Coupling of prefrontal gamma amplitude and theta phase is strengthened in trace eyeblink conditioning

► Cortical LFPs were recorded during acquisition in rat trace eyeblink conditioning. ► Lateral entorhinal, medial prefrontal cortices, and hippocampus were investigated. ► CS initiated locking of gamma power to concurrent theta phase in all three regions. ► With conditioning theta-gamma coupling became stronger only in prefrontal cortex. ► This suggests a better grouping of prefrontal neuronal firings with learning.