New approaches to the study of human brain networks underlying spatial attention and related processes

Cognitive processes, such as spatial attention, are thought to rely on extended networks in the human brain. Both clinical data from lesioned patients and fMRI data acquired when healthy subjects perform particular cognitive tasks typically implicate a wide expanse of potentially contributing areas, rather than just a single brain area. Conversely, evidence from more targeted interventions, such as transcranial magnetic stimulation (TMS) or invasive microstimulation of the brain, or selective study of patients with highly focal brain damage, can sometimes indicate that a single brain area may make a key contribution to a particular cognitive process. But this in turn raises questions about how such a brain area may interface with other interconnected areas within a more extended network to support cognitive processes. Here, we provide a brief overview of new approaches that seek to characterise the causal role of particular brain areas within networks of several interacting areas, by measuring the effects of manipulations for a targeted area on function in remote interconnected areas. In human participants, these approaches include concurrent TMS-fMRI and TMS-EEG, as well as combination of the focal lesion method in selected patients with fMRI and/or EEG measures of the functional impact from the lesion on interconnected intact brain areas. Such approaches shed new light on how frontal cortex and parietal cortex modulate sensory areas in the service of attention and cognition, for the normal and damaged human brain

Neural representations of the sense of self

The brain constructs representations of what is sensed and thought about in the form of nerve impulses that propagate in circuits and network assemblies (Circuit Impulse Patterns, CIPs). CIP representations of which humans are consciously aware occur in the context of a sense of self. Thus, research on mechanisms of consciousness might benefit from a focus on how a conscious sense of self is represented in brain. Like all senses, the sense of self must be contained in patterns of nerve impulses. Unlike the traditional senses that are registered by impulse flow in relatively simple, pauci-synaptic projection pathways, the sense of self is a system- level phenomenon that may be generated by impulse patterns in widely distributed complex and interacting circuits. The problem for researchers then is to identify the CIPs that are unique to conscious experience. Also likely to be of great relevance to constructing the representation of self are the coherence shifts in activity timing relations among the circuits. Consider that an embodied sense of self is generated and contained as unique combinatorial temporal patterns across multiple neurons in each circuit that contributes to constructing the sense of self. As with other kinds of CIPs, those representing the sense of self can be learned from experience, stored in memory, modified by subsequent experiences, and expressed in the form of decisions, choices, and commands. These CIPs are proposed here to be the actual physical basis for conscious thought and the sense of self. When active in wakefulness or dream states, the CIP representations of self act as an agent of the brain, metaphorically as an avatar. Because the selfhood CIP patterns may only have to represent the self and not directly represent the inner and outer worlds of embodied brain, the self representation should have more degrees of freedom than subconscious mind and may therefore have some capacity for a free-will mind of its own. S everal lines of evidence for this theory are reviewed. Suggested new research includes identifying distinct combinatorially coded impulse patterns and their temporal coherence shifts in defined circuitry, such as neocortical microcolumns. This task might be facilitated by identifying the micro-topography of field-potential oscillatory coherences among various regions and between different frequencies associated with specific conscious mentation. Other approaches can include identifying the changes in discrete conscious operations produced by focal trans-cranial magnetic stimulation

Three-dimensional speckle tracking echocardiography in the assessment of right ventricular dysfunction after surgical repair of tetralogy of Fallot.

Background: The combined effects of preoperative hypertrophy and hypoxia, possible intraoperative myocardial damage, type of reconstruction, and acquired postoperative lesions such as pulmonary regurgitation may result in impaired RV deformation in post-operative tetralogy of Fallot (TF). Recently 3D speckle tracking echocardiography (3DSTE) has been proposed to assess mechanical dyssynchrony in these patients but the role of electromechanical dysfunction is not completely clear. Methods: Sixteen patients after TF repair (aged 17-53years) with dilated right ventricle, right bundle branch block (QRS >120ms), and NYHA class I or greater were studied with twodimensional and three-dimensional speckle tracking echocardiography. Right ventricular enddiastolic and end-systolic volumes were measured from three-dimensional datasets and right ventricular ejection fraction (3D-RVEF) was obtained. Right intraventricular dyssynchrony was determined as the difference between the longest and shortest electromechanical coupling times in the basal septal and lateral RV segments. Interventricular dyssynchrony was determined as the difference between electromechanical coupling times in the basal lateral LV segment and the most delayed RV segment. Sixteeen age-matched healthy subjects were selected as controls. Results: Right intraventricular dyssynchrony (77.1+/-24.2ms vs 13.1+/-8.9ms) and interventricular dyssynchrony (74.7+/-22.2ms vs 11.4+/-7.9ms) were shown in patients compared to normal controls. Right intraventricular dyssynchrony correlated with RV longitudinal strain (r=0.62, p<0.005), 3D RV end-systolic volume (r=0.47, p=0.02), and QRS duration (r=0.39, p=0.03). Interventricular dyssynchrony correlated with RV longitudinal strain (r=0.73, p<0.001), RV systolic pressure (r=0.59, p<0.005), 3D-RVEF (r=0.53, p=0.003), and QRS duration (r=-0.44, p=0.031). Reduced RV strain, 3D-RVEF and prolonged QRS duration were the main determinant factors predicting RV dyssynchrony by multivariate analysis. On ROC curves RV strain and 3DRVEF had optimal predictive accuracy of the NYHA functional class and a larger area under the receiver operating characteristic curve than the QRS duration. Conclusions: In patients with repaired TF RV dyssynchrony is associated with reduced 3D-RVEF and RV 3DSTE parameters

