For example, those that had learned the maze six weeks after the injection had three times as much "activity" in their stained cells as those mice that learned the maze eight weeks after injection, when the stained cells were fully mature. Cells examined at less than six weeks’ old at the time of learning did not show as much activity as at six weeks, however. According to Frankland, this suggests that when neurons reach six weeks of age they are specifically recruited to form the brain networks that support new memories. According to Fankland, the example shows that neurons in mice’s brains are specially recmited When
A. they are six weeks old. B. they are eight weeks old. C. they are between six and eight weeks old. D. they are less than six weeks ol