The prediction of visual stimuli influences auditory loudness discrimination

The brain combines information from different senses to improve performance on perceptual tasks. For instance, auditory processing is enhanced by the mere fact that a visual input is processed simultaneously. However, the sensory processing of one modality is itself subject to diverse influences. Namely, perceptual processing depends on the degree to which a stimulus is predicted. The present study investigated the extent to which the influence of one processing pathway on another pathway depends on whether or not the stimulation in this pathway is predicted. We used an action–effect paradigm to vary the match between incoming and predicted visual stimulation. Participants triggered a bimodal stimulus composed of a Gabor and a tone. The Gabor was either congruent or incongruent compared to an action–effect association that participants learned in an acquisition phase.We tested the influence of action–effect congruency on the loudness perception of the tone. We observed that an incongruent–task-irrelevant Gabor stimulus increases participant’s sensitivity to loudness discrimination. An identical result was obtained for a second condition in which the visual stimulus was predicted by a cue instead of an action. Our results suggest that prediction error is a driving factor of the crossmodal interplay between vision and audition.     

Smallpox Inoculation (Variolation) in East Africa with Special Reference to the Practice Among the Boran and Gabra of Northern Kenya

Smallpox inoculation (variolation) was widely reported in sub-Sahara Africa before, during, and after the colonial era. The infective smallpox materials and techniques used, as well as the anatomical sites for inoculation, varied widely among different ethnic groups. The practice among the Boran and Gabra pastoralists of northern Kenya resembled that which was prevalent in a number of areas of Ethiopia. This is not surprising as the Boran also live in southern Ethiopia, and Gabra herdsmen frequently cross the border into this region. The Boran and Gabra technique for smallpox inoculation consisted of taking infective material from the vesicles or pustules of those with active smallpox, and scraping it into the skin on the dorsum of the lower forearm. Although the intent was to cause a local reaction and at most a mild form of smallpox, severe cases of the disease not infrequently resulted. Also, variolated individuals were capable of infecting others with smallpox, thereby augmenting outbreaks and sustaining them. The limited known reports of smallpox inoculation among the Boran and Gabra are presented in this communication. The expansion of vaccination with effective heat stable vaccines, the development of medical and public health infrastructures, and educational programs all contributed to the eventual disappearance of the practice among the Boran and Gabra.     

Discitis and sacroiliitis diagnosed 15 years after iatrogenic Mycobacterium xenopi inoculation

A patient was diagnosed with discitis and sacroiliitis due to Mycobacterium xenopi. He had a history of percutaneous nucleotomy performed 15 years earlier (in 1992) at the Clinique du Sport, Paris, France, during an outbreak of nosocomial M. xenopi infection at that institution. In 1997, magnetic resonance imaging performed as part of the routine follow-up program for patients who had surgery at the Clinique du Sport during the outbreak was not interpreted as indicating discitis; this assessment was confirmed by our review of the images. Bone and joint infections due to atypical mycobacteria are rare and can develop very slowly. To our knowledge, this is the first reported case of M. xenopi discitis with secondary extension to the sacroiliac joint in an immunocompetent patient.     

First inappropriate implantable cardioverter defibrillator therapy is often due to inaccurate device programming: analysis of the French OPERA registry

AIMS: Inappropriate therapy delivered by implantable cardioverter defibrillators (ICDs) remains a challenge. The OPERA registry measured the times to, and studied the determinants of, first appropriate (FAT) and inappropriate (FIT) therapies delivered by single-, dual- and triple-chamber [cardiac resynchronization therapy defibrillator (CRT-D)] ICD. METHODS AND RESULTS: We entered 636 patients (mean age = 62.0 ± 13.5 years; 88% men) in the registry, of whom 251 received single-, 238 dual-, and 147 triple-chamber ICD, for primary (30.5%) or secondary (69.5%) indications. We measured times to FAT and FIT as a function of multiple clinical characteristics, examined the effects of various algorithm components on the likelihood of FAT and FIT delivery, and searched for predictors of FAT and FIT. Over 22.8 ± 8.8 months of observation, 184 patients (28.9%) received FAT and 70 (11.0%) received FIT. Ventricular tachycardia (VT) was the trigger of 88% of FAT, and supraventricular tachycardia was the trigger of 91% of FIT. The median times to FIT (90 days; range 49-258) and FAT (171 days; 50-363) were similar. The rate of FAT was higher (P <0.001) in patients treated for secondary than primary indications, while that of FIT were similar in both groups. Out of 57 analysable FIT, 27 (47.4%) could have been prevented by fine tuning the device programming like the sustained rate duration or the VT discrimination algorithm. CONCLUSIONS: First inappropriate therapy occurred in 11% of 636 ICD recipients followed for ～2 years. Nearly 50% of FIT could have been prevented by improving device programming.     

Perineuronal nets protect fast-spiking interneurons against oxidative stress

A hallmark of schizophrenia pathophysiology is the dysfunction of cortical inhibitory GABA neurons expressing parvalbumin, which are essential for coordinating neuronal synchrony during various sensory and cognitive tasks. The high metabolic requirements of these fast-spiking cells may render them susceptible to redox dysregulation and oxidative stress. Using mice carrying a genetic redox imbalance, we demonstrate that extracellular perineuronal nets, which constitute a specialized polyanionic matrix enwrapping most of these interneurons as they mature, play a critical role in the protection against oxidative stress. These nets limit the effect of genetically impaired antioxidant systems and/or excessive reactive oxygen species produced by severe environmental insults. We observe an inverse relationship between the robustness of the perineuronal nets around parvalbumin cells and the degree of intracellular oxidative stress they display. Enzymatic degradation of the perineuronal nets renders mature parvalbumin cells and fast rhythmic neuronal synchrony more susceptible to oxidative stress. In parallel, parvalbumin cells enwrapped with mature perineuronal nets are better protected than immature parvalbumin cells surrounded by less-condensed perineuronal nets. Although the perineuronal nets act as a protective shield, they are also themselves sensitive to excess oxidative stress. The protection might therefore reflect a balance between the oxidative burden on perineuronal net degradation and the capacity of the system to maintain the nets. Abnormal perineuronal nets, as observed in the postmortem patient brain, may thus underlie the vulnerability and functional impairment of pivotal inhibitory circuits in schizophrenia.