Electrophysiology and anatomy data for: Projection-specific integration of convergent thalamic and retrosplenial signals in the presubicular head direction cortex

Head-direction (HD) signals function as the brain’s internal compass. They
are organized as an attractor and anchor to the environment via visual
landmarks. Here, we examine how thalamic HD signals and visual information
from the retrosplenial cortex combine in the presubiculum. We find that
monosynaptic excitatory connections from the anterior thalamic nucleus and
from retrosplenial cortex converge on single-layer 3 pyramidal neurons in
the dorsal portion of the mouse presubiculum. Independent dual wavelength
photostimulation of these inputs in slices leads to action potential
generation preferentially for near-coincident inputs, indicating that
layer 3 neurons can transmit a visually matched HD signal to the medial
entorhinal cortex. Layer 4 neurons, which innervate the lateral mammillary
nucleus, form a second step in the association of HD and landmark signals.
They receive little direct input from thalamic and retrosplenial axons. We
show that layer 4 cells are excited di-synaptically, transforming regular
spiking activity into bursts of action potentials, and that their firing
is enhanced by cholinergic agonists. Thus, a coherent sense of orientation
involves projection-specific translaminar processing in the presubiculum,
where neuromodulation facilitates landmark updating of HD signals in the
lateral mammillary nucleus.

头部方向（Head-direction, HD）信号相当于大脑的内部罗盘，该类信号以吸引子结构形式组织，并通过视觉地标锚定外界环境。本研究探讨了丘脑HD信号与来自retrosplenial皮层（retrosplenial cortex）的视觉信息在内嗅前皮层（presubiculum）中的整合机制。研究发现，来自丘脑前核（anterior thalamic nucleus）与retrosplenial皮层的单突触兴奋性连接，会聚于小鼠内嗅前皮层背侧区域的第3层锥体神经元上。对脑片内的这些输入通路进行独立双波长光刺激时，仅在输入信号近乎同步的情况下更易诱生动作电位，这表明第3层神经元可向内侧内嗅皮层（medial entorhinal cortex）传递与视觉信息匹配的HD信号。投射支配外侧乳头体核（lateral mammillary nucleus）的第4层神经元，则是HD信号与地标信号关联的第二级通路节点，这类神经元几乎不接收来自丘脑与retrosplenial皮层轴突的直接输入。本研究证实，第4层神经元通过双突触通路被激活，可将规则的锋电位放电活动转换为动作电位爆发，且其放电活动可被胆碱能激动剂（cholinergic agonists）增强。综上，连贯的方位感知依赖于内嗅前皮层内的投射特异性跨层加工，其中神经调控可促进外侧乳头体核内HD信号基于视觉地标的更新。