Bispectral index-guided propofol sedation during endoscopic ultrasonography

Background/Aims Bispectral index (BIS) monitors process and display electroencephalographic data are used to assess the depth of anesthesia. This study retrospectively evaluated the usefulness of BIS monitoring during endoscopic ultrasonography (EUS). Methods This study included 725 consecutive patients who underwent EUS under sedation with propofol. BIS monitoring was used in 364 patients and was not used in 361. The following parameters were evaluated: (1) median dose of propofol; (2) respiratory and circulatory depression; (3) occurrence of body movements; (4) awakening score >8 at the time; and (5) awakening score 2 hours after leaving the endoscopy room. Results The BIS group received a significantly lower median dose of propofol than the non-BIS group (159.2 mg vs. 167.5 mg; p=0.015) in all age groups. For patients aged ≥75 years, the reduction in heart rate was significantly lower in the BIS group than in the non-BIS group (1.2% vs. 9.1%; p=0.023). Moreover, the occurrence of body movements was markedly lower in the BIS group than in the non-BIS group (8.5% vs. 39.4%; p<0.001). Conclusions During EUS examination, BIS monitoring is useful for maintaining a constant depth of anesthesia, especially in patients 75 years of age or older

A Computationally Efficient Filter for Reducing Shot Noise in Low S/N Data.

Functional multineuron calcium imaging (fMCI) provides a useful experimental platform to simultaneously capture the spatiotemporal patterns of neuronal activity from a large cell population in situ. However, fMCI often suffers from low signal-to-noise ratios (S/N). The main factor that causes the low S/N is shot noise that arises from photon detectors. Here, we propose a new denoising procedure, termed the Okada filter, which is designed to reduce shot noise under low S/N conditions, such as fMCI. The core idea of the Okada filter is to replace the fluorescence intensity value of a given frame time with the average of two values at the preceding and following frames unless the focused value is the median among these three values. This process is iterated serially throughout a time-series vector. In fMCI data of hippocampal neurons, the Okada filter rapidly reduces background noise and significantly improves the S/N. The Okada filter is also applicable for reducing shot noise in electrophysiological data and photographs. Finally, the Okada filter can be described using a single continuous differentiable equation based on the logistic function and is thus mathematically tractable

Subcellular Imbalances in Synaptic Activity

The dynamic interactions between synaptic excitation and inhibition (E/I) shape membrane potential fluctuations and determine patterns of neuronal outputs; however, the spatiotemporal organization of these interactions within a single cell is poorly understood. Here, we investigated the relationship between local synaptic excitation and global inhibition in hippocampal pyramidal neurons using functional dendrite imaging in combination with whole-cell recordings of inhibitory postsynaptic currents. We found that the sums of spine inputs over dendritic trees were counterbalanced by a proportional amount of somatic inhibitory inputs. This online E/I correlation was maintained in dendritic segments that were longer than 50 μm. However, at the single spine level, only 22% of the active spines were activated with inhibitory inputs. This inhibition-coupled activity occurred mainly in the spines with large heads. These results shed light on a microscopic E/I-balancing mechanism that operates at selected synapses and that may increase the accuracy of neural information

Application of the median filter to fMCI data.

<p><b>A.</b> Left 20 traces are raw fluctuations in the OGB1 fluorescence intensities in the cell bodies numbered in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0157595#pone.0157595.g003" target="_blank">Fig 3A</a> and were median-filtered (right). <b>B-D.</b> Comparison of the signal (B), the background noise level (B) and its ratio (D) before and after median filtering. Each dot indicates a single cell. <i>P</i> was determined using Wilcoxon signed rank test for the same 100 cells as those used in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0157595#pone.0157595.g003" target="_blank">Fig 3C–3E</a>.</p

Comparisons of the frequency responses of the Okada, median, binomial, and Savitzky-Golay filters.

<p><b>A</b>. The mean ± SD power spectra of the 100 cells data same as used in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0157595#pone.0157595.g003" target="_blank">Fig 3</a> are shown in black, where those of Okada-filtered traces are shown in color. <b>B</b>-<b>D</b>. Same as <b>A</b>, but for the median (<b>B</b>, blue), binomial (<b>C</b>, red) and Savitzky-Golay (<b>D</b>, green) filtered traces. <b>E</b>. The mean frequency response of each filter is shown relative to the mean powers of the original traces.</p