Response Features Determining Spike Times

Interpreting messages encoded in single neuronal responses requires knowing which features of the responses carry information. That the number of spikes is an important part of the code has long been obvious. In recent years, it has been shown that modulation of the firing rate with about 25 ms precision carries information that is not available from the total number of spikes across the whole response. It has been proposed that patterns of exactly timed (1 ms precision) spikes, such as repeating triplets or quadruplets, might carry information that is not available from knowing about spike count and rate modulation. A model using the spike count distribution, the low pass filtered PSTH (bandwidth below 30 Hz), and, to a small degree, the interspike interval distribution predicts the numbers and types of exactly-timed triplets and quadruplets that are indistinguishable from those found in the data. From this it can be concluded that the coarse (<30 Hz) sequential correlation structure over time gives rise to the exactly timed patterns present in the recorded spike trains. Because the coarse temporal structure predicts the fine temporal structure, the information carried by the fine temporal structure must be completely redundant with that carried by the coarse structure. Thus, the existence of precisely timed spike patterns carrying stimulus-related information does not imply control of spike timing at precise time scales

Double power laws in income and wealth distributions

Close examination of wealth distributions reveal the existence of two distinct power law regimes. The Pareto exponents of the super-rich, identified for example in rich lists such as provided by Forbes are smaller than the Pareto exponents obtained for top earners in income data sets. Our extension of the Slanina model of wealth is able to reproduce these double power law features.Comment: 10 pages, 4 figures, conference APFA6, Lisboa, July 200

Training medical students to manage difficult circumstances- a curriculum for resilience and resourcefulness?

BACKGROUND: In response to the growing prevalence of physical and emotional burnout amongst medical students and practicing physicians, we sought to find a new methodology to scope a five-year undergraduate curriculum in detail to assess for teaching, learning objectives and experiences that seek to promote resilience in medical students. This was undertaken to test whether this methodology would enable curriculum discussions to enhance training for future cohorts through the introduction of a curriculum dedicated to the development of resilience and resourcefulness. METHODS: Based on literature review, a rating-scale was devised to generate quantitative data in four key areas of resilience; internal resources, lifestyle factors, external resources (self-mediated) and external resources (agent mediated). This scale was used to evaluate the entire five-year undergraduate curriculum of a medical school in the north of England through systematic evaluation of learning outcomes and planned activities. The methodology used was a four-stage process including i) identifying the learning objectives, ii) mapping them onto the criteria outlined, iii) assessing them against clear objective standards (planned, explicit, universal and quantifiable), and iv) rating data collected. RESULTS: The evaluation provided a clear, quantitative overview of the curriculum in terms of resilience building. Strengths and gaps were identified and work was undertaken leading to suggestions for change. This facilitated helpful discussions with course leaders and planners, received universally positive feedback and led to new learning objectives, activities and experiences that have been identified and begun to be implemented. CONCLUSIONS: "The HYMS CARE Criteria" and our methodology for assessing it in a medical school curriculum context, offers a valuable perspective to aid the planning of improvements in curricula. This model for scoping and structuring resilience related learning experiences is offered for consideration by other schools

How well can we estimate the information carried in neuronal responses from limited samples?

It is difficult to extract the information carried by neuronal responses about a set of stimuli because limited data samples result in biased estimates. Recently two improved procedures have been developed to calculate information from experimental results: a binning-and-correcting procedure and a neural network procedure. We have used data produced from a model of the spatiotemporal receptive fields of parvocellular and magnocellular lateral geniculate neurons to study the performance of these methods as a function of the number of trials used. Both procedures yield accurate results for one-dimensional neuronal codes. They can also be used to produce a reasonable estimate of the extra information in a three-dimensional code, in this instance, within 0.05-0.1 bit of the asymptotically calculated value - about 10% of the total transmitted information. We believe that this performance is much more accurate than previous procedures

Numerically resolved Radiation View Factors via Multi-GPU Accelerated Ray Tracing

A robust computational framework is presented to directly solve for the radiation view factors (Fij) of participatory surfaces within complex three-dimensional geometries. This framework exploits the embarrassingly-parallel nature of the formulation and solution of Fij through a multiple graphics processing units (GPU)-accelerated ray tracing scheme. The presented computational methodology was developed in Java and incorporated Aparapi for OpenCL compatibility. The surfaces of the geometries of interest are constructed via the creation of stereolithography (STL) files, which represent surfaces as tessellations. The shadow effect, where cast rays are obstructed by non-participatory surfaces, is handled via the Möller-Trumbore (MT) ray-triangle intersection algorithm. To ensure generality and robustness, a self-intersection algorithm is implemented for both planar and non-planar surfaces via the MT algorithm with back-face culling enabled. Validation of the algorithm was performed for a variety of three-dimensional geometries. The proposed multi-GPU framework was benchmarked to a conventional computer processing unit (CPU)-based version of the code and exhibited substantial decreases in computational time. Results indicate that near-linear speed-up is achievable with increasing numbers of GPUs. Additionally, a converging solution is obtained with increasing tessellation and GPU count, indicating no perceivable discrepancy in solutions in comparison to CPU and single-GPU based solutions

Long-Term Stability of Visual Pattern Selective Responses of Monkey Temporal Lobe Neurons

Many neurons in primate inferotemporal (IT) cortex respond selectively to complex, often meaningful, stimuli such as faces and objects. An important unanswered question is whether such response selectivity, which is thought to arise from experience-dependent plasticity, is maintained from day to day, or whether the roles of individual cells are continually reassigned based on the diet of natural vision. We addressed this question using microwire electrodes that were chronically implanted in the temporal lobe of two monkeys, often allowing us to monitor activity of individual neurons across days. We found that neurons maintained their selectivity in both response magnitude and patterns of spike timing across a large set of visual images throughout periods of stable signal isolation from the same cell that sometimes exceeded two weeks. These results indicate that stimulus-selectivity of responses in IT is stable across days and weeks of visual experience

Randomized trial of a DVD intervention to improve readiness to self-manage joint pain

Report of a randomized controlled trial of a motivational intervention to promote self-management of joint painA DVD (digital video disk) intervention to increase readiness to self-manage joint pain secondary to hemophilia was informed by a 2-phase, motivational-volitional model of readiness to self-manage pain, and featured the personal experiences of individuals with hemophilia. The DVD was evaluated in a randomized controlled trial in which 108 men with hemophilia completed measures of readiness to self-manage pain (Pain Stages of Change Questionnaire) before and 6 months after receiving the DVD plus information booklet (n = 57) or just the booklet (n = 51). The effect of the DVD was assessed by comparing changes in Pain Stages of Change Questionnaire scores (precontemplation, contemplation, and action/maintenance) between groups. The impact on pain coping, pain acceptance, and health-related quality of life was tested in secondary analyses. Repeated-measures analysis of variance, including all those with complete baseline and follow-up data regardless of use of the intervention, showed a significant, medium- sized, group time effect on precontemplation, with reductions among the DVD group but not the booklet group. Significant use time effects showed that benefits in terms of contemplation and action/maintenance were restricted to those who used the interventions at least once. The results show that low-intensity interventions in DVD format can improve the motivational impact of written information, and could be used to help prepare people with chronic pain for more intensive self-management interventions. The findings are consistent with a 2-phase, motivational-volitional model of pain self-management, and provide the first insights to our knowledge of readiness to self-manage pain in hemophilia.Haemophilia Society, U