A mouse prion protein transgene rescues mice deficient for the prion protein gene from purkinje cell degeneration and demyelination.

Disruption of both alleles of the prion protein gene, Prnp, renders mice resistant to prions; in a Prnp o/o line reported by some of us, mice progressively developed ataxia and Purkinje cell loss. Here we report torpedo-like axonal swellings associated with residual Purkinje cells in Prnp o/o mice, and we demonstrate abnormal myelination in the spinal cord and peripheral nerves in mice from two independently established Prnp o/o lines. Mice were successfully rescued from both demyelination and Purkinje cell degeneration by introduction of a transgene encoding wild-type mouse cellular prion protein. These findings suggest that cellular prion protein expression may be necessary to maintain the integrity of the nervous system.     

The influence of language proficiency on lexical semantic processing in native and late learners of English

We investigated the influence of English proficiency on ERPs elicited by lexical semantic violations in English sentences, in both native English speakers and native Spanish speakers who learned English in adulthood. All participants were administered a standardized test of English proficiency, and data were analyzed using linear mixed effects (LME) modeling. Relative to native learners, late learners showed reduced amplitude and delayed onset of the N400 component associated with reading semantic violations. As well, after the N400 late learners showed reduced anterior negative scalp potentials and increased posterior potentials. In both native and late learners, N400 amplitudes to semantically appropriate words were larger for people with lower English proficiency. N400 amplitudes to semantic violations, however, were not influenced by proficiency. Although both N400 onset latency and the late ERP effects differed between L1 and L2 learners, neither correlated with proficiency. Different approaches to dealing with the high degree of correlation between proficiency and native/late learner group status are discussed in the context of LME modeling. The results thus indicate that proficiency can modulate ERP effects in both L1 and L2 learners, and for some measures (in this case, N400 amplitude), L1-L2 differences may be entirely accounted for by proficiency. On the other hand, not all effects of L2 learning can be attributed to proficiency. Rather, the differences in N400 onset and the post-N400 violation effects appear to reflect fundamental differences in L1-L2 processing.     

Role of serotonergic 1A receptor dysfunction in depression associated with Parkinson's disease

Depression is frequent in Parkinson's disease, but its pathophysiology remains unclear. Two recent studies have investigated the role of serotonergic system at the presynaptic level. The objective of the present study was to use positron emission tomography and [(18)F]MPPF to investigate the role of postsynaptic serotonergic system dysfunction in the pathophysiology of depression in Parkinson's disease. Four parkinsonian patients with depression and 8 parkinsonian patients without depression were enrolled. Each patient underwent a scan using [(18)F]MPPF, a selective serotonin 1A receptor antagonist. Voxel-by-voxel statistical comparison of [(18)F]MPPF uptake of the 2 groups of parkinsonian patients and with 7 matched normal subjects was made using statistical parametric mapping (P uncorrected < .001). Compared with nondepressed parkinsonian patients, depressed patients exhibited reduced tracer uptake in the left hippocampus, the right insula, the left superior temporal cortex, and the orbitofrontal cortex. Compared with controls, nondepressed parkinsonian patients presented reduced [(18)F]MPPF uptake bilaterally in the inferior frontal cortex as well as in the right ventral striatum and insula. Compared with controls, [(18)F]MPPF uptake was decreased in depressed parkinsonian patients in the left dorsal anterior cingulate and orbitofrontal cortices, in the right hippocampic region, and in the temporal cortex. The present imaging study suggests that abnormalities in serotonin 1A receptor neurotransmission in the limbic system may be involved in the neural mechanisms underlying depression in patients with Parkinson's disease.     

Psychometric properties of the Mental Health and Social Inadaptation Assessment for Adolescents (MIA) in a population‐based sample

We report on the psychometric properties of the Mental Health and Social Inadaptation Assessment for Adolescents (MIA), a self‐report instrument for quantifying the frequency of mental health and psychosocial adaptation problems using a dimensional approach and based on the DSM‐5. The instrument includes 113 questions, takes 20–25 minutes to answer, and covers the past 12 months. A population‐based cohort of adolescents (n = 1443, age = 15 years; 48% males) rated the frequency at which they experienced symptoms of Attention Deficit Hyperactivity Disorder (ADHD), Conduct Disorder, Oppositional Defiant Disorder, Depression, Generalized Anxiety, Social Phobia, Eating Disorders (i.e. DSM disorders), Self‐harm, Delinquency, Psychopathy as well as social adaptation problems (e.g. aggression). They also rated interference with functioning in four contexts (family, friends, school, daily life). Reliability analyses indicated good to excellent internal consistency for most scales (alpha = 0.70–0.97) except Psychopathy (alpha = 0.46). The hypothesized structure of the instrument showed acceptable fit according to confirmatory factor analysis (CFA) [Chi‐square (4155) = 9776.2, p = 0.000; Chi‐square/DF = 2.35; root mean square error of approximation (RMSEA) = 0.031; Comparative Fit Index (CFI) = 0.864], and good convergent and discriminant validity according to multitrait‐multimethods analysis. This initial study showed adequate internal validity and reliability of the MIA. Our findings open the way for further studies investigating other validity aspects, which are necessary before recommending the wide use of the MIA in research and clinical settings.