Stroking or Buzzing? A Comparison of Somatosensory Touch Stimuli Using 7 Tesla fMRI.

Studying body representations in the brain helps us to understand how we humans relate to our own bodies. The in vivo mapping of the somatosensory cortex, where these representations are found, is greatly facilitated by the high spatial resolution and high sensitivity to brain activation available at ultra-high field. In this study, the use of different stimulus types for somatotopic mapping of the digits at ultra-high field, specifically manual stroking and mechanical stimulation, was compared in terms of sensitivity and specificity of the brain responses. Larger positive responses in digit regions of interest were found for manual stroking than for mechanical stimulation, both in terms of average and maximum t-value and in terms of number of voxels with significant responses to the tactile stimulation. Responses to manual stroking were higher throughout the entire post-central sulcus, but the difference was especially large on its posterior wall, i.e. in Brodmann area 2. During mechanical stimulation, cross-digit responses were more negative than during manual stroking, possibly caused by a faster habituation to the stimulus. These differences indicate that manual stroking is a highly suitable stimulus for fast somatotopic mapping procedures, especially if Brodmann area 2 is of interest

Functional connectivity and alterations in baseline brain state in humans

This work examines the influence of changes in baseline activity on the intrinsic functional connectivity fMRI (fc-fMRI) in humans. Baseline brain activity was altered by inducing anesthesia (sevoflurane end-tidal concentration 1%) in human volunteers and fc-fMRI maps between the pre-anesthetized and anesthetized conditions were compared across different brain networks. We particularly focused on low-level sensory areas (primary somatosensory, visual, and auditory cortices), the thalamus, and pain (insula), memory (hippocampus) circuits, and the default mode network (DMN), the latter three to examine higher-order brain regions. The results indicate that, while fc-fMRI patterns did not significantly differ (p<0.005; 20-voxel cluster threshold) in sensory cortex and in the DMN between the pre- and anesthetized conditions, fc-fMRI in high-order cognitive regions (i.e. memory and pain circuits) was significantly altered by anesthesia. These findings provide further evidence that fc-fMRI reflects intrinsic brain properties, while also demonstrating that 0.5 MAC sevoflurane anesthesia preferentially modulates higher-order connections

DTI tractography of theWernicke and Broca connectivity in right and left hander

We use DT-MRI and statistical fibre tracking in order to quantify the left-right asymmetry of connectivity between the posterior part of the superior temporal gyrus (Wernicke) and the homolateral pars opercularis of the frontal inferior gyrus (Broca) in 12 healthy subjects. Our results show that there is a left-right brain asymmetry in terms of connectivity. A right handed population has denser association pathways left which seems to be fairly constant over that population (small variance). The left handed population seems to be more heterogeneous in terms of lateralisation though if lateralized it will be frequently on the right

Multisensory interactions within human primary cortices revealed by BOLD dynamics.

Whether signals from different sensory modalities converge and interact within primary cortices in humans is unresolved, despite emerging evidence in animals. This is partially because of debates concerning the appropriate analyses of functional magnetic resonance imaging (fMRI) data in response to multisensory phenomena. Using event-related fMRI, we observed that simple auditory stimuli (noise bursts) activated primary visual cortices and that simple visual stimuli (checkerboards) activated primary auditory cortices, indicative of multisensory convergence. Moreover, analyses of blood oxygen level-dependent response dynamics revealed facilitation of hemodynamic response peak latencies and slopes for multisensory auditory-visual stimuli versus either unisensory condition, indicative of multisensory interactions within primary sensory cortices. Neural processing at the lowest cortical levels can be modulated by interactions between the senses. Temporal information in fMRI data can reveal these modulations and overcome analytic and interpretational challenges of more traditional procedures. In addition to providing an essential translational link with animal models, these results suggest that longstanding notions of cortical organization need to be revised to include multisensory interactions as an inherent component of functional brain organization

Airborne dust and high temperatures are risk factors for invasive bacterial disease

