The amygdala, an almond-shaped brain structure known as the seat of emotion, also contributes to higher thinking—including those “Aha” moments when we suddenly see the answer to a puzzle, a new study suggests. From functional magnetic resonance imaging (fMRI) analyses reported in the March 10 Neuron, Nava Rubin of New York University and colleagues found that amygdala activity during an instance of induced insight could predict, to some degree, participants’ long-term memory of the solution. Though ramifications for Alzheimer’s disease are unclear, the study suggests a larger role for the amygdala in memory than may have been previously appreciated.
“This article uses a clever design and nicely demonstrates the involvement of the amygdala in memory formation, especially during moments of surprise,” Trey Hedden of Massachusetts General Hospital, Boston, wrote in an e-mail to ARF.
Extensive research in rats and people has established that activation of the amygdala promotes formation of long-term memory, particularly of emotional experiences (see Hamann et al., 1999; for reviews, see Phelps and LeDoux, 2005; Cahill and McGaugh, 1996; McGaugh, 2004), but also less arousing ones (Roozendaal et al., 2008). For the current study, Rubin worked with first and second authors Rachel Ludmer and Yadin Dudai of Weizmann Institute of Science, Rehovot, Israel, to design experiments that would tease out brain mechanisms influencing memory of induced moments of insight.
The researchers showed participants 40 hard-to-recognize camouflaged images, eliciting after each an “Aha” moment by briefly presenting the original real-life picture (i.e., the “solution”). They showed the camouflage images again one week later, and gauged long-term memory by whether participants could correctly identify the embedded object without being shown the original picture. Functional MRI brain scans revealed several brain regions—most prominently, the amygdala—correlating with long-term memory of the solution. The researchers used the amygdala fMRI data to predict subsequent memory of the images in a separate group of participants. However, Hedden noted that the predictive power is “not especially strong,” correctly predicting memory outcome 62 percent of the time (50 percent is chance level).
Activity in visual, medial frontal, and parietal cortices also associated with memory retention. However, no such correlations showed up in the hippocampus or other memory areas of the medial temporal lobe that typically fade in AD. Lack of activity findings in neuroimaging studies are hard to interpret, though, Paul Reber of Northwestern University, Evanston, Illinois, pointed out in an e-mail to ARF. Furthermore, the authors do not report whether memory-related fMRI activity in the medial frontal and parietal areas “could also be used, either alone or in concert with the amygdala activity, to predict memory,” Hedden wrote. The data also leave open the possibility that the hippocampus, despite showing no memory-related fMRI effects, “could be involved in linking the camouflage image to the solution image that leads to later memory, and that this linkage is modulated by the observed amygdala activity,” Hedden noted (see full comment below).
Reber agreed that the results are less likely to suggest “a new role for the amygdala in memory formation,” but probably reflect known interactions between the amygdala and medial temporal lobe (MTL) areas. He is not sure the results easily apply to AD. However, given the relative sparing of the amygdala compared to hard-hit nearby memory areas, “we could stretch a bit to hypothesize that positive emotional experiences could help with memory formation in patients, perhaps especially sudden ones like insight,” he noted. Moreover, since the insight came from a cognitive task instead of other positive rewards such as money, food, or sex, the current data suggest “a wider range of ways to create the positive experiences that might help memory,” Reber wrote (see full comment below). “This effect might be more pronounced earlier in disease progression when there is less neuropathology in the traditional MTL memory system. That is, when the system is at least partly functional, it can be boosted by the insight response.”—Esther Landhuis
- Hamann SB, Ely TD, Grafton ST, Kilts CD. Amygdala activity related to enhanced memory for pleasant and aversive stimuli. Nat Neurosci. 1999 Mar;2(3):289-93. PubMed.
- Phelps EA, LeDoux JE. Contributions of the amygdala to emotion processing: from animal models to human behavior. Neuron. 2005 Oct 20;48(2):175-87. PubMed.
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No Available Further Reading
- Ludmer R, Dudai Y, Rubin N. Uncovering camouflage: amygdala activation predicts long-term memory of induced perceptual insight. Neuron. 2011 Mar 10;69(5):1002-14. PubMed.