Music to prevent deliriUm during neuroSurgerY (MUSYC): a single-centre, prospective randomised controlled trial.

OBJECTIVES: Delirium is a serious complication following neurosurgical procedures. We hypothesise that the beneficial effect of music on a combination of delirium-eliciting factors might reduce delirium incidence following neurosurgery and subsequently improve clinical outcomes. DESIGN: Prospective randomised controlled trial. SETTING: Single centre, conducted at the neurosurgical department of the Erasmus Medical Center, Rotterdam, the Netherlands. PARTICIPANTS: Adult patients undergoing craniotomy were eligible. INTERVENTIONS: Patients in the intervention group received preferred recorded music before, during and after the operation until day 3 after surgery. Patients in the control group were treated according to standard of clinical care. PRIMARY AND SECONDARY OUTCOME MEASURES: Primary outcome was presence or absence of postoperative delirium within the first 5 postoperative days measured with the Delirium Observation Screening Scale (DOSS) and, in case of a daily mean score of 3 or higher, a psychiatric evaluation with the latest Diagnostic and Statistical Manual of Mental Disorders (DSM-5) criteria. Secondary outcomes included anxiety, heart rate variability (HRV), depth of anaesthesia, delirium severity and duration, postoperative complications, length of stay and location of discharge. RESULTS: We enrolled 189 patients (music=95, control=94) from July 2020 through September 2021. Delirium, as assessed by the DOSS, was less common in the music (n=11, 11.6%) than in the control group (n=21, 22.3%, OR:0.49, p=0.048). However, after DSM-5 confirmation, differences in delirium were not significant (4.2% vs 7.4%, OR:0.47, p=0.342). Moreover, music increased the HRV (root mean square of successive differences between normal heartbeats, p=0.012). All other secondary outcomes were not different between groups. CONCLUSION: Our results support the efficacy of music in reducing the incidence of delirium after craniotomy, as found with DOSS but not after DSM-5 confirmation, substantiated by the effect of music on preoperative autonomic tone. Delirium screening tools should be validated and the long-term implications should be evaluated after craniotomy. TRIAL REGISTRATION NUMBER: Trialregister.nl: NL8503 and ClinicalTrials.gov: NCT04649450.

The reporting of neuropsychiatric symptoms in electronic health records of individuals with Alzheimer's disease: a natural language processing study.

BACKGROUND: Neuropsychiatric symptoms (NPS) are prevalent in the early clinical stages of Alzheimer's disease (AD) according to proxy-based instruments. Little is known about which NPS clinicians report and whether their judgment aligns with proxy-based instruments. We used natural language processing (NLP) to classify NPS in electronic health records (EHRs) to estimate the reporting of NPS in symptomatic AD at the memory clinic according to clinicians. Next, we compared NPS as reported in EHRs and NPS reported by caregivers on the Neuropsychiatric Inventory (NPI). METHODS: Two academic memory clinic cohorts were used: the Amsterdam UMC (n = 3001) and the Erasmus MC (n = 646). Patients included in these cohorts had MCI, AD dementia, or mixed AD/VaD dementia. Ten trained clinicians annotated 13 types of NPS in a randomly selected training set of n = 500 EHRs from the Amsterdam UMC cohort and in a test set of n = 250 EHRs from the Erasmus MC cohort. For each NPS, a generalized linear classifier was trained and internally and externally validated. Prevalence estimates of NPS were adjusted for the imperfect sensitivity and specificity of each classifier. Intra-individual comparison of the NPS classified in EHRs and NPS reported on the NPI were conducted in a subsample (59%). RESULTS: Internal validation performance of the classifiers was excellent (AUC range: 0.81-0.91), but external validation performance decreased (AUC range: 0.51-0.93). NPS were prevalent in EHRs from the Amsterdam UMC, especially apathy (adjusted prevalence = 69.4%), anxiety (adjusted prevalence = 53.7%), aberrant motor behavior (adjusted prevalence = 47.5%), irritability (adjusted prevalence = 42.6%), and depression (adjusted prevalence = 38.5%). The ranking of NPS was similar for EHRs from the Erasmus MC, although not all classifiers obtained valid prevalence estimates due to low specificity. In both cohorts, there was minimal agreement between NPS classified in the EHRs and NPS reported on the NPI (all kappa coefficients < 0.28), with substantially more reports of NPS in EHRs than on NPI assessments. CONCLUSIONS: NLP classifiers performed well in detecting a wide range of NPS in EHRs of patients with symptomatic AD visiting the memory clinic and showed that clinicians frequently reported NPS in these EHRs. Clinicians generally reported more NPS in EHRs than caregivers reported on the NPI.

