Martin Elton

Auditory event-related potentials to deviant stimuli during drowsiness and stage 2 sleep

Twelve subjects were tested using a 3-tone auditory oddball paradigm consisting of a standard 1000 Hz tone (P = 80%) and two deviants, namely, a 1200 Hz tone and a 2000 Hz tone (both P = 10%). Testing took place in 3 conditions: (1) attend, in which the subject had to count one of the deviant tones; (2) ignore, in which the subject read a book; and (3) sleep, in which the subject was encouraged to go to sleep during presentation of the tones. In the awake conditions stimulus deviance elicited mismatch negativity (MMN) and P3. During drowsiness, no separate mismatch negativity (MMN) could be detected, but the 2000 Hz tone evoked a broad fronto-central early negative deflection, suggesting an overlap of N1 and MMN. In the same condition, P210, N330 and P430 appeared, all being sensitive to magnitude of deviance. During stage 2, the P210, N330 and P430 amplitudes increased, most notably to the large deviant. These data indicate that differential processing of auditory inputs is maintained during drowsiness and stage 2 sleep, but do not support the notion that MMN or P3 activity comparable to the waking state occurs to oddball stimuli during this stage. It is hypothesised that during light sleep, scanning of the environment is performed by a different system than in the awake state and that during drowsiness a gradual switch between these two systems takes place.

Functional correlates of callosal atrophy in relapsing- remitting multiple sclerosis patients. A preliminary MRI study.

In multiple sclerosis (MS), periventricular lesions produce atrophy of the corpus callosum (CC), as evidenced by magnetic resonance imaging (MRI). We investigated whether CC atrophy in relapsing-remitting MS patients is related to functional deficits. We compared 14 mildly disabled (mean Expanded Disability Status Scale score 2.7) relapsing-remitting MS patients with 14 age- und sexmatched controls. CC size was determined using sagittal Tl-weighted MRI. The function of the CC was studied using a neuropsychological battery and neurophysiological evaluation based on visual stimulation using a divided visual field paradigm. The total area of the CC in patients (mean 5.3 cm2) was significantly (P=0.002) smaller than in controls (mean 6.6 cm2). Patients showed left ear extinction using the dichotic listening test and impaired name learning, which was correlated with atrophy of the splenium. There were no differences in interhemispheric transfer time between patients and controls. Marked atrophy of the CC can be encountered in relapsingremitting MS patients. The associated cerebral disconnection correlated with atrophy of expected regions of the CC, thus supporting topographical organization.

Prevalence of Mental Illness in Germany and the United States: Comparison of the Upper Bavarian Study and the Epidemiologic Catchment Area Program

The objective of the present study was to compare data on the prevalence of mental illness in Germany and the United States. For this purpose, data from the Upper Bavarian Study (UBS) and the Epidemiologic Catchment Area (ECA) are presented and compared. In both studies, personal interviews were administered to a sample of community residents. The UBS sample consisted of 1,847 persons aged > or = 18 years, and the ECA study consisted of 24,371 household members aged > or = 18 years in five sites; 1,876 persons from the ECA sample lived in rural sites, and they were used for comparison with the (rural) UBS sample. The diagnostic classification (according to DSM-III) obtained by clinical interviewers in the UBS and by lay interviewers in the ECA was used. The total 6-month prevalence for any axis I Diagnostic Interview Schedule mental disorder (corrected for sample stratifications and adjusted for age) was 18.5% in the (rural) UBS, 18.0% in the total ECA sample (five sites), and 13.4% in the rural sites of the ECA. High morbidity rates for substance use disorders (UBS, 5.8%; ECA rural sites, 3.4%) and affective disorders (UBS, 6.8%; ECA rural sites, 4.1%) were observed in both studies. The 6-month prevalence rates for alcohol use disorders (3.1% considered marked or severe) were 5.1% in the UBS and 2.9% in the ECA rural sites. Concerning anxiety disorders (UBS, 1.6%; ECA rural sites, 6.7%) there was a substantial difference between the studies, which mainly resulted from a higher prevalence of phobia in the ECA program. There were higher rates of dysthymia (3.8% considered marked or severe) in the UBS (5.4%) than in the ECA rural sites (2.6%), whereas the rate of major depression was somewhat lower in UBS (1.4%) as compared with the ECA rural sites (2.4%). Alcohol use disorder was the most frequent category of mental disorder for men in both studies; for women, affective disorder and phobia (in the ECA) were the most frequent categories. Despite differences in methodology concerning sampling, instruments, and case identification the similarities between the results of the two studies were considerable.

