Effects of dual task demands on the accuracy of smooth pursuit eye movements

The effect of attention allocation on smooth pursuit eye movements (SPEM) was investigated. Eye movements were electrooculographically recorded in 27 healthy subjects who tracked a visual target that moved horizontally with constant or unpredictably varying velocity. In some trials, subjects performed additional auditory discrimination tasks varying in difficulty. Pursuit error decreased when attention was divided between both tasks. The pattern of results is incompatible with the assumption made in previous research that attention enhancement improves SPEM accuracy. Rather, ocular smooth pursuit appears to be executed in the automatic mode, although intentional and selective processes must contribute. Moreover, controlled attention directed to the tracking task interfered with smooth pursuit. A reinterpretation of earlier studies in which visual monitoring tasks were used to improve eye tracking is needed.

Stability of the mismatch negativity under different stimulus and attention conditions

OBJECTIVE

Mismatch negativities (MMN) elicited by frequency and duration changes in a sequence of repetitive tones were recorded in test and retest sessions from 45 subjects.

METHODS

Tones presented with a stimulus onset asynchrony (SOA) of 0.5 s were to be ignored while attention had no instructed focus in one group and was directed to an active visual vigilance task in a second group of subjects.

RESULTS

MMN amplitude was larger for duration deviants, the focus of attention had no systematic effect. Individual replicability of the MMN amplitudes was generally better when duration deviants were used. In addition, directing attention to the visual task increased the retest reliability of the duration deviance MMN. In this condition, the test-retest correlation coefficients were above 0.8 at all frontal scalp sites (0.87 at F4).

CONCLUSIONS

The study shows that the deviant type as well as the attentional condition may have substantial effects on the stability and replicability of MMN potentials. The choice of the appropriate task condition is essential for using the MMN in group comparisons and as a diagnostic tool in individual cases.

[Development of the AMDP module for identification of obsessive- compulsive symptoms. Conceptualization and empirical results]

Results of epidemiology and comorbidity studies have recently demonstrated the psychopathological relevance of obsessive-compulsive symptoms. Therefore the "Arbeitsgemeinschaft für Methodik und Diagnostik in der Psychiatrie" (AMDP) has started to develop a rating scale for a quick and precise assessment of obsessive-compulsive symptoms. The actual version of the scale comprises 20 items on the dimensions "description", "distress and impairment" and "emotion and cognition". The results of a first empirical study (n = 137, psychiatric in- and outpatients) demonstrated excellent internal consistency (Cronbach's alpha = 0.92), a split-half reliability of 0.89 (Spearman-Brown), a test-retest reliability of r = 0.86 and good convergent validity with the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) and the Hamburger Zwangsinventar (HZI). The factor-analytical distribution of the 20 items revealed a 4-factor structure of the scale. The results are presented and their implications on further steps of the development of the scale are discussed.

Dipole localization and test-retest reliability of frequency and duration mismatch negativity generator processes

The mismatch negativity (MMN) is an event related potential component elicited by changes in duration, frequency or intensity of the stimuli during repetitive series of equal standard stimuli. In the present study we compared duration and frequency MMN using dipole source analysis concerning both the test-retest reliability of MMN-amplitudes and the locations of the potential sources. Furthermore, the influence of attention for test-retest-reliability was studied. Therefore, two groups of healthy subjects were investigated with different attentional manipulations. Twenty-one healthy subjects had to perform a visual attention task during the recording and 21 healthy subjects had no additional task to perform. All subjects were studied twice with a time interval of 3 weeks. Test-retest reliability was sufficiently high for the frequency but slightly lower for the duration MMN. The locations of the frequency and duration MMN-dipoles were in the auditory cortex with a more anterior and caudal location for the frequency MMN-dipoles. The latter finding supports the hypothesis that the frequency and duration MMNs have separate neuronal generators.

Identification of input variables for feature based artificial neural networks-saccade detection in EOG recordings

Though artificial neural networks (ANN) are excellent tools for pattern recognition problems when signal to noise ratio is low, the identification of decision relevant features for ANN input data is still a crucial issue. The experience of the ANN designer and the existing knowledge and understanding of the problem seem to be the only links for a specific construction. In the present study a backpropagation ANN based on modified raw data inputs showed encouraging results. Investigating the specific influences of prototypical input patterns on a specially designed ANN led to a new sparse and efficient input data presentation. This data coding obtained by a semiautomatic procedure combining existing expert knowledge and the internal representation structures of the raw data based ANN yielded a list of feature vectors, each representing the relevant information for saccade identification. The feature based ANN produced a reduction of the error rate of nearly 40% compared with the raw data ANN. An overall correct classification of 92% of so far unknown data was realized. The proposed method of extracting internal ANN knowledge for the production of a better input data representation is not restricted to EOG recordings, and could be used in various fields of signal analysis.

