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Our perceptual system is adept at exploiting sensory regularities to better extract information about our environment. One clear example of this is how the sensory and multisensory systems can utilize consistency to group sensory features into a perceptual object and segregate objects from each other and background noise. Leveraging tenets of object-based attention and multisensory binding, we sought whether this ability scaled with the strength of that consistency. We presented participants with amplitude modulated (AM) auditory and visual streams and asked them to detect imbedded orthogonal, near-threshold frequency modulation (FM) events. We modulated the correlation of the streams by varying the phase of the visual AM. In line with a previous report, we first observed peak performance that was shifted from 0°. After accounting for this, we found that across participants discriminability of the FM event linearly improved with correlation. Additionally, we sought to answer a question left dangling from our previous report as to the possible explanation for the phase shift. We found that phase shift correlated with auditory and visual response time differences, but not point of subjective simultaneity, suggesting differences in sensory processing times may account for the observed phase shift. These results suggest that our perceptual system can bind multisensory features across a spectrum of temporal correlations, a process necessary for multisensory binding in complex environments where unrelated signals may have small errant correlations.

Background: The incidence of aneurysmal subarachnoid hemorrhage (SAH) reported in the literature has been very variable. Many authors have proposed a geographical variation in incidence, but others have dismissed this as being due to insufficient pickup rate. In India also, these arguments abound. Our aim was to find out if geographical variations exist in the incidence of aneurysmal SAH and whether the incidence of aneurysmal SAH was truly less in India as compared to the literature. Materials and Methods: The data from 182 consecutive cases of SAH admitted to this institution between March 1999 and July 2003 were used for this study. Results: There were 84 females and 98 males in this study. More than half of the patients were hypertensive. Four-vessel angiogram was done in 113 patients, of whom sixty-nine were normal. Of the patients with hypertension, 92% had angiogram done and was normal in 65% of cases. Conclusions: This study from a large general hospital in South India shows that the incidence of aneurysmal rupture as a cause of SAH is much less in India and probably in the Indian subcontinent in comparison with the western literature thus demonstrating geographical variations in the incidence of aneurysmal SAH. It is concluded that aneurysms as a cause of SAH are still less in India and that we are not missing anything. This study is intended to help target scarce, expensive resources toward more common pathologies.

The aim of this study was to assess the correlation of overall survival with tumor location (lobar vs. deep grey matter) and with other clinical and imaging variables in a cohort of patients with high grade gliomas.Adult patients with newly diagnosed supratentorial WHO grade 3 and 4 gliomas were evaluated. Clinical data included demographics, symptoms at presentation, treatment variables, and overall survival. Radiological data included tumor side, site (deep vs. lobar) and size, extent of peritumoral edema, and presence of midline shift. Biostatistics were carried out using log rank tests and univariate and multivariate Cox regression models.A total of 121 patients were investigated, 23 (19.0%) with WHO grade 3 and 98 (81.0%) with WHO grade 4 gliomas. Tumors had lobar location in 96 cases (79.3%) and deep grey matter location in 25 cases (20.7%). Median survival time for all patients was 26 weeks (IQR: 14-53). Patients with deep tumors survived significantly longer than those with lobar gliomas (log rank test, p=0.0083). Extensive brain edema significantly shortened survival (log rank test, p=0.0003). Presence of midline shift (1 cm) was a statistically significant risk factor for shorter survival (log rank test, p0.0001). The univariate Cox regression model demonstrated statistical significance for the variables age, side, site and size of tumor, presence of extensive edema, and presence of mass effect (1 cm). In the multivariate Cox models, tumor grade, site and size showed statistical significance.This study suggests that patients with deep grey matter gliomas may survive significantly longer after the initial diagnosis than those with tumors in a lobar location. This is a potentially novel finding, which may corroborate the theory of differential invasion of glioma cells in different microenvironments of the brain, but remains to be confirmed in future prospective studies.

Context: The importance of brainstem auditory evoked potential monitoring in reducing hearing loss during microvascular decompression for trigeminal neuralgia is now accepted. However the extent of the changes in the pattern of these potentials and the safe limits to which these changes are relevant in reducing postoperative hearing loss have not been established. Aims: The aim of this study is to quantify these changes and relate these to the postoperative hearing loss. Settings and Design: This study was done at the Walton Centre for neurology and neurosurgery, Liverpool, United Kingdom. The study was designed to give a measure of the change in the wave pattern following microvascular decompression and relate it to postoperative hearing loss. Materials and Methods: Seventy-five patients undergoing microvascular decompression for trigeminal neuralgia had preoperative and postoperative hearing assessments and intraoperative brainstem auditory evoked potential monitoring. Statistical Analysis Used: Chi-square tests. Results: It was found that the wave V latency was increased by more than 0.9ms in nine patients, eight of whom suffered significant postoperative hearing loss as demonstrated by audiometry. It was also seen that progressive decrease in amplitude of wave V showed progressive hearing loss with 25% loss when amplitude fell by 50 and 100% loss when wave V was lost completely. However most of the patients did not have a clinically manifest hearing loss. Conclusions: A per-operative increase in the latency of wave V greater than 0.9 ms and a fall of amplitude of wave V of more than 50% indicates a risk to hearing.