Anatomy and Physiology of Macaque Visual Cortical Areas V1, V2, and V5/MT: Bases for Biologically Realistic Models

The cerebral cortex of primates encompasses multiple anatomically and physiologically distinct areas processing visual information. Areas V1, V2, and V5/MT are conserved across mammals and are central for visual behavior. To facilitate the generation of biologically accurate computational models of primate early visual processing, here we provide an overview of over 350 published studies of these three areas in the genus Macaca, whose visual system provides the closest model for human vision. The literature reports 14 anatomical connection types from the lateral geniculate nucleus of the thalamus to V1 having distinct layers of origin or termination, and 194 connection types between V1, V2, and V5, forming multiple parallel and interacting visual processing streams. Moreover, within V1, there are reports of 286 and 120 types of intrinsic excitatory and inhibitory connections, respectively. Physiologically, tuning of neuronal responses to 11 types of visual stimulus parameters has been consistently reported. Overall, the optimal spatial frequency (SF) of constituent neurons decreases with cortical hierarchy. Moreover, V5 neurons are distinct from neurons in other areas for their higher direction selectivity, higher contrast sensitivity, higher temporal frequency tuning, and wider SF bandwidth. We also discuss currently unavailable data that could be useful for biologically accurate models.

Controlling Complexity of Cerebral Cortex Simulations-II: Streamlined Microcircuits

Recently, Markram et al. (2015) presented a model of the rat somatosensory microcircuit (Markram model). Their model is high in anatomical and physiological detail, and its simulation requires supercomputers. The lack of neuroinformatics and computing power is an obstacle for using a similar approach to build models of other cortical areas or larger cortical systems. Simplified neuron models offer an attractive alternative to high-fidelity Hodgkin-Huxley-type neuron models, but their validity in modeling cortical circuits is unclear. We simplified the Markram model to a network of exponential integrate-and-fire (EIF) neurons that runs on a single CPU core in reasonable time. We analyzed the electrophysiology and the morphology of the Markram model neurons with eFel and NeuroM tools, provided by the Blue Brain Project. We then constructed neurons with few compartments and averaged parameters from the reference model. We used the CxSystem simulation framework to explore the role of short-term plasticity and GABA <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow/><mml:mi>B</mml:mi></mml:msub></mml:math> and NMDA synaptic conductances in replicating oscillatory phenomena in the Markram model. We show that having a slow inhibitory synaptic conductance (GABA <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mrow/><mml:mi>B</mml:mi></mml:msub><mml:mrow><mml:mo>)</mml:mo></mml:mrow></mml:mrow></mml:math> allows replication of oscillatory behavior in the high-calcium state. Furthermore, we show that qualitatively similar dynamics are seen even with a reduced number of cell types (from 55 to 17 types). This reduction halved the computation time. Our results suggest that qualitative dynamics of cortical microcircuits can be studied using limited neuroinformatics and computing resources supporting parameter exploration and simulation of cortical systems. The simplification procedure can easily be adapted to studying other microcircuits for which sparse electrophysiological and morphological data are available.

Controlling Complexity of Cerebral Cortex Simulations-I: CxSystem, a Flexible Cortical Simulation Framework

Simulation of the cerebral cortex requires a combination of extensive domain-specific knowledge and efficient software. However, when the complexity of the biological system is combined with that of the software, the likelihood of coding errors increases, which slows model adjustments. Moreover, few life scientists are familiar with software engineering and would benefit from simplicity in form of a high-level abstraction of the biological model. Our primary aim was to build a scalable cortical simulation framework for personal computers. We isolated an adjustable part of the domain-specific knowledge from the software. Next, we designed a framework that reads the model parameters from comma-separated value files and creates the necessary code for Brian2 model simulation. This separation allows rapid exploration of complex cortical circuits while decreasing the likelihood of coding errors and automatically using efficient hardware devices. Next, we tested the system on a simplified version of the neocortical microcircuit proposed by Markram and colleagues ( 2015 ). Our results indicate that the framework can efficiently perform simulations using Python, C <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mo>+</mml:mo><mml:mo>+</mml:mo></mml:mrow></mml:math> , and GPU devices. The most efficient device varied with computer hardware and the duration and scale of the simulated system. The speed of Brian2 was retained despite an overlying layer of software. However, the Python and C <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mo>+</mml:mo><mml:mo>+</mml:mo></mml:mrow></mml:math> devices inherited the single core limitation of Brian2. The CxSystem framework supports exploration of complex models on personal computers and thus has the potential to facilitate research on cortical networks and systems.

