Bassett Joshua P, Tullman Matthew L, Taube Jeffrey S
Department of Psychological and Brain Sciences, Center for Cognitive Neuroscience, Dartmouth College, Hanover, New Hampshire 03755, USA.
J Neurosci. 2007 Jul 11;27(28):7564-77. doi: 10.1523/JNEUROSCI.0268-07.2007.
Head direction (HD) cells in the rodent limbic system are believed to correspond to a cognitive representation of directional heading in the environment. Lesions of vestibular hair cells disrupt the characteristic firing patterns of HD cells, and thus vestibular afference is a critical contributor to the HD signal. A subcortical pathway that may convey this information includes the dorsal tegmental nucleus of Gudden (DTN) and the lateral mammillary nucleus (LMN). To test the hypothesis that the DTN and LMN are critical components for generating HD cell activity, we made electrolytic lesions of the DTN or LMN in rats and screened for HD cell activity in the anterior thalamus. Directional activity was absent in all animals with complete LMN lesions and in animals with complete DTN lesions, although a few HD cells were isolated in animals with incomplete lesions. Some DTN-lesioned animals contained cells whose firing rates were modulated by angular head velocity. Although cells with bursting patterns of activity have been observed in the anterior dorsal nucleus of the thalamus of animals with disruption of vestibular inputs, this pattern of activity was not observed in either the LMN- or DTN-lesioned animals. The general absence of direction-specific activity in the anterior thalamus of animals with DTN or LMN lesions is consistent with the view that the DTN-LMN circuit is essential for the generation of HD cell activity.
啮齿动物边缘系统中的头方向(HD)细胞被认为与环境中方向朝向的认知表征相对应。前庭毛细胞的损伤会破坏HD细胞的特征性放电模式,因此前庭传入是HD信号的关键贡献因素。一条可能传递该信息的皮层下通路包括古登背侧被盖核(DTN)和外侧乳头体核(LMN)。为了验证DTN和LMN是产生HD细胞活动的关键组成部分这一假设,我们对大鼠的DTN或LMN进行了电解损伤,并在前丘脑筛选HD细胞活动。所有完全损毁LMN的动物以及完全损毁DTN的动物均未出现方向活动,尽管在不完全损伤的动物中分离出了少数HD细胞。一些损毁DTN的动物中含有其放电频率受头部角速度调制的细胞。尽管在前庭输入中断的动物丘脑前背核中观察到了具有爆发性活动模式的细胞,但在损毁LMN或DTN的动物中均未观察到这种活动模式。DTN或LMN损伤动物的前丘脑中普遍缺乏方向特异性活动,这与DTN-LMN回路对HD细胞活动的产生至关重要的观点一致。