A dual representation model of intrusive memory proposes that personally experienced
events give rise to two types of representation: an image-based, egocentric representation
based on sensory-perceptual features; and a more abstract, allocentric representation
that incorporates spatiotemporal context. The model proposes that intrusions reflect
involuntary reactivation of egocentric representations in the absence of a corresponding
allocentric representation. We tested the model by investigating the effect of alcohol
on intrusive memories and, concurrently, on egocentric and allocentric spatial memory.
With a double-blind independent group design participants were administered alcohol
(.4 or .8 g/kg) or placebo. A virtual environment was used to present objects and
test recognition memory from the same viewpoint as presentation (tapping egocentric
memory) or a shifted viewpoint (tapping allocentric memory). Participants were also
exposed to a trauma video and required to detail intrusive memories for 7 days, after
which explicit memory was assessed.
There was a selective impairment of shifted-view recognition after the low dose of
alcohol, whereas the high dose induced a global impairment in same-view and shifted-view
conditions. Alcohol showed a dose-dependent inverted "U"-shaped effect on intrusions,
with only the low dose increasing the number of intrusions, replicating previous work.
When same-view recognition was intact, decrements in shifted-view recognition were
associated with increases in intrusions.
The differential effect of alcohol on intrusive memories and on same/shifted-view
recognition support a dual representation model in which intrusions might reflect
an imbalance between two types of memory representation. These findings highlight
important clinical implications, given alcohol's involvement in real-life trauma.
Copyright 2010 Society of Biological Psychiatry. Published by Elsevier Inc. All rights