Health-related quality of life in patients with diastrophic dysplasia

Diastrophic dysplasia (DD), a congenital skeletal dysplasia, is characterized by short, disproportionate stature, multiple severe spinal and joint deformities, and normal mental status. The health-related quality of life (HRQOL) of patients with DD was measured by a standardized fifteen-dimensional (15D) method, that includes a questionnaire and a valuation task. Eighteen patients (5 males and 13 females) with a mean age of 23 years (range 17-31 years), representing half of the Finnish patients with DD in this age group, completed the questionnaire and the valuation task. The data obtained were compared with those of 273 age- and sex-matched controls. A 15D profile was drawn, and the average importance weight of each dimension and the average within-dimension level values were calculated for both groups. The average 15D score, describing the overall HRQOL, was derived for both groups using the evaluations of each group. The health profiles of the groups differed significantly in several dimensions. When the health levels within the dimensions were concerned, the controls rated all values deviating from "normal" lower than did the patients. The average 15D scores of the patients with DD were significantly lower than those of the controls. The 15D scores were higher in both groups when the evaluations of the patients with DD were used. The study showed that, although the overall HRQOL of the patients with DD was inferior to that of the controls, the patients showed greater adaptability to deviations in health status than did the controls.

Comparison of health-related quality of life in three subgroups of spinal cord injury patients

Health-related quality of life (HRQL) was evaluated in three subgroups of spinal cord injury (SCI) patients: (1) persons who had sustained a pediatric SCI (mean time from injury 20 years, age at injury 11.3 years, n = 36), (2) newly injured patients at the beginning of acute rehabilitation (mean age 35.3 years, n = 31), and (3) patients with a chronic SCI (mean time from injury 4.8 years, mean age at injury 35.2 years, n = 34). All the patients were clinically examined and structurally interviewed with a list of questions dealing with details of anamnestic information about injury, its treatment, possible complications and persons past and present psycho-social condition. HRQL was assessed by a generic fifteen-dimensional self-administered instrument (15D). The relative importance of the 15D dimensions and an overall judgement of health status were measured by a 0-100 visual analogue scale. Average importance weights of the dimensions of moving and working differed significantly in the three subgroups. Patients with pediatric SCI assigned the lowest importance for moving. The newly injured patients highly valued working capability. The HRQL scores of the patients who had sustained their injury in childhood were significantly higher than those of the newly injured patients or chronic patients. The tetraplegic patients estimated their HRQL significantly lower than patients with incomplete paraplegia. Of the three subgroups studied, those with pediatric SCI were well adjusted on the basis of anamnestic information and scored high on HRQL when compared with the other two subgroups. Patients injured in adulthood rated their overall HRQL lower and were often unable to return to work. Patients injured in childhood expressed better performance in physical functions than patients who had sustained their injury in adulthood. The subgroups did not differ in psychological functions.

Enzyme exposure and enzyme sensitisation in the baking industry

OBJECTIVES

To assess the exposure to enzymes and prevalence of enzyme sensitisation in the baking industry.

METHODS

A cross sectional study was conducted in four bakeries, one flour mill, and one crispbread factory. Sensitisation to enzymes, flours, and storage mites was examined by skin prick and radioallergosorbent (RAST) tests. 365 workers were tested. The workers were interviewed for work related respiratory and skin symptoms. Total dust concentrations were measured by a gravimetric method, and the concentration of alpha-amylase in air was measured by a catalytic method. An immunochemical method was used for measuring cellulase and xylanase in air.

RESULTS

Total measured dust concentrations were from 0.1 to 18 mg/m3, with highest values in dough making areas of bakeries. The alpha-amylase concentrations generally followed the total dust concentrations and reached the highest values < 6.6 micrograms/m3 in the same areas. Cellulase and xylanase varied with concentrations < 180 ng/m3 and < 40 ng/m3, respectively, in the flour mill and the crispbread factory. No cellulase, but concentrations of 1-200 ng/m3 xylanase, were found in the bakeries, probably indicating the natural xylanase activity of wheat. 12 workers (8%) in the bakeries, three (5%) in the flour mill, and four (3%) in the crispbread factory were skin prick positive to enzymes. The corresponding percentages of positive reactions to flours were 12%, 5%, and 8%.

CONCLUSIONS

The study confirmed that industrial enzymes in baking used as additives in a powdered form pose a risk of sensitisation. The no effect air concentrations for industrial enzymes are not known. Based on present knowledge, however, lowering exposures and eliminating short and high peaks by technical measures would lower the risk of sensitisation. This would be most effectively accomplished by shifting to non-dusty products.