Background The Sahel region of West Africa has the highest bacterial meningitis attack and case fatality rate in the world. The effect of climatic factors on patterns of invasive respiratory bacterial disease is not well documented. Objective We aimed to assess the link between climatic factors and occurrence of invasive respiratory bacterial disease in a Sahel region of Niger. Methods We conducted daily disease surveillance and climatic monitoring over an 8-year period between January 1, 2003, and December 31, 2010, in Niamey, Niger, to determine risk factors for bacterial meningitis and invasive bacterial disease. We investigated the mechanistic effects of these factors on Streptococcus pneumoniae infection in mice. Results High temperatures and low visibility (resulting from high concentrations of airborne dust) were identified as significant risk factors for bacterial meningitis. Dust inhalation or exposure to high temperatures promoted progression of stable asymptomatic pneumococcal nasopharyngeal carriage to pneumonia and invasive disease. Dust exposure significantly reduced phagocyte-mediated bacterial killing, and exposure to high temperatures increased release of the key pneumococcal toxin pneumolysin through increased bacterial autolysis. Conclusion Our findings show that climatic factors can have a substantial influence on infectious disease patterns, altering density of pneumococcal nasopharyngeal carriage, reducing phagocytic killing, and resulting in increased inflammation and tissue damage and consequent invasiveness. Climatic surveillance should be used to forecast invasive bacterial disease epidemics, and simple control measures to reduce particulate inhalation might reduce the incidence of invasive bacterial disease in regions of the world exposed to high temperatures and increased airborne dust

Investigating human audio-visual object perception with a combination of hypothesis-generating and hypothesis-testing fMRI analysis tools

Primate multisensory object perception involves distributed brain regions. To investigate the network character of these regions of the human brain, we applied data-driven group spatial independent component analysis (ICA) to a functional magnetic resonance imaging (fMRI) data set acquired during a passive audio-visual (AV) experiment with common object stimuli. We labeled three group-level independent component (IC) maps as auditory (A), visual (V), and AV, based on their spatial layouts and activation time courses. The overlap between these IC maps served as definition of a distributed network of multisensory candidate regions including superior temporal, ventral occipito-temporal, posterior parietal and prefrontal regions. During an independent second fMRI experiment, we explicitly tested their involvement in AV integration. Activations in nine out of these twelve regions met the max-criterion (A &lt; AV &gt; V) for multisensory integration. Comparison of this approach with a general linear model-based region-of-interest definition revealed its complementary value for multisensory neuroimaging. In conclusion, we estimated functional networks of uni- and multisensory functional connectivity from one dataset and validated their functional roles in an independent dataset. These findings demonstrate the particular value of ICA for multisensory neuroimaging research and using independent datasets to test hypotheses generated from a data-driven analysis

Somatotopic map and inter- and intra-digit distance in Brodmann area 2 by pressure stimulation

The somatotopic representation of the tactile stimulation on the finger in the brain is an essential part of understanding the human somatosensory system as well as rehabilitation and other clinical therapies. Many studies have used vibrotactile stimulations and reported finger somatotopic representations in the Brodmann area 3 (BA 3). On the contrary, few studies investigated finger somatotopic representation using pressure stimulations. Therefore, the present study aimed to find a comprehensive somatotopic representation (somatotopic map and inter- and intra-digit distance) within BA 2 of humans that could describe tactile stimulations on different joints across the fingers by applying pressure stimulation to three joints-the first (p1), second (p2), and third (p3) joints-of four fingers (index, middle, ring, and little finger). Significant differences were observed in the inter-digit distance between the first joints (p1) of the index and little fingers, and between the third joints (p3) of the index and little fingers. In addition, a significant difference was observed in the intra-digit distance between p1 and p3 of the little finger. This study suggests that a somatotopic map and inter- and intra-digit distance could be found in BA 2 in response to pressure stimulation on finger joints.ope

Assessing the determinants of stillbirths and early neonatal deaths using routinely collected data in an inner city area

BACKGROUND: Within the UK there is considerable variation in the perinatal mortality rate. The objective of this study was to assess the factors associated with stillbirths and early neonatal deaths (ENND) and the suitability of the available databases in a health authority with one of the highest rates in the country. METHODS: Two case-control studies were carried out in three hospital trusts in the Lambeth, Southwark and Lewisham Health Authority, London, using routinely collected information. In one study, 342 stillbirths and 1,368 controls were included, and in the other study, 205 ENND and 820 controls were included. In the two studies cases and controls were matched for hospital trust. RESULTS: A birthweight below 1.5 kg was found in 54% and 48% of the stillbirths and ENND, respectively. More than 50% of the cases, stillbirths and ENND, had a length of gestation below 32 weeks. Length of gestation, birthweight, emergency caesarean section and age of the mother were associated with stillbirths. Birthweight and Apgar score at 1 minute as a categorical variable were associated with ENND. There was no direct evidence of an effect of social deprivation on the outcomes of interest. CONCLUSION: Birthweight and length of gestation are the most influential factors on an unfavourable outcome. Conception at an older age has a serious impact on stillbirth rates. In our health authority social disadvantage did not have a direct impact on stillbirth and ENND. Maternity information systems should collect routine data on fewer variables, but their quality in terms of value, standardization and completion rates must improve