Prior studies have demonstrated that correlated variability changes with cognitive processes that improve perceptual performance. We tested whether correlated variability covaries with subjects' performance-whether performance improves quickly with attention or slowly with perceptual learning. We found a single, consistent relationship between correlated variability and behavioral performance, regardless of the time frame of correlated variability change. This correlated variability was oriented along the dimensions in population space used by the animal on a trial-by-trial basis to make decisions. That subjects' choices were predicted by specific dimensions that were aligned with the correlated variability axis clarifies long-standing paradoxes about the relationship between shared variability and behavior.

The trial-to-trial response variability that is shared between pairs of neurons (termed spike count correlations1 or rSC) has been the subject of many recent studies largely because it might limit the amount of information that can be encoded by neuronal populations. Spike count correlations are flexible and change depending on task demands2-7. However, the relationship between correlated variability and information coding is a matter of current debate2-14. This debate has been difficult to resolve because testing the theoretical predictions would require simultaneous recordings from an experimentally unfeasible number of neurons. We hypothesized that if correlated variability limits population coding, then spike count correlations in visual cortex should a) covary with subjects’ performance on visually guided tasks and b) lie along the dimensions in neuronal population space that contain information that is used to guide behavior. We focused on two processes that are known to improve visual performance: visual attention, which allows observers to focus on important parts of a visual scene15-17, and perceptual learning, which slowly improves observers’ ability to discriminate specific, well-practiced stimuli18-20. Both attention and learning improve performance on visually guided tasks, but the two processes operate on very different timescales and are typically studied using different perceptual tasks. Here, by manipulating attention and learning in the same task, subjects, trials, and neuronal populations, we show that there is a single, robust relationship between correlated variability in populations of visual neurons and performance on a change-detection task. We also propose an explanation for the mystery of how correlated variability might affect performance: it is oriented along the dimensions of population space used by the animal to make perceptual decisions. Our results suggest that attention and learning affect the same aspects of the neuronal population activity in visual cortex, which may be responsible for learning- and attention-related improvements in behavioral performance. More generally, our study provides a framework for leveraging the activity of simultaneously recorded populations of neurons, cognitive factors, and perceptual decisions to understand the neuronal underpinnings of behavior.

Prolonged OR, re-transplantation, and high-volume intraoperative transfusion have been associated with increased risk for IC in adult LT recipients. Antifungal prophylaxis is recommended for adult patients with these risk factors. There are limited data on the incidence of and risk factors for IC in pediatric LT recipients. A retrospective cohort study of all pediatric LT patients at the CHOP between 2000 and 2012 and the CHP between 2004 and 2012 was performed to define the incidence of IC within 30 days of LT. A 3:1 matched case-control study with incidence density sampling was performed. Conditional logistic regression analyses were used to explore risk factors associated with IC. Among 397 recipients, the incidence of IC was 2.5%. Bivariate analyses showed that ICU admission prior to transplant, OR > 10 h, intraoperative volume infusion of >300 mL/kg, and broad-spectrum antibiotics were significantly associated with IC. In a multivariate model, only ICU admission remained significantly associated with IC. Antifungal prophylaxis was not significantly protective against IC. The low incidence of IC and lack of an identified protective effect from antifungal prophylaxis suggest that prophylaxis in pediatric LT recipients should not be routinely recommended to prevent IC events in the first 30 days post-transplant.

IntroductionDementia is a devastating illness. The clinical criteria for dementia focus on cognitive and functional impairment. However patients' relationships are also affected, including their intimate and sexual relationships. These relationships are an important part of an adult life, particularly in young adults and are part of a person's identity and self-esteem. A great deal of research has explored the impact of late onset dementia on couples' relationships. This study aims to explore the impact of young onset dementia (YOD) on intimate and sexual relationships.Objectives(a) To explore the lived experiences of couples with YOD with regard to their sexual and intimate relationships; (b) To explore any issues in this area and to report what these problems are (for both the partner and the pwYOD); (c) To identify strategies that couples have found helpful in maintaining a close sexual and intimate relationship where one person has a diagnosis of YOD; (d) To identify issues frequently raised by study participants (as well as strategies/actions that have helped to maintain a close relationship) and (e) Use these issues to inform the development of an appropriate future clinical intervention. Where enough data is available, to relate the findings to: (i) The severity of the pwYOD's illness; (ii) The type of dementia; (iii) Gender and (iv) The type of relationship the couple had before the pwYOD developed dementia.MethodsWe are in the progress of interviewing patients and their partners, with the plan to recruit in total 10–20 individuals from 8–12 couples. We have completed five interviews with further interviews planned for the near future.Interviews will be transcribed and thematically analysed. To date, interviews have highlighted important challenges and needs, including the setup of group, individual, and couple interventions.