The cognitive auditory cortex: task-specificity of stimulus representations

Auditory cortex (AC), like subcortical auditory nuclei, represents properties of auditory stimuli by spatiotemporal activation patterns across neurons. A tacit assumption of AC research has been that the multiplicity of functional maps in primary and secondary areas serves a refined continuation of subcortical stimulus processing, i.e. a parallel orderly analysis of distinct properties of a complex sound. This view, which was mainly derived from exposure to parametric sound variation, may not fully capture the essence of cortical processing. Neocortex, in spite of its parcellation into diverse sensory, motor, associative, and cognitive areas, exhibits a rather stereotyped local architecture. The columnar arrangement of the neocortex and the quantitatively dominant connectivity with numerous other cortical areas are two of its key features. This suggests that cortex has a rather common function which lies beyond those usually leading to the distinction of functional areas. We propose that task-relatedness of the way, how any information can be represented in cortex, is one general consequence of the architecture and corticocortical connectivity. Specifically, this hypothesis predicts different spatiotemporal representations of auditory stimuli when concepts and strategies how these stimuli are analysed do change. We will describe, in an exemplary fashion, cortical patterns of local field potentials in gerbil, of unit spiking activity in monkey, and of fMRI signals in human AC during the execution of different tasks mainly in the realm of category formation of sounds. We demonstrate that the representations reflect context- and memory-related, conceptual and executional aspects of a task and that they can predict the behavioural outcome.     

Predictive value of normal sperm morphology: a structured literature review

The aim of the study was to conduct a structured review of theliterature published on the use of normal sperm morphology,as an indicator of male fertility potential in the in-vitrofertilization (IVF) situation, and to establish the universalpredictive value of this semen parameter. Published literaturein which normal sperm morphology was used to predict fertilizationand pregnancy, during the period 1978-1996, was reviewed. Atotal of 216 articles were identified by the sourcing methodology,but only 49 provided data that could be tabulated and analysed.Of these, only 18 provided sufficient data for statistical analysis.Fifteen studies used the strict criteria to evaluate sperm morphology,two used World Health Organization (WHO) guidelines and oneused both the strict criteria and the WHO guidelines. All thestudies (n=10) using the 5 and 14% normal sperm morphology thresholds(strict criteria) produced positive predictive values for IVFsuccess. In the prediction of pregnancy, 82% (9/11) and 75%(6/8) of the studies produced positive predictive values whenusing the 5% and 14% thresholds respectively. Aggregating thedata produced around the 5% normal sperm morphology threshold(strict criteria), the overall fertilization rates were 59.3%(1979/3337; per oocyte) for the 4% group and 77.6% (10345/13327;per oocyte) for the >4% group, and the overall pregnancyrates were 15.2% (60/395; per cycle) and 26.0% (355/1368; percycle) respectively. The no-transfer rates across the 5% thresholdwere 24.0% (86/359; per cycle) in the 4% group compared to 7.4%(80/1088; per cycle) in the >4% group. The inclusion of anaccurately evaluated normal sperm morphology count as an integralpart of the standard semen analysis makes this analysis stillthe most cost-effective means of evaluating the male factor.     

Single-Photon Emission Computed Tomographic Perfusion Imaging in Autopsy-Diagnosed Dementia

Physiological imaging of regional cerebral blood flow with single-photon emission computed tomography (SPECT) has been proposed to be diagnostically useful in the evaluation of patients with dementia because of the frequent finding of temporal and parietal lobe hypoperfusion in patients with Alzheimer's disease (AD). A major limitation of SPECT to date has been the selection of patients using clinical criteria, which may be unreliable in excluding patients with non-Alzheimer dementias from study. SPECT with the perfusion tracer ¹²³l-N-isopropyl-p-iodoamphetamine was used to study 16 dementia patients who were subsequently followed to autopsy, as well as 16 elderly control subjects. Eleven dementia patients had the diagnosis of AD confirmed by autopsy, while 5 had other, nonAD dementias. SPECT perfusion patterns were evaluated as regional ratios of lobar radioactivity counts normalized to either activity counts in the occipital lobes (occipital ratio) or activity counts in the entire tomographic slice (whole-slice ratio). Results showed that the relative frontal perfusion differentiated non-AD patients from control subjects and AD patients regardless of which ratio method was used, while temporal and parietal relative perfusion ratios were more effective at differentiating AD from non-AD patients when the whole-slice ratio was used, although the ratio used did not affect the differentiation of AD patients from control subjects. Scatterplots of the whole-slice ratio in the right parietal and left temporal lobes showed no overlap between AD and non-AD patients and control subjects. These results support the diagnostic utility of SPECT in the clinical evaluation of dementia patients, particularly in distinguishing AD from non-AD dementias during life.     

