The hippocampus is thought to generate and maintain a place code - based on sensory cues and self-motion signals - while mammals move through an environment. A new study reports, however, that mice exhibited considerable degradation of their hippocampal place code when the animals discontinued their involvement in a virtual navigation task, despite there being no change in their environment, suggesting that the internal state of the animal has a major influence on spatial maps.The authors used calcium imaging to measure the activity of place cells - pyramidal neurons that selectively fire when animals reach certain positions in an environment - in the CA1 hippocampal region of mice while the animals performed a goal-directed navigation task.
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