Biomaterial Database

Behavior of neurons in the abducens nucleus of the alert cat--I. Motoneurons. 1986

J M Delgado-Garcia, and F del Pozo, and R Baker

The activity of 53 antidromically identified abducens motoneurons was analyzed in alert cats during spontaneous and vestibular induced eye movements. Conduction velocities ranged from 13 to 70 m/s and all motoneurons increased their discharge rates with successive eye positions in the abducting direction. Motoneurons were recruited from -19 degrees to +7 degrees. Within the oculomotor range frequency saturation was never observed for any cell. The slope of rate-position (k) relationships ranged from 2 to 17.7 spikes/s/deg (n = 40, mean 8.7 +/- 2.5). Regression analysis showed that the rate-position plots could be fit by straight lines but in most cases exponential curves produced slightly better statistical fits. Steeper slopes suggest that successively larger increases in k are required for the lateral rectus muscle to maintain more eccentric fixations in the on direction. Interspike intervals for a constant eye position exhibited low variability (less than 3.5%) for fixations shorter than 1 s. Over longer periods, variability increased in proportion to the duration of the fixation in exponential-like fashion up to 14%. Abducens motoneurons showed considerable variability in frequency during repeated fixations of the same eye position. Discharge rates were found to depend upon both the direction of the previous eye movement and, more importantly, the animal's level of alertness. The rate-position regression lines for fixation periods after saccades in the on direction significantly differed in slopes (100%) and thresholds (20%) from those in the off direction. The observed static hysteresis in abducens motoneuron behavior was in opposite direction to that previously described for the mechanical properties of the lateral rectus. This suggests both neural and mechanical factors are significantly involved in determining final eye position. The animal's level of alertness was evaluated in this study by counting the number of saccadic movements/s occurring in "alert" (1 +/- 0.2 saccades/s), and "drowsy" (0.5 +/- 0.2 saccades/s) circumstances. Comparison of the rate-position regression lines between the two conditions showed a significant decrease in slopes (100%) and elevation of thresholds (70%). Discharge rate of abducens motoneurons increased abruptly 8.9 +/- 2.8 ms prior to saccades in the horizontal on direction, and decreased 14.8 +/- 4.05 m before saccades in the off direction. During purely vertical saccades the firing frequency of abducens motoneurons did not change. Burst frequency did not saturate during saccades, but increased with saccadic velocity in a linear fashion.(ABSTRACT TRUNCATED AT 400 WORDS)

