A 16-year-old boy suffers a concussion during an ice hockey game and is rushed to the emergency room. A CT scan of the brain reveals a cerebral contusion of the left frontal lobe. The boy lies comatose for 3 days but eventually regains consciousness. Which of the following cells is the principal mediator of scar formation in the central nervous system of this patient?
Fibroblasts Glial cells Neurons Oligodendrocytes