2013年8月26日月曜日

The Head-Direction Signal Is Critical for Navigation Requiring a Cognitive Map but Not for Learning a Spatial Habit

Brett Gibson, William N. Butler, Jeffery S. Taube
Current Biology, Volume 23, Issue 16, 1536-1540, 25 July 2013

適切な方向への移動には、「自分がどちらを向いているか、つまり頭の向き(Head-direction:HD)」をコードするニューロンの情報と「自分が居る場所」をコードするニューロンの情報を組み合わせる事が重要。
ただし、移動自体がすでに習慣化(habit-associated directional strategyを使用)している場合は、HDニューロンが活動していなくても適切な方向選択ができる。

Head-direction (HD) cells fire as a function of an animal’s directional heading in the horizontal plane during two-dimensional navigational tasks [1]. The information from HD cells is used with place and grid cells to form a spatial representation (cognitive map) of the environment [2,3]. Previous studies have shown that when rats are inverted (upside down), they have difficulty learning a task that requires them to find an escape hole from one of four entry points but that they can learn it when released from one or two start points [4]. Previous reports also indicate that the HD signal is disrupted when a rat is oriented upside down [5,6]. Here we monitored HD cell activity in the two-entry-point version of the inverted task and when the rats were released from a novel start point. We found that despite the absence of direction-specific firing in HD cells when inverted, rats could successfully navigate to the escape hole when released from one of two familiar locations by using a habit-associated directional strategy. In the continued absence of normal HD cell activity, inverted rats failed to find the escape hole when started from a novel release point. The results suggest that the HD signal is critical for accurate navigation in situations that require a flexible allocentric cognitive mapping strategy, but not for situations that utilize habit-like associative spatial learning.

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