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The paramedian pontine reticular formation, or PPRF, is a brain region, without clearly defined borders, in the center of the pons. It is involved in the coordination of eye movements, particularly saccades.

Contents 1 Inputs, outputs, functions 2 Lesions 3 See also 4 References 5 External links

[edit] Inputs, outputs, functions

The PPRF is located anterior and lateral to the medial longitudinal fasciculus (MLF). It receives input from the superior colliculus via the predorsal bundle and from the frontal eye fields via frontopontine fibers. The rostral PPRF probably coordinates horizontal saccades; the caudal PPRF may be the generator of both horizontal and vertical saccades. In particular, activity of the excitatory burst neurons (EBNs) in the PPRF generates the "pulse" movement that initiates a saccade. In the case of horizontal saccades the "pulse" information is conveyed via axonal fibers to the abducens nucleus, initiating lateral eye movements. The angular velocity of the eye during horizontal saccade ranges from 100 to 700 degrees per second. Larger saccades have faster pulses; the PPRF is involved in this determination.^[1]

[edit] Lesions

Unilateral lesions of the PPRF produce characteristic findings:^[2]

• Loss of horizontal saccades directed towards the side of the lesion, no matter the current position of gaze
• Contralateral gaze deviation (acute lesions, such as early stroke, only)
• Gaze-evoked lateral nystagmus on looking away from the side of the lesion
• Bilateral lesions produce horizontal gaze palsy and slowing of vertical saccades

[edit] See also

• Ophthalmoparesis
• Internuclear ophthalmoplegia
• One and a half syndrome
• Multiple sclerosis
• Stroke

[edit] References

1. ^  Brazis, P.W., Masdeu, J.C., and Biller, J. Localization in Clinical Neurology, 4th edition. Lippincott, Williams, and Wilkins, Philadelphia, 2001; pp. 213-216. ISBN 0-7817-2843-6
2. ^  Adapted from Leigh, R.J., and Zee, D.S. The Neurology of Eye Movements, 3rd edition. Oxford University Press, Oxford, England, 1999; p. 499. ISBN 0-19-512-972-5

[edit] External links

• BrainInfo at the University of Washington ancil-479

v·d·e Brain: rhombencephalon (hindbrain)
Myelencephalon/medulla	anterior/ventral: Arcuate nucleus of medulla • Pyramid (Decussation) • Olivary body • Inferior olivary nucleus • Anterior median fissure • Ventral respiratory group posterior/dorsal: VII,IX,X: Solitary/tract • XII, X: Dorsal • IX,X,XI: Ambiguus • IX: Inferior salivatory nucleus • Gracile nucleus/Cuneate nucleus/Accessory cuneate nucleus • Area postrema • Posterior median sulcus • Dorsal respiratory group raphe/reticular: Sensory decussation • Reticular formation (Gigantocellular nucleus, Parvocellular reticular nucleus, Ventral reticular nucleus, Lateral reticular nucleus, Paramedian reticular nucleus) • Raphe nuclei (Obscurus, Magnus, Pallidus) tracts: Corticospinal tract (Lateral, Anterior) • Inferior cerebellar peduncle • Olivocerebellar tract • Spinocerebellar (Dorsal, Ventral) • Spinothalamic tract • PCML (Posterior external arcuate fibers, Internal arcuate fibers, Medial lemniscus) • Extrapyramidal (Rubrospinal tract, Vestibulospinal tract, Tectospinal tract)
Metencephalon/pons	anterior/ventral: Superior olivary nucleus • Basis pontis (Pontine nuclei, Middle cerebellar peduncles) posterior/dorsal: Pontine tegmentum (Trapezoid body, Superior medullary velum, Locus ceruleus, MLF, Vestibulocerebellar tract, V Principal Spinal & Motor, VI, VII, VII: Superior salivary nucleus) • VIII-c (Dorsal, Anterior)/VIII-v (Lateral, Superior, Medial, Inferior) raphe/reticular: Reticular formation (Caudal pontine reticular nucleus, Oral pontine reticular nucleus, Tegmental pontine reticular nucleus, Paramedian pontine reticular formation) • Median raphe nucleus Apneustic center • Pneumotaxic center
Metencephalon/cerebellum	Vermis • Flocculus • Arbor vitae • Cerebellar tonsil • Inferior medullary velum Molecular layer (Stellate cell, Basket cell, Parallel fiber) • Purkinje cell layer (Purkinje cell) • Granule cell layer (Golgi cell) • Mossy fibers • Climbing fiber Deep cerebellar nuclei (Dentate, Emboliform, Globose, Fastigial)
Fourth ventricle	apertures (Median, Lateral) • Rhomboid fossa (Vagal trigone, Hypoglossal trigone, Obex, Sulcus limitans, Facial colliculus, Medial eminence) • Lateral recess

This page uses content from the English-language version of Wikipedia. The original article was at Paramedian pontine reticular formation. The list of authors can be seen in the page history. As with Psychology Wiki, the text of Wikipedia is available under the GNU Free Documentation License.