Effects of the DICE Method to Improve Timely Recognition and Treatment of Neuropsychiatric Symptoms in Early Alzheimer's Disease at the Memory Clinic: The BEAT-IT Study.

BACKGROUND: Neuropsychiatric symptoms (NPS) are highly prevalent in Alzheimer's disease (AD) and are associated with negative outcomes. However, NPS are currently underrecognized at the memory clinic and non-pharmacological interventions are scarcely implemented. OBJECTIVE: To evaluate the effectiveness of the Describe, Investigate, Create, Evaluate (DICE) method™ to improve the care for NPS in AD at the memory clinic. METHODS: We enrolled sixty community-dwelling people with mild cognitive impairment or AD dementia and NPS across six Dutch memory clinics with their caregivers. The first wave underwent care as usual (n = 36) and the second wave underwent the DICE method (n = 24). Outcomes were quality of life (QoL), caregiver burden, NPS severity, NPS-related distress, competence managing NPS, and psychotropic drug use. Reliable change index was calculated to identify responders to the intervention. A cost-effectiveness analysis was performed and semi-structured interviews with a subsample of the intervention group (n = 12). RESULTS: The DICE method did not improve any outcomes over time compared to care as usual. Half of the participants of the intervention group (52%) were identified as responders and showed more NPS and NPS-related distress at baseline compared to non-responders. Interviews revealed substantial heterogeneity among participants regarding NPS-related distress, caregiver burden, and availability of social support. The intervention did not lead to significant gains in quality-adjusted life years and well-being years nor clear savings in health care and societal costs. CONCLUSION: The DICE method showed no benefits at group-level, but individuals with high levels of NPS and NPS-related distress may benefit from this intervention.

DeltaScan for the Assessment of Acute Encephalopathy and Delirium in ICU and non-ICU Patients, a Prospective Cross-Sectional Multicenter Validation Study.

OBJECTIVES: To measure the diagnostic accuracy of DeltaScan: a portable real-time brain state monitor for identifying delirium, a manifestation of acute encephalopathy (AE) detectable by polymorphic delta activity (PDA) in single-channel electroencephalograms (EEGs). DESIGN: Prospective cross-sectional study. SETTING: Six Intensive Care Units (ICU's) and 17 non-ICU departments, including a psychiatric department across 10 Dutch hospitals. PARTICIPANTS: 494 patients, median age 75 (IQR:64-87), 53% male, 46% in ICUs, 29% delirious. MEASUREMENTS: DeltaScan recorded 4-minute EEGs, using an algorithm to select the first 96 seconds of artifact-free data for PDA detection. This algorithm was trained and calibrated on two independent datasets. METHODS: Initial validation of the algorithm for AE involved comparing its output with an expert EEG panel's visual inspection. The primary objective was to assess DeltaScan's accuracy in identifying delirium against a delirium expert panel's consensus. RESULTS: DeltaScan had a 99% success rate, rejecting 6 of the 494 EEG's due to artifacts. Performance showed and an Area Under the Receiver Operating Characteristic Curve (AUC) of 0.86 (95% CI: 0.83-0.90) for AE (sensitivity: 0.75, 95%CI=0.68-0.81, specificity: 0.87 95%CI=0.83-0.91. The AUC was 0.71 for delirium (95%CI=0.66-0.75, sensitivity: 0.61 95%CI=0.52-0.69, specificity: 72, 95%CI=0.67-0.77). Our validation aim was an NPV for delirium above 0.80 which proved to be 0.82 (95%CI: 0.77-0.86). Among 84 non-delirious psychiatric patients, DeltaScan differentiated delirium from other disorders with a 94% (95%CI: 87-98%) specificity. CONCLUSIONS: DeltaScan can diagnose AE at bedside and shows a clear relationship with clinical delirium. Further research is required to explore its role in predicting delirium-related outcomes.

