Validation of the RBD Symptom Severity Scale in the North American Prodromal Synucleinopathy Consortium

BACKGROUND AND OBJECTIVES

REM sleep behavior disorder (RBD) is a parasomnia characterized by dream enactment. The International RBD Study Group developed the RBD Symptom Severity Scale (RBDSSS) to assess symptom severity for clinical or research use. We assessed the psychometric and clinimetric properties of the RBDSSS in participants enrolled in the North American Prodromal Synucleinopathy (NAPS) Consortium for RBD.

METHODS

NAPS participants, who have polysomnogram-confirmed RBD, and their bedpartners completed the RBDSSS (participant and bedpartner versions). The RBDSSS contains 8 questions to assess the frequency and severity/impact of (1) dream content, (2) vocalizations, (3) movements, and (4) injuries associated with RBD. Total scores for participant (maximum score = 54) and bedpartner (maximum score = 38) questionnaires were derived by multiplying frequency and severity scores for each question. The Clinical Global Impression Scale of Severity (CGI-S) and RBD symptom frequency were assessed by a physician during a semistructured clinical interview with participants and, if available, bedpartners. Descriptive analyses, correlations between overall scores, and subitems were assessed, and item response analysis was performed to determine the scale's validity.

RESULTS

Among 261 study participants, the median (interquartile range) score for the RBDSSS-PT (participant) was 10 (4-18) and that for the RBDSSS-BP (bedpartner) was 8 (4-15). The median CGI-S was 3 (3-4), indicating moderate severity. RBDSSS-BP scores were significantly lower in women with RBD (6 vs 9, p = 0.02), while there were no sex differences in RBDSSS-PT scores (8 vs 10.5, p = 0.615). Positive correlations were found between RBDSSS-PT vs RBDSSS-BP (Spearman rs = 0.561), RBDSSS-PT vs CGI-S (rs = 0.556), and RBDSSS-BP vs CGI-S (rs = 0.491, all p < 0.0001). Item response analysis showed a high discriminatory value (range 1.40-2.12) for the RBDSSS-PT and RBDSSS-BP (1.29-3.47).

DISCUSSION

We describe the RBDSSS with adequate psychometric and clinimetric properties to quantify RBD symptom severity and good concordance between participant and bedpartner questionnaires and between RBDSSS scores and clinician-assessed global severity.

Frequency of Orthostatic Hypotension in Isolated REM Sleep Behavior Disorder

BACKGROUND AND OBJECTIVES

Although orthostatic hypotension (OH) can be an early feature of autonomic dysfunction in isolated REM sleep behavior disorder (iRBD), no large-scale studies have examined the frequency of OH in iRBD. In this study, we prospectively evaluated the frequency of OH in a large multicenter iRBD cohort.

METHODS

Participants 18 years or older with video polysomnogram-confirmed iRBD were enrolled through the North American Prodromal Synucleinopathy consortium. All participants underwent 3-minute orthostatic stand testing to assess the frequency of OH, and a Δ heart rate/Δ systolic blood pressure (ΔHR/ΔSBP) ratio <0.5 was used to define reduced HR augmentation, suggestive of neurogenic OH. All participants completed a battery of assessments, including the Scales for Outcomes in Parkinson Disease-Autonomic Dysfunction (SCOPA-AUT) and others assessing cognitive, motor, psychiatric, and sensory domains.

RESULTS

Of 340 iRBD participants (65 ± 10 years, 82% male), 93 (27%) met criteria for OH (ΔHR/ΔSBP 0.37 ± 0.28; range 0.0-1.57), and of these, 72 (77%) met criteria for OH with reduced HR augmentation (ΔHR/ΔSBP 0.28 ± 0.21; range 0.0-0.5). Supine hypertension (sHTN) was present in 72% of those with OH. Compared with iRBD participants without OH, those with OH were older, reported older age of RBD symptom onset, and had worse olfaction. There was no difference in autonomic symptom scores as measured by SCOPA-AUT.

DISCUSSION

OH and sHTN are common in iRBD. However, as patients may have reduced autonomic symptom awareness, orthostatic stand testing should be considered in clinical evaluations. Longitudinal studies are needed to clarify the relationship between OH and phenoconversion risk in iRBD.

TRIAL REGISTRATION INFORMATION

ClinicalTrials.gov: NCT03623672; North American Prodromal Synucleinopathy Consortium.

Evolution of Prodromal Multiple System Atrophy from REM Sleep Behavior Disorder: A Descriptive Study

BACKGROUND

Prodromal multiple system atrophy (MSA) has been characterized mainly by retrospective chart reviews. Direct observation and tracking of prodromal markers in MSA have been very limitedObjective:To report the baseline characteristics and evolution of prodromal markers of MSA as they were prospectively measured in patients with idiopathic/isolated REM sleep behavior disorder (iRBD)Methods:Patients with iRBD were evaluated as part of a comprehensive protocol repeated annually. The protocol included assessment of motor, sleep, psychiatric, and autonomic symptoms supplemented by motor examination, quantitative motor testing, neuropsychological examination, orthostatic blood pressure measurement, and tests of olfaction and color vision. Patients who eventually developed MSA were described and compared with those who phenoconverted to Lewy body disease (Parkinson's disease and dementia with Lewy bodies).

RESULTS

Of 67 phenocoverters, 4 developed MSA-P and 63 developed Lewy body disease. An additional 2 MSA-C patients were seen at baseline, already with cerebellar signs. Compared to those with Lewy body disease, those with MSA-P were younger, had less severe loss of tonic REM sleep atonia, more insomnia symptoms, and better olfaction. Clinically-evident autonomic dysfunction was not invariable in prodromal stages, often developing proximate to or after motor phenoconversion. Of the autonomic symptoms, genitourinary dysfunction was the first to develop in all cases. Olfaction and cognition remained normal throughout the prodromal and clinical disease course, in clear contrast to patients with Lewy body disease.

CONCLUSION

Prodromal MSA progresses rapidly, often without substantial autonomic dysfunction, and with preserved olfaction and cognition throughout its prodromal course.

Speech Biomarkers in Rapid Eye Movement Sleep Behavior Disorder and Parkinson Disease

Objective

This multilanguage study used simple speech recording and high‐end pattern analysis to provide sensitive and reliable noninvasive biomarkers of prodromal versus manifest α‐synucleinopathy in patients with idiopathic rapid eye movement sleep behavior disorder (iRBD) and early‐stage Parkinson disease (PD).