UI	MeSH Term	Description	Entries
D009046	Motor Neurons	Neurons which activate MUSCLE CELLS.	Neurons, Motor,Alpha Motorneurons,Motoneurons,Motor Neurons, Alpha,Neurons, Alpha Motor,Alpha Motor Neuron,Alpha Motor Neurons,Alpha Motorneuron,Motoneuron,Motor Neuron,Motor Neuron, Alpha,Motorneuron, Alpha,Motorneurons, Alpha,Neuron, Alpha Motor,Neuron, Motor
D009431	Neural Conduction	The propagation of the NERVE IMPULSE along the nerve away from the site of an excitation stimulus.	Nerve Conduction,Conduction, Nerve,Conduction, Neural,Conductions, Nerve,Conductions, Neural,Nerve Conductions,Neural Conductions
D011930	Reaction Time	The time from the onset of a stimulus until a response is observed.	Response Latency,Response Speed,Response Time,Latency, Response,Reaction Times,Response Latencies,Response Times,Speed, Response,Speeds, Response
D012044	Regression Analysis	Procedures for finding the mathematical function which best describes the relationship between a dependent variable and one or more independent variables. In linear regression (see LINEAR MODELS) the relationship is constrained to be a straight line and LEAST-SQUARES ANALYSIS is used to determine the best fit. In logistic regression (see LOGISTIC MODELS) the dependent variable is qualitative rather than continuously variable and LIKELIHOOD FUNCTIONS are used to find the best relationship. In multiple regression, the dependent variable is considered to depend on more than a single independent variable.	Regression Diagnostics,Statistical Regression,Analysis, Regression,Analyses, Regression,Diagnostics, Regression,Regression Analyses,Regression, Statistical,Regressions, Statistical,Statistical Regressions
D002415	Cats	The domestic cat, Felis catus, of the carnivore family FELIDAE, comprising over 30 different breeds. The domestic cat is descended primarily from the wild cat of Africa and extreme southwestern Asia. Though probably present in towns in Palestine as long ago as 7000 years, actual domestication occurred in Egypt about 4000 years ago. (From Walker's Mammals of the World, 6th ed, p801)	Felis catus,Felis domesticus,Domestic Cats,Felis domestica,Felis sylvestris catus,Cat,Cat, Domestic,Cats, Domestic,Domestic Cat
D004558	Electric Stimulation	Use of electric potential or currents to elicit biological responses.	Stimulation, Electric,Electrical Stimulation,Electric Stimulations,Electrical Stimulations,Stimulation, Electrical,Stimulations, Electric,Stimulations, Electrical
D005071	Evoked Potentials	Electrical responses recorded from nerve, muscle, SENSORY RECEPTOR, or area of the CENTRAL NERVOUS SYSTEM following stimulation. They range from less than a microvolt to several microvolts. The evoked potential can be auditory (EVOKED POTENTIALS, AUDITORY), somatosensory (EVOKED POTENTIALS, SOMATOSENSORY), visual (EVOKED POTENTIALS, VISUAL), or motor (EVOKED POTENTIALS, MOTOR), or other modalities that have been reported.	Event Related Potential,Event-Related Potentials,Evoked Potential,N100 Evoked Potential,P50 Evoked Potential,N1 Wave,N100 Evoked Potentials,N2 Wave,N200 Evoked Potentials,N3 Wave,N300 Evoked Potentials,N4 Wave,N400 Evoked Potentials,P2 Wave,P200 Evoked Potentials,P50 Evoked Potentials,P50 Wave,P600 Evoked Potentials,Potentials, Event-Related,Event Related Potentials,Event-Related Potential,Evoked Potential, N100,Evoked Potential, N200,Evoked Potential, N300,Evoked Potential, N400,Evoked Potential, P200,Evoked Potential, P50,Evoked Potential, P600,Evoked Potentials, N100,Evoked Potentials, N200,Evoked Potentials, N300,Evoked Potentials, N400,Evoked Potentials, P200,Evoked Potentials, P50,Evoked Potentials, P600,N1 Waves,N2 Waves,N200 Evoked Potential,N3 Waves,N300 Evoked Potential,N4 Waves,N400 Evoked Potential,P2 Waves,P200 Evoked Potential,P50 Waves,P600 Evoked Potential,Potential, Event Related,Potential, Event-Related,Potential, Evoked,Potentials, Event Related,Potentials, Evoked,Potentials, N400 Evoked,Related Potential, Event,Related Potentials, Event,Wave, N1,Wave, N2,Wave, N3,Wave, N4,Wave, P2,Wave, P50,Waves, N1,Waves, N2,Waves, N3,Waves, N4,Waves, P2,Waves, P50
D000010	Abducens Nerve	The 6th cranial nerve which originates in the ABDUCENS NUCLEUS of the PONS and sends motor fibers to the lateral rectus muscles of the EYE. Damage to the nerve or its nucleus disrupts horizontal eye movement control.	Cranial Nerve VI,Sixth Cranial Nerve,Abducent Nerve,Nerve VI,Nervus Abducens,Abducen, Nervus,Abducens, Nervus,Abducent Nerves,Cranial Nerve VIs,Cranial Nerve, Sixth,Nerve VI, Cranial,Nerve VIs,Nerve VIs, Cranial,Nerve, Abducens,Nerve, Abducent,Nerve, Sixth Cranial,Nerves, Sixth Cranial,Nervus Abducen,Sixth Cranial Nerves
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D012399	Rotation	Motion of an object in which either one or more points on a line are fixed. It is also the motion of a particle about a fixed point. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)	Clinorotation,Clinorotations,Rotations