Damage to the right frontal eye fields will most likely cause a defect of saccades in which direction?

• A. Right saccade defect
• B. Left saccade defect
• C. Upward saccade defect
• D. Downward saccade defect

Answer: (B)

Frontal eye fields control voluntary horizontal saccades to the opposite side. A lesion in the right frontal eye fields disrupts generation of leftward (contralateral) saccades because the right FEF normally drives saccades toward the left via the horizontal gaze pathway to the contralateral brainstem (PPRF). So you would expect a left saccade defect. Vertical saccades are governed mainly by midbrain vertical gaze centers (riMLF), not the frontal eye fields, so a right FEF lesion doesn’t primarily produce vertical saccade deficits. Clinically, you may also see eyes biased toward the side of the lesion at rest, with slowed or absent leftward saccades on testing.