A new study has revealed the neurophysiological reasons why we can remember when we last saw a lost object, but still forget where we left it. It turns out these are pretty similar to the reasons why we can remember a person’s face, but still forget his or her name.
The research focused on the interactions between three brain regions known to be involved in different kinds of memory: the temporal lobe’s perirhinal cortex (PRC), which is involved in recognizing familiar objects we detect with our senses; the hippocampus, which helps us recognize familiar places; and the medial prefrontal cortex (mPFC), which is involved in working memory and decision-making.
As reported in the Journal of Neuroscience, Dr. Clea Warburton and Dr. Gareth Barker at Bristol University’s School of Physiology and Pharmacology tested rats with different types of brain lesions on a variety of performance tasks (the functions of many areas in rat brains have proven to be pretty reliable predictors of how corresponding areas in human brains behave). The scientists found that each type of recognition depends on a different interaction between the brain areas they studied:
The hippocampus was crucial for object location, object-in-place, and recency recognition memory, but not for the novel object preference task … [and] object-in-place and recency recognition memory performance depended on a functional interaction between the hippocampus and either the perirhinal or medial prefrontal cortices.
In other words, although the hippocampus does play a crucial part in object location memory (e.g., where the remote is) and recency recognition memory (e.g., where we last saw it), this brain structure doesn’t work alone – it needs to communicate with the PRC and the mPFC to accomplish either of these tasks:
Neither ‘object-in-place’ or ‘temporal order recognition’ memories could be formed if communication between the hippocampus and either the perirhinal cortex, or the medial prefrontal cortex, was broken. In other words, disconnecting the regions prevented the ability to remember both where objects had been, and in which order.
Though rodents…well, most rodents…don’t have to worry about remembering each others’ names, this study tells us a lot about why our memories sometimes malfunction in such odd ways, like forgetting where we left the keys or the remote, even though we can easily picture them in all sorts of places we’ve seen them before. And then there’s presque vu – the sense that a word is “right on the tip of our tongues.” Though we might devote a huge amount of mental resources to working on problems like these, we can still come up dry if we’re trying remember in the wrong way – and in fact, actively trying to remember in one certain way may even be counterproductive.
So the next time you’re trying to remember where you left the remote – or awkwardly fumbling for someone’s name, just slow down, give your brain a breather, and let the answer come on its own. You might be surprised how easily you find it.