Before addressing what happens to
memories within an emotional context, I would first like to argue that there is
no such thing as not having an emotional context during encoding or retrieval
of memories. We may not always have a strong valence for everything that
happens in our lives, but we are constantly experiencing emotion of some sort.
Whether that experience is low-level like boredom or fatigue, or high level
such as in deep sorrow or great joy, I cannot imagine a time where I have not
experienced some mood. But for the sake of argument, I will focus on memories
that occur during a strong emotional context.
According
to current memory literature, both positive and negative memories are better
encoded than less emotionally salient experiences. Based on fMRI studies, (among
other mechanisms) this deeper encoding is most likely due to amygdala
activation- both for positive and negative memories. In a 2006 study by
Kensinger and Schacter, they found activation of the amygdala during encoding
for positive and negative items. This activity later predicted recall for these
emotionally salient items. However, this effect did not extend beyond highly
emotional items. In keeping with my earlier statement, I would argue that the
amygdala actually was engaged even during the more neutral items, but that the
activation was so weak that it could not be picked up in the fMRI BOLD signal.
In any case, this research demonstrates that the limbic system, and the
amygdala in particular, are more active during emotionally charged situations
and allow for deeper encoding.
It makes evolutionary sense that
emotionally engaging experiences (especially negative ones) should be better
encoded. It’s beneficial for an organism to remember to avoid negative
experiences that hurt its chance of survival, and positive experiences should
be better remembered in order to seek out similar beneficial situations. Thus,
it is unsurprising that highly emotional memories engage neural systems beyond
the medial temporal lobe.
However, extreme mood at memory
retrieval can occasionally be detrimental. In a 2005 research study,
researchers found that inducing a positive mood during recall led to more false
memories in the Deese-Roediger-McDermott paradigm. However, inducing negative
mood during recall did not show this effect. This research demonstrates that
while heightened emotion during encoding can be overall beneficial, that same
state during retrieval ends up causing people to falsely identify lure items as
old. Thus, extreme emotion can be a double-edged sword when it comes to memory.
Guastella, A. J., Mitchell, P. B., & Mathews, F. (2008).
Oxytocin enhances the encoding of positive social memories in humans. Biological
psychiatry, 64(3), 256-258.
Kensinger, E. A., & Schacter, D. L. (2006). Amygdala
activity is associated with the successful encoding of item, but not source,
information for positive and negative stimuli. The Journal of
Neuroscience, 26(9), 2564-2570.
Storbeck, J., & Clore, G. L. (2005). With sadness comes
accuracy; with happiness, false memory mood and the false memory effect. Psychological
Science, 16(10), 785-791.
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