Characteristics of obsessive-compulsive symptoms in Tourette's syndrome, obsessive-compulsive disorder, and Parkinson's disease

A high incidence of obsessions and compulsions is documented in basal ganglia disorders, especially in patients with Tourette's syndrome (TS). A comparison of patients with obsessive-compulsive disorder (OCD), TS, and Parkinson's disease (PD) revealed significantly higher total scores in both OCD and TS patients than in a healthy control group on the Maudsley obsessive-compulsive inventory (MOCI) and the Hamburg obsessive-compulsive inventory (HZI-K), two self-report measures of obsessive-compulsive symptoms. On most subscales (especially Checking, Ordering, and Counting/touching), TS patients scored higher than controls. Patients with Parkinson's disease merely scored higher on the subscale 'Ordering' of the HZI-K. Differences between OCD patients and TS patients were evident on the MOCI subscales 'Checking' and 'Slowness/Repetition' as well as on the MOCI total score and on the HZI subscales 'Cleaning' and 'Obsessive Thoughts'. On these scales, TS patients reported fewer symptoms than OCD patients. Stepwise discriminant analysis with preselected single items as variables was used to look for specific symptom patterns of OCD and TS. Seventy-eight percent of the patients could be correctly classified with respect to their diagnoses on the basis of only two items of the HZI-K. One item asks for fearful obsessive thoughts, which was found in 90% of the OCD patients; the second item represented echo phenomena, found in 56% of the TS patients. It is concluded that considering specific patterns of obsessive-compulsive psychopathology may contribute to a more reliable differential diagnosis in OCD and TS and help to avoid misdiagnosis of OCD in TS patients.

ERP changes in alcoholics with and without alcohol psychosis

The present study compared alterations of event-related brain potentials (ERPs) in subgroups of chronic alcoholics with different complications during alcohol withdrawal. Twenty alcoholics with only mild to moderate alcohol withdrawal symptoms, two groups of alcoholics with histories of either delirium tremens (n = 9) or alcohol hallucinosis (n = 13), and a control group of 38 nonalcoholics were examined. Patients were tested in unmedicated state and not earlier than 14 days after drinking cessation. An auditory Oddball paradigm and a visual Letter Matching paradigm were used as cognitive tasks. In the auditory task, all alcoholic groups exhibited delayed N200 and P300 latencies and a reduced P300 amplitude as compared to nonalcoholics. In the visual task, only P300 amplitude was significantly diminished. Patients having suffered from delirium tremens or alcohol hallucinosis showed greater Oddball P300 amplitudes than alcoholics with uncomplicated withdrawal syndrome. Furthermore, delirium and hallucinosis patients differed in their ERPs, with hallucinosis patients showing an earlier P300 peak in both the auditory Oddball and the Letter Matching task. It is concluded that changes in ERPs during abstinence might reflect specific neurophysiological dysfunctions in alcoholics prone to different alcohol-related psychoses.

CNV, PINV and probe-evoked potentials in schizophrenics

Distractibility and temporal modulation of attention in schizophrenics were studied using a visual reaction time task with additional auditory probe stimuli during the forewarning period or between trials. The probes were thought to exert a distracting influence, especially on schizophrenics, and at the same time they generated auditory EPs which allowed to track the modulation of cortical excitability during response preparation. The midline distribution of the terminal contingent negative variation (tCNV) and the amplitude of the postimperative negative variation (PINV) were clearly different in 20 DSM III-R schizophrenics, as compared with 20 alcoholics and 20 normal controls. In schizophrenics, the more frontal distribution of the tCNV was associated with a higher degree of psychopathology (measured with the Brief Psychiatric Rating Scale) and with delayed reactions. Probes between trials reduced tCNV and PINV in all subjects alike. However, this effect could not be attributed to distraction, because reaction times were faster in these trials, possibly due to an alerting effect of the auditory probes. The N100 and P300 amplitudes to probes in the forewarning period, i.e., during the negative potential shift of the CNV, were significantly enhanced in all groups. Apparently there is a state of increased cortical excitability during the CNV which is not selectively "tuned" toward relevant stimuli. In schizophrenia, the temporal and topographical regulation of this excitability is disturbed.

Information processing during eye tracking as revealed by event-related potentials in schizophrenics, alcoholics, and healthy controls

To further explore the hypothesis that schizophrenics are more distractable and/or have reduced processing resources available, event-related potentials (ERPs) and smooth pursuit eye movements (SPEM) were investigated in 20 medicated schizophrenics, 19 detoxified chronic alcoholics, and in a control group of 20 healthy subjects. Groups were matched for age and education. Eye tracking tasks and auditory oddball tasks were performed separately as well as simultaneously. In addition, an eye tracking condition with a task-irrelevant tone sequence was used to assess the effect of distraction. Schizophrenics showed a trend for poorer SPEM performance; alcoholics had no dysfunction in this task. Tracking accuracy did not change in either group when additional auditory stimuli were presented. P300 latency was delayed in both schizophrenics and alcoholics. P300 amplitude showed no overall group difference but it increased during the dual task in normals whereas it remained constant in patients. N100 amplitude was generally larger during the more complex conditions indicating heightened unspecific arousal. It is suggested that normals use increased arousal to mobilize additional resources and to allocate them to stimulus evaluation but schizophrenics and alcoholics are unable to do so. Results are more conform to a limited resources concept than to a filter deficit model of cognitive disturbances in schizophrenia and alcoholism.

