The interaction between emotion and memory is a central issue in cognitive neuroscience (for a review, see LaBar & Cabeza, 2006). Emotion often has an enhancing effect on episodic memory; in general, emotional events tend to be remembered better than neutral events. According to McGaugh's modulation hypothesis, the memory-enhancing effect of emotion reflects the influence of the amygdala (i.e., an emotion region) on the MTL memory system (i.e., a memory region). Additionally, the emotion effect may be mediated by changes in cognitive processes such as semantic processing and working memory. We have investigated the enhancing effect of emotion during both phases of episodic memory: (a) encoding and (b) retrieval.

• Dolcos, F., LaBar, K. S., & Cabeza, R. (2006). The memory-enhancing effect of emotion: Functional neuroimaging evidence. In B. Uttl, N. Ohta, & A. L. Siegenthaler (Eds.), Memory and emotion: Interdisciplinary perspectives (pp. 107-134). Malden, MA: Blackwell Publishing.
• LaBar, K. S., & Cabeza, R. (2006). Cognitive neuroscience of emotional memory. Nature Reviews Neuroscience, 7, 54-64.

Encoding

In an event-related potentials (ERP) study, we found that remembered pictures were associated with a positive-going ERP effect, which occurred earlier for emotional than for neutral pictures (Dolcos & Cabeza, 2002). This finding suggests that emotional information has privileged access to processing resources, possibly leading to better memory formation. In a subsequent fMRI study of encoding, we found that remembered emotional pictures (both pleasant and unpleasant) were associated with greater activity in the amygdala and the MTL memory system (Dolcos et al., 2004a). Activity in these two regions was significantly correlated when participants were encoding emotional pictures but not when they were encoding neutral pictures. These results provide direct support for the modulation hypothesis. Additionally, we also found greater encoding activity for emotional than neutral pictures in left ventrolateral and dorsolateral PFC regions (Dolcos et al., 2004b), which are regions associated with semantic processing and working memory. Thus, the beneficial effect of emotion on memory seems to involve direct influences of the amygdala on the MTL memory system as well as indirect influences of emotion on PFC-mediated cognitive operations.

• Dolcos, F., LaBar, K. S., & Cabeza, R. (2004a). Interaction between the amygdala and the medial temporal lobe memory system predicts better memory for emotional events. Neuron, 42, 855-863. (Must Read label in Faculty of 1000)
  
• Dolcos, F., LaBar, K. S., & Cabeza, R. (2004b). Dissociable effects of arousal and valence on prefrontal activity indexing emotional evaluation and subsequent memory: An event-related fMRI study. Neuroimage, 23, 64-74.
• Dolcos, F., Graham, R., LaBar, K. S., & Cabeza, R. (2003). Coactivation of the amygdala and the hippocampus predicts better recall for emotional than for neutral pictures. Brain and Cognition, 51, 221-223.
• Dolcos, F., & Cabeza, R. (2002). Event-related potentials of emotional memory: Encoding pleasant, unpleasant, and neutral pictures. Cognitive, Affective, and Behavioral Neuroscience, 2, 252-263.

Retrieval

Emotion may enhance memory not only during encoding, but also during retrieval. Previous functional neuroimaging studies of emotional retrieval used brief study-test delays, thereby confounding activity during retrieval with consolidation processes. To address this issue, we scanned participants one year after they originally encoded emotional and neutral pictures (Dolcos et al., 2005). Additionally, we used a paradigm that distinguished between recollection-based and familiarity-based recognition responses. Consistent with prior behavioral evidence, we found that the enhancing effect of emotion during retrieval occurred for recollection but not for familiarity. As in the case of encoding, amygdala and MTL activity and interactions were greater for emotional than for neutral stimuli. Moreover, in the amygdala and the hippocampus these effects were greater for recollection-based than for familiarity-based responses. This result suggests a synergistic mechanism whereby emotion enhances memory and memory enhances emotion. This idea has implications for understanding post-traumatic stress disorder (PTSD).

• Dolcos, F., LaBar, K. S., & Cabeza, R. (2005). Remembering one year later: Role of the amygdala and medial temporal lobe memory system in retrieving emotional memories. Proceedings of the National Academy of Sciences, USA, 102, 2626-2631.