The laboratory rat is generally not considered a model for study of the mammalian visual system. However, there are advantages to a simpler model which contains the basic elements seen in higher mammals, but lacking some complexities. Here we begin a series of studies of the rat visual thalamus, examining the presence of burst firing mode during spontaneous and visually elicited activity, properties well known to occur in higher species such as cat and primate. Data were obtained from the dLGN of halothane anaesthetised, gallamine paralysed, hooded rats. Eyes were protected with zero power contact lenses, without corrective lenses or ocular drugs. Single units were recorded using tungsten-in-glass microelectrodes with the aid of the Cortex software suite for collection and visual stimulation, and data analysed in Matlab using Matoff. Data was obtained from 20 cells. Thalamic "Bursts" are recognized as a series of spikes fired at short ISI ( 50-100ms). While one cell showed no burst firing, the remainder all exhibited some bursting, both during spontaneous activity (where this was present) and during visually elicited responses. Most bursts comprised only 2 spikes, but bursts of up to 5 spikes were also seen and were often found at the onset of the visual response. The results indicate that rat visual thalamus responds much like higher species and therefore remains a useful generic model of the mammalian visual system.

Supported: MECBFU2005-00502