Bypassing the Saccadic Pulse Generator: Possible Control of Head Movement Trajectory by Rat Superior Colliculus
Tóm tắt
Saccades produced by electrical stimulation of the superior colliculus in primates are influenced primarily by the location of the stimulating electrode, with the suprathreshold intensity or frequency of the stimulating pulse train having little effect. Any given collicular site produces a characteristic movement of relatively fixed amplitude and velocity. In accordance with this finding, in models of the saccadic eye movement system the superior colliculus specifies the change of eye position: the velocity of movement components are determined by ‘pulse generators’ located between the superior colliculus and the oculomotor neurons. Previous findings in rodents, however, have suggested that eye and head movements induced by stimulation at some collicular sites may be critically dependent on stimulation parameters, implying that in these animals the superior colliculus has access to a non‐saccadic control system. To investigate this possibility, rats with electrodes implanted into the lateral intermediate layers were stimulated with pulse trains of varying frequency and duration, and the resultant head movements analysed from video tape. At seven of the nine sites studied, amplitude of the horizontal component of the head movement was linearly related to stimulating frequency for fixed‐duration trains, in some cases over a ten‐fold range. Subsequent variation of train duration showed that amplitude was affected not by frequency as such, but by the number of pulses in the train; frequency was related to the mean velocity of the movement. By appropriate setting of these parameters, independent control of head movement amplitude and velocity could be achieved. These results suggest that the rodent superior colliculus may be able to control head movement without recourse to a pulse generator, and thus influence the trajectory of the movement directly. If so, it may prove to be a useful preparation for testing theories of trajectory formation.
Từ khóa
Tài liệu tham khảo
Bean C. P., 1974, A theory of microstimulation of myelinated fibres, J. Physiol. (Lond.), 243, 514
Becker W., 1989, The Neurobiology of Saccadic Eye Movements, 13
Bizzi E., 1981, Handbook of Physiology: The Nervous System. Motor Control
Bizzi E., 1972, Central programming and peripheral feedback during eye‐head coordination in monkeys, Bibl. Ophthal., 82, 220
Carpenter R. H. S., 1988, Movements of the Eyes
Dean P., 1988, Progress in Brain Research, 27
Grantyn R., 1988, Neuroanatomy of the Oculomotor System, 273
Grossberg S., 1989, Neural Dynamics of Adaptive Sensory‐Motor Control
Guitton D., 1990, Gaze control in the cat: studies and modeling of the coupling between orienting eye and head movements in different behavioural tasks, J. Neurophysiol., 64, 509, 10.1152/jn.1990.64.2.509
Harting J. K., 1984, The Comparative Neurology of the Optic Tectum, 687
Keller E. L., 1974, Participation of medial pontine reticular formation in eye movement generation in monkey, J. Neurophysiol., 37, 316, 10.1152/jn.1974.37.2.316
King S. M., 1990, Collicular control of rat head movement: further evidence for position and velocity guided control mechanisms, Neurosci. Lett., 50
King S. M., 1990, Head movement control in rat: can the superior colliculus bypass the saccadic pulse generator, Eur. J. Neurosci., 164
May P. J., 1989, Laminar origins of the descending tectal pathways in macaque monkey, Soc. Neurosci. Abstr., 15, 99
Moschovakis A. K., 1988, Structure‐function relationships in the primate superior colliculus. I. Morphological classification of efferent neurons, J. Neurophysiol., 60, 232, 10.1152/jn.1988.60.1.232
Munoz D. P., 1987, Tecto‐reticulo‐spinal‐neurons have discharges coding the velocity profiles of eye and head orienting movements, Soc. Neurosci. Abstr., 13, 112
Munoz D. P., 1989, Fixation and orientation control by the tecto‐reticulo‐spinal system in the cat whose head is unrestrained, Rev. Neurol.(Paris), 145, 567
Robinson D. A., 1975, Basic Mechanisms of Ocular Motility and Their Clinical Implications, 337
Rohrer W. H., 1987, Saccade‐related burst cells in the superior colliculus: relationship of activity with saccadic velocity, Soc. Neurosci. Abstr., 13, 1092
Schiller P. H., 1972, Single‐unit recording and stimulation in superior colliculus of the alert rhesus monkey, J. Neurophysiol., 35, 915, 10.1152/jn.1972.35.6.915
Sparks D. L., 1989, The Neurobiology of Saccadic Eye Movements, 213
Tomlinson R. D., 1986, Combined eye‐head gaze shifts in the primate I. Metrics, J. Neurophysiol., 566, 1542, 10.1152/jn.1986.56.6.1542
Gisbergen J. A. M., 1989, The Neurobiology of Saccadic Eye Movements, 69