Does hemispheric lateralization influence functional and cardiovascular outcomes after stroke?: an analysis of placebo-treated patients from prospective acute stroke trials

<p><b>Background and Purpose:</b> The influence of stroke lateralization on functional and cardiovascular outcome after stroke is not well established. We evaluated the influence of hemispheric lateralization among patients enrolled in prospective acute stroke trials.</p> <p><b>Methods:</b> We obtained data from the VISTA database for acute stroke trials which reported lateralization. Baseline data, cardiac adverse events, and 90-day outcomes were compared between right and left hemisphere stroke patients. A "hemisphere unbiased" subscore of the NIHSS which omitted items strongly associated with lateralized cognitive deficits was also compared for trials which reported individual NIHSS item scores. A multivariable analysis of outcome predictors was performed.</p> <p><b>Results:</b> Three acute stroke trials met the prespecified inclusion criteria. 1644 placebo-treated patients with documented hemispheric lateralization were included in the analysis. Baseline NIHSS was higher for left hemisphere patients (mean 16.2, versus 12.8 right, P < 0.001); there was no difference in the "hemisphere unbiased" NIHSS subscore (10.88 left, 11.08 right, n=687, P= 0.49). There was no difference between hemispheres in 90-day modified Rankin Score (3.43 left, 3.29 right, P=0.13), mortality (22.1% left, 19.5% right, P=0.20), or cardiac adverse events (P=0.71). Hemispheric lateralization was not an independent predictor of outcome in the multivariable analysis after controlling for the hemispheric bias intrinsic to the NIHSS.</p> <p><b>Conclusions:</b> There is no difference in functional outcome between patients with right or left hemisphere stroke. Use of the baseline NIHSS score to predict stroke outcome must take hemispheric lateralization into account. Stroke lateralization is not an important predictor of cardiac adverse events or 90-day mortality.</p&gt

Marmots do not consistently use their left eye to respond to an approaching threat but those that did fled sooner.

In many vertebrates, the brain's right hemisphere which is connected to the left visual field specializes in the processing of information about threats while the left hemisphere which is connected to the right visual field specializes in the processing of information about conspecifics. This is referred to as hemispheric lateralization. But individuals that are too predictable in their response to predators could have reduced survival and we may expect selection for somewhat unpredictable responses. We studied hemispheric lateralization in yellow-bellied marmots Marmota flaviventer, a social rodent that falls prey to a variety of terrestrial and aerial predators. We first asked if they have lateralized responses to a predatory threat. We then asked if the eye that they used to assess risk influenced their perceptions of risk. We recorded the direction marmots were initially looking and then walked toward them until they fled. We recorded the distance that they responded to our experimental approach by looking, the eye with which they looked at us, and the distance at which they fled (i.e., flight initiation distance; FID). We found that marmots had no eye preference with which they looked at an approaching threat. Furthermore, the population was not comprised of individuals that responded in consistent ways. However, we found that marmots that looked at the approaching person with their left eye had larger FIDs suggesting that risk assessment was influenced by the eye used to monitor the threat. These findings are consistent with selection to make prey less predictable for their predators, despite underlying lateralization

Development of lateralization of the magnetic compass in a migratory bird

The magnetic compass of a migratory bird, the European robin (Erithacus rubecula), was shown to be lateralized in favour of the right eye/left brain hemisphere. However, this seems to be a property of the avian magnetic compass that is not present from the beginning, but develops only as the birds grow older. During first migration in autumn, juvenile robins can orient by their magnetic compass with their right as well as with their left eye. In the following spring, however, the magnetic compass is already lateralized, but this lateralization is still flexible: it could be removed by covering the right eye for 6 h. During the following autumn migration, the lateralization becomes more strongly fixed, with a 6 h occlusion of the right eye no longer having an effect. This change from a bilateral to a lateralized magnetic compass appears to be a maturation process, the first such case known so far in birds. Because both eyes mediate identical information about the geomagnetic field, brain asymmetry for the magnetic compass could increase efficiency by setting the other hemisphere free for other processes

How to deal with an open abdomen?