Methods

We performed a multicenter study across the Czech, English, German, French, and Italian languages at 7 centers in Europe and North America. A total of 448 participants (337 males), including 150 with iRBD (mean duration of iRBD across language groups 0.5–3.4 years), 149 with PD (mean duration of disease across language groups 1.7–2.5 years), and 149 healthy controls were recorded; 350 of the participants completed the 12‐month follow‐up. We developed a fully automated acoustic quantitative assessment approach for the 7 distinctive patterns of hypokinetic dysarthria.

Results

No differences in language that impacted clinical parkinsonian phenotypes were found. Compared with the controls, we found significant abnormalities of an overall acoustic speech severity measure via composite dysarthria index for both iRBD (p = 0.002) and PD (p < 0.001). However, only PD (p < 0.001) was perceptually distinct in a blinded subjective analysis. We found significant group differences between PD and controls for monopitch (p < 0.001), prolonged pauses (p < 0.001), and imprecise consonants (p = 0.03); only monopitch was able to differentiate iRBD patients from controls (p = 0.004). At the 12‐month follow‐up, a slight progression of overall acoustic speech impairment was noted for the iRBD (p = 0.04) and PD (p = 0.03) groups.

Interpretation

Automated speech analysis might provide a useful additional biomarker of parkinsonism for the assessment of disease progression and therapeutic interventions. ANN NEUROL 2021;90:62–75

280 Is blue-enriched light more effective than red light to enhance vigilance and cognitive performance in Parkinson’s Disease?

Introduction

Approximately 50% (between 16–74%) of adults with Parkinson’s disease (PD) show excessive daytime sleepiness. Besides its important role for vision, light conveys a powerful stimulating signal for alertness and cognition. Recent research has demonstrated that the blue part of light spectrum is the most efficient in enhancing vigilance and cognitive performance in young and older healthy individuals, thanks to a specific photoreception system within the eye which is particularly sensitive to blue wavelength. The aim of this pilot study was to compare the effects of blue-enriched light exposure (BL) and red-light placebo exposure (RL) on psychomotor vigilance and cognitive performance in adults with PD.

Methods

Sixteen participants with idiopathic PD (64.0±5.5 yrs, 6 women, Hoehn and Yahr status: 2) completed a brief neuropsychological assessment to exclude dementia, self-reported questionnaires and a complete eye examination in screening visits. The one-day experimental procedure included 1.25 h period of baseline dim-light exposition, followed by two light conditions presented in a counterbalanced design and separated by 15 minutes in dim-light: 1.25 h of BL at 959lux and 1.25 h of placebo RL condition at 472lux. Both light conditions were delivered by Luminette®. Data were normalized according to baseline dim-light evaluation. Mixed analyses of variance (2 light conditions X 2 orders) were performed to compare performance on an auditory psychomotor vigilance task (A-PVT) and an auditory 2-back cognitive tasks (A-2-back) during light exposure.

Results

We observed no significant effect of light conditions, orders and no interaction on reaction time (RT) and number of correct answers for the A-2-Back task. Furthermore, there was no significant difference between BL and RL on A-PVT performance including median RT, shift in optimum RT (i.e.,mean RT from fastest 10% RT), and duration of response in the lapse domain (i.e.,mean RT from slowest 10% RT).

Conclusion

These preliminary results do not support the notion that blue-enriched white light exposure is more efficient than red light exposure to stimulate psychomotor vigilance and cognitive performance in adults with PD. Next steps of analyses will compare the effects of BL and RL on subjective sleepiness and EEG cortical activation in the same population.

Support (if any)

CIHC & QPN

524 NAPS

Introduction

Rapid Eye Movement (REM) Sleep Behavior Disorder (RBD) is characterized by a lack of muscle atonia during REM sleep with dream enactment. RBD is regarded as a prodromal synucleinopathy as a high proportion of patients eventually phenoconvert to Parkinson’s Disease and related synucleinopathies, suggesting RBD may be an early non-motor symptom of disease. Accordingly, patients with RBD are ideally situated to test potential therapeutic interventions to prevent phenoconversion to synucleinopathy. However, RBD itself, and associated patient registries, are rare. The North American Prodromal Synucleinopathy Consortium (formed in 2018) establishes a multisite registry of RBD patients with standardized neurological, neuropsychiatric, and neuropsychological assessments and biomarker collection. The present work reports baseline characteristics of this RBD patient database at its current state.

Methods

Seven participating sites have contributed n=170 polysomnographically-confirmed RBD patients. Data includes past medical and family history, self-report questionnaires, and neuropsychological, motor, sensory, and autonomic function testing. Additionally, all subjects have contributed blood, and a subset of subjects have contributed cerebrospinal fluid samples to the National Centralized Repository for Alzheimer’s Disease and Related Dementias for future analysis. A final diagnosis for each subject was determined through an adjudication process by NAPS Consortium PIs; subjects were categorized as ether: 1) isolated RBD, 2) RBD+, 3) Early Symptomatic, or 4) Phenoconverted.

Results

Of the n=170 subjects, there were n=39 isolated RBD, n=81 RBD+, n=45 Early Symptomatic, and n=4 Phenoconverted. Isolated RBD subjects have no other early neurodegeneration signs/symptoms, those with RBD+ have at least one other identifiable early/mild symptom. The early symptomatic group includes those with mild or subjective cognitive impairment, pure autonomic failure, or possible multiple systems atrophy. The Phenoconverted group consists of those with Dementia with Lew Bodies, Dementia NOS, Parkinson’s Disease, or Parkinson’s NOS. The distribution of impairment across the 5 major domains (motor, cognitive, autonomic, sensory, and psychiatric) for each of the 4 groups will be described.

Conclusion

This interim analysis presents data on n=170 subjects. The target enrollment is n=360 across the 7 original sites plus 3 new sites. Future work will follow these subjects longitudinally to assess rates and predictors of phenoconversion.

Support (if any)

NIH NIA R34 AG056639 (YJ, BB)

Interhemispheric differences in P1 and N1 amplitude in EEG and MEG differ across older individuals with a concussion compared with age-matched controls

We studied the effects of mild traumatic brain injury (mTBI) in an aging population. We examined visual search with event-related potentials (ERPs) and event-related fields (ERF) for a lateral color singleton focusing on the P1 and N1 in each hemisphere. Forty participants (19 mTBI and 21 controls) aged 50 to 72 performed a visual search task, while we recorded their magnetoencephalogram (MEG) with simultaneous electroencephalogram (EEG). We compared visual ERPs and ERFs and associated cortical activity estimated using MEG source localization. Relative to matched controls, participants with an mTBI had a smaller P1 in the left hemisphere and a smaller N1 in the right hemisphere. Also, mTBI participants showed inversed activation patterns across the hemispheres during the N1 in MEG compared with controls. This is the first study to investigate the impact of mTBI on neuronal source activations during early visual processing in an aging population. Results showed that when aging individuals suffer from an mTBI, there are perturbations in the amplitude and hemispheric dominance patterns in the visual P1 and N1 responses that are visible for months to years following the injury. Our findings indicate that mTBI can lead to modifications of sensory and/or perceptual responses, suggesting possible adaptive functional reorganization following mTBI.

