Properties of velocity-mechanosensitive neurons of the cat ventrobasal thalamic nucleus with special reference to the concept of convergence.

Neurons in the ventrobasal (VB) thalamic nucleus of lightly anesthetized cats were studied in order to analyze their discharge properties in response to controlled mechanical stimuli. Properties of the vast majority of the neuronal population largely resemble those of peripheral sensitive mechanoreceptors in their response to the velocity and, to a more limited extent, the amplitude component, of skin and hair displacement within restricted receptive fields. Detailed examination reveals some 'complex' characteristics suggestive of central integration in about 11% of VB neurons. Complex properties appear to indicate convergent input reflecting receptive field organization, the variety of velocity-related discharges and patterns of inhibition. The rarity of isolated 'surround' inhibition and the definition of what constitutes 'lemniscal' properties are discussed in the context of these and other related findings.