Rapid feature selective neuronal synchronization through correlated latency shifting

Spontaneous brain activity could affect processing if it were structured,. We show that neuron pairs in cat primary visual cortex exhibited correlated fluctuations in response latency, particularly when they had overlapping r eceptive fields or similar orientation preferences. Correlations occurred w ithin and across hemispheres, but only when local field potentials (LFPs) o scillated in the gamma-frequency range (40-70 Hz). In this range, LFP fluct uations preceding response onset predicted response latencies; negative (po sitive) LFPs were associated with early (late) responses. Oscillations belo w 10 Hz caused covariations in response amplitude, but exhibited no columna r selectivity or coordinating effect on latencies. Thus, during high gamma activity, spontaneous activity exhibits distinct, column-specific correlati on patterns. Consequently, cortical cells undergo coherent fluctuations in excitability that enhance temporal coherence of responses to contours that are spatially contiguous or have similar orientation. Because synchronized responses are more likely than dispersed responses to undergo rapid and joi nt processing, spontaneous activity may be important in early visual proces ses.