Intracellular studies of the convergence of sensory input on caudate neurons of cat.

Quantitative analyses of the intracellular responses to peripheral stimuli were made in a 172 neurons recorded in the head of the caudate nucleus (Cd) of cat. Responsiveness of Cd neurons was tested using auditory and somatosensory stimuli which were presented unilaterally. We found that most cells (99%) responded to both auditory and somatosensory stimuli. Excitation followed by inhibition (i.e. E-I response) was the primary pattern of intracellular response occurring approximately 75% of the time. Qualitative and quantitative analyses revealed marked similarities in the amplitudes and time courses of the intracellular responses following supramaximal stimulation of the peripheral stimuli studied. Similarly, analyses of 40 pairs of simultaneously recorded neurons revealed a marked homogeneity in the intracellular responses to the same stimulus even though the recordings were made several mm apart. The most striking feature of the simultaneous recordings was that the peaks of the initial E-I response and the afterpotentials often occurred in register after a peripheral stimulus. Furthermore, changes in the responses of pairs of simultaneously recorded neurons co-varied. Because the striatum typically demonstrates spontaneous rhythmic activity, these data suggest that a peripheral stimulus has the potential of briefly synchronizing Cd's neuronal activity.