Hippocampal activity is modulated during episodic memory retrieval. Most consistently, a relative increase in activity during confident retrieval is observed. Dorsolateral prefrontal cortex (DLPFC) is also activated during retrieval, but may be more generally activated during cognitive-control processes. The "default network," regions activated during rest or internally focused tasks, includes the hippocampus, but not DLPFC. Therefore, DLPFC and the hippocampus should diverge during difficult tasks suppressing the default network. It is unclear, however, whether a difficult episodic memory retrieval task would suppress the default network due to difficulty or activate it due to internally directed attention. We hypothesized that a task requiring episodic retrieval followed by rumination on the retrieved item would increase DLPFC activity, but paradoxically reduce hippocampal activity due to concomitant suppression of the default network. In the present study, blocked and event-related fMRI were used to examine hippocampal activity during episodic memory recollection and postretrieval processing of paired associates. Subjects were asked to make living/nonliving judgments about items visually presented (classify) or items retrieved from memory (recall-classify). Active and passive baselines were used to differentiate task-related activity from default-network activity. During the "recall-classify" task, anterior hippocampal activity was selectively reduced relative to "classify" and baseline tasks, and this activity was inversely correlated with DLPFC. Reaction time was positively correlated with DLPFC activation and default-network/hippocampal suppression. The findings demonstrate that frontal and hippocampal activity are dissociated during difficult episodic retrieval tasks and reveal important considerations for interpreting hippocampal activity associated with successful episodic retrieval.

Objective Ciclovía or Open Streets initiatives support physical activity through cycling/rolling, and walking/running. We evaluated San Diego’s first Open Streets event, CicloSDias, to document attendance, reach and marketing, and effects on social cohesion, businesses, and physical activity. Methods The comprehensive evaluation consisted of a city-wide survey 1 week before and after the event (n=805), counts of event attendees, and surveys of event attendees (n=713) and businesses (n=26). Results An estimated 8,311 people attended the event. Attendees had an average of 144 minutes (SD=85) of physical activity, 97% met the 30 minute/day guideline, and 39% met the 150 minute/week guideline during the event. 27% of attendees would have been inactive without the event. Awareness of the event was 10% before and 26% after the event. When comparing event attendees to San Diego residents, Latinos and non-white race/ethnicities were under-represented. Restaurants/pubs, services, and most retail stores excluding liquor stores and food markets reported positive or neutral impacts on business. Conclusion Open Street initiatives are promising ways to promote physical activity and are desired by the community. Positive effects were observed for physical activity, social cohesion, and businesses, though reach should be expanded to include more underserved community members. Evaluating Open Streets is important for sustaining and improving these efforts.