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)