Relation between oscillatory activity and long-range synchronization in cat visual cortex.

Recent theoretical studies have suggested that oscillatory firing patterns with frequencies in the gamma band (30-70 Hz) may be instrumental for the establishment of synchrony among widely distributed neurons if synchrony is to be achieved by reciprocal connections. We have now investigated the relationship between synchrony and oscillations in cat visual cortex. Our results show that when synchronization of neuronal activity occurs over distances of > 2 mm in primary visual cortex, or occurs between the two hemispheres, it is almost always associated with oscillatory firing patterns, whereas synchronization over short distances occurs also in the absence of oscillations. Furthermore, our results indicate that short-range interactions affect both the firing rate of the respective neurons and the timing of their discharges, whereas only the latter is influenced by long-range interactions. These data support the hypothesis that oscillatory activity can contribute to the establishment of long-range synchrony in a network of reciprocally coupled neurons.