Abstract
Navigation first requires accurate perception of one's spatial orientation
within the environment, which consists of knowledge about location
and directional heading. Cells within several limbic system areas
of the mammalian brain discharge allocentrically as a function of
the animal's directional heading, independent of the animal's location
and ongoing behavior. These cells are referred to as head direction
(HD) cells and are believed to encode the animal's perceived directional
heading with respect to its environment. Although HD cells are found
in several areas, the principal circuit for generating this signal
originates in the dorsal tegmental nucleus and projects serially,
with some reciprocal connections, to the lateral mammillary nucleus
? anterodorsal thalamus ? PoS, and terminates in the entorhinal cortex.
HD cells receive multimodal information about landmarks and self-generated
movements. Vestibular information appears critical for generating
the directional signal, but motor/proprioceptive and landmark information
are important for updating it.
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