Memory reactivation during sleep does not act holistically on object memory.

Memory reactivation during sleep is thought to facilitate memory consolidation. Most sleep reactivation research has examined how reactivation of specific facts, objects, and associations benefits their overall retention. However, our memories are not unitary, and not all features of a memory persist in tandem over time. Instead, our memories are transformed, with some features strengthened and others weakened. Does sleep reactivation drive memory transformation? We leveraged the Targeted Memory Reactivation technique in an object category learning paradigm to examine this question. Participants (20 female, 14 male) learned three categories of novel objects, where each object had unique, distinguishing features as well as features shared with other members of its category. We used a real-time EEG protocol to cue the reactivation of these objects during sleep at moments optimized to generate reactivation events. We found that reactivation improved memory for distinguishing features while worsening memory for shared features, suggesting a differentiation process. The results indicate that sleep reactivation does not act holistically on object memories, instead supporting a transformation process where some features are enhanced over others.

Factor variation as a function of disaster stress

In an attempt to standardise the use of at least one particular test in studies of post-disaster stress, the factor structure of four forms of the Hookins Symptom Checklist were examined by means of a new comparison technique on three sets of data. The outcome showed that only the shortest of the forms --the HSCL-21-- had a robust three-factor structure in at least two out of the three data sets. The factors were identified as General Feelings of Distress (GFD), Somatic Distress (SD) and Performance Difficulty (PD). The aberrant set of data, which was obtained from a group under extreme stress at the time, was explained in terms of the anxiety, preoccupation and hypervigilance of the subjects. The same HSCL-21 also had a general factor that was identified as total distress in all three sets. Consequently the HSCL-21 is to be recommended as a brief, useful, and factorially stable post-disaster assessment questionnaire.(AU)