Prediction of Stress and Mental Workload during Police Academy Training Using Ultra-Short-Term Heart Rate Variability and Breathing Analysis

Heart rate variability (HRV) has been studied in the context of human behavior analysis and many features have been extracted from the inter-beat interval (RR) time series and tested as correlates of constructs such as mental workload, stress and anxiety. Such constructs are crucial in assessing quality-of-life of individuals, as well as their overall performance when doing critical tasks. Most studies, however, have been conducted in controlled laboratory environments with artificially-induced psychological responses. While this assures that high quality data are collected, the amount of data is limited and the transferability of the findings to more ecologically-appropriate settings remains unknown. Additionally, it is desirable for such mental state monitoring systems to have high temporal resolution, thus allowing for quick feedback and adaptive decision making. In this article, we explore the use of features computed from time windows much shorter than typically reported in the literature. More specifically, we evaluate the potential of HRV and breathing features computed over so-called ultra-short-term segments (i.e., < 5 minutes) for stress and mental workload prediction. Experiments with 27 police academy trainees show that short time windows as low as 60 seconds can provide useful insights, in particular for mental workload assessment. Moreover, the fusion of HRV and breathing features showed to be an important aspect for reliable behavioural assessment in highly ecological settings.

Risk and predictors of dementia and parkinsonism in idiopathic REM sleep behaviour disorder: a multicentre study

Idiopathic REM sleep behaviour disorder (iRBD) is a powerful early sign of Parkinson's disease, dementia with Lewy bodies, and multiple system atrophy. This provides an unprecedented opportunity to directly observe prodromal neurodegenerative states, and potentially intervene with neuroprotective therapy. For future neuroprotective trials, it is essential to accurately estimate phenoconversion rate and identify potential predictors of phenoconversion. This study assessed the neurodegenerative disease risk and predictors of neurodegeneration in a large multicentre cohort of iRBD. We combined prospective follow-up data from 24 centres of the International RBD Study Group. At baseline, patients with polysomnographically-confirmed iRBD without parkinsonism or dementia underwent sleep, motor, cognitive, autonomic and special sensory testing. Patients were then prospectively followed, during which risk of dementia and parkinsonsim were assessed. The risk of dementia and parkinsonism was estimated with Kaplan-Meier analysis. Predictors of phenoconversion were assessed with Cox proportional hazards analysis, adjusting for age, sex, and centre. Sample size estimates for disease-modifying trials were calculated using a time-to-event analysis. Overall, 1280 patients were recruited. The average age was 66.3 ± 8.4 and 82.5% were male. Average follow-up was 4.6 years (range = 1-19 years). The overall conversion rate from iRBD to an overt neurodegenerative syndrome was 6.3% per year, with 73.5% converting after 12-year follow-up. The rate of phenoconversion was significantly increased with abnormal quantitative motor testing [hazard ratio (HR) = 3.16], objective motor examination (HR = 3.03), olfactory deficit (HR = 2.62), mild cognitive impairment (HR = 1.91-2.37), erectile dysfunction (HR = 2.13), motor symptoms (HR = 2.11), an abnormal DAT scan (HR = 1.98), colour vision abnormalities (HR = 1.69), constipation (HR = 1.67), REM atonia loss (HR = 1.54), and age (HR = 1.54). There was no significant predictive value of sex, daytime somnolence, insomnia, restless legs syndrome, sleep apnoea, urinary dysfunction, orthostatic symptoms, depression, anxiety, or hyperechogenicity on substantia nigra ultrasound. Among predictive markers, only cognitive variables were different at baseline between those converting to primary dementia versus parkinsonism. Sample size estimates for definitive neuroprotective trials ranged from 142 to 366 patients per arm. This large multicentre study documents the high phenoconversion rate from iRBD to an overt neurodegenerative syndrome. Our findings provide estimates of the relative predictive value of prodromal markers, which can be used to stratify patients for neuroprotective trials.

Screening for prodromal Parkinson's disease in the general community: a sleep-based approach

OBJECTIVE/BACKGROUND

Neuroprotective therapy for Parkinson's disease (PD) is most likely to be effective if provided in its prodromal stages. However, identifying prodromal PD is difficult because PD is relatively uncommon, and most markers are nonspecific. Rapid eye movement (REM) sleep behavior disorder (RBD) is by far the strongest clinical marker of prodromal PD, but most patients do not seek out medical attention. Developing an efficient way of diagnosing RBD from the general community may be the most practical method to detect prodromal PD.

METHODS

We developed a screening strategy that began with a newspaper advertisement containing a single-question screen for RBD. All screen-positive subjects underwent an interview based on the Innsbruck RBD inventory aimed to optimize the positive predictive value. Those who passed both screens underwent confirmatory polysomnography. The proportion of screened RBD patients who met the International Parkinson and Movement Disorder Society (MDS) criteria for prodromal PD was assessed. A broad array of clinical markers of neurodegeneration was compared between newspaper-screened RBD patients and 130 RBD patients clinically referred to the sleep center.

RESULTS

Of 111 RBD-screen-positive participants, 40 (36%) passed the secondary screen, and 29 underwent full polysomnography. Of these 29 patients, 19 were ultimately proven to have RBD (PPV = 66%), 12 (63%) of whom met the criteria for prodromal PD. Compared to patients referred to the sleep center, newspaper-screened patients had similar age, sex, olfaction, autonomic function, and color vision. However, motor and cognitive assessments were slightly better in newspaper-screened patients.

CONCLUSIONS

A multistep screening approach using RBD screening questionnaires and telephone follow-up can efficiently identify prodromal PD in the general community.

