Practice Effects on a Working Memory Task in Adult Survivors of Pediatric Brain Tumors: An fMRI Investigation

Behavioral studies have documented impaired working memory in childhood brain tumor survivors; however, neural mechanisms have yet to be identified using fMRI. The current study investigated BOLD response differences between twenty survivors (Mean age=23.1(4.14), 55% female) and twenty age- and gender-matched controls from the start to the end of a twenty minute 3-back task. There were no differences in task performance between groups or over time. Effects of practice were present in left prefrontal regions, with both groups showing decreases in activation as the task progressed. There were qualitative and quantitative differences in the brain regions that survivors recruited relative to controls in bilateral prefrontal (including the dorsolateral prefrontal cortex) and parietal cortices. Findings suggest that areas under top-down control of the dorsolateral prefrontal cortex become less activated with practice, and that survivors may require more top-down processing and attentional control to perform at similar levels to healthy controls

Structural Network Properties and Their Relation to Cognitive Flexibility and Neurological Risk Factors in Adult Survivors of Pediatric Brain Tumors

Neuroimaging techniques have been used to investigate the neurobiological mechanisms of cognitive deficits in survivors of childhood brain tumors. Graph theory is a quantitative method that characterizes brains as a complex system. By modeling brain regions as ‘nodes’ and white matter tracts between each brain region pair as ‘edges,’ graph theory provides metrics that quantify the topological properties of networks. Given that brain tumor survivorship is associated with focal and diffuse impairments, a network analysis can provide complementary information to previous neuroimaging studies in this clinical group. This study used diffusion-weighted imaging and deterministic tractography to examine the properties of the structural networks in 38 adult survivors of pediatric brain tumors (Mean age=22.5, 55% female, mean years post diagnosis=14.1 (6.2), Range post diagnosis = 4.5-30 years). Results of this study suggest that long term survivorship is associated with altered structural networks with respect to measures of integration, segregation, and centrality. Further, properties of the network mediate differences in cognitive flexibility performance between survivors and healthy peers, and mediate the relationship between cumulative neurological risk and cognitive flexibility performance

Cumulative Neurological Factors Associated with Long-term Outcomes in Adult Survivors of Childhood Brain Tumors

Prior research has demonstrated the reliability and validity of the Neurological Predictor Scale (NPS) in relation to childhood brain tumor survivor outcomes; however, its use has not been examined in adult long-term survivors. The current study examines the concurrent validity of the NPS with long-term intellectual and adaptive outcomes in adult survivors of childhood brain tumors relative to individual variables alone. A total of 68 adult survivors of childhood brain tumors (M = 24 years old, SD = 4) almost 16 years post diagnosis (SD = 6) completed intellectual evaluations using the Wechsler Abbreviated Scale of Intelligence (WASI). Survivors\u27 adaptive functioning skills were assessed via informant structured clinical interviews (SIB-R). NPS scores were computed from data acquired from medical records. The NPS was significantly associated with intellectual (R2 = 0.208, p \u3c .05) and adaptive outcomes (R2 = 0.30, p \u3c .05) over and above individual risk factors. Approximately 18% of long-term survivors were identified as impaired in intellectual outcomes, and 29% were identified as impaired in adaptive functioning in everyday life skills. The NPS quantifies the cumulative effects of treatment and neurological sequelae experienced by both short- and long-term survivors of childhood brain tumors. It is a useful and easy measure to employ in clinical research that focuses on quantifying the neurological risk factors associated with long-term intellectual and adaptive functioning outcomes in adult survivors of childhood brain tumors

Neural underpinnings of working memory in adult survivors of childhood brain tumors

