Redundant variables and Granger causality.

We discuss the use of multivariate Granger causality in presence of redundant variables: the application of the standard analysis, in this case, leads to under estimation of causalities. Using the un-normalized version of the causality index, we quantitatively develop the notions of redundancy and synergy in the frame of causality and propose two approaches to group redundant variables: (i) for a given target, the remaining variables are grouped so as to maximize the total causality and (ii) the whole set of variables is partitioned to maximize the sum of the causalities between subsets. We show the application to a real neurological experiment, aiming to a deeper understanding of the physiological basis of abnormal neuronal oscillations in the migraine brain.

Multiscale analysis of short term heart beat interval, arterial blood pressure, and instantaneous lung volume time series.

Motivations: Physiological systems are ruled by mechanisms operating across multiple temporal scales. A recently proposed approach, multiscale entropy analysis, measures the complexity at different time scales and has been successfully applied to long term electrocardiographic recordings. The purpose of this work is to show the applicability of this methodology, rooted on statistical physics ideas, to short term time series of simultaneously acquired samples of heart rate, blood pressure and lung volume, from healthy subjects and from subjects with chronic heart failure.

Effects of levetiracetam vs topiramate and placebo on visually evoked phase synchronization changes of alpha rhythm in migraine.

Objective: Recent theories about migraine pathogenesis have outlined an abnormal central processing of sensory signals, also suggested by an abnormal pattern of EEG hyper-synchronization under visual stimulation. The aim of the present study was to test the efficacy of topiramate and levetiracetam vs placebo in a double blind project observing the effects of the three treatments on the EEG synchronization in the alpha band under sustained flash stimulation.

Methods: Forty-five migraine without aura outpatients (MO) were selected and randomly assigned to 100mg topiramate, 1000 mg levetiracetam or placebo treatment.

Red blood cell (RBC) surface acetylcholinesterase showing a hemorheological pattern during glaucoma treatment.

Background: Glaucoma is currently attributed to two different possible pathogenetic mechanisms: mechanical (the ocular damage is induced by physical injury), and vascular (the ocular damage is sustained by ischemia of the optic nerve head).

Aim: We considered the possibility that several anti-glaucoma drugs (beta-blockers, carbonic anhydrase inhibitors and prostaglandins) could have an influence on optic nerve head hemorheology and oxygen supply.

Materials And Method: We studied 4 groups of 10 subjects each: a control group, and 3 primary open angle glaucoma (POAG) groups, treated with topical beta-blockers, (10 patients), carbonic anhydrase inhibitors (CAI), and prostaglandin analogs (PG), respectively.