Appropriate open abdomen treatment is one of the key elements in the management of patients who require decompressive laparotomy or in whom the abdomen is left open prophylactically. Apart from fluid control and protection from external injury, fluid evacuation and facilitation of early closure are now the goals of open abdomen treatment. Abdominal negative pressure therapy has emerged as the most appropriate method to reach these goals. Especially when combined with strategies that allow progressive approximation of the fascial edges, high closure rates can be obtained. Intra-abdominal pressure measurement can be used to guide the surgical strategy and continued attention to intra-abdominal hypertension is necessary. This paper reviews recent advances as well as identifying the remaining challenges in patients requiring open abdomen treatment. The new classification system of the open abdomen is an important tool to use when comparing the efficacy of different strategies, as well as different systems of temporary abdominal closure

When does right functional hemispheric lateralization arise? Evidence from preterm infants

In recent years, magnetic resonance imaging (MRI) has allowed researchers to individuate an earlier morphological development of the right hemisphere compared to the left hemisphere before birth. Anatomical asymmetry, however, does not necessarily mean functional asymmetry and whether the anatomical differences between hemispheres at this early age are paralleled by functional specializations is still unknown. Here we show electrophysiological evidence of an early functional right lateralization for pitch processing arising by 30 gestational weeks, not before, in preterm newborns

Testosterone and grasp-reflex differences in human neonates

According to the Geschwind-Behan-Galaburda (GBG) hypothesis, prenatal testosterone (T) causes a slowing in the development of the left brain with a consequent compensatory growth in the right brain, creating a reverse organisation of the cerebral lateralisation. That is, left- and right-handedness might be associated with high and low prenatal T levels, respectively. To test this hypothesis, the relations of T levels (umbilical cord blood) to grasp-reflex strengths were studied in human neonates. Handedness was assessed by measuring the grasp-reflex strengths from the right and left hands in 10 trials from each hand alternatively. There were two handedness groups: right-handers (R-L significantly greater than zero) and left-handers (significantly smaller than zero). Contrary to the GBG model, the mean free T concentration was found to be significantly higher in right-handers than left-handers for males and females. There was no significant difference in the total T levels between right- and left-handers. Free T concentrations positively correlated with R-L grasp-reflex strengths, i.e. right-handedness increased as T increased, and left-handedness increased as T decreased. Contrary to these positive correlations, T negatively correlated with the grasp-reflex strengths from the right and left hands. These results partly supported the GBG hypothesis for this spinal-motor-asymmetry model. Total T did not significantly correlate with grasp-reflex strengths. The results suggest that prenatal T may at least play a role in prenatal determination of spinal motor lateralisation, with a possible consequent upward regulation of cerebral lateralisation

The evolution of brain lateralization: A game theoretical analysis of population structure

In recent years, it has become apparent that behavioural and brain lateralization is the rule rather than the exception among vertebrates. The study of lateralization has been so far the province of neurology and neuropsychology. We show how such research can be integrated with evolutionary biology to more fully understand lateralization. In particular, we address the fact that, within a species, left- and right-type individuals are often in a definite proportion different from 1/2 (e.g., hand use in humans). We argue that traditional explanations of brain lateralization (that it may avoid costly duplication of neural circuitry and reduce interference between functions) cannot account for this fact, because increased individual efficiency is unre- lated to the frequency of left- and right-type individuals in a population. A further puzzle is that, if a majority of individuals are of the same type, individual behaviour becomes more predictable to other organisms. Here we show that alignment of the direction of behavioural asymmetries in a population can arise as an evolutionarily stable strategy (ESS), when individually asymmetrical organisms must coordinate their behaviour with that of other asymmetrical organisms. Thus, brain and behavioural lateralization, as we know it in humans and other vertebrates, may have evolved under basically "social" selection pressures