The recognition and management of neuropsychiatric symptoms in early Alzheimer's disease: a qualitative study among Dutch memory clinic physicians.

BACKGROUND: Timely recognition and treatment of neuropsychiatric symptoms (NPS) in Alzheimer's disease (AD) dementia may improve quality of life, reduce caregiver burden, and delay disease progression. However, management of NPS in early AD dementia remains challenging. To date, little is known about the specific challenges for memory clinic-based physicians. The aims of this qualitative study were to obtain insights regarding the recognition and treatment of NPS in AD dementia in the memory clinic, to identify challenges experienced by physicians while managing NPS, and to examine the attitudes of memory clinic physicians on the role of the memory clinic in the care for NPS in early AD dementia. METHODS: Semi-structured interviews were conducted with 13 physicians working at a memory clinic in the Netherlands (n = 7 neurologist, n = 6 geriatrician, 46% female). The data were analyzed by two independent researchers using thematic analysis. RESULTS: We observed large variation among Dutch memory clinic physicians regarding care practices, expertise, and attitudes on the role of the memory clinic considering NPS in AD dementia. The most prominent challenges that memory clinic physicians experienced while managing NPS included that the outpatient setting complicates the recognition and treatment of NPS, a lack of experience, knowledge, and/or resources to adequately apply non-pharmacological interventions, and a lack of consensus among physicians on the role of the memory clinic in NPS recognition and management. CONCLUSIONS: We identified challenges that need to be addressed to improve the early recognition and adequate management of NPS in AD dementia at the memory clinic.

Biweekly fluctuations of neuropsychiatric symptoms according to the Neuropsychiatric Inventory: Erratic symptoms or scores?

OBJECTIVES: This study investigates the stability of neuropsychiatric symptoms (NPS) assessed biweekly using the Neuropsychiatric Inventory (NPI) in a memory clinic population during a 6 week period. METHODS: Twenty-three spousal caregivers (mean [SD] age = 69.7 [8.8], 82.6% female) of 23 patients (43.5% had dementia) completed all assessments. The NPI was assessed four times during 6 weeks. We examined whether NPI domains were present during all four assessments, studied within-person variation for each NPI domain, and calculated Spearman's correlations between subsequent time-points. Furthermore, we associated repeated NPI assessments with repeated measures of caregiver burden to examine the clinical impact of changes in NPI scores over time. RESULTS: The course of NPS was highly irregular according to the NPI, with only 35.8% of the NPI domains that were present at baseline persisted during all 6 weeks. We observed large within-person variation in the presence of individual NPI domains (61.3%, range 37.5%-83.9%) and inconsistent correlations between NPI assessments (e.g., range rs  = 0.20-0.57 for agitation, range rs  = 0.29-0.59 for anxiety). Higher NPI total scores were related to higher caregiver burden (rs  = 0.60, p < 0.001), but changes in NPI total scores were unrelated to changes in caregiver burden (rs  = 0.16, p = 0.20). CONCLUSIONS: We observed strong fluctuations in NPI scores within very short time windows raising the question whether this represents erratic symptoms and/or scores. Further studies are needed to investigate the origins of these fluctuations.

Sex differences in neuropsychiatric symptoms in Alzheimer's disease dementia: a meta-analysis.

