Modelling human choices: MADeM and decision‑making

Research supported by FAPESP 2015/50122-0 and DFG-GRTK 1740/2. RP and AR are also part of the Research, Innovation and Dissemination Center for Neuromathematics FAPESP grant (2013/07699-0). RP is supported by a FAPESP scholarship (2013/25667-8). ACR is partially supported by a CNPq fellowship (grant 306251/2014-0)

Differential Responses to High-Frequency Electrical Stimulation in Brisk-Transient and Delta Retinal Ganglion Cells

Retinal microprostheses strive to evoke a sense of vision in individuals blinded by outer retinal degenerative diseases, by electrically stimulating the surviving retina. It is widely suspected that a stimulation strategy that can selectively activate different retinal ganglion cell types will improve the quality of evoked phosphenes. Previous efforts towards this goal demonstrated the potential for selective ON and OFF brisk-transient cell activation using high-rate (2000 pulses per second, PPS) stimulation. Here, we build upon this earlier work by testing an additional rate of stimulation and additional cell populations. We find considerable variability in responses both within and across individual cell types, but show that the sensitivity of a ganglion cell to repetitive stimulation is highly correlated to its single-pulse threshold. Consistent with this, we found thresholds for both stimuli to be correlated to soma size, and thus likely mediated by the properties of the axon initial segment. The ultimate efficacy of high-rate stimulation will likely depend on several factors, chief among which are (a) the residual ganglion types, and (b) the stimulation frequency.Fonds zur Förderung der wissenschaftlichen Forschung (FWF)35293532

Frequency responses of rat retinal ganglion cells

<div>This repository contains the data associated with the manuscript, "Frequency responses of rat retinal ganglion cells", by Alex E. Hadjinicolaou et al., published in PLOS ONE. There are three components:</div><div><br></div><div>* recordings: whole-cell recordings from retinal ganglion cells (RGCs) [recordings.7z];</div><div>* reconstructions: morphological reconstructions from a subset of the recorded RGCs [ANU.7z | NVRI, part 1-3.7z]; and</div><div>* figures: MATLAB code used to generate the manuscript figures.</div><div><br></div><div>Note that there is not always a 1-1 relationship between the recording name (e.g. 050211r1c3) and the Cell ID associated with the reconstruction (in this case, 20110502_c2). The Excel sheet "recordings" within the file "data summary.xlsx" lists these associations. The "morphology" sheet within the same file contains the soma/dendritic field data obtained from measurements made using FIJI, an ImageJ-based analysis program. Morphological classification was guided by Sun W, Li N, He S. Large-scale morophological survey of rat retinal ganglion cells. Vis Neurosci. 2002;19: 483–493.</div

The effect of dendritic field size on the frequency response of retinal ganglion cells.

<p>Panels (A–D) show the mean frequency response of A2, C2, D1 and D2 RGC types. Within each RGC type, cells are grouped and their frequency responses averaged according to their dendritic field diameter. Within each RGC type, cells with the largest dendritic fields are shown in black and those with the smallest dendritic fields are shown in grey. For comparison, the frequency response, averaged over all cells of a given type, irrespective of dendritic field size, is shown by the dashed line. Black dots indicate statistically significant differences between large-field and small-field RGC responses (t-tests, p < 0.05). Panels (E–H) show distributions of dendritic field diameter for each of the A2, C2, D1 and D2 RGC types, respectively.</p

Patch-clamp recording of responses to sinusoidal stimulus currents.

<p>Representative membrane potential recordings from an A2o-type retinal ganglion cell, during intracellular injection of sinusoidal stimulation currents (70 pA) at (A) 10 Hz, (B) 25 Hz, and (C) 60 Hz. The frequency and phase of the injected currents are indicated by the sinusoids (gray) shown below each membrane potential recording (black). The dashed line indicates 0 mV.</p

Reconstruction of recorded cell morphology.

<p>Representative confocal image stacks typical of those used for classification of recorded retinal ganglion cells (RGCs) according to their morphological cell type. Examples are shown for representative (A) A-type, (B) B-type, (C) C-type, (D) D-type, (E) ON [C2i], (F) OFF [A2o], and (G) ON-OFF [D2] RGCs. Panels (E–G) show the <i>en face</i> representation (top), revealing the scale and extent of the dendritic arborisation, and a cross-section (bottom), revealing where the dendrites of each cell stratify within the inner plexiform layer (IPL). Long-dashed lines indicate the boundary of the IPL and short-dashed lines indicate the approximate boundary between the two sublaminae. Recorded cells were labelled, via the patch pipette, with Alexa488 (green). Other cells in the ganglion cell layer (GCL) and inner nuclear layer (INL) were labelled with propidium iodide (red).</p

Intrinsic Physiological Properties of RGC Subtypes.

<p>Intrinsic Physiological Properties of RGC Subtypes.</p

The effect of soma size on the frequency response of retinal ganglion cells.

<p>Panels (A–D) show the mean frequency response of A2, C2, D1 and D2 RGC types, respectively. Within each RGC type, cells are grouped and their frequency responses averaged according to their soma diameter. Within each RGC type, cells with the largest soma diameters are shown in black and those with the smallest soma diameters are shown in grey. For comparison, the frequency response, averaged over all cells of a given type, irrespective of soma diameter, is shown by the dashed line. Panels (E–H) show distributions of soma diameter for each of the A2, C2, D1 and D2 RGC types, respectively.</p

On Transient qualification of LOBI/MOD2, SPES, LSTF and BETHSY nodalizations for RELAP5/MOD2 code

The results obtained in a more-than-a-decade application of thermal-hydraulic system codes to the analysis of experiments performed in Integral Test Facilities (ITF) and Separate Effect test Facilities (SETF) including the participation to several International Standard Problems (ISP) and Standard Problem Exercises (SPE), organized by OECD/NEA/CSNI (Organization for Economic Cooperation and Development / Nuclear Energy Agency / Committee on the Safety of Nuclear Installations) and by IAEA (international Atomic Energy Agency), respectively, suggested the need for new methods and procedures for code application. The words nodalization-qualification, qualitative-accuracy-evaluation, quantitative-accuracy-evaluation, and acceptability-thresholds were introduced. The present document deals with nodalization qualification at the transient level for the LOBI/mod2 available at the EURATOM JRC of Ispra (Italy), the SPES, available at the SIET research center in Piacenza, Italy, the LSTF available at the Tokai-Mura Research Center of JAERI in Japan and the BETHSY available at the CEA-CENG research center in Grenoble, France. The activity in this case is based upon the analysis of one experiment performed in each ITF, respectively: criteria for accepting the results of the comparison with calculated data are fixed from the application of the FFTBM (Fast Fourier Transform Based Method)