Prospective memory: encoding and
retrieval
Sam Gilbert
Institute of Cognitive Neuroscience
Background
• Prospective memory (PM) refers to our ability to encode intentions
for future behaviour, then act on those intentions at the appropriate
time
• Several recent fMRI studies have investigated brain mechanisms
supporting this ability (Benoit et al., in prep; Burgess et al., 2001,
2003; Gilbert et al., in press; Okuda et al., 1998, 2007; Reynolds et
al., in press; Simons et al., 2006)
• These studies have all investigated retrieval of delayed intentions.
The present study will look at encoding as well
Previous studies
• Typically, participants are engaged in an “ongoing task”, e.g. making
a button-press response to a series of words to indicate whether
they have 4 or 6 letters
• PM conditions: continue performing the ongoing task, but press a
different button if you see an animal word
PM > ongoing only
ongoing only > PM
Burgess et al., 2001
Burgess et al., 2003
Design
Ongoing task: 2-back
SONG
PM encode
REST
SONG
yes
PM store (1 – 5 trials)
WEAR
no
REST
no
WEAR
SWIM
CASE
NOTE
SWIM
PM retrieve: press different key
yes
no
Control: PM encode
no
no
no
Control: PM store (1 – 5 trials)
Control: PM retrieve
Analyses
• PM storage trials versus control: expect signal change in BA 10
• PM encoding versus control: same regions as involved in retrieval?
• Subsequent prospective memory effect: encoding-related activity
that distinguishes subsequent hits from misses?
• Each PM cue will appear twice in the experiment. Half of blocks use
words, half pictures. Multi-voxel pattern analysis to find out whether
the intention can be decoded from storage trials (specific intention /
word versus picture)
Methods
• Standard EPI imaging parameters: 3mm x 3mm x 3mm voxels, 33
slices, TR=2.5s
• 3s per trial; 7 trials per ‘miniblock’ (i.e. PM or control), total: 48 PM, 48
control trials
• 6 runs of approx 6 minutes + 6 minute structural scan: total scanner time
= 42 mins
• Analysis in SPM5