Objective: Adult survivors of childhood brain tumors are at risk for cognitive performance deficits that require the core cognitive skill of working memory. Our goal was to examine the neural mechanisms underlying working memory performance in survivors. Method: We studied the working memory of adult survivors of pediatric posterior fossa brain tumors using a letter n-back paradigm with varying cognitive workload (0-, 1-, 2-, and 3-back) and functional magnetic resonance imaging as well as neuropsychological measures. Results: Survivors of childhood brain tumors evidenced lower working memory performance than demographically-matched healthy controls. Whole-brain analyses revealed significantly greater blood-oxygen level dependent (BOLD) activation in the left superior / middle frontal gyri and left parietal lobe during working memory (2-back versus 0-back contrast) in survivors. Left frontal BOLD response negatively correlated with 2- and 3-back working memory performance, Auditory Consonant Trigrams (ACT), and Digit Span Backwards. In contrast, parietal lobe BOLD response negatively correlated with 0-back (vigilance task) and ACT. Conclusions: The results revealed that adult survivors of childhood posterior fossa brain tumors recruited additional cognitive control resources in the prefrontal lobe during increased working memory demands. This increased prefrontal activation is associated with lower working memory performance and is consistent with the allocation of latent resources theory

Hippocampal Volume and Auditory Attention on a Verbal Memory Task with Adult Survivors of Pediatric Brain Tumor

Objective: We examined the nature of verbal memory deficits and the possible hippocampal underpinnings in long-term adult survivors of childhood brain tumor. Method: 35 survivors (M=24.10±4.93 years at testing; 54% female), on average 15 years post-diagnosis, and 59 typically developing adults (M=22.40±4.35 years, 54% female) participated. Automated FMRIB Software Library (FSL) tools were used to measure hippocampal, putamen, and whole brain volumes. The California Verbal Learning Test – Second Edition (CVLT-II) was used to assess verbal memory. Results: Hippocampal (F(1,91)=4.06, ηp2=.04), putamen (F(1,91)=11.18, ηp2=.11), and whole brain (F(1,92)=18.51, ηp2=.17) volumes were significantly lower for survivors than controls (pr=.62, pr=.09; r=.08), for survivors and controls. Verbal memory indices of auditory attention list span (Trial 1) (F (1,92)=12.70, η2=.12) and final list learning (Trial 5) (F (1,92)=6.01, η2=.06) were significantly lower for survivors (pr=.43, p=.01) with auditory attention, but none of the other CVLT-II indices. Secondary analyses for the effect of treatment factors are presented. Conclusion: Volumetric differences between survivors and controls exist for the whole brain and for subcortical structures on average 15 years post-diagnosis. Treatment factors seem to have a unique effect on subcortical structures. Memory differences between survivors and controls are largely contingent upon auditory attention list span. Only hippocampal volume is associated with the auditory attention list span component of verbal memory. These findings are particularly robust for survivors treated with radiation

Indication of critical scaling in time during the relaxation of an open quantum system

Phase transitions correspond to the singular behavior of physical systems in response to continuous control parameters like temperature or external fields. Near continuous phase transitions, associated with the divergence of a correlation length, universal power-law scaling behavior with critical exponents independent of microscopic system details is found. Recently, dynamical quantum phase transitions and universal scaling have been predicted and also observed in the non-equilibrium dynamics of isolated quantum systems after a quench, with time playing the role of the control parameter. However, signatures of such critical phenomena in time in open systems, whose dynamics is driven by the dissipative contact to an environment, were so far elusive. Here, we present results indicating that critical scaling with respect to time can also occur during the relaxation dynamics of an open quantum system described by mixed states. We experimentally measure the relaxation dynamics of the large atomic spin of individual Caesium atoms induced by the dissipative coupling via spin-exchange processes to an ultracold Bose gas of Rubidium atoms. For initial states far from equilibrium, the entropy of the spin state is found to peak in time, transiently approaching its maximum possible value, before eventually relaxing to its lower equilibrium value. Moreover, a finite-size scaling analysis based on numerical simulations shows that it corresponds to a critical point with respect to time of the dissipative system in the limit of large system sizes. It is signalled by the divergence of a characteristic length at a critical time, characterized by critical exponents that are found to be independent of system details

Tailoring ergodicity through selective A-site doping in the Bi1/2Na1/2TiO3-Bi1/2K1/2TiO3 system

The morphotropic phase boundary composition Bi1/2Na1/2TiO3-20 mol. % Bi1/2K1/2TiO3 was chosen as initial material to do selective A-site aliovalent doping replacing Na and K by 1 at. % La, respectively. The materials were studied macroscopically by measuring dielectric and electromechanical properties. The Na-replaced material has a lower freezing temperature Tfr, lower remanent polarization and remanent strain, and thus a higher degree of ergodicity than the K-replaced material. These results are contrasted with local poling experiments and hysteresis loops obtained from piezoresponse force microscopy. The faster relaxation of the tip-induced local polarization and the lower remanent state in bias-on and-off loops confirm the higher degree of ergodicity of the Na-replaced material. The difference in functional properties is attributed to small variations in chemical pressure achieved through selective doping. Raman results support this working hypothesis. ??? 2015 AIP Publishing LLCopen1

Molecular diversity of anthracnose pathogen populations associated with UK strawberry production suggests multiple introductions of three different Colletotrichum species.

