The head direction (HD) system functions as a compass with member neurons robustly increasing their firing rates when the animal’s head points in a specific direction. HD neurons may be driven by peripheral sensors or, as computational models postulate, internally-generated (‘attractor’) mechanisms. We addressed the contributions of stimulus-driven and internally-generated activity by recording ensembles of HD neurons in the antero-dorsal thalamic nucleus and the postsubiculum of mice by comparing their activity in various brain states. The temporal correlation structure of HD neurons is preserved during sleep, characterized by a 60°-wide correlated neuronal firing (‘activity packet’), both within as well as across these two brain structures. During REM, the spontaneous drift of the activity packet was similar to that observed during waking and accelerated tenfold during slow wave sleep. These findings demonstrate that peripheral inputs impinge upon an internally-organized network, which provides amplification and enhanced precision of the head-direction signal.
When spinal circuits generate rhythmic movements it is important that the neuronal activity remains within stable bounds to avoid saturation and to preserve responsiveness. Here, we simultaneously record from hundreds of neurons in lumbar spinal circuits of turtles and establish the neuronal fraction that operates within either a ‘mean-driven’ or a ‘fluctuation–driven’ regime. Fluctuation-driven neurons have a ‘supralinear’ input-output curve, which enhances sensitivity, whereas the mean-driven regime reduces sensitivity. We find a rich diversity of firing rates across the neuronal population as reflected in a lognormal distribution and demonstrate that half of the neurons spend at least 50 0pt3.5pt% of the time in the ‘fluctuation–driven’ regime regardless of behavior. Because of the disparity in input–output properties for these two regimes, this fraction may reflect a fine trade–off between stability and sensitivity in order to maintain flexibility across behaviors.DOI:
http://dx.doi.org/10.7554/eLife.18805.001
BackgroundThe emergency department (ED) represents an environment with a high density of invasive, and thus, infection-prone procedures. The two primary goals of this study were (1) to define the number of hand-rubs needed for an individual patient care at the ED and (2) to optimize hand hygiene (HH) compliance without increasing workload.MethodsProspective tri-phase (6-week observation phases interrupted by two 6-week interventions) before after study to determine opportunities for and compliance with HH (WHO definition). Standard operating procedures (SOPs) were optimized for invasive procedures during two predefined intervention periods (phases I and II) to improve workflow practices and thus compliance with HH.Results378 patient cases were evaluated with 5674 opportunities for hand rubs (HR) and 1664 HR performed. Compliance significantly increased from 21% (545/2603) to 29% (467/1607), and finally 45% (652/1464; all p<0.001) in phases 1, 2, and 3, respectively. The number of HR needed for one patient care significantly decreased from 22 to 13 for the non-surgical and from 13 to 7 for the surgical patients (both p<0.001) due to improved workflow practices after implementing SOPs. In parallel, the number of HR performed increased from 3 to 5 for non-surgical (p<0.001) and from 2 to 3 for surgical patients (p=0.317). Avoidable opportunities as well as glove usage instead of HR significantly decreased by 70% and 73%, respectively.ConclusionsOur study provides the first detailed data on HH in an ED setting. Importantly, HH compliance improved significantly without increasing workload.
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