Answer:
Amygdala.
Explanation:
Amygdala is located in the the temporal lobe of the brain. These are the group of neurons almond in shape. They plays an important role in emotional and limbic system.
Julie boo her roommate Jan. Jan experience the fear. In this case the sensory input has been generated through the thalamus and reached directly to the amydala of the brain. The boo input is associated with the feeling and emotion of fear.
Thus, the answer is amygdala.