The functional connectivity of the hippocampus with its primary cortical input, the entorhinal cortex, is organized topographically. In area CA1 of the hippocampus, this leads to different functional gradients along the proximodistal and septotemporal axes of spatial/sensory responsivity and spatial resolution respectively. CA1 ripples, a network phenomenon, allow us to test whether the hippocampal neural network shows corresponding gradients in functional connectivity along the two axes. We studied the occurrence and propagation of ripples across the entire proximodistal axis along with a comparable spatial range of the septotemporal axis of dorsal CA1. We observed that ripples could occur at any location, and their amplitudes were independent of the tetrode location along the proximodistal and septotemporal axes. When a ripple was detected on a particular tetrode (“reference tetrode”), however, the probability of cooccurrence of ripples and ripple amplitude observed on the other tetrodes decreased as a function of distance from the reference tetrode. This reduction was greater along the proximodistal axis than the septotemporal axis. Furthermore, we found that ripples propagate primarily along the proximodistal axis. Thus, over a spatial scale of ∼1.5 mm, the network is anisotropic along the two axes, complementing the topographically organized cortico‐hippocampal connections.

中文翻译：

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沿大鼠背侧 CA1 的近端和颞间隔轴的波纹的差异传播。

海马与其主要皮质输入内嗅皮质的功能连接是按地形组织的。在海马区 CA1 中，这导致分别沿空间/感觉响应性和空间分辨率的近端轴和间隔轴的不同功能梯度。CA1 涟漪是一种网络现象，让我们能够测试海马神经网络是否在两个轴上显示出相应的功能连接梯度。我们研究了整个近端轴上波纹的发生和传播，以及背侧 CA1 的时间间隔轴的可比空间范围。我们观察到波纹可以发生在任何位置，并且它们的幅度与沿近端轴和间隔轴的四极体位置无关。然而，当在特定四极管（“参考四极管”）上检测到波纹时，在其他四极管上观察到的波纹同时发生的概率和波纹幅度随着与参考四极管的距离而降低。这种减少沿近远轴比间隔轴更大。此外，我们发现波纹主要沿近端轴传播。因此，在~1.5 mm的空间尺度上，网络沿两个轴是各向异性的，补充了地形组织的皮质-海马连接。这种减少沿近远轴比间隔轴更大。此外，我们发现波纹主要沿近端轴传播。因此，在~1.5 mm的空间尺度上，网络沿两个轴是各向异性的，补充了地形组织的皮质-海马连接。这种减少沿近远轴比间隔轴更大。此外，我们发现波纹主要沿近端轴传播。因此，在~1.5 mm的空间尺度上，网络沿两个轴是各向异性的，补充了地形组织的皮质-海马连接。