Neurones in cat gracile nucleus with both local and widefield inputs.

1. Forty-three neurones were isolated in the cat gracile nucleus that could be driven by electrical stimulation of the ipsilateral forefoot or the contralateral hind food as well as having a normal low threshold localized receptive field on the ipsilateral hind limb. 2. Twenty-five (58%) of the cells were found to have axons projecting to the contralateral ventrobasal thalamus. 3. Most of the cells could only be driven from the 'widefield' receptive field on the forefoot or contralateral hindfoot by percutaneous electrical stimulation. 4. These results are discussed in the context of a model of the gracile nucleus in whick these occasional 'widefield' connexions are considered to be errors in connectivity which are not normally effective due to the patterns of excitation and inhibition in the normally functioning nucleus. 5. In this model, electrical stimulation is an abnormal type of stimulation that can drive cells through these erroneous connexions.