The Journal of Neuroscience, July 11, 2007, 27(28):7564-7577; doi:10.1523/JNEUROSCI.0268-07.2007
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Behavioral/Systems/Cognitive
Lesions of the Tegmentomammillary Circuit in the Head Direction System Disrupt the Head Direction Signal in the Anterior Thalamus
Joshua P. Bassett,
Matthew L. Tullman, and
Jeffrey S. Taube
Department of Psychological and Brain Sciences, Center for Cognitive Neuroscience, Dartmouth College, Hanover, New Hampshire 03755
Correspondence should be addressed to Jeffrey S. Taube, Department of Psychological and Brain Sciences, Dartmouth College, 6207 Moore Hall, Hanover, NH 03755. Email: jeffrey.taube{at}dartmouth.edu
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 DTNLMN circuit is essential for the generation of HD cell activity.
Key words: head direction cell; anterodorsal thalamic nucleus; dorsal tegmental nucleus; lateral mammillary nuclei; navigation; place cell
Received Aug. 31, 2006;
revised May 9, 2007;
accepted May 28, 2007.
Correspondence should be addressed to Jeffrey S. Taube, Department of Psychological and Brain Sciences, Dartmouth College, 6207 Moore Hall, Hanover, NH 03755. Email: jeffrey.taube{at}dartmouth.edu