Making Memories: Brain Activity that Predicts How Well Visual Experience Will Be Remembered

1. Making Memories: Brain Activity that Predicts How Well Visual Experience Will Be Remembered Presented by: David Wu James B. Brewer, Zuo Zhao, John E. Desmond, Gary H. Glover, John D. E. Gabrieli

2. Background Information • Most important regions for declarative memory: parahippocampal cortex and some regions of frontal cortex • Traditionally fMRI studies used block designs with novel versus repeated scenes to determine which brain areas encode declarative memory • Confounds: could be a response to novelty and not encoding, or could reflect habituation, reduced attention or strategic differences because activation is averaged over long predictable blocks • This study attempts to resolve these confound by using a event-related design, where separate activations are recorded for each stimulus

3. Design • 6 right-handed subjects (3F, 3M, aged 22-32) • 4 fMRI scans consisting of 24 pictures of indoor and outdoor scenes • 30 minutes later, given an unexpected memory test which consisted of all the previously seen pictures and 32 new pictures • Judge whether each picture was clearly remembered, familiar, or forgotten

4. Results • 7 regions where activity level predicted whether pictures would be remembered, familiar or forgotten • 1 was in the right inferior frontal sulcal region of the dorsolateral prefrontal cortex • 6 were in bilateral parahippocampal cortex • Activations greater for remembered compared with familiar (t(5)=3.55, P<0.05) • And for familiar than forgotten (t(5)=4.56, P<0.01)

5. Results Right dorsolateral prefrontal cortex (upper right slice 1) Bilateral parahippocampal cortex (all other regions) Displays voxels with significant positive correlations between event-related activations to pictures and subsequent memory for those pictures.

6. Results Examples of average signal intensity in each region Graph D shows mean voxel response in parahippocampal areas showing significant correlation with subsequent memory in each subject

7. Discussion • The activated prefrontal area is related to spatial working memory tasks • Memory for scenes determined by spatial working memory processes in the right prefrontal area, and long-term memory processes in the bilateral parahippocampal areas • Has been proposed two regions constitute a neural circuit that mediates the formation of spatial long-term memories

8. My Opinion • Strengths: • Simple and effective design that produced unambiguous results • Concise paper that was very easy to read • Limitations • Did not image the entire brain, there could be other activation areas that were not found • Small sample size • Future Direction: Do different areas predict how well you will remember words, objects or faces?

9. Bibliography • Brewer J. B., Zhao Z., Desmond J. E., Glover G. H., Gabrieli J. D. E. (1998). Making Memories: Brain Activity that Predicts How Well Visual Experience Will Be Remembered. Science, 281(5380): 1185-1187