta rhythm in the hippocampus.
在体内观察到的海马体节律是海马体内细胞和突触特性与海马体外的紧张性以及周期性输入之间复杂相互作用的结果。为了产生稳定的节律，海马体回路应该有在特定频率下振荡的潜力。体外研究揭示了多种支持θ节律产生的机制，θ节律是海马体的主要运作模式。在海马体及相关结构中，细胞膜在去极化至接近阈膜电位时能够以θ节律振荡；细胞膜也会进行调整以与以θ频率施加的外部信号发生共振。当提供必要的紧张性兴奋时，仅通过突触连接的海马体网络就能产生θ节律。最后，来自隔区和内嗅皮质的θ范围内的节律性输入倾向于使整个海马体结构及相关结构中的振荡同步，从而以统一的活动模式运作。基于在脑片和脑片培养物中获得的结果，本综述展示了这种多层次结构，它有助于确保海马体中θ节律的轻易产生和可靠维持。
