Synchronization of local neural networks in the somatosensory cortex: A comparison of stationary and moving stimuli

Spontaneous and stimulus-induced responses were recorded from neighboring g roups of neurons by an array of electrodes in the primary (SI) somatosensor y cortex of intact, halothane-anesthetized cats. Cross-correlation analysis was used to characterize the coordination of spontaneous activity and the responses to peripheral stimulation with moving or stationary air jets. Alt hough synchronization was detected in only 10% (88 of 880) of the pairs of single neurons that were recorded, cross-correlation analysis of multiunit responses revealed significant levels of synchronization in 64% of the 123 recorded electrode pairs. Compared with spontaneous activity, both stationa ry and moving air jets caused substantial increases in the rate, proportion , and temporal precision of synchronized activity in local regions of SI co rtex. Among populations of neurons that were synchronized by both types of air-jet stimulation, the mean rate of synchronized activity was significant ly higher during moving air-jet stimulation than during stationary air-jet stimulation. Moving air jets also produced significantly higher correlation coefficients than stationary air jets in the raw cross-correlograms (CCGs) but not in the shift-corrected CCGs. The incidence and rate of stimulus-in duced synchronization varied with the distance separating the recording sit es. For sites separated by less than or equal to 300 mu m, 80% of the multi unit responses displayed significant levels of synchronization during both types of air-jet stimulation. For sites separated by less than or equal to 500 mu m, only 37% of the multiunit responses were synchronized by discrete stimulation with a single air jet. Measurements of the multiunit CCG peak half-widths showed that the correlated activity produced by moving air jets had slightly less temporal variability than that produced by stationary ai r jets. These results indicate that moving stimuli produce greater levels o f synchronization than stationary stimuli among local groups of SI neurons and suggest that neuronal synchronization may supplement the changes in fir ing rate which code intensity and other attributes of a cutaneous stimulus.