Complex span tasks and hippocampal recruitment during working memory.

The working memory (WM) system is vital to performing everyday functions that require attentive, non-automatic processing of information. However, its interaction with long term memory (LTM) is highly debated. Here, we used fMRI to examine whether a popular complex WM span task, thought to force the displacement of to-be-remembered items in the focus of attention to LTM, recruited medial temporal regions typically associated with LTM functioning to a greater extent and in a different manner than traditional neuroimaging WM tasks during WM encoding and maintenance. fMRI scans were acquired while participants performed the operation span (OSPAN) task and an arithmetic task. Results indicated that performance of both tasks resulted in significant activation in regions typically associated with WM function. More importantly, significant bilateral activation was observed in the hippocampus, suggesting it is recruited during WM encoding and maintenance. Right posterior hippocampus activation was greater during OSPAN than arithmetic. Persitimulus graphs indicate a possible specialization of function for bilateral posterior hippocampus and greater involvement of the left for WM performance. Recall time-course activity within this region hints at LTM involvement during complex span.

Shock index in diagnosing early acute hypovolemia.

OBJECTIVE: The aim of this study was to determine the hemodynamic response and calculated shock index (SI=heart rate [HR]/systolic blood pressure [SBP]) in early acute blood loss. METHODS: This was a prospective observational study that enrolled healthy blood donors. Patients were excluded if not eligible for blood donation. Baseline vital signs were obtained, 450 mL of blood was removed over 20 minutes, and vital signs were repeated immediately postdonation while lying and after 1 and 5 minutes of standing. Difference was tested using a paired t test with P<.01 set for significance. RESULTS: Forty-six patients were enrolled; means for each time interval are shown below with 95% confidence intervals. CONCLUSIONS: A significant elevation in mean SI was observed in healthy volunteers after standing for 1 and 5 minutes. Although significant changes in HR and SBP were observed, these indices were still within "normal" limits. The SI may be more useful in early hemorrhage than either the HR or SBP alone.