Pause for effect: A 10-s interviewer wait time gives children time to respond to open-ended prompts.

When researchers and helping professionals interview children about a target event, how long should they tolerate silence before delivering another prompt? In other words, at what point are children so unlikely to begin talking again that continued silence would likely be unproductive? To test the reasonableness of a 10-s wait time guideline during open-ended prompting, we analyzed the wait times of research assistants (N = 7) who interviewed with a 10-s guideline, timed how quickly children responded to prompts, and also timed pauses within children's event narratives. In our sample (105 conversations with children aged 4-8 years), interviewers complied fully with the 10-s rule in the majority of interviews, children often paused for longer than 5 s before beginning to talk about the event or continuing a narrative, and more than 96% of children's pauses that were followed by event information fell within the 10-s window. These findings show that the 10-s wait time was a practical guideline that gave children time to respond without peppering interviews with uncomfortably long pauses. We conclude that adding wait time guidelines to protocols for interviewing children, and augmenting guidelines with wait time training for research assistants and helping professionals, could improve the quality of information obtained from children and advance our understanding of age differences in event memory.

Transplantation of mesenchymal stem cells that overexpress NT-3 produce motor improvements without axonal regeneration following complete spinal cord transections in rats.

Transplanting stem cells engineered to overexpress trophic factors can improve motor abilities and facilitate axon regeneration following spinal cord injury. This study compared several transplantation paradigms using mesenchymal stem cells (MSCs) that overexpress the multi-neurotrophin, NT-3/D15A (NT-3-MSCs), to determine if different grafting strategies can elicit improved axon regeneration and/or behavioral outcomes following a complete T9 spinal transection. At one week post-transection, NT-3-MSCs were transplanted above, and at several locations below, the lesion site. A rostral-to-caudal gradient of NT-3-MSCs was produced by incrementally increasing the number of transplanted cells at locations distal to the transection. Motor function was analyzed using the Basso, Beattie, and Bresnahan scale for 7-weeks post-injury. The corticospinal tract was traced using biotinylated dextran amines, while raphespinal fibers were visualized using immunohistochemistry. Cell viability was assessed using transplants of NT-3-MSCs that express tdTomato. Retrograde tracing using fluorogold, as well as spinal re-transections, were performed to discriminate between a supra-spinal or reflexive influence of regained motor functions. NT-3-MSC transplants improved motor outcomes and tissue continuity at the transection site, however retrograde tracing using fluorogold revealed no evidence of axon regeneration. A spinal re-transection also failed to eliminate the improvement in motor outcomes produced by the transplant. We conclude that transplantation of NT-3-MSCs can improve motor function and morphological outcomes following a complete spinal transection without promoting axonal regeneration.