Department of Bioengineering, Brain Institute, University of Utah, Salt Lake City, Utah, 84112, USA.
J Neurosci. 2013 Apr 3;33(14):6027-40. doi: 10.1523/JNEUROSCI.3892-12.2013.
In active networks, excitatory and inhibitory synaptic inputs generate membrane voltage fluctuations that drive spike activity in a probabilistic manner. Despite this, some cells in vivo show a strong propensity to precisely lock to the local field potential and maintain a specific spike-phase relationship relative to other cells. In recordings from rat medial entorhinal cortical stellate cells, we measured spike phase-locking in response to sinusoidal "test" inputs in the presence of different forms of background membrane voltage fluctuations, generated via dynamic clamp. We find that stellate cells show strong and robust spike phase-locking to theta (4-12 Hz) inputs. This response occurs under a wide variety of background membrane voltage fluctuation conditions that include a substantial increase in overall membrane conductance. Furthermore, the IH current present in stellate cells is critical to the enhanced spike phase-locking response at theta. Finally, we show that correlations between inhibitory and excitatory conductance fluctuations, which can arise through feedback and feedforward inhibition, can substantially enhance the spike phase-locking response. The enhancement in locking is a result of a selective reduction in the size of low-frequency membrane voltage fluctuations due to cancellation of inhibitory and excitatory current fluctuations with correlations. Hence, our results demonstrate that stellate cells have a strong preference for spike phase-locking to theta band inputs and that the absolute magnitude of locking to theta can be modulated by the properties of background membrane voltage fluctuations.
在活性网络中，兴奋性和抑制性突触输入会产生膜电压波动，以概率方式驱动尖峰活动。尽管如此，体内的一些细胞显示出强烈的倾向，可以精确地锁定局部场电位，并相对于其他细胞保持特定的尖峰相位关系。在大鼠内侧隔核星形细胞的记录中，我们在存在通过动态钳制产生的不同形式的背景膜电压波动的情况下，测量了对正弦“测试”输入的尖峰相位锁定。我们发现星形细胞对θ（4-12 Hz）输入表现出强烈而稳健的尖峰相位锁定。这种响应发生在广泛的背景膜电压波动条件下，包括整体膜电导的大幅增加。此外，星形细胞中的 IH 电流对于增强的θ相位锁定反应至关重要。最后，我们表明，通过反馈和前馈抑制产生的抑制性和兴奋性电导波动之间的相关性可以大大增强尖峰相位锁定反应。锁定的增强是由于由于抑制性和兴奋性电流波动的相关性而导致低频膜电压波动的大小选择性减小。因此，我们的结果表明，星形细胞对θ带输入的尖峰相位锁定具有强烈的偏好，并且对θ的锁定的绝对幅度可以通过背景膜电压波动的特性来调制。
