One of the recent and exciting advances in the field of functional brain imaging has been the development of methods for extracting localized correlates of brain activity on a trial by trial basis (Rosen et al., 1998). These methods allow us to explore memory phenomenon that are revealed only based on subject performance. In one such example (Wagner et al., 1998), we had subjects process words one at a time under conditions that would encourage many -- but not all -- of the words to be remembered. We then tested their memory for the words and examined the neural activity associated with those words that were later remebered as compared to those words that were forgotten. One of the results from this study is highlighted in the summary diagram above.


While most of our research has focussed on understanding the brain pathways active during healthy brain function, we have also explored the question of what happens when the brain is damaged. One such study involved patient LF1, a 72 year old man who suffered a stroke damaging a portion of his left frontal lobe. The remarkable finding was that LF1 could do many speech generation and word production tasks that normally activate the portion of left frontal cortex he had damaged. These preserved functions suggested he might be using alternative brain areas to compensate. We imaged LF1 using positron emision tomography (PET) and found that, whereas normal young subjects activate left frontal cortex during word generation, patient LF1 actiavated right frontal cortex as shown in the image above (see also Buckner et al., 1996)