Differential Emergence and Stability of Sensory and Temporal Representations in Context-Specific Hippocampal Sequences

Hippocampal spiking sequences encode external stimuli and spatiotemporal intervals, linking sequential experiences in memory, but the dynamics controlling the emergence and stability of such diverse representations remain unclear. Using two-photon calcium imaging in CA1 while mice performed an olfactory working-memory task, we recorded stimulus-specific sequences of "odor-cells" encoding olfactory stimuli followed by "time-cells" encoding time points in the ensuing delay. Odor-cells were reliably activated and retained stable fields during changes in trial structure and across days. Time-cells exhibited sparse and dynamic fields that remapped in both cases. During task training, but not in untrained task exposure, time-cell ensembles increased in size, whereas odor-cell numbers remained stable. Over days, sequences drifted to new populations with cell activity progressively converging to a field and then diverging from it. Therefore, CA1 employs distinct regimes to encode external cues versus their variable temporal relationships, which may be necessary to construct maps of sequential experiences.

Accuracy of physician self-estimation of time spent during patient care in the emergency department

Objective

Accurate measurement of physicians' time spent during patient care stands to inform emergency department (ED) improvement efforts. Direct observation is time consuming and cost prohibitive, so we sought to determine if physician self-estimation of time spent during patient care was accurate.

Methods

We performed a prospective, convenience-sample study in which research assistants measured time spent by ED physicians in patient care. At the conclusion of each observed encounter, physicians estimated their time spent. Using Mann-Whitney U tests and Spearman's rho, we compared physician estimates to actual time spent and assessed for associations of encounter characteristics and physician estimation.

Results

Among 214 encounters across 10 physicians, we observed a medium-sized correlation between actual and estimated time (Spearman's rho = 0.63, p < 0.001), and in aggregate, physicians underestimated time spent by a median of 0.1 min. An equal number of encounters were overestimated and underestimated. Underestimated encounters were underestimated by a median of 5.1 min (interquartile range [IQR] 2.5-9.8) and overestimated encounters were overestimated by a median of 4.3 min (IQR 2.5-11.6)-26.3% and 27.9% discrepancy, respectively. In terms of actual time spent, underestimated encounters (median 19.3 min, IQR 13.5-28.3) were significantly longer than overestimated encounters (median 15.3 min, IQR 11.3-20.5) (p < 0.001).

Conclusions

Physician self-estimation of time spent was accurate in aggregate, providing evidence that it is a valid surrogate marker for larger-scale process improvement and research activities, but likely not at the encounter level. Investigations exploring mechanisms to augment physician self-estimation, including modeling and technological support, may yield pathways to make self-estimation valid also at the encounter level.