Which structure is the horizontal gaze center?

Which structure is the horizontal gaze center?

• A. Frontal eye fields
• B. Paramedian pontine reticular formation
• C. Superior colliculus
• D. Medial longitudinal fasciculus

Answer: (B)

Horizontal gaze is controlled by a brainstem center in the pons that directly commands the eyes to move together side to side. This center is the paramedian pontine reticular formation, which drives the abducens motor neurons to move the ipsilateral eye and, through connections in the medial longitudinal fasciculus, coordinates the contralateral oculomotor nucleus to move the other eye in the same direction. In other words, the PPRF acts as the horizontal gaze center, generating the saccadic command and linking the two eyes for a coordinated horizontal shift. Frontal eye fields contribute to voluntary horizontal saccades by signaling the contralateral PPRF, but they are not the horizontal gaze center themselves. The superior colliculus participates in saccade planning and also feeds into the PPRF, aiding initiation. The medial longitudinal fasciculus is the tract that conveys signals between the abducens and oculomotor nuclei to keep gaze conjugate; it’s essential for coordination but is not the center that generates horizontal gaze.

Horizontal gaze is controlled by a brainstem center in the pons that directly commands the eyes to move together side to side. This center is the paramedian pontine reticular formation, which drives the abducens motor neurons to move the ipsilateral eye and, through connections in the medial longitudinal fasciculus, coordinates the contralateral oculomotor nucleus to move the other eye in the same direction. In other words, the PPRF acts as the horizontal gaze center, generating the saccadic command and linking the two eyes for a coordinated horizontal shift.

Frontal eye fields contribute to voluntary horizontal saccades by signaling the contralateral PPRF, but they are not the horizontal gaze center themselves. The superior colliculus participates in saccade planning and also feeds into the PPRF, aiding initiation. The medial longitudinal fasciculus is the tract that conveys signals between the abducens and oculomotor nuclei to keep gaze conjugate; it’s essential for coordination but is not the center that generates horizontal gaze.