Two routes to emotional memory: distinct neural processes for valence and arousal

Abstract

Prior investigations have demonstrated that emotional information is often better remembered than neutral information, but they have not directly contrasted effects attributable to valence and those attributable to arousal. By using functional MRI and behavioral studies, we found that distinct cognitive and neural processes contribute to emotional memory enhancement for arousing information versus valenced, nonarousing information. The former depended on an amygdalar-hippocampal network, whereas the latter was supported by a prefrontal cortex-hippocampal network implicated in controlled encoding processes. A behavioral companion study, with a divided-attention paradigm, confirmed that memory enhancement for valenced, nonarousing words relied on controlled encoding processes: concurrent task performance reduced the enhancement effect. Enhancement for arousing words occurred automatically, even when encoding resources were diverted to the secondary task.

Fig. 1.

Activation in the left amygdala (A), left anterior hippocampus (B), and left inferior parietal lobule (C) was greater during the encoding of emotional words (with or without arousal) than neutral words.

Fig. 2.

Activation in the left inferior PFC (BA 47) (A) and dorsolateral PFC (BA 9/46) (B) was greater during the encoding of valence-only words as compared with arousing words or neutral words.

Fig. 3.

Subsequent memory analyses showing areas of greater activation during encoding of words later remembered (rem) versus words later forgotten (for). Activation in the left amygdala (A) and left anterior hippocampus (B) related to subsequent memory for the arousing words, whereas activation in the left hippocampus (B) and left inferior PFC (C) were associated with subsequent memory for the valence-only words and the neutral words. During encoding of the valence-only words, the difference between later remembered and forgotten words was greater than was the case during encoding of the neutral words. Specifically, activation was greater for remembered valence-only words as compared with remembered neutral words.

Fig. 4.

For arousing words that were later remembered, the activation in the hippocampus and the amygdala correlated significantly (r = 0.60; P < 0.01; dotted line represents linear trend line).