Stress administered prior to encoding impairs neutral but enhances emotional long-term episodic memories

Abstract

Stressful events frequently comprise both neutral and emotionally arousing information, yet the impact of stress on emotional and neutral events is still not fully understood. The hippocampus and frontal cortex have dense concentrations of receptors for stress hormones, such as cortisol, which at high levels can impair performance on hippocampally dependent memory tasks. Yet, the same stress hormones can facilitate memory for emotional information, which involves interactions between the hippocampus and amygdala. Here, we induced psychosocial stress prior to encoding and examined its long-term effects on memory for emotional and neutral episodes. The stress manipulation disrupted long-term memory for a neutral episode, but facilitated long-term memory for an equivalent emotional episode compared with a control condition. The stress manipulation also increased salivary cortisol, catecholamines as indicated by the presence of alpha-amylase, heart rate, and subjectively reported stress. Stressed subjects reported more false memories than nonstressed control subjects, and these false memories correlated positively with cortisol levels, providing evidence for a relationship between stress and false memory formation. Our results demonstrate that stress, when administered prior to encoding, produces different patterns of long-term remembering for neutral and emotional episodes. These differences likely emerge from differential actions of stress hormones on memory-relevant regions of the brain.

Figure 1.

Mean salivary cortisol, heart rate, and subjective stress ratings in the Stress and Control groups.

Figure 2.

The impact of stress on recall memory. Stress resulted in recall of more elements from the emotional story, but fewer elements from the neutral story, compared with the control condition.

Figure 3.

The impact of stress on recognition memory. Stress resulted in better recognition of the emotional story, but poorer recognition of the neutral story, compared with the control condition.

Figure 4.

The impact of stress on false memory. Stressed subjects falsely recalled more slides than control subjects, but only for the neutral story.

Figure 5.

Positive correlation between salivary cortisol and false memory recall.

Figure 6.

Experimental timeline.