Friday, January 09, 2004

Memory Supression Revealed New research published in Science provides compelling evidence to confirm a concept that Freud described over 100 years ago when he proposed the existence of a voluntary repressive* mechanism that pushes unwanted memories out of consciousness. There has been little empirical evidence to verify this process and the idea of memory suppression/repression has been somewhat controversial and no brain mechanism could be found that would confirm the process - until now. To mimic the brain's process in the lab, researchers had subjects first learn pairs of words such as ordeal-roach, steam-train and jaw-gum. Then they were given the first member of each word pair and asked either to think of the second word, or to suppress awareness of the second word. Subjects performed this task while being scanned in a functional magnetic resonance imaging (fMRI) machine. From these images, researchers can determine which parts of the brain are in use for different tasks. At the completion of this phase, the scientists tested the subjects' memory for all of the word pairs and confirmed that suppressing awareness of unwanted memories resulted in memory inhibition. The fMRI images of the subjects' brain activity during this procedure revealed for the first time strong neurobiological evidence for a novel idea about how memory repression occurs that is quite simple: unwanted memories can be suppressed with brain areas similar to that used when we try to stop overt physical actions. In essence, it appears that the brain systems that permit one to stop an arm motion midstream can be recruited to inhibit or stop an unwanted memory retrieval. Instead of inhibiting activity in brain regions having to do with physical action, however, these control processes reduce brain activation in the hippocampus, a structure known to be involved in conscious memories of the past. This reduction in hippocampal activity led the subjects to forget the rejected experiences. An interesting aspect of this study is that the researchers could predict how much forgetting people would experience. Controlling unwanted memories was associated with increased dorsolateral prefrontal activation, reduced hippocampal activation, and impaired retention of those memories. Both prefrontal cortical and right hippocampal activations predicted the magnitude of forgetting. These results confirm the existence of an active forgetting process and establish a neurobiological model for guiding inquiry into motivated forgetting. The scientists conclude that these findings "begin to specify central features of a neurobiological model of memory control that people may use to adapt their mental environment in response to traumatic experiences." The study provides the first neurobiological model of the voluntary form of repression proposed by Freud, a model that integrates this otherwise controversial proposal with widely accepted and fundamental mechanisms for controlling behavior. This study replicates a finding reported earlier in the journal Nature by the same authors. * The authors qualified their definition of repression vs suppression by stating that it is sometimes stated that Freud intended a distinction between Repression and Suppression, with the former being unconscious, and the latter, conscious. However, scholars of Freud have noted that this strong distinction in terminology is a distortion of Freud's view introduced by Anna Freud, and that Freud used Repression to refer to both conscious and nonconscious acts. We use the term Repression but limit our discussion to its conscious variety. Sigmund Freud,  Psychopathology of Everyday Life Freud on Repression Nature 410, 366 - 369 (2001) Science Jan 9 2004: 232-235 12:01:33 AM    comment []

© Copyright 2004 rsk. Last update: 2/18/04; 11:55:54 PM.