Parkinson's Disease Genetic Loci in Rapid Eye Movement Sleep Behavior Disorder

Rapid eye movement (REM) sleep behavior disorder (RBD) is a prodromal condition for Parkinson's disease (PD) and other synucleinopathies, which often occurs many years before the onset of PD. We analyzed 261 RBD patients and 379 controls for nine PD-associated SNPs and examined their effects, first upon on RBD risk and second, on eventual progression to synucleinopathies in a prospective follow-up in a subset of patients. The SCARB2 rs6812193 (OR = 0.67, 95 % CI = 0.51-0.88, p = 0.004) and the MAPT rs12185268 (OR-0.43, 95 % CI-0.26-0.72, p = 0.001) were associated with RBD in different models. Kaplan-Meier survival analysis in a subset of RBD patients (n = 56), demonstrated that homozygous carriers of the USP25 rs2823357 SNP had progressed to synucleinopathies faster than others (log-rank p = 0.003, Breslow p = 0.005, Tarone-Ware p = 0.004). As a proof-of-concept study, these results suggest that RBD may be associated with at least a subset of PD-associated genes, and demonstrate that combining genetic and prodromal clinical data may help identifying individuals that are either more or less susceptible to develop synucleinopathies. More studies are necessary to replicate these results, and identify more genetic factors affecting progression from RBD to synucleinopathies.

Parkinson risk in idiopathic REM sleep behavior disorder: preparing for neuroprotective trials

OBJECTIVE

To precisely delineate clinical risk factors for conversion from idiopathic REM sleep behavior disorder (RBD) to Parkinson disease, dementia with Lewy bodies, and multiple system atrophy, in order to enable practical planning and stratification of neuroprotective trials against neurodegenerative synucleinopathy.

METHODS

In a 10-year prospective cohort, we tested prodromal Parkinson disease markers in 89 patients with idiopathic RBD. With Kaplan-Meier analysis, we calculated risk of neurodegenerative synucleinopathy, and using Cox proportional hazards, tested the ability of prodromal markers to identify patients at higher disease risk. By combining predictive markers, we then designed stratification strategies to optimally select patients for definitive neuroprotective trials.

RESULTS

The risk of defined neurodegenerative synucleinopathy was high: 30% developed disease at 3 years, rising to 66% at 7.5 years. Advanced age (hazard ratio [HR] = 1.07), olfactory loss (HR = 2.8), abnormal color vision (HR = 3.1), subtle motor dysfunction (HR = 3.9), and nonuse of antidepressants (HR = 3.5) identified higher risk of disease conversion. However, mild cognitive impairment (HR = 1.8), depression (HR = 0.63), Parkinson personality, treatment with clonazepam (HR = 1.3) or melatonin (HR = 0.55), autonomic markers, and sex (HR = 1.37) did not clearly predict clinical neurodegeneration. Stratification with prodromal markers increased risk of neurodegenerative disease conversion by 200%, and combining markers allowed sample size reduction in neuroprotective trials by >40%. With a moderately effective agent (HR = 0.5), trials with fewer than 80 subjects per group can demonstrate definitive reductions in neurodegenerative disease.

CONCLUSIONS

Using stratification with simply assessed markers, it is now not only possible, but practical to include patients with RBD in neuroprotective trials against Parkinson disease, multiple system atrophy, and dementia with Lewy bodies.

Predictors of dementia in Parkinson disease: a prospective cohort study

OBJECTIVE

We investigated an array of possible markers of early dementia in Parkinson disease.

METHODS

We performed a comprehensive assessment of autonomic, sleep, psychiatric, visual, olfactory, and motor manifestations in 80 patients with Parkinson disease who were dementia-free at baseline. After 4.4 years' follow-up, patients were evaluated for dementia. Predictive variables were assessed using logistic regression adjusting for disease duration, follow-up duration, age, and sex.

RESULTS

Of 80 patients, 27 (34%) developed dementia. Patients destined to develop dementia were older and more often male (odds ratio [OR] = 3.64, p = 0.023). Those with baseline mild cognitive impairment had increased dementia risk (OR = 22.5, p < 0.001). REM sleep behavior disorder at baseline dramatically increased dementia risk (OR = 49.7, p = 0.001); however, neither daytime sleepiness nor insomnia predicted dementia. Higher baseline blood pressure increased dementia risk (OR = 1.37 per 10 mm Hg, p = 0.032). Orthostatic blood pressure drop was strongly associated with dementia risk (OR = 1.84 per 10 mm Hg, p < 0.001); having a systolic drop of >10 mm Hg increased dementia odds 7-fold (OR = 7.3, p = 0.002). Abnormal color vision increased dementia risk (OR = 3.3, p = 0.014), but olfactory dysfunction did not. Among baseline motor variables, proportion of gait involvement (OR = 1.12, p = 0.023), falls (OR = 3.02, p = 0.042), and freezing (OR = 2.63, p = 0.013), as well as the Purdue Pegboard Test (OR = 0.67, p = 0.049) and alternate tap test (OR = 0.97, p = 0.033) predicted dementia.

CONCLUSION

Cardiovascular autonomic dysfunction, REM sleep behavior disorder, color discrimination ability, and gait dysfunction strongly predict development of dementia in Parkinson disease.

Antidepressants and REM sleep behavior disorder: isolated side effect or neurodegenerative signal?

OBJECTIVES

Antidepressants, among the most commonly prescribed medications, trigger symptoms of REM sleep behavior disorder (RBD) in up to 6% of users. Idiopathic RBD is a very strong prodromal marker of Parkinson disease and other synuclein-mediated neurodegenerative syndromes. It is therefore critically important to understand whether antidepressant-associated RBD is an independent pharmacologic syndrome or a sign of possible prodromal neurodegeneration.

DESIGN

Prospective cohort study.

SETTING

Tertiary sleep disorders center.

PARTICIPANTS

100 patients with idiopathic RBD, all with diagnosis confirmed on polysomnography, stratified to baseline antidepressant use, with 45 matched controls.

MEASUREMENTS/RESULTS

Of 100 patients, 27 were taking antidepressants. Compared to matched controls, RBD patients taking antidepressants demonstrated significant abnormalities of 12/14 neurodegenerative markers tested, including olfaction (P = 0.007), color vision (P = 0.004), Unified Parkinson Disease Rating Scale II and III (P < 0.001 and 0.007), timed up-and-go (P = 0.003), alternate tap test (P = 0.002), Purdue Pegboard (P = 0.007), systolic blood pressure drop (P = 0.029), erectile dysfunction (P = 0.002), constipation (P = 0.003), depression indices (P < 0.001), and prevalence of mild cognitive impairment (13% vs. 60%, P < 0.001). All these abnormalities were indistinguishable in severity from RBD patients not taking antidepressants. However, on prospective follow-up, RBD patients taking antidepressants had a lower risk of developing neurodegenerative disease than those without antidepressant use (5-year risk = 22% vs. 59%, RR = 0.22, 95%CI = 0.06, 0.74).

