Coordination of eye and head components of movements evoked by stimulation of the paramedian pontine reticular formation
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Constant frequency microstimulation of the paramedian pontine reticular formation (PPRF) in head-restrained monkeys evokes a constant velocity eye movement. Since the PPRF receives significant projections from structures that control coordinated eye-head movements, we asked whether stimulation of the pontine reticular formation in the head-unrestrained animal generates a combined eye-head movement or only an eye movement. Microstimulation of most sites yielded a constant-velocity gaze shift executed as a coordinated eye-head movement, although eye-only movements were evoked from some sites. The eye and head contributions to the stimulation-evoked movements varied across stimulation sites and were drastically different from the lawful relationship observed for visually-guided gaze shifts. These results indicate that the microstimulation activated elements that issued movement commands to the extraocular and, for most sites, neck motoneurons. In addition, the stimulation-evoked changes in gaze were similar in the head-restrained and head-unrestrained conditions despite the assortment of eye and head contributions, suggesting that the vestibulo-ocular reflex (VOR) gain must be near unity during the coordinated eye-head movements evoked by stimulation of the PPRF. These findings contrast the attenuation of VOR gain associated with visually-guided gaze shifts and suggest that the vestibulo-ocular pathway processes volitional and PPRF stimulation-evoked gaze shifts differently.
KeywordsGaze shifts PPRF Saccade Superior colliculus Head movements Spinal cord
We thank Dennis Murray for surgical assistance and animal care, and Kathy Pearson for software development. The study was funded by NIH grants EY001189, EY007001, EY007009 and EY015485.
- Gandhi NJ, Sparks DL (2000) Microstimulation of the pontine reticular formation in monkey: effects on coordinated eye-head movements. Soc Neurosci Abstr 109.8Google Scholar
- Grantyn A, Berthoz A (1988) The role of the tectoreticulospinal system in the control of head movement. In: Peterson BW, Richmond FJ (eds) Control of head movement. Oxford University Press, New York, pp 224–244Google Scholar
- Grantyn A, Ong-Meang Jacques V, Berthoz A (1987) Reticulo-spinal neurons participating in the control of synergic eye and head movements during orienting in the cat. II. Morphological properties as revealed by intra-axonal injections of horseradish peroxidase. Exp Brain Res 66:355–377PubMedGoogle Scholar
- Leigh RJ, Zee DS (1999) The neurology of eye movements. Oxford University Press, New YorkGoogle Scholar
- Phillips JO, Ling L, Fuchs AF (2001) A comparison of excitatory and inhibitory burst neuron activity during active head-unrestrained gaze shifts. Soc Neurosci Abstr 405.10Google Scholar
- Sklavos SG, Gandhi NJ, Sparks DL, Porrill J, Dean P (2002) Mechanics of oculomotor plant estimated from effects of abducens microstimulation. Soc Neurosci Abstr 463.5Google Scholar
- Zar JH (1999) Biostatistical analysis. Prentice-Hall, Upper Saddle River, NJGoogle Scholar