Event-related potentials to tones in the absence and presence of sleep spindles

The present study focused on event‐related potentials to tones in the presence and absence of sleep spindles. Six undergraduates were studied throughout an experimental night, following an adaptation session. The event‐related potentials to tone stimuli were averaged for each subject. Separate averages were determined for trials on which no sleep spindle occurred 2 s before or after a tone and trials in which spindle activity was present. Both voltage distribution maps and multivariate analysis of the waveforms produced significant differences between these conditions, which could be seen as a higher initial positive component and sustained positivity over the averaged epoch in the presence of spindles. Spectral analysis indicated that this result could not solely be ascribed to residual sigma activity in the spindle‐present average. The results may provide insights into the functional role of sleep spindles in humans in addition to that suggested by a neurophysiological model of inhibition.

Mortality risk and mental disorders : longitudinal results from the Upper Bavarian Study

The object of the study was the assessment of the mortality risk for persons with a mental disorder in an unselected representative community sample assessed longitudinally. Subjects from a rural area in Upper Bavaria (Germany) participated in semi-structured interviews conducted by research physicians in the 1970s (first assessment) and death-certificate diagnoses were obtained after an interval up to 13 years later. The sample consisted of 1668 community residents aged 15 years and over. Cox regression estimates resulted in an odds ratio of 1.35 (confidence interval 1.01 to 1.81) for persons with a mental disorder classified as marked to very severe. The odds ratio increased with increasing severity of mental illness from 1.04 from mild disorders, 1.30 for marked disorders, to 1.64 for severe or very severe disorders. The relative risk (odds ratio) for persons with a mental disorder only and no somatic disorder was 1.22, for persons with only a somatic disorder 2.00, and for those with both a mental and somatic disorder 2.13. The presence of somatic illness was responsible for most of the excess mortality. Somatic disorders associated with excess mortality in mental disorders were diseases of the nervous system or sensory organs, diseases of the circulatory system, diseases of the gastrointestinal tract, and diseases of the skeleton, muscles and connective tissue (ICD-8). Thus, while mental illness alone had a limited effect on excess mortality, comorbidity with certain somatic disorders had a significant effect.

Why do we produce errors of commission? An ERP study of stimulus deviance detection and error monitoring in a choice go/no-go task.

The present study investigated event‐related brain potential (ERP) reflections of stimulus deviance detection and error monitoring recorded during a go/no‐go auditory oddball task. The mismatch negativity and error negativity were analysed as indices of these processes, respectively. We examined whether errors of commission occurred because of failures to detect stimulus deviance. On error trials the mismatch negativity amplitude did not differ between big and small deviant stimuli and was clearly reduced as compared with mismatch negativity amplitude on correct trials. Following an error response an error negativity was elicited, the amplitude of which was unaffected by stimulus deviancy. This pattern of ERP results was interpreted as supporting the defective deviance detection hypothesis.

Ergebnisse des 2. Querschnittes der Oberbayerischen Verlaufsuntersuchung

Eine wesentliche methodische Voraussetzung fur den sinnvollen Vergleich zweier Querschnitte im Rahmen einer Verlaufsuntersuchung ist die Verwendung derselben Kriterien zur Fallidentifikation. Nachdem in dem 5-Jahres-Intervall keine wesentlichen oder gar gravierenden Veranderungen im Untersuchungsgebiet stattfanden, ist fur beide Querschnitte eine etwa gleich hohe Morbiditatsrate zu erwarten. Beim Vergleich der beiden Pravalenzstichproben (70er Jahre und 80er Jahre, 15 Jahre und alter) ergab sich eine Punktpravalenz (7 Tage) von 19, 2% fur den ersten Querschnitt und 21, 2% fur den zweiten Querschnitt fur psychische Erkrankungen mit Schweregrad 2, 3 oder 4. Da sich die Stichproben teilweise uberlappen, sind die sonst ublichen statistischen Tests nicht anwendbar. Es handelt sich weder um rein verbundene noch um vollig unabhangige Stichproben. Wenn man trotz dieser Tatsache mittels Chi-Quadrat-Test oder Konfigurationsfrequenz-Analyse testet, ergibt sich fur die 7-Tage-Pravalenz-rate zum 1. und 2. Querschnitt (S ≥ 2) kein Unterschied. In Abbildung 3.1.1 a sind auch die Pravalenzraten fur leichte psychische Erkrankungen (Schweregrad = 1) angegeben, welche fur den ersten Querschnitt 20, 1% und fur den zweiten Querschnitt 16, 8% betrugen (Punktpravalenz). 57, 2% der Pravalenzstichprobe der 80er Jahre hatten weder bei der Untersuchung noch in dem vorausgehenden 5-Jahres-lntervall eine leichte oder schwerere psychische Erkrankung und weitere 10, 9% hatten in diesem Zeitraum nur leichte psychische Auffalligkeiten; 32, 0% zeigten in diesem Zeitraum psychische Erkrankungen mit Schweregrad 2, 3 oder 4. Eine psychische Erkrankung mit Schweregrad 2 entspricht in der Regel zumindest einer Behandlungsbedurftigkeit durch den Hausarzt.