Electrophysiological correlates of remembering emotional pictures.

Extensive evidence shows that emotional events tend to be remembered in greater detail and with an enhanced sense of vividness compared to neutral events. The current study investigated the neural correlates of this phenomenon during retrieval using the event-related potentials technique (ERP). Participants were asked to perform a memory recognition test of previously studied ("Old") and unstudied ("New") emotional and neutral pictures encoded a week before the test session. Next, they were asked to perform a Remember-Know task (Gardiner and Java, 1993) for each "old" decision. ERPs were created for retrieval activity corresponding to six conditions: Remember-Emotional, Remember-Neutral, Know-Emotional, Know-Neutral, New-Emotional and New-Neutral. Results showed that negative emotion enhanced three distinct subtypes of the electrophysiological old-new effect specifically for old items associated with a "Remember" judgment. This effect was observed for ERP old-new effects conforming to an early frontal P2 old-new effect peaking at ~180 ms, a midfrontal old-new effect starting at ~300 ms (the "FN400") and a late positive complex (LPC) with parietal maxima observed at 500-700 ms. In addition, a breakdown of our data in different levels of emotional arousal revealed that the relationship between ERP correlates of retrieval and arousal conformed to a nonlinear, inverted U-shaped function for posterior late effects (500-700) and to a linear function for early effects (P2 and FN400). Taken together, these results suggest that multiple retrieval subprocesses contribute to the emotional enhancement of recollective experience.

The effects of a distracting N-back task on recognition memory are reduced by negative emotional intensity.

Memory performance is usually impaired when participants have to encode information while performing a concurrent task. Recent studies using recall tasks have found that emotional items are more resistant to such cognitive depletion effects than non-emotional items. However, when recognition tasks are used, the same effect is more elusive as recent recognition studies have obtained contradictory results. In two experiments, we provide evidence that negative emotional content can reliably reduce the effects of cognitive depletion on recognition memory only if stimuli with high levels of emotional intensity are used. In particular, we found that recognition performance for realistic pictures was impaired by a secondary 3-back working memory task during encoding if stimuli were emotionally neutral or had moderate levels of negative emotionality. In contrast, when negative pictures with high levels of emotional intensity were used, the detrimental effects of the secondary task were significantly attenuated.

Visual attention and emotional memory: recall of aversive pictures is partially mediated by concurrent task performance.

The emotional enhancement of memory is often thought to be determined by attention. However, recent evidence using divided attention paradigms suggests that attention does not play a significant role in the formation of memories for aversive pictures. We report a study that investigated this question using a paradigm in which participants had to encode lists of randomly intermixed negative and neutral pictures under conditions of full attention and divided attention followed by a free recall test. Attention was divided by a highly demanding concurrent task tapping visual processing resources. Results showed that the advantage in recall for aversive pictures was still present in the DA condition. However, mediation analyses also revealed that concurrent task performance significantly mediated the emotional enhancement of memory under divided attention. This finding suggests that visual attentional processes play a significant role in the formation of emotional memories.

The effects of emotional intensity on ERP correlates of recognition memory.

The effects of negative emotional intensity on memory-related brain activity were tested by using human scalp event-related potentials (ERP). A neural index of memory function--the electrophysiological 'Old-New' effect--was obtained from participants undertaking a memory recognition test of previously studied ('old') and unstudied ('new') pictures of variable levels of negative emotional intensity. The magnitude of the old-new effect was compared across four different levels of linearly increasing stimulus emotional intensity. Results revealed an inverted-U-shaped effect of emotional intensity on the magnitude of ERP old-new differences starting at 300 ms after stimulus onset. These results suggest that moderate negative emotions can enhance memory brain function, whereas extreme levels of emotional intensity have the potential of inhibiting memory function. Results are discussed in terms of their implications for neurobiological and psychological models of emotion-memory interactions.