A computer model of intermediate cerebellum dynamic operations in motor control

An intermediate cerebellum theoretical model for processing central programming discharges and muscle force signals is described which can perform a correct motor task under different peripheral perturbations (loads). An indispensable condition is that the simulated interpositus nucleus cells controlling a given effector (muscle) are inhibited by impulses coming from that effector (negative feedback from muscle force detectors). The hypothesis is proposed that the intermediate cerebellum can act via the rubrospinal tract as an interface between programming and executing motor structures.     

Gamma-irradiation effects on phosphatidylcholine multilayer liposomes: calorimetric, NMR, and spectrofluorimetric studies

Chemical and structural modifications in multilayer liposomes of synthetic phosphatidylcholine induced by gamma irradiation are investigated with different techniques. Fluorescence anisotropy of the DPH probe and differential scanning calorimetry reveal a broadening of the main lipid transition and the disappearance of pretransition. Fluorescence anisotropy is shown to be higher in the irradiated sample and particularly so at low temperatures. NMR and TLC results show that lysolecithin and palmitic acid are formed with a consequent change in bilayer organization. The possibility that these modifications may account for the permeability variations observed in irradiated natural membranes is discussed.     

Robust emergence of small-world structure in networks of spiking neurons

Spontaneous activity in biological neural networks shows patterns of dynamic synchronization. We propose that these patterns support the formation␣of a small-world structure—network connectivity␣optimal for distributed information processing. We␣present numerical simulations with connected Hindmarsh–Rose neurons in which, starting from random connection distributions, small-world networks evolve as a result of applying an adaptive rewiring rule. The rule connects pairs of neurons that tend fire in synchrony, and disconnects ones that fail to synchronize. Repeated application of the rule leads to small-world structures. This mechanism is robustly observed for bursting and irregular firing regimes.