Optimal management strategies for placenta accreta

Objective  To determine which interventions for managing placenta accreta were associated with reduced maternal morbidity.
Design  Retrospective cohort study.
Setting  Two tertiary care teaching hospitals in Utah.
Population  All identified cases of placenta accreta from 1996 to 2008.
Methods  Cases of placenta accreta were identified using standard ICD-9 codes for placenta accreta, placenta praevia, and caesarean hysterectomy. Medical records were then abstracted for maternal medical history, hospital course, and maternal and neonatal outcomes. Maternal and neonatal complications were compared according to antenatal suspicion of accreta, indications for delivery, preoperative preparation, attempts at placental removal before hysterectomy, and hypogastric artery ligation.
Main outcome measures  Early morbidity (prolonged maternal intensive care unit admission, large volume of blood transfusion, coagulopathy, ureteral injury, or early re-operation) and late morbidity (intra-abdominal infection, hospital re-admission, or need for delayed re-operation).
Results  Seventy-six cases of placenta accreta were identified. When accreta was suspected, scheduled caesarean hysterectomy without attempting placental removal was associated with a significantly reduced rate of early morbidity compared with cases in which placental removal was attempted (67 versus 36%, P = 0.038). Women with preoperative bilateral ureteric stents had a lower incidence of early morbidity compared with women without stents (18 versus 55%, P = 0.018). Hypogastric artery ligation did not reduce maternal morbidity.
Conclusions  Scheduled caesarean hysterectomy with preoperative ureteric stent placement and avoiding attempted placental removal are associated with reduced maternal morbidity in women with suspected placenta accreta.     

Comparison of three-dimensional virtual endoscopy with bronchoscopy in patients with oesophageal carcinoma infiltrating the tracheobronchial tree.

Virtual endoscopy (VE) is a technique for performing simulated bronchoscopy using helical CT data of the tracheobronchial tree. In order to evaluate a virtual three-dimensional (3D) endoluminal procedure for the tracheobronchial tree, comparison was made between bronchoscopy, axial CT images and minimal intensity projections (MIP). 21 patients were referred for helical CT because of oesophageal carcinoma shown by bronchoscopy to infiltrate into the trachea or bronchi. Axial CT images obtained on a helical scanner were transferred to a Sparc20 workstation. VE was compared with the axial CT images and the MIP concerning additional information on the location and degree of stenosis gained after 3D reconstruction of the inner surface of the tracheobronchial tree. The accuracy of this VE system was compared with bronchoscopy. Follow-up was performed in two patients to evaluate the tracheobronchial system after stent implantation. All stenoses were identified by VE with no statistically significant difference in detection of location or grading of the stenosis to real time bronchoscopy. Passage of subtotal stenosis was only possible with VE. VE is suitable for following up stent implantation. Submucosal lesions of the tracheobronchial tree could not be detected by VE. There was no statistically significant difference regarding the location of the stenoses between VE, axial CT slices, MIP and bronchoscopy. The VE showed only a statistically significant difference with regard to the degree of stenosis which was underrated on axial CT slices and MIPs. Pitfalls including mucus plugs and wall defects due to the wrong threshold value were a limitation of VE. VE is presently too time-consuming to use in every patient with an infiltrating tumour into the tracheobronchial tree. In conclusion, while VE cannot replace endoscopy of the tracheobronchial tree or the oesophagus, it is an accurate and non-invasive method for identifying endoluminal tumours, grading stenoses and visualizing the tracheobronchial tree beyond stenoses in a small number of patients who are not amenable to endoscopy.     

PET of malignant cerebral tumors after interstitial brachytherapy. Demonstration of metabolic activity and correlation with clinical outcome

Positron emission tomography (PET) with rubidium-82 (82Rb) and fluorine-18-fluorodeoxyglucose (18F-FDG) was used to diagnose active tumor recurrence and to differentiate this from radiation injury after interstitial irradiation of malignant gliomas. Patients were studied when they presented with radiological or clinical deterioration after an initial period of posttreatment stabilization. Forty studies were performed in 34 patients. The 82Rb was used as a blood-brain barrier tracer to localize the lesion. Uptake of 18F-FDG by the lesion was then compared to uptake by adjacent brain in order to make a diagnosis of active tumor recurrence (higher or equal lesion uptake) or no active tumor (lower uptake). Radiation injury was diagnosed by the exclusion of active tumor. A retrospective clinical diagnosis was established in 38 cases by following the patients' progress for 8 to 142 weeks after the PET study. In two cases, no follow-up diagnosis could be determined. The PET results agreed with the follow-up diagnosis in 15 of 17 cases of active tumor and 17 of 21 cases of radiation injury. Histological examination of surgically resected tissue obtained after the PET study was performed in 18 patients (nine with tumor regrowth and nine with radiation injury). This showed apparently viable tumor as well as necrosis in all cases, regardless of eventual clinical outcome. Some cells from the irradiated volume may appear morphologically intact, but have little or no metabolic or clinical activity. The functional nature of the PET-FDG technique allows diagnosis of tumor activity, which cannot be demonstrated by anatomic imaging studies or by histological examination. The addition of a blood-brain barrier tracer to the 18F-FDG study aids in differentiating normal brain uptake from tumor activity and improves the accuracy of the technique.