We find a novel state in which the network activity is simultaneously localized in both maps. In this state, a fixed cue 4SC-202 mw presented to the network does not determine uniquely the location of the bump, i.e. the response is unreliable, with neurons not
always responding when their preferred input is present. When the tuned input varies smoothly in time, the neuronal responses become reliable and selective for the environment: the subset of neurons responsive to a moving input in one map changes almost completely in the other map. This form of remapping is a non-trivial transformation between the tuned input to the network and the resulting tuning curves of the neurons. The new state of the network could be related to the formation of direction selectivity in one-dimensional environments and hippocampal remapping. The applicability of the model is not confined to self-position representations; we show an instance of the network solving a simple delayed
“Background: Chronic cannabis use has been associated with memory deficits and a volume reduction of the hippocampus, but none of the studies accounted for different effects of tetrahydrocannabinol (THC) and cannabidiol (CBD).
Methods: Using a voxel based morphometry approach optimized for small subcortical structures (DARTEL) gray matter (GM) concentration and volume of the hippocampus were measured in 11 chronic recreational cannabis users and 13 healthy controls, and correlated with THC and CBD from hair analyses. GM volume was calculated by modulating selleck products Screening Library VBM using jacobian determinants derived from the spatial normalization.
Results: Cannabis users showed lower GM volume located in a cluster of the right anterior hippocampus (P(uncorr) = 0.002: effect size Cohen’s d = 1.34). In a regression analysis an inverse correlation of the ratio THC/CBD with the volume of the right hippocampus (P(uncorr) p < 0.001, Cohen’s d = 3.43) was observed. Furthermore Cannabidiol correlated positively with GM concentration (unmodulated VBM data), but not with GM volume (modulated VBM) in the bilateral
hippocampus (P = 0.03 after correction for hippocampal volume; left hippocampus Cohen’s d = 4.37 and right hippocampus 4.65).
Conclusions: Lower volume in the right hippocampus in chronic cannabis users was corroborated. Higher THC and lower CBD was associated with this volume reduction indicating neurotoxic effects of THC and neuroprotective effects of CBD. This confirms existing preclinical and clinical results. As a possible mechanism the influence of cannabinoids on hippocampal neurogenesis is suggested. (c) 2010 Elsevier Ireland Ltd. All rights reserved.”
“Transparent copolymers composed of hexa (allyl 4-hydroxybenzoate) cyclotriphosphazene (compound 1) and styrene as potential halogen-free, flame-retardant optical resins were prepared by radical copolymerization.