A novel stimulus system for applying tactile stimuli to the macrovibrissae in electrophysiological experiments.

The rat's vibrissae are a wonderful system for the study of sensory neural encoding in relation to behaviour because the vibrissae are easily identifiable and accessible for manipulation, allowing easy application of a variety of different types of deflections that mimic natural whisking. Here we report the development of a powerful and flexible method for precisely deflecting these vibrissae. Recordings from CNS neurons showed, in response to variations in the parameters of a trapezoid whisker deflection stimulus that mimics the basic unit of whisking, a variety of complex responses as well as complex interactions between different response components. The recordings also included a response that is reported to be found during active whisking (movement under muscle control) and not passive whisker movements and thus to differentiate active from passive whisker deflections. Thus, this system could well be used in anaesthetized animals to apply whisker deflections that well mimic natural active whisking in awake animals, thereby allowing highly detailed study of the neuronal responses and neuronal interactions found with natural whisking behaviour.