1. The responses of single cells to mechanical movements of individual whiskers have been recorded from the ventro-basal complex of the thalamus, in rats under urethane or barbiturate anaesthesia.2. With ramp-shaped displacements of a whisker above a critical velocity, the cells gave a short latency response of 1-5 impulses, while with sinusoidal movement (1-35 Hz) they usually responded with 1-2 impulses per cycle.3. The cells did not respond to maintained deflexions of a whisker. Small static displacements did not modify the response to a superimposed movement; larger static displacements reduced or abolished the response.4. Three-quarters of the cells were found to be particularly sensitive to movements in one quadrant (90° or less). For any one cell, there was no obvious relationship between the most sensitive direction and the position of the whisker on the face.5. The ramp amplitude appeared to have little effect on the response. However, increases in ramp velocity decreased the response latency and, in some cells, increased the number of impulses per ramp.6. Other studies have shown that most afferent nerve fibres from whiskers give slowly adapting responses and the possible modification of these thalamic responses, by anaesthesia, is discussed.
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