BACKGROUND: Neuropsychiatric symptoms (NPS) are common in individuals with Alzheimer's disease (AD) dementia, but substantial heterogeneity exists in the manifestation of NPS. Sex differences may explain this clinical variability. We aimed to investigate the sex differences in the prevalence and severity of NPS in AD dementia. METHODS: Literature searches were conducted in Embase, MEDLINE/PubMed, Web of Science Core Collection, Cochrane Central Register of Controlled Trials, PsycINFO, and Google Scholar from inception to February 2021. Study selection, data extraction, and quality assessment were conducted in duplicate. Effect sizes were calculated as odds ratios (OR) for NPS prevalence and Hedges' g for NPS severity. Data were pooled using random-effects models. Sources of heterogeneity were examined using meta-regression analyses. RESULTS: Sixty-two studies were eligible representing 21,554 patients (61.2% females). The majority of the included studies had an overall rating of fair quality (71.0%), with ten studies of good quality (16.1%) and eight studies of poor quality (12.9%). There was no sex difference in the presence of any NPS (k = 4, OR = 1.35 [95% confidence interval 0.78, 2.35]) and overall NPS severity (k = 13, g = 0.04 [- 0.04, 0.12]). Regarding specific symptoms, female sex was associated with more prevalent depressive symptoms (k = 20, OR = 1.60 [1.28, 1.98]), psychotic symptoms (general psychosis k = 4, OR = 1.62 [1.12, 2.33]; delusions k = 12, OR = 1.56 [1.28, 1.89]), and aberrant motor behavior (k = 6, OR = 1.47 [1.09, 1.98]). In addition, female sex was related to more severe depressive symptoms (k = 16, g = 0.24 [0.14, 0.34]), delusions (k = 10, g = 0.19 [0.04, 0.34]), and aberrant motor behavior (k = 9, g = 0.17 [0.08, 0.26]), while apathy was more severe among males compared to females (k = 11, g = - 0.10 [- 0.18, - 0.01]). There was no association between sex and the prevalence and severity of agitation, anxiety, disinhibition, eating behavior, euphoria, hallucinations, irritability, and sleep disturbances. Meta-regression analyses revealed no consistent association between the effect sizes across studies and method of NPS assessment and demographic and clinical characteristics. DISCUSSION: Female sex was associated with a higher prevalence and greater severity of several specific NPS, while male sex was associated with more severe apathy. While more research is needed into factors underlying these sex differences, our findings may guide tailored treatment approaches of NPS in AD dementia.

Music to prevent deliriUm during neuroSurgerY (MUSYC) Clinical trial: a study protocol for a randomised controlled trial.

INTRODUCTION: Delirium is a neurocognitive disorder characterised by an acute and temporary decline of mental status affecting attention, awareness, cognition, language and visuospatial ability. The underlying pathophysiology is driven by neuroinflammation and cellular oxidative stress.Delirium is a serious complication following neurosurgical procedures with a reported incidence varying between 4% and 44% and has been associated with increased length of hospital stay, increased amount of reoperations, increased costs and mortality.Perioperative music has been reported to reduce preoperative anxiety, postoperative pain and opioid usage, and attenuates stress response caused by surgery. We hypothesize that this beneficial effect of music on a combination of delirium eliciting factors might reduce delirium incidence following neurosurgery and subsequently improve clinical outcomes. METHODS: This protocol concerns a single-centred prospective randomised controlled trial with 6 months follow-up. All adult patients undergoing a craniotomy at the Erasmus Medical Center in Rotterdam are eligible. The music group will receive recorded music through an overear headphone before, during and after surgery until postoperative day 3. Patients can choose from music playlists, offered based on music importance questionnaires administered at baseline. The control group will receive standard of clinical careDelirium is assessed by the Delirium Observation Scale and confirmed by a delirium-expert psychiatrist according to the DSM-5 criteria. Risk factors correlated with the onset of delirium, such as cognitive function at baseline, preoperative anxiety, perioperative medication use, depth of anaesthesia and postoperative pain, and delirium-related health outcomes such as length of stay, daily function, quality of life (ie, EQ-5D, EORTC questionnaires), costs and cost-effectiveness are collected. ETHICS AND DISSEMINATION: This study is being conducted in accordance with the Declaration of Helsinki. The Medical Ethics Review Board of Erasmus University Medical Center Rotterdam, The Netherlands, approved this protocol. Results will be disseminated via peer-reviewed scientific journals and conference presentations. TRIAL REGISTRATION NUMBERS: NL8503 and NCT04649450.