The TURP Sindrome: importance of expiratory ethanol measurement and high serum levels of glycine.

OBJECTIVE: In a prospective study it was our intention to evaluate the reliability and the predictive value of expiratory ethanol for the early detection of the occurrence of TURP syndrome and emphasize the role of the serum levels of glycine in clinical manifestation. METHODS: We studied 30 patients scheduled for elective traditional transuretral resection of the prostate performed with subarachnoid anesthesia. Serum sodium and glycine concentrations, serum osmolality and end-expiratory ethanol levels were monitored at scheduled intervals. Continuous heart rate and blood pressure monitoring was performed during the perioperative period in the operativing room and, later, in the recovery room. Occurrence of cardiocirculatory, respiratory and neurologic symptoms were recorded. Statistics included Bonferroni's t-test and Fisher's exact test. A decision level plot for end-expiratory ethanol level was performed for the choice of predictivity criterion. RESULTS: In our population we identified three groups of patients: Group I (15 patients) in which no symptom was recorded; Group II (6 patients) in which non-specific anesthesia-related symptoms occurred; Group III (9 patients) in which TURP syndrome of various degree of severity was observed. In this group of patients changes in serum sodium and glycine concentrations, serum osmolality and end-expiratory ethanol levels were significantly different compared with the other two groups. In regard to end-expiratory ethanol levels, we identified a cut-off point at 0.05 mg/ml. In Group III two patients developed transient blindness. These patients had the highest serum glycine concentrations (> 4000 mumol/ml). Mortality was nil. CONCLUSIONS: Our data show the reliability and accuracy of end-expiratory ethanol levels as a predictive test of the occurrence of TURP syndrome. Further, we emphasize the role of serum glycine concentration in the occurrence of neurologic symptoms related to the transurethral resection of the prostate

Utility of Strain Echocardiography at Rest and After Stress Testing in Arrhythmogenic Right Ventricular Dysplasia

The introduction of speckle tracking imaging (STI) allowed the quantification of the regional myocardial function in the right ventricular (RV) free wall using deformation parameters. We sought to evaluate the potential utility of STI at rest and after stress to predict arrhythmogenic RV dysplasia (ARVD). We studied 19 patients with ARVD (diagnosed according to the task force criteria) and 19 healthy age- and gender-matched subjects. Both 2-dimensional and 3-dimensional echocardiography were performed. The RV and left ventricular annular peak systolic velocities were measured using tissue Doppler imaging. The RV-left ventricular peak systolic longitudinal strain (LS) was obtained in the basal, mid, and apical segments in the apical 4-chamber view using STI. An exercise stress-echocardiographic test was undertaken using bicycle ergometry with the patient in the supine position for all patients, and the indexes were assessed at peak effort. The STI measurements were determined using offline analysis programs. The 3-dimensional RV ejection fraction and strain were significantly lower in patients with ARVD than in the controls. The RV strain values at rest did not change significantly during maximum physical effort in the patients with ARVD. The receiver operating characteristic curves suggested that the thresholds offering an adequate compromise between sensitivity and specificity for the detection of ARVD were 9.35 cm/s for the RV annular peak systolic velocity (area under the curve 0.81), 42% for 3-dimensional RV ejection fraction (area under the curve 0.85), -25% for mean global RV-LS (area under the curve 0.86), -18% for the lowest peak systolic RV-LS (area under the curve 0.88), and -1.2 for peak minus baseline global change of stress RV-LS (area under the curve 0.92). In conclusion, STI at rest and during stress might enable quantitative assessment of RV function and the detection of ARVD and have potential clinical value in the treatment of these patients