Induction and activity-dependent reversal of persistent LTP and LTD in lateral perforant path synapses in vivo

The reversibility of long-term potentiation (LTP) and heterosynaptic long-term depression (LTD) lasting weeks was examined in the lateral perforant path of freely moving adult Sprague-Dawley rats. LTP lasting weeks was rapidly reversed within minutes by high-frequency heterosynaptic stimulation of the medial perforant path, in an N-methyl-D-aspartate receptor-dependent manner. LTP reversal also occurred, albeit more slowly and to a lesser extent, when animals were given 1-3 weeks of overnight exposure to an enriched environment (EE). LTD likewise was reversed upon repeated EE exposure. A covert similarity between the degrees of LTP and LTD reversal was revealed when the small potentiation effect of EE treatment by itself on lateral path responses was taken into account. Despite its ability to reverse previously acquired synaptic plasticity, two weeks of EE treatment had no effect on animals' retention of the platform location in a spatial watermaze task, although it did facilitate new learning. These data are in agreement with the hypothesis that hippocampal synapses retain the capacity for rapid synaptic change even when otherwise relatively stable plasticity has previously been induced. Slow reversal of such plasticity did not correlate with a loss of memory retention, possibly because either slow changes permit reorganization of representations such that both old and new information can be accommodated, or else the new information is synaptically represented in orthogonal fashion to the old information.     

Changes in older Dutch adults’ role networks after moving

Using the convoy model (R. L. Kahn & T. C. Antonucci, 1980), this study examined the differential impact of relocation, depending on the distance moved, on the size of 3 types of role networks. A total of 890 Dutch nonmovers and 445 movers (aged 55–86 years) were selected from the Longitudinal Aging Study Amsterdam. Results of analyses of variance showed that the neighbor networks changed most after relocation. Long‐distance movers discontinued the largest number of relationships with fellow club members. As expected, moving did not affect coworker networks. The findings show that, consistent with the convoy model, role networks proved to be unstable. Older adults, however, restored their partial networks at the second observation by starting new relationships.