Neuropsychiatric and Cognitive Symptoms Across the Alzheimer Disease Clinical Spectrum: Cross-sectional and Longitudinal Associations.

BACKGROUND AND OBJECTIVES: To investigate the prevalence and trajectories of neuropsychiatric symptoms (NPS) in relation to cognitive functioning in a cohort of ß-amyloid-positive (A+) individuals across the Alzheimer disease (AD) clinical spectrum. METHODS: In this single-center observational study, we included all individuals who visited the Alzheimer Center Amsterdam and had a clinical diagnosis of subjective cognitive decline (SCD), mild cognitive impairment (MCI), or probable AD dementia and were A+. We measured NPS with the Neuropsychiatric Inventory (NPI), examining total scores and the presence of specific NPI domains. Cognition was assessed across 5 cognitive domains and with the Mini-Mental State Examination (MMSE). We examined trajectories including model-based trends for NPS and cognitive functioning over time. We used linear mixed models to relate baseline NPI scores to cognitive functioning at baseline (whole-sample) and longitudinal time points (subsample n = 520, mean 1.8 [SD 0.7] years follow-up). RESULTS: We included 1,524 A+ individuals from the Amsterdam Dementia Cohort with A+ SCD (n = 113), A+ MCI (n = 321), or A+ AD dementia (n = 1,090). NPS were prevalent across all clinical AD stages (≥1 NPS 81.4% in SCD, 81.2% in MCI, 88.7% in dementia; ≥1 clinically relevant NPS 54.0% in SCD, 50.5% in MCI, 66.0% in dementia). Cognitive functioning showed a uniform gradual decline; while in contrast, large intraindividual heterogeneity of NPS was observed over time across all AD groups. At baseline, we found associations between NPS and cognition in dementia that were most pronounced for NPI total scores and MMSE (range ß = -0.18 to -0.11, false discovery rate [FDR]-adjusted p < 0.05), while there were no cross-sectional relationships in SCD and MCI (range ß = -0.32 to 0.36, all FDR-adjusted p > 0.05). There were no associations between baseline NPS and cognitive functioning over time in any clinical stage (range ß = -0.13 to 0.44, all FDR-adjusted p > 0.05). DISCUSSION: NPS and cognitive symptoms are both prevalent across the AD clinical spectrum, but show a different evolution during the course of the disease.

Early recognition and treatment of neuropsychiatric symptoms to improve quality of life in early Alzheimer's disease: protocol of the BEAT-IT study.

BACKGROUND: Neuropsychiatric symptoms (NPS) are very common in patients with mild cognitive impairment (MCI) and Alzheimer's disease (AD) dementia and are associated with various disadvantageous clinical outcomes including a negative impact on quality of life, caregiver burden, and accelerated disease progression. Despite growing evidence of the efficacy of (non)pharmacological interventions to reduce these symptoms, NPS remain underrecognized and undertreated in memory clinics. The BEhavioural symptoms in Alzheimer's disease Towards early Identification and Treatment (BEAT-IT) study is developed to (1) investigate the neurobiological etiology of NPS in AD and (2) study the effectiveness of the Describe, Investigate, Create, Evaluate (DICE) approach to structure and standardize the current care of NPS in AD. By means of the DICE method, we aim to improve the quality of life of AD patients with NPS and their caregivers who visit the memory clinic. This paper describes the protocol for the intervention study that incorporates the latter aim. METHODS: We aim to enroll a total of 150 community-dwelling patients with MCI or AD and their caregivers in two waves. First, we will recruit a control group who will receive care as usual. Next, the second wave of participants will undergo the DICE method. This approach consists of the following steps: (1) describe the context in which NPS occur, (2) investigate the possible causes, (3) create and implement a treatment plan, and (4) evaluate whether these interventions are effective. Primary outcomes are the quality of life of patients and their caregivers. Secondary outcomes include NPS change, caregiver burden, caregivers' confidence managing NPS, psychotropic medication use, the experiences of patients and caregivers who underwent the DICE method, and the cost-effectiveness of the intervention. CONCLUSIONS: This paper describes the protocol of an intervention study that is part of the BEAT-IT study and aims to improve current recognition and treatment of NPS in AD by structuring and standardizing the detection and treatment of NPS in AD using the DICE approach. TRIAL REGISTRATION: The trial was registered on the Netherlands Trial Registry ( NTR7459 ); registered 6 September 2018.

