It is well recognized that the HC directly projects to the PFC (Swanson 1981; Ferino et al. 1987; Thierry et al. 2000; Jay and Witter 1991; Hoover and Vertes 2007). The directionality of HC-to-PFC theta synchronization has been demonstrated by recording PFC neurons firing phase locked to delayed hippocampal theta oscillations (Siapas et al. 2005). Theta synchronization is thought to play a key role in early stages of the learning, as theta coherence between these two structures increases during working memory tasks (Benchenane et al. 2010; O'Neill et al. 2013; Anderson et al. 2010; Jones and Wilson 2005; Hyman et al. 2005). For example,Benchenane et al. (2010) demonstrated in rats that coherence in theta oscillations between the HC and PFC peaked at choice points in a Y maze, and coherence was significantly greater after learning a new rule (Benchenane et al. 2010). Anderson et al. (2010) recorded from the temporal cortex and PFC in epilepsy patients with implanted electrodes, and demonstrated increased theta coherence between HC and PFC during recall tasks that was predominately driven in the HC-to-PFC direction. In
