What happens in your brain when you try to commit something to memory? What strategies do you use when studying information? Most of us would find it hard to answer this question, but some people use specific strategies to perform amazing feats of memory. Kirchhoff and Buckner have studied how different strategies affect memory performance, and how brain activation can reflect these techniques.

The subjects of the study were asked to look at pairs of interacting objects — for example, a banana in a truck — and were told that their memory for the images would be tested later. While they studied the images, the activity in their brains was measured using functional MRI, and later they were quizzed on the strategies they had used to remember the information.

Among the participants, encoding strategies varied greatly. Two types of strategy, which the authors call 'verbal elaboration' and 'visual inspection', were correlated with subsequent performance on a retrieval task, whereas 'mental imagery' and 'memory retrieval' strategies were not. In addition, subjects who used the greatest number of different encoding strategies showed the best performance in the test. Further analysis showed that the verbal elaboration and visual inspection strategies independently improved memory performance.

When they studied the strategy-use data together with the brain imaging results, the authors discovered that specific strategies were correlated with activity in different parts of the brain. In particular, the verbal elaboration strategy was associated with prefrontal activity in areas that contribute to verbal processing, whereas the visual inspection strategy was associated with activity in an object-processing area of the extrastriate cortex.

Finally, the authors investigated whether activity in these regions during encoding was directly correlated with memory performance on a subsequent test. As they predicted, activity associated with effective encoding strategies was also correlated with successful recall.

These results shed light on the ways in which people use different strategies — and different parts of the brain — to perform the same task. This is likely to explain a significant part of the individual variation that is seen in functional imaging studies of memory encoding, as well as helping us to understand and perhaps improve memory performance.