CONCLUSIONS

Although patients with antidepressant-associated RBD have a lower risk of neurodegeneration than patients with "purely-idiopathic" RBD, markers of prodromal neurodegeneration are still clearly present. Development of RBD with antidepressants can be an early signal of an underlying neurodegenerative disease.

Mild cognitive impairment in patients with Parkinson's disease is associated with increased cortical degeneration

Mild cognitive impairment (MCI) can occur early in the course of Parkinson's disease (PD), and its presence increases the risk of developing dementia. Determining the cortical changes associated with MCI in PD, thus, may be useful in predicting the future development of dementia. To address this objective, 37 patients with PD, divided into 2 groups according to the presence or absence MCI (18 with and 19 without) and 16 matched controls, underwent anatomic magnetic resonance imaging. Corticometry analyses were performed to measure the changes in cortical thickness and surface area as well as their correlation with disease duration. Compared with healthy controls, the PD-MCI group exhibited increased atrophy and changes of local surface area in the bilateral occipital, left temporal, and frontal cortices; whereas the PD non-MCI group exhibited only unilateral thinning and decreased surface area in the occipital lobe and in the frontal cortex. In addition, a comparison between the PD-MCI and PD non-MCI groups revealed increased local surface area in the occipital lobe, temporal lobe, and postcentral gyrus for the cognitively impaired patients. It is noteworthy that, in the PD-MCI group, cortical thickness had a significant negative correlation with disease duration in the precentral, supramarginal, occipital, and superior temporal cortices; whereas, in the PD non-MCI group, such a correlation was absent. The findings from this study reveal that, at the same stage of PD evolution, the presence of MCI is associated with a higher level of cortical changes, suggesting that cortical degeneration is increased in patients with PD because of the presence of MCI.

Prodromal autonomic symptoms and signs in Parkinson's disease and dementia with Lewy bodies

Pathologic staging systems suggest that autonomic dysfunction may be an early manifestation of Parkinson's disease and dementia with Lewy bodies. However, direct evidence is limited, and no prospective studies have measured when autonomic dysfunction starts before disease. Patients with idiopathic rapid eye movement (REM) sleep behavior disorder are at very high risk of developing neurodegenerative synucleinopathy, providing an opportunity to directly observe the development of autonomic dysfunction from prodromal stages of neurodegeneration. Patients with idiopathic REM sleep behavior disorder were followed annually in a prospective cohort that was established in 2004. Urinary, orthostatic, erectile, and constipation symptoms and systolic blood pressure drop from lying to standing were assessed annually. Patients who eventually developed defined synucleinopathy were compared with age-matched controls. The evolution of autonomic measures was assessed with regression analysis to determine when markers first deviated from control values. Sensitivity and specificity of autonomic markers for identification of prodromal disease were calculated. Of 91 patients, 32 developed disease. In prodromal stages, there was substantial autonomic dysfunction observable at least 5 years before diagnosis. On regression analysis, autonomic dysfunction appeared to progress slowly over prodromal periods. The estimated onset of autonomic dysfunction ranged from 11 years to 20 years, and systolic drop (20.4 years) and constipation (15.3 years) had the earliest estimates. Systolic drop, erectile dysfunction, and constipation could identify disease up to 5 years before diagnosis with sensitivity ranging from 50% to 90%. By directly observing development of neurodegenerative synucleinopathy, we confirmed that autonomic dysfunction can occur early in neurodegenerative synucleinopathy, even as long as 20 years before defined disease. © 2013 Movement Disorder Society.

REM Sleep Behavior Disorder and Prodromal Neurodegeneration - Where Are We Headed?

Rapid eye movement (REM) sleep behavior disorder (RBD) is characterized by loss of normal atonia during REM sleep, such that patients appear to act out their dreams. The most important implication of research into this area is that patients with idiopathic RBD are at very high risk of developing synuclein-mediated neurodegenerative disease (Parkinson's disease [PD], dementia with Lewy bodies [DLB], and multiple system atrophy), with risk estimates that approximate 40–65% at 10 years. Thus, RBD disorder is a very strong feature of prodromal synucleinopathy. This provides several opportunities for future research. First, patients with REM sleep behavior disorder can be studied to test other predictors of disease, which could potentially be applied to the general population. These studies have demonstrated that olfactory loss, decreased color vision, slowing on quantitative motor testing, and abnormal substantia nigra neuroimaging findings can predict clinical synucleinopathy. Second, prospectively studying patients with RBD allows a completely unprecedented opportunity to directly evaluate patients as they transition into clinical neurodegenerative disease. Studies assessing progression of markers of neurodegeneration in prodromal PD are beginning to appear. Third, RBD are very promising subjects for neuroprotective therapy trials because they have a high risk of disease conversion with a sufficiently long latency, which provides an opportunity for early intervention. As RBD research expands, collaboration between centers will become increasingly essential.

Rapid eye movement sleep behavior disorder as a biomarker for neurodegeneration: the past 10 years

Since its original description, idiopathic rapid eye movement sleep behavior disorder (RBD) has become a well-established risk factor for neurodegenerative disease. Studies from sleep centers have found that at least 40-65% of patients with idiopathic RBD will develop a defined neurodegenerative phenotype over 10 years. This elevated risk of neurodegeneration has been recently confirmed in a population-based study of probable RBD. When a defined syndrome develops, it is almost always a 'synucleinopathy' (Parkinson's disease, Dementia with Lewy Bodies or multiple system atrophy). Often, manifestations of parkinsonism and cognitive impairment overlap. The ability of RBD to predict disease has major implications for development of neuroprotective therapy. First, RBD is a prodromal marker with a disease risk sufficiently high for design of neuroprotective trials. Second, study of idiopathic RBD allows prospective testing of other predictive markers of neurodegeneration. Third, it allows an unprecedented direct examination of the evolution of prodromal disease into defined neurodegenerative syndromes. This review summarizes what is known about the risk of neurodegeneration in idiopathic RBD, the utility of prodromal/predictive markers in synuclein-mediated neurodegeneration, and the evolution of motor and non-motor markers in prodromal stages.

