Preserved local but disrupted contextual figure-ground influences in an individual with abnormal function of intermediate visual areas

Visual perception depends not only on local stimulus features but also on their relationship to the surrounding stimulus context, as evident in both local and contextual influences on figure-ground segmentation. Intermediate visual areas may play a role in such contextual influences, as we tested here by examining LG, a rare case of developmental visual agnosia. LG has no evident abnormality of brain structure and functional neuroimaging showed relatively normal V1 function, but his intermediate visual areas (V2/V3) function abnormally. We found that contextual influences on figure-ground organization were selectively disrupted in LG, while local sources of figure-ground influences were preserved. Effects of object knowledge and familiarity on figure-ground organization were also significantly diminished. Our results suggest that the mechanisms mediating contextual and familiarity influences on figure-ground organization are dissociable from those mediating local influences on figure-ground assignment. The disruption of contextual processing in intermediate visual areas may play a role in the substantial object recognition difficulties experienced by LG.     

The thing that should not be: predictive coding and the uncanny valley in perceiving human and humanoid robot actions

Using functional magnetic resonance imaging (fMRI) repetition suppression, we explored the selectivity of the human action perception system (APS), which consists of temporal, parietal and frontal areas, for the appearance and/or motion of the perceived agent. Participants watched body movements of a human (biological appearance and movement), a robot (mechanical appearance and movement) or an android (biological appearance, mechanical movement). With the exception of extrastriate body area, which showed more suppression for human like appearance, the APS was not selective for appearance or motion per se. Instead, distinctive responses were found to the mismatch between appearance and motion: whereas suppression effects for the human and robot were similar to each other, they were stronger for the android, notably in bilateral anterior intraparietal sulcus, a key node in the APS. These results could reflect increased prediction error as the brain negotiates an agent that appears human, but does not move biologically, and help explain the 'uncanny valley' phenomenon.     

Double blind randomised controlled trial of topical glyceryl trinitrate in anal fissure.

AIMS: To determine the effectiveness and safety of topical glyceryl trinitrate (GTN) in the management of acute anal fissure in children. METHODS: Individual children were randomised to receive GTN paste or placebo for six weeks in addition to oral senna and lactulose. Patients took laxatives alone for a further 10 weeks. Each week a research nurse telephoned families to assess pain scores and give advice. Main outcome measures were validated standardised pain scores and time to painless defaecation. RESULTS: Forty subjects were recruited from 46 eligible children; 31 children completed the trial (13 in the GTN group and 18 in the placebo group). No differences in the proportion of those achieving pain free defaecation with relation to time were seen between the two groups. Similarly, there were no significant differences in pain scores between the two groups over the 16 week study period. However, in both groups pain scores had decreased significantly. There were no differences in the incidence of rectal bleeding, faecal soiling, presence of visible fissure, skin tag, or faecal loading at outpatient review at the time of recruitment, or at 6 weeks and 16 weeks. No serious adverse effects were observed. CONCLUSIONS: This study suggests that 0.2% GTN paste is ineffective in the treatment of acute anal fissures in childhood. However the overall fissure healing rate is high (84%) with associated reduction in pain scores, suggesting that a nurse based treatment programme can achieve a high rate of fissure healing.     

Coupling between cerebral blood flow and cerebral blood volume: Contributions of different vascular compartments

A better understanding of the coupling between changes in cerebral blood flow (CBF) and cerebral blood volume (CBV) is vital for furthering our understanding of the BOLD response. The aim of this study was to measure CBF‐CBV coupling in different vascular compartments during neural activation. Three haemodynamic parameters were measured during a visual stimulus. Look‐Locker flow‐sensitive alternating inversion recovery was used to measure changes in CBF and arterial CBV (CBV_a) using sequence parameters optimized for each contrast. Changes in total CBV (CBV_tot) were measured using a gadolinium‐based contrast agent technique. Haemodynamic changes were extracted from a region of interest based on voxels that were activated in the CBF experiments. The CBF‐CBV_tot coupling constant α_tot was measured as 0.16 ± 0.14 and the CBF‐CBV_a coupling constant α_a was measured as 0.65 ± 0.24. Using a two‐compartment model of the vasculature (arterial and venous), the change in venous CBV (CBV_v) was predicted for an assumed value of baseline arterial and venous blood volume. These results will enhance the accuracy and reliability of applications that rely on models of the BOLD response, such as calibrated BOLD.     

Expression of histamine H1 receptors on cultured histiocytic lymphoma cells

Histamine H1 receptors were identified in U937 human histiocytic lymphoma cells using a radioligand binding technique with [3H]mepyramine. Reversible high-affinity binding with this ligand was obtained, and specificity of binding for selected H1 agonists and antagonists was demonstrated. Competition binding experiments with mepyramine and histamine yielded results consistent with single-site binding for mepyramine and two-site binding for histamine. Dissociation constants for the high- and low-affinity histamine binding states were 6.8 X 10(-6) and 2.4 X 10(-4) M respectively. The high-affinity state for histamine binding was abolished when the membranes were coincubated with 100 microM guanosine-5'-O-(3-thiotriphosphate) (GTP gamma S). Saturation binding studies yielded an average of 66 fmol/mg protein binding sites (6000 receptors per cell) with a [3H]mepyramine KD of 9.6 nM. When differentiation of these cells was induced by phorbol-myristate-acetate, receptor density increased by 73% to 114 fmol/mg protein. This increase in receptor density was inhibited by actinomycin D and cycloheximide. Exposure of native and differentiated U937 cells to 10(-5) and 10(-4) M histamine for 24 hr resulted in a dose-dependent down-regulation in receptor density. The data indicate that U937 cells may provide a model cell line for the study of histamine receptor gene expression.     

A controlled trial of sip-feed supplements in elderly orthopaedic patients

The potential nutritional and clinical benefits of sip-feed supplements were investigated by means of a controlled trial in elderly female patients admitted for orthopaedic surgery. A nutritional risk assessment procedure (Nutritional Risk Questionnaire, NRQ) was used to identify patients who might benefit from supplementation. Patients identified as high risk who did not receive supplements showed significant losses in triceps skinfold thickness (TSF) and mid-upper arm muscle circumference (MUAMC) measurements during hospitalization. Such changes were not observed in high-risk supplemented patients, but significant losses of MUAMC were also recorded in a group of patients who failed to comply with the supplement. No differences in biochemical parameters, muscle function, or clinical outcome were observed between supplemented and unsupplemented and non-compliant patients. The problems of poor compliance to sip-feed supplements and failure to observe clinical benefit in supplemented patients are discussed.     

A possible mechanism for the dose-response relationship observed for renal mesenchymal tumours induced in the rat by a single dose of N-nitrosodimethylamine

The incidence of renal mesenchymal tumours induced in rats by N-nitrosodimethylamine (NDMA) is related to the dose in a sigmoidal dose-response curve. Each kidney bears only one or two tumours at 20-24 months. In contrast, one week after dosing, a large number of preneoplastic proliferative foci is present, the incidence of which is linearly related to dose and directly proportional to methylation of DNA by NDMA. It is suggested that most of these foci are removed by host defense mechanisms before they can progress to tumour, thus accounting for the sigmoid shape of the dose-response curve for the tumours.