De ongelijke verdeling van gezondheid. Verslag van een conferentie gehouden op 16-17 maart 1987

Political Scienc

De maatschappelijke gevolgen van erfelijkheidsonderzoek. Verslag van een Conferentie gehouden op 16-17 juni 1988

Health; Heredit

Verdeelmodel Welzijnswet 1984

In het kader van de Rapportage Welzijnswet (van het ministerie van WVC) zijn verschillende malen gegevens verzameld voor het meerjarige onderzoeksproject Veranderingen in het Welzijnswerk. De gegevens behelzen door gemeenten uitgegeven bedragen aan verschillende activiteiten/instellingen

Human Vestibulo-Ocular Reflex Adaptation: Consolidation Time Between Repeated Training Blocks Improves Retention

We sought to determine if separating vestibulo-ocular reflex (VOR) adaptation training into training blocks with a consolidation (rest) period in between repetitions would result in improved VOR adaptation and retention. Consolidation of motor learning refers to the brain benefitting from a rest period after prior exposure to motor training. The role of consolidation on VOR adaptation is unknown, though clinicians often recommend rest periods as a part of vestibular rehabilitation. The VOR is the main gaze stabilising system during rapid head movements. The VOR is highly plastic and its gain (eye/head velocity) can be increased via training that induces an incrementally increasing retinal image slip error signal to drive VOR adaptation. The unilateral incremental adaptation technique typically consists of one 15-min training block leading to an increase in VOR gain of ~ 10 % towards the training side. We tested nine normal subjects, each over six separate sessions/days. Three training protocols/sessions were 5 min each (1 × 5-min training) and three training protocols/sessions were 55 min each. Each 55-min protocol comprised 5-min training, 20-min rest, 5-min training, 20-min rest, 5-min training (3 × 5-min training). Active and passive VOR gains were measured before and after training. For training with consolidation breaks, VOR gain retention was measured over 1 h. The VOR gain increase after 1 × 5-min training was 3.1 ± 2.1 % (P < 0.01). One might expect that repeating this training three times would result in × 3 total increase of 9.3 %; however, the gain increase after 3 × 5-min training was only 7.1 ± 2.8 % (P < 0.001), suggesting that consolidation did not improve VOR adaptation for our protocols. However, retention was improved by the addition of consolidation breaks, i.e. gains did not decrease over 1 h (P = 0.43). These data suggest that for optimal retention VOR adaptation exercises should be performed over shorter repeated blocks

Simultaneous and opposing horizontal VOR adaptation in humans suggests functionally independent neural circuits

The healthy vestibulo-ocular reflex (VOR) ensures that images remain on the fovea of the retina during head rotation to maintain stable vision. VOR behavior can be measured as a summation of linear and nonlinear properties although it is unknown whether asymmetric VOR adaptation can be performed synchronously in humans. The purpose of the present study is twofold. First, examine whether the right and left VOR gains can be synchronously adapted in opposing directions. Second, to investigate whether the adaptation context transfers between both sides. Three separate VOR adaptation sessions were randomized such that the VOR was adapted Up-bilaterally, Down-bilaterally, or Mixed (one side up, opposite side down). Ten healthy subjects completed the study. Subjects were tested while seated upright, 1 meter in front of a wall in complete dark. Each subject made active (self-generated) head impulse rotations for 15 min while viewing a gradually increasing amount of retinal slip. VOR training demand changed by 10% every 90 s. The VOR changed significantly for all training conditions. No significant differences in the magnitude of VOR gain changes between training conditions were found. The human VOR can be simultaneously driven in opposite directions. The similar magnitude of VOR gain changes across training conditions suggests functionally independent VOR circuits for each side of head rotation that mediate simultaneous and opposing VOR adaptations. NEW & NOTEWORTHY Our results indicate that humans have the adaptive capacity for concurrent and opposing directions of vestibulo-ocular reflex (VOR) motor learning. Context specificity of VOR adaptation is dependent on the error signal being unilateral or bilateral, which we illustrate via a lack of VOR gain transfer using unique adaptive demands

Preventing acute respiratory infections and diarrhoea in child care centres

This study was designed to explore the physical characteristics and child care practices of child care centres as potential risk factors for respiratory infections and diarrhoea in children 3-35 mo of age. A dynamic cohort averaging 667 children from 40 child care centres in Campinas (Brazil) was followed up for 8 mo. Direct structured observations were made to collect information on the centres' physical structure, child activities and child care practices. Despite their good infrastructures, hand washing in the centres was infrequent, and nearly 30% of diaper changes were unhygienic. Risk factors for diarrhoea included the presence of flies during meals, infrequent child hand washing before meals, and infrequent child hand washing after defecation, with relative risks of 1.33, 1.73 and 1.63, respectively. There was 33% less diarrhoea in classes where soap was frequently used during diapering. Contrary to our hypotheses, ventilation, group size and child density were not associated with respiratory infections, as was the case for most other factors studied. Only mixing of groups and a larger classroom area were found to be negatively associated with lower and upper respiratory infections, respectively. The results indicate that improving hygiene practices is the only intervention in child care centre characteristics with good potential to reduce diarrhoea among attendees. For respiratory infections, no modifiable characteristic with intervention potential was identified.88101113111

The Effect of Visual Contrast on Human Vestibulo-Ocular Reflex Adaptation

The vestibulo-ocular reflex (VOR) is the main retinal image stabilising mechanism during rapid head movement. When the VOR does not stabilise the world or target image on the retina, retinal image slip occurs generating an error signal that drives the VOR response to increase or decrease until image slip is minimised, i.e. VOR adaptation occurs. Visual target contrast affects the human smooth pursuit and optokinetic reflex responses. We sought to determine if contrast also affected VOR adaptation. We tested 12 normal subjects, each over 16 separate sessions. For sessions 1–14, the ambient light level (lx) during adaptation training was as follows: dark, 0.1, 0.2, 0.3, 0.5, 0.7, 1, 2, 8, 16, 32, 64, 128 and 255 lx (light level for a typical room). For sessions 15–16, the laser target power (related to brightness) was halved with ambient light at 0 and 0.1 lx. The adaptation training lasted 15 min and consisted of left/right active head impulses. The VOR gain was challenged to increment, starting at unity, by 0.1 every 90 s for rotations to the designated adapting side and fixed at unity towards the non-adapting side. We measured active and passive VOR gains before and after adaptation training. We found that for both the active and passive VOR, there was a significant increase in gain only towards the adapting side due to training at contrast level 1.5 k and above (2 lx and below). At contrast level 261 and below (16 lx and above), adaptation training resulted in no difference between adapting and non-adapting side gains. Our modelling suggests that a contrast threshold of ~ 1000, which is 60 times higher than that provided by typical room lighting, must be surpassed for robust active and passive VOR adaptation. Our findings suggest contrast is an important factor for adaptation, which has implication for rehabilitation programs