Rapid eye movement sleep behavior disorder and subtypes of Parkinson's disease

Numerous studies have explored the potential relationship between rapid eye movement sleep behavior disorder (RBD) and manifestations of PD. Our aim was to perform an expanded extensive assessment of motor and nonmotor manifestations in PD to identify whether RBD was associated with differences in the nature and severity of these manifestations. PD patients underwent polysomnography (PSG) to diagnose the presence of RBD. Participants then underwent an extensive evaluation by a movement disorders specialist blinded to PSG results. Measures of disease severity, quantitative motor indices, motor subtypes, therapy complications, and autonomic, psychiatric, visual, and olfactory dysfunction were assessed and compared using regression analysis, adjusting for disease duration, age, and sex. Of 98 included patients, 54 had RBD and 44 did not. PD patients with RBD were older (P = 0.034) and were more likely to be male (P < 0.001). On regression analysis, the most consistent links between RBD and PD were a higher systolic blood pressure (BP) change while standing (-23.9 ± 13.9 versus -3.5 ± 10.9; P < 0.001), a higher orthostatic symptom score (0.89 ± 0.82 versus 0.44 ± 0.66; P = 0.003), and a higher frequency of freezing (43% versus 14%; P = 0.011). A systolic BP drop >10 could identify PD patients with RBD with 81% sensitivity and 86% specificity. In addition, there was a probable relationship between RBD and nontremor predominant subtype of PD (P = 0.04), increased frequency of falls (P = 0.009), and depression (P = 0.009). Our results support previous findings that RBD is a multifaceted phenomenon in PD. Patients with PD who have RBD tend to have specific motor and nonmotor manifestations, especially orthostatic hypotension.

How does parkinsonism start? Prodromal parkinsonism motor changes in idiopathic REM sleep behaviour disorder

Parkinsonism, as a gradually progressive disorder, has a prodromal interval during which neurodegeneration has begun but cardinal manifestations have not fully developed. A systematic direct assessment of this interval has never been performed. Since patients with idiopathic REM sleep behaviour disorder are at very high risk of parkinsonism, they provide a unique opportunity to observe directly the development of parkinsonism. Patients with idiopathic REM sleep behaviour disorder in an ongoing cohort study were evaluated annually with several quantitative motor measures, including the Unified Parkinson's Disease Rating Scale, Purdue Pegboard, alternate-tap test and timed up-and-go. Patients who developed parkinsonism were identified from this cohort and matched according to age to normal controls. Their results on motor testing from the preceding years were plotted, and then assessed with regression analysis, to determine when markers first deviated from normal values. Sensitivity and specificity of quantitative motor markers for diagnosing prodromal parkinsonism were assessed. Of 78 patients, 20 developed parkinsonism. On regression analysis, the Unified Parkinson's Disease Rating Scale first intersected normal values at an estimated 4.5 years before diagnosis. Voice and face akinesia intersected earliest (estimated prodromal interval = 9.8 years), followed by rigidity (4.4 years), gait abnormalities (4.4 years) and limb bradykinesia (4.2 years). Quantitative motor tests intersected normal values at longer prodromal intervals than subjective examination (Purdue Pegboard = 8.6 years, alternate-tap = 8.2, timed up-and-go = 6.3). Using Purdue Pegboard and the alternate-tap test, parkinsonism could be detected with 71-82% sensitivity and specificity 3 years before diagnosis, whereas a Unified Parkinson's Disease Rating Scale score >4 identified prodromal parkinsonism with 88% sensitivity and 94% specificity 2 years before diagnosis. Removal of action tremor scores improved sensitivity to 94% and specificity to 97% at 2 years before diagnosis (cut-off >3). Although distinction between conditions was often difficult, prodromal dementia with Lewy bodies appeared to have a slower progression than Parkinson's disease (prodromal interval = 6.0 versus 3.8 years). Using a cut-off of Unified Parkinson's Disease Rating Scale >3 (excluding action tremor), 25% of patients with 'still-idiopathic' REM sleep behaviour disorder demonstrated evidence of possible prodromal parkinsonism. Therefore, using direct assessment of motor examination before parkinsonism in a REM sleep behaviour disorder, we have estimated a prodromal interval of ∼4.5 years on the Unified Parkinson's Disease Rating Scale; other quantitative markers may detect parkinsonism earlier. Simple quantitative motor measures may be capable of reliably detecting parkinsonism, even before a clinical diagnosis can be made by experienced movement disorders neurologists.

Cardiac autonomic dysfunction in idiopathic REM sleep behavior disorder

More than 50% of persons with idiopathic REM sleep behavior disorder (RBD) will develop Parkinson's disease or Lewy body dementia. Symptom screens and metaiodobenzylguanine (MIBG)-scintigraphy suggest autonomic abnormalities in idiopathic RBD, but it is unclear whether autonomic abnormalities can predict neurodegenerative disease. From a cohort of 99 patients with idiopathic RBD, we selected those who developed parkinsonism or dementia. These were matched by age, sex, and follow-up duration to patients with RBD who remained disease free and to matched controls. From the polysomnographic trace performed at baseline evaluation, measures of beat-to-beat RR variability including time domains (mean RR-interval and RR-standard deviation) and frequency domains (low and high frequency components) were retrospectively assessed. Twenty-one patients with idiopathic RBD who developed neurodegenerative disease were included (Parkinson's disease-11, multiple system atrophy-1, and dementia-9). Age at PSG was 66 years, and 86% were male. PSG was performed on average 6.7 years before defined neurodegenerative disease. Comparing all patients with idiopathic RBD to controls, there were significant reductions in RR-standard deviation (24.6 ± 2.2 ms vs. 35.2 ± 3.5 ms, P = 0.006), very low frequency components (238.6 ± 99.6 ms(2) vs. 840.1 ± 188.3 ms(2), P < 0.001), and low frequency components (127.8 ± 26.3 ms(2) vs. 288.7 ± 66.2 ms(2), P = 0.032). However, despite clear differences between patients with idiopathic RBD and controls, there were no differences in any measure between those who did or did not develop disease. RR-variability analysis demonstrates substantial autonomic dysfunction in idiopathic RBD. However, this dysfunction is identical in patients who will or will not develop defined neurodegenerative disease. This suggests that autonomic dysfunction is linked with RBD independent of associated Parkinson's disease or Lewy body dementia.

Polysomnographic diagnosis of idiopathic REM sleep behavior disorder

The presence of either excessive tonic chin EMG activity during REM sleep, or excessive phasic submental or limb EMG twitching is required to diagnose REM sleep behavior disorder (RBD). The aim was to identify cut-off values and to assess the sensitivity and specificity of these values taken separately or combined to diagnose idiopathic RBD patients. Eighty patients presenting with a clinical diagnosis of idiopathic RBD and 80 age- and gender-matched normal controls were studied in the sleep laboratory. Receiver operating characteristic curves were drawn to find optimal cut-off values for three REM sleep EMG parameters. Tonic and phasic EMG activity were measured in the chin, but not in the limbs. Videos were examined during the recording but were not systematically reviewed by the authors. Total correct classification of 81.9% was found for tonic chin EMG density ≥30%; 83.8% for phasic chin EMG density ≥15% and 75.6% for ≥24 leg movements per hour of REM sleep. Five patients did not fulfill any of these three polysomnographic (PSG) criteria. Conversely, one subject of the control group met the PSG criteria for RBD. This study estimates the diagnostic value of a visual scoring method for the diagnosis of idiopathic RBD and establishes cut-off values to be used in clinical and research set-ups. For the five RBD patients who did not show chin EMG abnormalities, it cannot be excluded that they had increased phasic EMG activity in the upper limbs and presented visible motor activity.

