Evidence for symptomatic convergence of schizophrenia and N-methyl-D-aspartate glutamate receptor (NMDA-R) encephalitis highlights the need for an assessment of antibody prevalence and specificity for distinct disease mechanisms in patients with a diagnosis of schizophrenia among glutamatergic pathophysiologic abnormalities in psychiatric disorders. Objectives: To compare the specificity and prevalence of NMDA-R antibodies in schizophrenia (DSM-IV criteria) with those of other psychiatric diagnoses and to determine whether antibody subtypes characterize overlap with and distinction from those in NMDA-R encephalitis. Design: Serum from 459 patients admitted with acute schizophrenia, major depression (MD), and borderline personality disorder (BLPD) or individuals serving as matched controls was obtained from our scientific blood bank. To explore epitope specificity and antibody subtype, IgA/IgG/IgM NMDA-R (NR1a or NR1a/NR2b) and ␣-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate receptors (AMPA-R) (GluR1/GluR2) serum antibodies were determined. Participants: Two hundred thirty matched healthy controls were compared with patients (unmedicated for at least 6 weeks) with schizophrenia (n=121), MD (n=70), or BLPD (n=38). Main Outcome Measures: The primary outcome was the overall number of seropositive cases for NMDA-R and AMPA-R antibodies; the secondary outcome was disease specificity of IgA/IgG/IgM antibodies and epitope specificity for clinical subgroups. Results: Diverse NMDA-R antibodies were identified in 15 subjects, primarily those with an initial schizophrenia diagnosis (9.9%), opposed to MD (2.8%), BLPD (0), and controls (0.4%). Retrospectively, 2 patients initially classified as having catatonic or disorganized schizophrenia were reclassified as having misdiagnosed NMDA-R encephalitis (presence of specific serum and cerebrospinal fluid IgG NR1a antibodies). In all other seropositive cases, the antibodies consisted of classes IgA and/or IgM or were directed against NR1a/NR2b (not against NR1a alone). None of the patients or controls had antibodies against AMPA-R. Conclusions: Acutely ill patients with an initial schizophrenia diagnosis show an increased prevalence of NMDA-R antibodies. The repertoire of antibody subtypes in schizophrenia and MD is different from that with NMDA-R encephalitis. The latter disorder should be considered as a differential diagnosis, particularly in young females with acute disorganized behavior or catatonia.

Introduction We examined the association between cerebrospinal fluid (CSF) biomarkers of Alzheimer's disease, neural novelty responses, and brain volume in predementia old age. Methods We conducted a cross-sectional analysis of the observational, multicentric DZNE-Longitudinal Cognitive Impairment and Dementia Study (DELCODE) study. Seventy-six participants completed task functional magnetic resonance imaging and provided CSF (40 cognitively unimpaired, 21 experiencing subjective cognitive decline, and 15 with mild cognitive impairment). We assessed the correlation between CSF biomarkers and whole-brain functional magnetic resonance imaging novelty responses to scene images. Results Total tau levels were specifically and negatively associated with novelty responses in the right amygdala and right hippocampus. Mediation analyses showed no evidence that these associations were dependent on the volume of hippocampus/amygdala. No relationship was found between phosphorylated-tau or Aβ 42 levels and novelty responses. Discussion Our data show that CSF levels of total tau are associated with anatomically specific reductions in novelty processing, which cannot be fully explained by atrophy.

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Objective:To determine the nature and extent of minor neuropsychological deficits in patients with subjective cognitive decline (SCD) and their association with cerebrospinal fluid (CSF) biomarkers of Alzheimer’s disease (AD).Method:We analyzed data from n=449 cognitively normal participants (n=209 healthy controls, n=240 SCD patients) from an interim data release of the German Center for Neurodegenerative Diseases Longitudinal Cognitive Impairment and Dementia Study (DELCODE). An extensive neuropsychological test battery was applied at baseline for which we established a latent, five cognitive domain factor structure comprising learning & memory, executive functions, language abilities, working memory and visuospatial functions. We compared groups regarding global and domain-specific performance and correlated performance with different CSF markers of AD pathology.Results:We observed worse performance (Cohen’s d≈0.25-0.5, adjusted for age-, sex differences with ANCOVA) in global performance, memory, executive functions and language abilities for the SCD group compared to healthy controls. In addition, worse performance in these domains was moderately (r≈0.3) associated with lower CSF-Aβ42/40 and CSF-Aβ42/ptau181 in the whole sample and specifically in the SCD subgroup.Conclusions:Within the spectrum of clinically unimpaired (i.e., “pre- mild cognitive impairment”) cognitive performance, SCD is associated with minor deficits in memory, executive function and language abilities. The association of these subtle cognitive deficits with AD CSF biomarkers speaks to their validity and potential use for the early detection of underlying preclinical AD.

Objective:To determine if following a Mediterranean-like diet (MeDi) relates to cognitive functions and in vivo biomarkers for Alzheimer’s disease (AD), we analyzed cross-sectional data from the German Longitudinal Cognitive Impairment and Dementia StudyMethod:The sample (n=512, mean age: 69.5±5.9 years) included 169 cognitively normal participants and subjects at higher AD risk (53 AD relatives, 209 SCD and 81 MCI). We defined MeDi adherence based on the Food Frequency Questionnaire. Brain volume outcomes were generated via voxel-based morphometry on T1-MRI and cognitive performance with an extensive neuropsychological battery. AD-related biomarkers (Aβ42/40 ratio, pTau181) in cerebrospinal fluid were assessed in n=226 individuals. We analyzed the associations between MeDi and the outcomes with linear regression models controlling for several covariates. Additionally, we applied hypothesis-driven mediation and moderation analysis.Results:Higher MeDi adherence related to larger mediotemporal gray matter volume (p<0.05 FWE corrected), better memory (β±SE = 0.03 ± 0.02; p=0.038), and less amyloid (Aβ42/40 ratio, β±SE = 0.003 ± 0.001; p=0.008) and pTau181 pathology (β±SE = -1.96±0.68; p=0.004). Mediotemporal volume mediated the association between MeDi and memory (40% indirect mediation). Finally, MeDi favorably moderated the associations between Aβ42/40 ratio, pTau181 and mediotemporal atrophy. Results were consistent correcting for ApoE-ε4 status.Conclusion:Our findings corroborate the view of MeDi as a protective factor against memory decline and mediotemporal atrophy. Importantly, they suggest that these associations might be explained by a decrease of amyloidosis and tau-pathology. Longitudinal and dietary intervention studies should further examine this conjecture and its treatment implications.