Fragaria × ananassa (common name: strawberry) is a globally cultivated hybrid species belonging to Rosaceae family. Colletotrichum acutatum sensu lato (s.l.) is considered to be the second most economically important pathogen worldwide affecting strawberries. A collection of 148 Colletotrichum spp. isolates including 67 C. acutatum s.l. isolates associated with the phytosanitary history of UK strawberry production were used to characterize multi-locus genetic variation of this pathogen in the UK, relative to additional reference isolates that represent a worldwide sampling of the diversity of the fungus. The evidence indicates that three different species C. nymphaeae, C. godetiae and C. fioriniae are associated with strawberry production in the UK, which correspond to previously designated genetic groups A2, A4 and A3, respectively. Among these species, 12 distinct haplotypes were identified suggesting multiple introductions into the country. A subset of isolates was also used to compare aggressiveness in causing disease on strawberry plants and fruits. Isolates belonging to C. nymphaeae, C. godetiae and C. fioriniae representative of the UK anthracnose pathogen populations showed variation in their aggressiveness. Among the three species, C. nymphaeae and C. fioriniae appeared to be more aggressive compared to C. godetiae. This study highlights the genetic and pathogenic heterogeneity of the C. acutatum s.l. populations introduced into the UK linked to strawberry production

Analysis on the clinical features of 22 basaloid squamous cell carcinoma of the lung

<p>Abstract</p> <p>Background</p> <p>Basaloid squamous cell carcinoma of the lung is a rare and highly malignant tumor mostly observed in the proximal bronchi. Basaloid squamous cell carcinoma of the lung cases typically show rapid clinical progression, very poor prognosis and special pathological morphology. This project aimed to examine the clinical features of basaloid squamous cell carcinoma of the lung and the factors related to its prognosis; and to compare survival outcomes between basaloid squamous cell carcinoma and poorly differentiated squamous cell carcinomas (PDSC).</p> <p>Methods</p> <p>Between January 2004 and December 2008, pathological sections from basaloid squamous cell carcinoma and PDSC of the lung were collected and retrospectively analyzed at Tianjin Medical University Cancer Institute and Hospital. Data analysis was performed using Statistical Package for the Social Sciences (SPSS11.0). The Kaplan-Meier method was used to calculate the survival rate. Log-rank test was used to compare the differences in survival rate between the two groups. The factors influencing prognosis were analyzed using the Cox proportional hazard model.</p> <p>Results</p> <p>A total of 120 pathological sections were used in the analysis of this study-22 from basaloid squamous cell carcinoma cases and 98 from PDSC cases. Compared to the PDSC group, the basaloid squamous cell carcinoma group had a larger proportion of female patients (p = 0.001); however it had higher proportion of male smokers (p = 0.003). There were no statistically significant differences in survival rate between the two groups (χ²= 1.200, p = 0.273). Additionally, prognosis of basaloid squamous cell carcinoma is significantly influenced by treatment mode and clinical stages of the tumor. The post-operation mortality hazard of patients treated with a combination chemotherapy and radiotherapy was 1.296 times higher than other treatment modes (<it>p </it>= 0.025). Increases in post-operation mortality hazard ratio were also associated with more advanced clinical stage of tumors (χ²trend = 11.907, <it>p </it>= 0.000).</p> <p>Conclusions</p> <p>This study demonstrated that basaloid squamous cell carcinoma and PDSC have very similar clinical features, and there are no significant differences in survival rates between the two groups. Hence, we conclude that in the short term, the same clinical treatments and therapeutic modes can be administered to patients with basaloid squamous cell carcinoma and PDSC of the lung.</p