Clinical prediction of Parkinson's disease: planning for the age of neuroprotection

As a chronic progressive disease, Parkinson's disease (PD) has a presymptomatic interval; that is, a period during which the pathological process has begun, but motor signs required for the clinical diagnosis are absent. The ability to identify this preclinical stage may be critical in the development and eventual use of neuroprotective therapy. Recently proposed staging systems of PD have suggested that degeneration may occur initially in areas outside the substantia nigra, suggesting that non-motor manifestations may be markers of presymptomatic PD. Decreased olfaction has recently been demonstrated to predict PD in prospective pathological studies, although the lead time may be relatively short, and the positive predictive value is low. Idiopathic RBD has a very high predictive value, with approximately 50% of affected individuals developing PD or dementia within 10 years. This implies that idiopathic RBD patients are ideal candidates to test potential preclinical markers. However, the specificity of symptom screens for RBD is not established, not all persons with PD develop RBD, and there are only limited ways to predict which RBD patients will develop PD. Other simple screens based upon autonomic symptoms, depression and personality changes, quantitative motor testing and other sleep disorders may also be useful markers, but have not been extensively tested. Other more expensive measures such as detailed autonomic testing, cardiac MIBG-scintigraphy, dopaminergic imaging and transcranial ultrasound may be especially useful in defining disease risk in those identified through primary screening.

Severity of REM atonia loss in idiopathic REM sleep behavior disorder predicts Parkinson disease

BACKGROUND

Over 50% of persons with idiopathic REM sleep behavior disorder (RBD) will develop Parkinson disease (PD) or dementia. At present, there is no way to predict who will develop disease. Since polysomnography is performed in all patients with idiopathic RBD at diagnosis, there is an opportunity to analyze if baseline sleep variables predict eventual neurodegenerative disease.

METHODS

In a longitudinally studied cohort of patients with idiopathic RBD, we identified those who had developed neurodegenerative disease. These patients were matched by age, sex, and follow-up duration to patients with RBD who remained disease-free and to controls. Polysomnographic variables at baseline (i.e., before development of neurodegenerative disease) were compared between groups.

RESULTS

Twenty-six patients who developed neurodegenerative disease were included (PD 12, multiple system atrophy 1, dementia 13). The interval between polysomnogram and disease onset was 6.7 years, mean age was 69.5, and 81% were male. There were no differences between groups in sleep latency, sleep time, % stages 2-4, % REM sleep, or sleep efficiency. However, patients with idiopathic RBD who developed neurodegenerative disease had increased tonic chin EMG activity during REM sleep at baseline compared to those who remained disease-free (62.7 +/- 6.0% vs 41.0 +/- 6.0%, p = 0.020). This effect was seen only in patients who developed PD (72.9 +/- 6.0% vs 41.0 +/- 6.0%, p = 0.002), and not in those who developed dementia (54.3 +/- 10.3, p = 0.28). There was no difference in phasic submental REM EMG activity between groups.

CONCLUSIONS

In patients with REM sleep behavior disorder initially free of neurodegenerative disease, the severity of REM atonia loss on baseline polysomnogram predicts the development of Parkinson disease.

Quantifying the risk of neurodegenerative disease in idiopathic REM sleep behavior disorder

OBJECTIVE

Idiopathic REM sleep behavior disorder (RBD) is a potential preclinical marker for the development of neurodegenerative diseases, particularly Parkinson disease (PD) and Lewy body dementia. However, the long-term risk of developing neurodegeneration in patients with idiopathic RBD has not been established. Obtaining an accurate picture of this risk is essential for counseling patients and for development of potential neuroprotective therapies.

METHODS

We conducted a follow-up study of all patients seen at the sleep disorders laboratory at the Hôpital du Sacré Coeur with a diagnosis of idiopathic RBD. Diagnoses of parkinsonism and dementia were defined according to standard criteria. Survival curves were constructed to estimate the 5-, 10-, and 12-year risk of developing neurodegenerative disease.

RESULTS

Of 113 patients, 93 (82%) met inclusion criteria. The mean age of participants was 65.4 years and 75 patients (80.4%) were men. Over the follow-up period, 26/93 patients developed a neurodegenerative disorder. A total of 14 patients developed PD, 7 developed Lewy body dementia, 4 developed dementia that met clinical criteria for AD, and 1 developed multiple system atrophy. The estimated 5-year risk of neurodegenerative disease was 17.7%, the 10-year risk was 40.6%, and the 12-year risk was 52.4%.

CONCLUSIONS

Although we have found a slightly lower risk than other reports, the risk of developing neurodegenerative disease in idiopathic REM sleep behavior disorder is substantial, with the majority of patients developing Parkinson disease and Lewy body dementia.

REM sleep behaviour disorder in Parkinson's disease is associated with specific motor features

BACKGROUND

Rapid eye movement (REM) sleep behaviour disorder (RBD) is commonly associated with Parkinson's disease (PD), and recent studies have suggested that RBD in PD is associated with increased cognitive impairment, waking EEG slowing, autonomic impairment and lower quality of life on mental health components. However, it is unclear whether the association of RBD in PD has implications for motor manifestations of the disease.

METHODS

The study evaluated 36 patients with PD for the presence of RBD by polysomnography. Patients underwent an extensive evaluation on and off medication by a movement disorders specialist blinded to the polysomnography results. Measures of disease severity, quantitative motor indices, motor subtypes, complications of therapy and response to therapy were assessed and compared using regression analysis that adjusted for disease duration and age.

RESULTS

Patients with PD and RBD were less likely to be tremor predominant (14% vs 53%; p<0.02) and had a lower proportion of their Unified Parkinson Disease Rating Scale (UPDRS) score accounted for by tremor (8.2% vs 19.0%; p<0.01). An increased frequency of falls was noted among patients with RBD (38% vs 7%; p = 0.04). Patients with RBD demonstrated a lower amplitude response to their medication (UPDRS improvement 16.2% vs 34.8%; p = 0.049). Markers of overall disease severity, quantitative motor testing and motor complications did not differ between groups.

