The role of the cerebral cortex in postural responses to externally induced perturbations

The ease with which we avoid falling down belies a highly sophisticated and distributed neural network for controlling reactions to maintain upright balance. Although historically these reactions were considered within the sub cortical domain, mounting evidence reveals a distributed network for postural control including a potentially important role for the cerebral cortex. Support for this cortical role comes from direct measurement associated with moments of induced instability as well as indirect links between cognitive task performance and balance recovery. The cerebral cortex appears to be directly involved in the control of rapid balance reactions but also setting the central nervous system in advance to optimize balance recovery reactions even when a future threat to stability is unexpected. In this review the growing body of evidence that now firmly supports a cortical role in the postural responses to externally induced perturbations is presented. Moreover, an updated framework is advanced to help understand how cortical contributions may influence our resistance to falls and on what timescale. The implications for future studies into the neural control of balance are discussed.

Contribution of primary motor cortex to compensatory balance reactions

Background: Rapid compensatory arm reactions represent important response strategies following an unexpected loss of balance. While it has been assumed that early corrective actions arise largely from sub-cortical networks, recent findings have prompted speculation about the potential role of cortical involvement. To test the idea that cortical motor regions are involved in early compensatory arm reactions, we used continuous theta burst stimulation (cTBS) to temporarily suppress the hand area of primary motor cortex (M1) in participants prior to evoking upper limb balance reactions in response to whole body perturbation. We hypothesized that following cTBS to the M1 hand area evoked EMG responses in the stimulated hand would be diminished. To isolate balance reactions to the upper limb participants were seated in an elevated tilt-chair while holding a stable handle with both hands. The chair was held vertical by a magnet and was triggered to fall backward unpredictably. To regain balance, participants used the handle to restore upright stability as quickly as possible with both hands. Muscle activity was recorded from proximal and distal muscles of both upper limbs.

Results: Our results revealed an impact of cTBS on the amplitude of the EMG responses in the stimulated hand muscles often manifest as inhibition in the stimulated hand. The change in EMG amplitude was specific to the target hand muscles and occasionally their homologous pairs on the non-stimulated hand with no consistent effects on the remaining more proximal arm muscles.

Conclusions: Present findings offer support for cortical contributions to the control of early compensatory arm reactions following whole-body perturbation.

Enhanced inflammatory responses in alpha-tocopherol transfer protein null mice

The liver preferentially secretes alpha-tocopherol into plasma under the control of the hepatic alpha-tocopherol transfer protein (alpha-TTP). alpha-TTP-null mice (Ttpa(-/-) mice) are vitamin E deficient, therefore were used for investigations of in vivo responses to sub-normal tissue alpha-tocopherol concentrations during inflammation. Increased basal oxidative stress in Ttpa(-/-) mice was documented by increased plasma lipid peroxidation, and superoxide production by bone marrow-derived neutrophils stimulated in vitro with phorbol 12-myristate 13-acetate. Lipopolysaccharide (LPS) injected intraperitoneally induced increases in lung and liver HO-1 and iNOS, as well as plasma NO(x) in Ttpa(+/+) mice. LPS induced more modest increases in these markers in Ttpa(-/-) mice, while more marked increases in plasma IL-10 and lung lavage TNF alpha were observed. Taken together, these results demonstrate that alpha-tocopherol is important for proper modulation of inflammatory responses and that sub-optimal alpha-tocopherol concentrations may derange inflammatory-immune responses.

Legal Responses to Racism: Innovation and Retrenchment in Ireland

Following decades in which the absence of immigration allowed Governments to claim there was no problem of racism in Ireland, the 1990s saw Ireland adopt new equality measures to combat racism. Whilst these innovations are important and even innovative, paradoxically they are accompanied by policy initiatives which indicate the equality agenda is still very much a controversial one and possibly even in retreat. More radical reforms are needed than merely tinkering with the Equality laws.

Teachers and pupils: educational experiences and school based responses to the conflict in Northern Ireland

This article describes a study which examined (a) the impact of the political conflict on teachers' and ppils' experiences of education in Northern Ireland and (b) the impact of curricular-based interventions designed to support the ppils and reduce prejudice. The focus of the second part of the article is on the prejudice reduction initiatives identified. A total of 44 staff and 78 pupils spread across 8 schools participated and both teachers' and ppils' perspectives were identified, the latter being an extremely important dimension which has rarely been addressed in previous studies of this area. The findings, which highlight the complexity of the impact of the political conflict, are considered to have both practical and theoretical implications for prejudice reduction programs.

The effect of videotapes of animals on cardiovascular responses to stress

Animals have long been noted for their ability to moderate cardiovascular responses to stress. To date, however, little attention has been directed towards the ability of videotapes of animals to buffer people from challenges. This study thus explored the effect of five video conditions (fish, bird, primate, control 1 [humans], control 2 [blank screen]) on the heart rate and blood pressure of 100 volunteers before and after exposure to a cognitive stressor. Twenty participants were randomly assigned to each of the video conditions. Both the heart rate and blood pressure (diastolic and systolic) of the participants were recorded after a 10 minute period of relaxation (phase 1), following 10 minutes of exposure to the appropriate video for that condition (phase 2) and again, following a 10 minute period of reading aloud, i.e. a cognitive stressor (phase 3). The videos encouraged relaxation, with participants in all conditions exhibiting significantly (p < 0.001) lower levels of heart rate and blood pressure in phase 2 than phases 1 or 3. Individuals exposed to the videos of birds, fish and primates showing significantly (p < 0.001) lower levels of heart rate and blood pressure in phase 3 than individuals exposed to the control videos. It is concluded that videotapes of certain animals can reduce cardiovascular responses to psychological stress and may help to buffer viewers from anxiety, at least in the short term.