Which statement distinguishes M-type ganglion cells?

• A. They are small and highly color selective.
• B. They are large, fast, and sensitive to motion and low contrast.
• C. They project to the LGN only.
• D. They have high spatial resolution.

Answer: (B)

Magnocellular (M-type) ganglion cells are specialized for speed and dynamic changes in vision. They have large cell bodies and receptive fields, which support rapid signaling and broad sampling of the visual scene. Their responses are transient and fast, giving high temporal resolution that makes them particularly good at detecting motion and rapid luminance changes, including stimuli with low contrast. Because their strength is motion and timing rather than fine detail or color, they are not color selective—that role belongs to the parvocellular pathway. They also tend to have lower spatial resolution due to their large receptive fields, which contrasts with the high spatial detail provided by the parvocellular pathway. While M-type cells do project to the LGN (to the magnocellular layers) and contribute to early visual processing, the defining trait here is their large size, fast signaling, and sensitivity to motion and low-contrast changes.