Effect of local and general fatiguing exercises on disturbed and static postural control

This study compared the effect of local and general fatiguing exercise on disturbed and static postural control performances. Surface electromyography and center of pressure signals were respectively recorded during self-initiated perturbation test and static postural stability test from 7 young male subjects. Local fatiguing exercise was performed using intermittent isometric knee extensions at the level of 40% of maximal voluntary torques. General fatiguing exercise was implemented with rowing ergometer at a speed of 200 ± 5 m/min. Results of disturbed postural tests showed no significant change of anticipatory postural adjustment (APAs) organizations in individual muscles following both fatiguing exercises, but observed larger APAs coactivations in trunk and dorsal muscle pairs following local than general fatiguing exercise, and larger compensatory postural adjustments (CPAs) coactivation in dorsal muscle pair after both fatiguing exercises. In addition, the results of static postural tests indicated efficient static postural stability accompanying the down-weighting of visual input and the up-weighting of vestibular/somatosensory component following both fatiguing exercises. These findings evidenced a general compensation in the central nervous system in response to the neuromuscular deficiencies induced by local fatiguing exercise and put forward the function of sensory recalibration in maintaining postural stability under fatigue conditions.     

The neural subjective frame: from bodily signals to perceptual consciousness

The report ‘I saw the stimulus’ operationally defines visual consciousness, but where does the ‘I’ come from? To account for the subjective dimension of perceptual experience, we introduce the concept of the neural subjective frame. The neural subjective frame would be based on the constantly updated neural maps of the internal state of the body and constitute a neural referential from which first person experience can be created. We propose to root the neural subjective frame in the neural representation of visceral information which is transmitted through multiple anatomical pathways to a number of target sites, including posterior insula, ventral anterior cingulate cortex, amygdala and somatosensory cortex. We review existing experimental evidence showing that the processing of external stimuli can interact with visceral function. The neural subjective frame is a low-level building block of subjective experience which is not explicitly experienced by itself which is necessary but not sufficient for perceptual experience. It could also underlie other types of subjective experiences such as self-consciousness and emotional feelings. Because the neural subjective frame is tightly linked to homeostatic regulations involved in vigilance, it could also make a link between state and content consciousness.     

Levels of pesticide residues in breast milk and the associated risk assessment

The aim of this study was to determine the types and levels of organochlorine pesticides (OCPs) present in the human milk collected from cities in eastern and central Saudi Arabia. This study is part of assessment of various persistent organic pollutants (POPs) in human milk in four cities of eastern and central Saudi Arabia, namely, Riyadh, Al-Kharj, Al-Jobail and Al-Dammam. Milk samples were collected from 50 donors according to the WHO/UNEP protocol for monitoring human milk for POPs. The OCPs in each of the 50 milk samples were analyzed using as triple quadrupole gas chromatography mass spectrometry-mass spectrometry detection (GC–MS/MS). Quality assurance included the analysis of blank, spiked and reference samples. Sixteen different OCPs were identified namely: aldrin, dieldrin, endrin, hexachlorobenzene, alpha, beta, gamma and delta hexachlorocycohexame, pp’-,op’-DDT, pp’-DDE, pp’-DDD, alpha and gamma chlordane, heptachlor, mirex and methoxychlor. The results of the analysis OCPs in human milk samples indicated that the tested positive samples for one or more pesticide at the limits of determination used in this study. As required by the Stockholm Convention on POPs, the levels of certain POPs in human milk will serve as an indicator of the effectiveness of the treaty in eliminating or reducing emissions of selected POPs. This study contributes to that effort by providing seline data on current levels of OPCs in human milk in Saudi Arabia.