CONCLUSIONS

The presence of altered motor subtypes in PD with RBD suggests that patients with PD and RBD may have a different underlying pattern of neurodegeneration than PD patients without RBD.

REM sleep behavior disorder and REM sleep without atonia in Parkinson's disease

OBJECTIVE

To determine the frequency of REM sleep behavior disorder (RBD) among patients with PD using both history and polysomnography (PSG) recordings and to further study REM sleep muscle atonia in PD.

BACKGROUND

The reported occurrence of RBD in PD varies from 15 to 47%. However, no study has estimated the frequency of RBD using PSG recordings or analyzed in detail the characteristics of REM sleep muscle atonia in a large group of unselected patients with PD.

METHODS

Consecutive patients with PD (n = 33) and healthy control subjects (n = 16) were studied. Each subject underwent a structured clinical interview and PSG recording. REM sleep was scored using a method that allows the scoring of REM sleep without atonia.

RESULTS

One third of patients with PD met the diagnostic criteria of RBD based on PSG recordings. Only one half of these cases would have been detected by history. Nineteen (58%) of 33 patients with PD but only 1 of 16 control subjects had REM sleep without atonia. Of these 19 patients with PD, 8 (42%) did not present with behavioral manifestations of RBD, and their cases may represent preclinical forms of RBD associated with PD. Moreover, the percentage of time spent with muscle atonia during REM sleep was lower among patients with PD than among healthy control subjects (60.1% vs 93.2%; p = 0.003).

CONCLUSIONS

RBD and REM sleep without atonia are frequent in PD as shown by PSG recordings.

[Rapid-eye-movement sleep disorders in Parkinson's disease]

During the past 10 years, there has been an increasing interest in the study of rapid-eye-movement (REM) sleep in neurodegenerative diseases and more particulary in Parkinson's disease (PD). This interest is justified by the strong association observed between these diseases and REM sleep behavior disorder (RBD). In the first section of this paper, a critical review of the literature on the presence of REM sleep disorders in PD is presented. Studies that show an association between PD and RBD are reviewed. Studies that report the presence of other REM sleep disorders in PD (short latency, abnormal length and/or proportion of REM sleep, increasing occurrence of hallucinations) are then discussed. Limitations of the criteria proposed by Rechtschaffen et Kales (1968) for the quantification of REM sleep are also presented. Some authors believe that dopaminergic (DA) agents used in the treatment of PD (levodopa, bromocriptine, pergolide, pramipexole and selegiline) could be a responsable factor for the occurence of REM sleep disorders observed in this disease. The literature concerning the impact of these DA agents on human REM sleep is therefore critically reviewed. It is concluded that DA agents cannot explain on their own the presence of REM sleep disorders in PD. Other causes, among which the disturbance of some neurochemical systems linked to the neuropathological process of the disease, must be considered in order to explain these REM sleep disorders. In the second section of this paper, we present the different pathophysiological hypotheses proposed to explain REM sleep disorders in PD, such as a dysfunction of the cholinergic, noradrenergic, serotonergic, dopaminergic or GABAergic neurons. Emphasis is placed on the role of cholinergic neurons of the pedunculopontine and laterodorsal tegmental nuclei, structures shown to be particularly impaired in PD. Neurophysiological, neuroanatomical and neuropharmacological studies demonstrate that these neurons are strongly implicated in the different REM sleep parameters (muscular atonia, electroencephalographic desynchronisation, ponto-geniculo-occipital spikes). Finally, future research directions are proposed.

Performance of patients with schizophrenia on the Wisconsin Card Sorting Test (WCST)

OBJECTIVE

To directly compare the performance of patients with schizophrenia and control subjects on the Wisconsin Card Sorting Test (WCST). Specifically, we sought to verify if there are significant differences on the "classical" WCST measurements (perseverative errors and number of categories), as well as on more rarely reported scores, and assess the extent to which patients with schizophrenia can improve their performance with card-by-card instructions and continuous verbal reinforcement.

DESIGN

Prospective cross-sectional study.

SETTING

Psychiatry department in a university-affiliated hospital.

PARTICIPANTS

30 patients with schizophrenia, diagnosed according to DSM-IV criteria, and 30 control subjects, matched to patients according to age and education.

INTERVENTION

The WCST was administered according to the criteria of Heaton, and a subgroup of the patients with schizophrenia was given a retest after an explanation of the WCST and verbal reinforcements.

RESULTS

Patients with schizophrenia succeeded on fewer categories (t = 23.3, p < 0.001), committed more perseverative errors (t = 15.6, p < 0.001), made more perseverative responses (t = 14.6, p < 0.001), needed more trials to succeed at the first category (t = 9.2, p < 0.003) and gave significantly lower conceptual level responses (t = 14.1, p < 0.001) than the controls. However, on retest, patients with schizophrenia committed significantly fewer perseverative errors (t = 5.1, p < 0.001) and showed higher conceptual level responses (t = -3.45, p < 0.003).

CONCLUSION

Consistent with a hypothesis of frontal dysfunction in schizophrenia, patients with schizophrenia tend to show a perseverative deficit; however, some are able to partially overcome this deficit when given verbal reinforcement.

[Deficit in suppression of interference in visual information processing by schizophrenic subjects]

Although many studies have indicated information processing deficits in schizophrenic patients, the precise nature and underlying causes of these deficits remain largely uncertain. One prominent hypothesis is that these patients show insufficient attentional inhibition. This deficit to inhibition has been linked to certain cognitive disorders in schizophrenic patients, including attention deficits, as well as to some clinical symptoms, especially those involving delusional thought, hallucinations,and poor contact with reality. The hypothesis of deficient attentional inhibition, although attractive in some ways, is difficult to work with, because it is not easy to directly measure "attentional inhibition". Several studies involving normal subjects have linked attentional inhibition with performance on a task demanding the suppression of distracting information: the presumption is that efficient attentional inhibition will permit rapid responses because the distracting information will be quickly suppressed, allowing undistracted processing of the target information. The present study measures schizophrenic patients' performance on a task demanding suppression of rapidly-presented visual information. An important methodological feature of this study is that performance is measured in terms of "percent correct responses" rather than the reaction time measures typically used in tasks demanding distractor suppression, such as Stroop-like selective attention tasks. Since reaction times are not considered, the results cannot be interpreted in terms of deficient response organization and execution. Schizophrenic (18) and normal (18) subjects underwent trials in which a visual target was the second of two stimuli presented in rapid succession. Interference produced by a non-target significantly impaired perception of the target for schizophrenic patients. This effect persisted longer in the schizophrenic subjects possibly because of deficient attentional inhibition.