Candidate CSPG4 mutations and induced pluripotent stem cell modeling implicate oligodendrocyte progenitor cell dysfunction in familial schizophrenia.

Schizophrenia is highly heritable, yet its underlying pathophysiology remains largely unknown. Among the most well-replicated findings in neurobiological studies of schizophrenia are deficits in myelination and white matter integrity; however, direct etiological genetic and cellular evidence has thus far been lacking. Here, we implement a family-based approach for genetic discovery in schizophrenia combined with functional analysis using induced pluripotent stem cells (iPSCs). We observed familial segregation of two rare missense mutations in Chondroitin Sulfate Proteoglycan 4 (CSPG4) (c.391G > A [p.A131T], MAF 7.79 × 10-5 and c.2702T > G [p.V901G], MAF 2.51 × 10-3). The CSPG4A131T mutation was absent from the Swedish Schizophrenia Exome Sequencing Study (2536 cases, 2543 controls), while the CSPG4V901G mutation was nominally enriched in cases (11 cases vs. 3 controls, P = 0.026, OR 3.77, 95% CI 1.05-13.52). CSPG4/NG2 is a hallmark protein of oligodendrocyte progenitor cells (OPCs). iPSC-derived OPCs from CSPG4A131T mutation carriers exhibited abnormal post-translational processing (P = 0.029), subcellular localization of mutant NG2 (P = 0.007), as well as aberrant cellular morphology (P = 3.0 × 10-8), viability (P = 8.9 × 10-7), and myelination potential (P = 0.038). Moreover, transfection of healthy non-carrier sibling OPCs confirmed a pathogenic effect on cell survival of both the CSPG4A131T (P = 0.006) and CSPG4V901G (P = 3.4 × 10-4) mutations. Finally, in vivo diffusion tensor imaging of CSPG4A131T mutation carriers demonstrated a reduction of brain white matter integrity compared to unaffected sibling and matched general population controls (P = 2.2 × 10-5). Together, our findings provide a convergence of genetic and functional evidence to implicate OPC dysfunction as a candidate pathophysiological mechanism of familial schizophrenia.

Neuropsychiatric Symptoms Complicating the Diagnosis of Alzheimer's Disease: A Case Report.

Neuropsychiatric symptoms (NPS) are increasingly recognized as a core element of Alzheimer's disease (AD); however, clinicians still consider AD primarily as a cognitive disorder. We describe a case in which the underrecognition of NPS as part of AD resulted in substantial delay of an AD diagnosis, a wrong psychiatric diagnosis, and the organization of inappropriate care. The aim of this paper is to acknowledge NPS as an (early) manifestation of AD and to suggest features that may point toward underlying AD in older adults with late-life behavioral changes.

A balanced translocation disrupting BCL2L10 and PNLDC1 segregates with affective psychosis.

Affective psychoses are a group of severe psychiatric disorders, including schizoaffective disorder and bipolar I disorder, together affecting ∼1% of the population. Despite their high heritability, the molecular genetics and neurobiology of affective psychosis remain largely elusive. Here, we describe the identification of a structural genetic variant segregating with affective psychosis in a family with multiple members suffering from bipolar I disorder or schizoaffective disorder, bipolar type. A balanced translocation involving chromosomes 6 and 15 was detected by karyotyping and fluorescence in-situ hybridization (FISH). Using whole-genome sequencing, we rapidly delineated the translocation breakpoints as corresponding intragenic events disrupting BCL2L10 and PNLDC1. These data warrant further consideration for BCL2L10 and PNLDC1 as novel candidates for affective psychosis. © 2016 The Authors. American Journal of Medical Genetics Part B: Neuropsychiatric Genetics Published by Wiley Periodicals, Inc.

