Neuronal synchrony is a key mechanism for defining relationships in the brain. Traditional methods of analyzing individual neurons have limitations in detecting internal coordination of responses. Multielectrode recordings reveal that neurons in the visual cortex synchronize their firing with high precision when activated by a single contour, but not when activated by different contours. This synchronization is associated with oscillatory activity in the gamma frequency range (30-50 Hz). Synchronization is not merely a result of stimulus timing but reflects context-dependent interactions within the cortical network. Two complementary strategies for binding distributed neuronal activity are binding by convergence and dynamic binding. Binding by convergence involves axonal convergence to a common target, while dynamic binding involves enhancing the saliency of responses relative to others. These strategies are implemented through different types of cortico-cortical connections. Temporal cues are also important for perceptual grouping. Studies show that spatially distributed contour elements are bound perceptually if they appear or change synchronously. Temporal resolution of this mechanism is high, with offsets of less than 10 ms still supporting perceptual grouping. The magnocellular pathway mediates temporal cues, while the parvocellular pathway mediates non-temporal cues. Neuronal transmission can achieve high temporal precision, as evidenced by the consistent firing patterns of neurons in the auditory and visual cortex. Synchronization of responses is crucial for enhancing the saliency of responses and facilitating binding. Synchronized responses are more effective in triggering postsynaptic spikes than asynchronous ones. Internal synchronization can serve as a signature of relatedness, similar to externally induced synchronization. It allows for the binding of distributed activity according to brain-set criteria and can be used in flexible, context-dependent processing. Internal synchronization is detectable through direct correlation analysis of simultaneously recorded neurons. Dynamic grouping is essential for resolving superposition problems in cortical processing. Coarse coding allows for efficient representation of features, but requires dynamic binding to disambiguate overlapping stimuli. Dynamic binding can be achieved through selective attention mechanisms, which enhance the discharge rate of neurons responding to relevant features. Synchronization and rate modulation can coexist and complement each other. Synchronization enhances discharge rates of target cells, while sustained rate codes provide stable representations. Both mechanisms are necessary for accurate processing of complex stimuli. Internal synchronization must meet several criteria to serve as a reliable signature of relatedness. It must be rapid, independent of discharge rate, precise, and related to specific perceptual or motor processes. Synaptic gain modifications allow for learning and the formation of stable assemblies of neurons. The precision of internal synchronization is comparable to externally induced synchronization, especially in an activated desynchronized state. This precision is crucial for accurate processing of temporal relationships in the brain.Neuronal synchrony is a key mechanism for defining relationships in the brain. Traditional methods of analyzing individual neurons have limitations in detecting internal coordination of responses. Multielectrode recordings reveal that neurons in the visual cortex synchronize their firing with high precision when activated by a single contour, but not when activated by different contours. This synchronization is associated with oscillatory activity in the gamma frequency range (30-50 Hz). Synchronization is not merely a result of stimulus timing but reflects context-dependent interactions within the cortical network. Two complementary strategies for binding distributed neuronal activity are binding by convergence and dynamic binding. Binding by convergence involves axonal convergence to a common target, while dynamic binding involves enhancing the saliency of responses relative to others. These strategies are implemented through different types of cortico-cortical connections. Temporal cues are also important for perceptual grouping. Studies show that spatially distributed contour elements are bound perceptually if they appear or change synchronously. Temporal resolution of this mechanism is high, with offsets of less than 10 ms still supporting perceptual grouping. The magnocellular pathway mediates temporal cues, while the parvocellular pathway mediates non-temporal cues. Neuronal transmission can achieve high temporal precision, as evidenced by the consistent firing patterns of neurons in the auditory and visual cortex. Synchronization of responses is crucial for enhancing the saliency of responses and facilitating binding. Synchronized responses are more effective in triggering postsynaptic spikes than asynchronous ones. Internal synchronization can serve as a signature of relatedness, similar to externally induced synchronization. It allows for the binding of distributed activity according to brain-set criteria and can be used in flexible, context-dependent processing. Internal synchronization is detectable through direct correlation analysis of simultaneously recorded neurons. Dynamic grouping is essential for resolving superposition problems in cortical processing. Coarse coding allows for efficient representation of features, but requires dynamic binding to disambiguate overlapping stimuli. Dynamic binding can be achieved through selective attention mechanisms, which enhance the discharge rate of neurons responding to relevant features. Synchronization and rate modulation can coexist and complement each other. Synchronization enhances discharge rates of target cells, while sustained rate codes provide stable representations. Both mechanisms are necessary for accurate processing of complex stimuli. Internal synchronization must meet several criteria to serve as a reliable signature of relatedness. It must be rapid, independent of discharge rate, precise, and related to specific perceptual or motor processes. Synaptic gain modifications allow for learning and the formation of stable assemblies of neurons. The precision of internal synchronization is comparable to externally induced synchronization, especially in an activated desynchronized state. This precision is crucial for accurate processing of temporal relationships in the brain.