Human episodic memory consists of bound, highly rich, multisensory experiences. The sensory cortices that process the sensory information that form part of these memories are distributed across the brain in specialised areas. The binding of the information processed by these sensory regions is likely facilitated by long-term potentiation. This mechanism relies on the precise timing of neural activity. Theta oscillations, a dominant, low-frequency neural oscillation in the hippocampus, is a candidate mechanism involved in facilitating the precise timing required for LTP to take place. Indeed, studies in animals have suggested as much. However, evidence for a causal role of theta oscillations in human associative memory formation is lacking. By modulating the luminance of movies and the amplitude of sounds in an associative memory task, we manipulated the degree of phase synchrony between the respective sensory cortices. We show that associative memory was improved if the stimuli were presented in-phase. Through the experiments presented in this thesis, we provide direct evidence of the causal role of theta oscillations in human memory: Human associative memory relies on the phase of a theta-frequency mechanism