Nonvisual complex spike signals in the rabbit cerebellar flocculus.

In addition to the well-known signals of retinal image slip, floccular complex spikes (CSs) also convey nonvisual signals. We recorded eye movement and CS activity from Purkinje cells in awake rabbits sinusoidally oscillated in the dark on a vestibular turntable. The stimulus frequency ranged from 0.2 to 1.2 Hz, and the velocity amplitude ranged from 6.3 to 50°/s. The average CS modulation was evaluated at each combination of stimulus frequency and amplitude. More than 75% of the Purkinje cells carried nonvisual CS signals. The amplitude of this modulation remained relatively constant over the entire stimulus range. The phase response of the CS modulation in the dark was opposite to that during the vestibulo-ocular reflex (VOR) in the light. With increased frequency, the phase response systematically shifted from being aligned with contraversive head velocity toward peak contralateral head position. At fixed frequency, the phase response was dependent on peak head velocity, indicating a system nonlinearity. The nonvisual CS modulation apparently reflects a competition between eye movement and vestibular signals, resulting in an eye movement error signal inferred from nonvisual sources. The combination of this error signal with the retinal slip signal in the inferior olive results in a net error signal reporting the discrepancy between the actual visually measured eye movement error and the inferred eye movement error derived from measures of the internal state. The presence of two error signals requires that the role of CSs in models of the floccular control of VOR adaption be expanded beyond retinal slip.

Bidirectional parallel fiber plasticity in the cerebellum under climbing fiber control.

Cerebellar parallel fiber (PF)-Purkinje cell (PC) synapses can undergo postsynaptically expressed long-term depression (LTD) or long-term potentiation (LTP) depending on whether or not the climbing fiber (CF) input is coactivated during tetanization. Here, we show that modifications of the postsynaptic calcium load using the calcium chelator BAPTA or photolytic calcium uncaging result in a reversal of the expected polarity of synaptic gain change. At higher concentrations, BAPTA blocks PF-LTP. These data indicate that PF-LTD requires a higher calcium threshold amplitude than PF-LTP induction and suggest that CF activity acts as a polarity switch by providing dendritic calcium transients. Moreover, previous CF-LTD induction changes the relative PF-LTD versus -LTP induction probability. These findings suggest that bidirectional cerebellar learning is governed by a calcium threshold rule operating "inverse" to the mechanism previously described at other glutamatergic synapses (BCM rule) and that the LTD/LTP induction probability is under heterosynaptic climbing fiber control.

Mechanisms underlying cerebellar motor deficits due to mGluR1-autoantibodies.

Patients with Hodgkin's disease can develop paraneoplastic cerebellar ataxia because of the generation of autoantibodies against mGluR1 (mGluR1-Abs). Yet, the pathophysiological mechanisms underlying their motor coordination deficits remain to be elucidated. Here, we show that application of IgG purified from the patients' serum to cerebellar slices of mice acutely reduces the basal activity of Purkinje cells, whereas application to the flocculus of mice in vivo evokes acute disturbances in the performance of their compensatory eye movements. In addition, the mGluR1-Abs block induction of long-term depression in cultured mouse Purkinje cells, whereas the cerebellar motor learning behavior of the patients is affected in that they show impaired adaptation of their saccadic eye movements. Finally, postmortem analysis of the cerebellum of a paraneoplastic cerebellar ataxia patient showed that the number of Purkinje cells was significantly reduced by approximately two thirds compared with three controls. We conclude that autoantibodies against mGluR1 can cause cerebellar motor coordination deficits caused by a combination of rapid effects on both acute and plastic responses of Purkinje cells and chronic degenerative effects.