Lesions on the Supra-Chiasmatic Nucleus disrupt which functions?

• A. Circadian rhythm and sense of time
• B. Memory and learning
• C. Motor coordination
• D. Language processing

Answer: (A)

The suprachiasmatic nucleus (SCN) serves as the brain’s master clock, coordinating 24-hour rhythms in wakefulness, sleep, body temperature, and hormone release by syncing peripheral clocks throughout the body. It receives light information from the retina and uses that cue to set the timing of these cycles, including melatonin production from the pineal gland. When the SCN is damaged, the regular circadian rhythms and the body's sense of time are disrupted, leading to irregular sleep–wake patterns and related physiological changes. The other functions—memory and learning, motor coordination, and language processing—rely on different brain regions (hippocampus and cortex for memory, cerebellum and motor pathways for movement, and language areas in the cortex for speech), so they aren’t directly controlled by the SCN.