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| Direct Suppression vs Thought Substitution |
To better understand this process, the scientists at the MRC Cognition and Brain Sciences Unit at the University of Cambridge sought to discover the neural mechanisms behind intentional blocking of memories from awareness. The two hypotheses of how we intentionally forget are: 1. We directly suppress the memory from entering consciousness or 2. We substitute another more pleasant memory for the one we are trying to forget. It turns out that we can do both! What’s more, not only do we have two methods of forgetting, these methods use completely different neural circuits.
Their study consisted of subjects learning word associations (ex. BEACH-AFRICA). They then used functional magnetic resonance imaging to map activity in two groups: one group was instructed to intentionally try to block out the associated word while the other was given substitute associations (ex. BEACH-SNORKEL) which they were instructed to use to try to supersede the previous associated word (AFRICA). The scientists found that distinct regions of the brain were selectively activated in each method, which were equally effective at blocking memory. Direct suppression led to the inhibition of the hippocampus, which is important for memory retrieval, through the activation of the right dorsolateral prefrontal cortex. In contrast, thought substitution led to activation of the left caudal and the midventrolateral PFC, areas that deal with selective memory recall and proactive interference.
The discovery of these two distinct neural pathways that both end with the same result (intentional forgetting), could have implications for disorders like PTSD. One circuit may be more suited for certain types of memories, or perhaps certain types of people. Understanding these mechanisms could result in better focused treatments. Of course, more research needs to be conducted to determine if these circuits have differential effects with targets other than learned semantic memories. But this study helps to elucidate the mysterious process of forgetting and the different ways in which we can accomplish that task.
Original article: Roland G. Benoit, Michael C. Anderson. Opposing Mechanisms Support the Voluntary Forgetting of Unwanted Memories. Neuron, 2012; 76 (2): 450 DOI: 10.1016/j.neuron.2012.07.025
This article brings up an interesting point about replacing old memories. Personally, I never thought of that as being effective treatment, as it seems very difficult for some memories I'd like to forget. I have heard of distracting yourself from memories before in a rather enthralling study about how people with PTSD can cope better after playing tetris. I'd like to find out more about the different pathways - I'm curious to find out whether one way is more effective than the other (though this article states they're equal) or if one way is more effective than the other for each individual. Thanks for this!
ReplyDeleteHere's an article from Time magazine about Tetris and PTSD: http://healthland.time.com/2010/11/10/study-playing-tetris-to-prevent-ptsd-flashbacks/
This article was fascinating to me, mainly because it is sometimes more easy to remember the bad memories than the good ones.I believe that has to do a bit of who we are. Whether we are an optimist or a pessimist. This can really affect our mood and I think by reminding what the good things we have in life we can improve ourselves.
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