Oculomotor function at low temperature: antarctic versus temperate fish.
The peripheral oculomotor system can be modelled as a first order linear system (Montgomery, 1983), and hence specified by its characteristic frequency and 'd.c.' gain. These parameters can be determined by recording eye movements produced by stimulation of the abducens nerve with sinusoidally modulated pulse trains, and compare well with those independently derived from the relationship between motoneurone firing and spontaneous eye movement. Characteristic frequency and gain of the peripheral oculomotor system were determined for two species of antarctic teleost and one temperate species, to examine temperature compensation within a complete motor output pathway. Compared with low temperature function in temperate fish, the characteristic frequency is clearly temperature compensated in antarctic fish, which explains in part the observed temperature compensation of their rapid eye movement. The 'd.c.' gain of the peripheral oculomotor system is inversely related to temperature, providing an automatic compensation for possible reductions in central nervous system output and sensory gain at low temperature.
D000818:Animals; D000864:Antarctic Regions; D002980:Climate; D003081:Cold Climate; D005399:Fishes / Q000502:physiology*; D008954:Models, Biological; D009801:Oculomotor Muscles / Q000502:physiology*; D009802:Oculomotor Nerve / Q000502:physiology*; D013045:Species Specificity; D013696:Temperature