Acute effects of alcohol on intrusive memory development and viewpoint dependence in spatial memory support a dual representation model.
BACKGROUND
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.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Bisby
James A
JA
Clinical Psychopharmacology Unit, University College London, United Kingdom. j.bisby@ucl.ac.uk
King
John A
JA
Brewin
Chris R
CR
Burgess
Neil
N
Curran
H Valerie
HV
D000223:Adaptation, Psychological / Q000187:drug effects*; D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D002492:Central Nervous System Depressants / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D000431:Ethanol / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008297:Male; D008568:Memory / Q000187:drug effects*; D008960:Models, Psychological; D021641:Recognition, Psychology / Q000187:drug effects*; D012016:Reference Values; D012094:Repression, Psychology; D013313:Stress Disorders, Post-Traumatic / Q000503:physiopathology / Q000523:psychology*; D055815:Young Adult
D002492:Central Nervous System Depressants; D000431:Ethanol