Tuesday, December 10, 2013

Imaging the the updating of true and false memories.

When we recall, or reactivate a memory, we render it susceptible to alterations such as incorporating relevant new information, so that it might be then stored again in an altered form. Schacter and collaborators at Harvard show show more of what is going on in our brains as reactivation-induced updating both enhances and distorts memory. This process has important implications for understanding the unreliability of eyewitness memories. Here is their abstract:
We remember a considerable number of personal experiences because we are frequently reminded of them, a process known as memory reactivation. Although memory reactivation helps to stabilize and update memories, reactivation may also introduce distortions if novel information becomes incorporated with memory. Here we used functional magnetic resonance imaging (fMRI) to investigate the neural mechanisms mediating reactivation-induced updating in memory for events experienced during a museum tour. During scanning, participants were shown target photographs to reactivate memories from the museum tour followed by a novel lure photograph from an alternate tour. Later, participants were presented with target and lure photographs and asked to determine whether the photographs showed a stop they visited during the tour. We used a subsequent memory analysis to examine neural recruitment during reactivation that was associated with later true and false memories. We predicted that the quality of reactivation, as determined by online ratings of subjective recollection, would increase subsequent true memories but also facilitate incorporation of the lure photograph, thereby increasing subsequent false memories. The fMRI results revealed that the quality of reactivation modulated subsequent true and false memories via recruitment of left posterior parahippocampal, bilateral retrosplenial, and bilateral posterior inferior parietal cortices. However, the timing of neural recruitment and the way in which memories were reactivated contributed to differences in whether memory reactivation led to distortions or not. These data reveal the neural mechanisms recruited during memory reactivation that modify how memories will be subsequently retrieved, supporting the flexible and dynamic aspects of memory.

1 comment:

  1. The researchers stripped all human emotional memory content out of the study, presumably because messy feelings would confound their conclusions. The study used non-emotional pictures only.

    It is curious that the researchers want to apply this study to eyewitness accounts. What are the chances that an eyewitness to a murder or a violent accident or crime would have a non-emotional memory of the event?

    The study’s exclusion of emotional memories especially calls into doubt that the “finding” that “..stronger reliving improved memory..” would also apply to reliving of emotional memories.

    The researchers did not include in this study the portions of the feeling brain, other than the hippocampus, that would likely participate in the reliving of emotional memories.

    The researchers thus have too narrow a basis for a finding about “memory” that could apply across the entire spectrum of what can be termed “memory.”