How is saccadic movement managed in the brain?

Question

I haven't been able to find any decent articles on this specific topic. So I have three (hopefully quick) questions:

1. What part of the brain is actively controlling saccadic movement?
2. If this part were to be removed, does saccadic movement cease to exist and cause the person to go blind from not being able to look around?
3. Additionally, is there a disorder which eliminates saccadic movement in some way?

Answer 1

1. The superior colliculus can be regarded as the center of saccadic eye movement. It contains a topographically organized representation of the visual space in its upper layers, and saccade-related activity in its deeper layers (Van Gisbergen et al., 1987).
2. Ablation of the superior colliculus unilaterally eliminates saccades contralateral to the lesion, and hence bilateral ablation will likely eliminate all saccades (Schiller et al., 1987). However, the superior colliculi do not mediate conscious vision, but mediate eye movements. Blindness results after ablation of the primary visual cortex, and obviously after removal of the retinae, or the optic nerves. Also note that "not being able to look around" is not dependent only on saccadic eye movement, because head-scanning is still possible.
3. A number of conditions may affect saccades. For example, stroke in the brain stem affecting the superior colliculi or cranial nerves may slow saccades and lesions in the brain stem may abolish them completely (Ramat et al., 2007).

<sub>References
- Ramat et al., Brain (2007; 130: 10–35
- Schiller et al., J Neurophysiol (1987); 57(4): 1033-49
- Van Gisbergen et al., Neurosci (1987), 21(2): 541-55</sub>

Answer 2

I agree with much of AliceD's well-cited answer, but here are a few extras.

1. What part of the brain is actively controlling saccadic movement?

It is not clear how you would choose just one area of the brain, given that a whole network of cortical and sub-cortical areas are involved, and what you mean by "actively controlling". The superior colliculus is certainly a good candidate, but signals pass through the reticular formation of the brainstem to the eye muscles. In the cortex, the superior colliculus receives projections from the frontal eye fields and the parietal cortex, thought to involve guided attention. Munoz (2002, pdf) is a short review of this network.

2. If this part were to be removed, does saccadic movement cease to exist and cause the person to go blind from not being able to look around?
3. Additionally, is there a disorder which eliminates saccadic movement in some way?

It follows from the above that there are many lesions which would affect/remove saccades. As noted by AliceD, this does not mean the person will go blind. One interesting case reported a patient with eye paralyis (due to fibrosis of the ocular muscles) who made "head saccades" in order to scan the world in a similar way.

Gilchrist, I. D., Brown, V., & Findlay, J. M. (1997). Saccades without eye movements. Nature, 390(6656), 130-131.

Munoz, D. P. (2002). Commentary: saccadic eye movements: overview of neural circuitry. Progress in brain research, 140, 89-96.