[Compulsive disorder and Gilles de la Tourette syndrome. On the differential diagnosis of organic and psychogenic compulsive symptoms]

A high prevalence of obsessions and compulsions is recognized in patients with Gilles-de-la-Tourette syndrome. Comparison of a group of patients with Gilles-de-la-Tourette syndrome with a group with obsessive-compulsive disorder, using the diagnostic criteria of the DSM-III-R, showed significantly higher scores in both groups of patients in the Hamburg obsessive-compulsive inventory (short version) than in a control group. When selected items from this Inventory were entered in a discriminant analysis, it was shown that there were specific differences in the obsessive-compulsive symptoms in the Gilles-de-la-Tourette syndrome compared to an obsessive-compulsive disorder. Eighty-eight percent of the patients were correctly classified with respect to their diagnosis with eight items of the Hamburg obsessive-compulsive inventory. This result leads to the conclusion that differential observation of the psychopathology of obsessions and compulsions can contribute to the differential diagnosis in obsessive-compulsive disorder and Gilles-de-la-Tourette syndrome, which is still underdiagnosed in Germany compared to epidemiological data in the USA. Moreover, the different psychopathology may reflect differences between a neurotic and an organic basis for obsessions and compulsions.

Lateralization of the Bereitschaftspotential to the left hemisphere in patients with major depression

Fourteen patients with major depression and 18 healthy subjects performed a Bereitschaftspotential (BP) paradigm, which required them to clench the right fist at self-paced intervals. The BP was calculated as the integrated negative amplitude from BP onset to movement onset. The latter was defined by recording the electromyogram (EMG) from the right forearm. To evaluate lateralization, the integrated BPs at C3, C4, P3, and P4 were analyzed. In depressives, a significant asymmetry of the BP to the left was found, whereas in normals the BP was nearly symmetrically distributed around the midline. Three patients were retested when clinically improved. At that time the asymmetry to the left hemisphere had nearly vanished. This asymmetry to the left hemisphere is interpreted as a cortical deactivation of the right cerebral hemisphere and seems to be a state marker of depression.

Effects of elevated triiodothyronine on cognitive performance and mood in healthy subjects

The acute effects of experimentally elevated triiodothyronine (T3) serum levels were investigated in 14 healthy male subjects. After oral application of 100 micrograms triiodothyronine on 3 consecutive days a battery of neuropsychological tests and rating scales for mood and bodily complaints were administered. Results show slight mood disturbances but no cognitive impairment caused by T3 level changes. Time intervals were estimated as being longer than in euthyroid state, and word production showed a trend to accelerate. It is concluded that the immediate effects of elevated circulating T3 on cognition and mood are merely discrete. More severe cognitive impairments reported in hyperthyroid patients are probably due to long-term effects on the brain.

No short-term changes of cognitive performance and mood after single doses of two different lithium retard preparations

This double-blind crossover study investigated the effects of single doses of lithium carbonate (36.6 mval), lithium-sulfate (36 mval), and placebo within the first six hours after administration. The subjects were nine healthy volunteers. The target variables were physical complaints, mood, memory, visuomotor speed, and time estimation. Subjects showed no significant impairment of performance in the cognitive tests and no subjective changes of well-being under lithium. Therefore, it seems that lithium-induced alterations of memory and mood reported in the literature develop very slowly and do not appear after a single dose.

Prevalence of alcohol and drug abuse in schizophrenic inpatients

All schizophrenic patients admitted consecutively either to the Psychiatric Hospital of the University of Munich (group 1, N = 183) or the Mental State Hospital Haar/Munich (group 2, N = 447) between 1.8.1989 and 1.2.1990 were examined to assess prevalence estimates for substance abuse in schizophrenic inpatients. Psychiatric diagnosis were made according to ICD-9 criteria. Psychopathology and psychosocial variables were documented by means of the AMDP-protocol on admission and discharge. The diagnostic procedure included a detailed semi-structured interview concerning the individual alcohol and drug history and sociodemographic data, the Munich Alcoholism Screening Test (MALT), a physical examination and the screening of various laboratory parameters such as GGT and MCV, among others. The results show that substance abuse is a very common problem in schizophrenics. Lifetime prevalence rates for substance abuse were estimated at 21.8% in group 1 and 42.9% in group 2, 3-month prevalence rates for substance abuse were estimated at 21.3% resp. 29.0%. Alcohol abuse was by far the most common type of abuse with prevalence estimates being 17.4% resp. 34.6%. Prevalence rates for substance abuse were much higher in the more "chronic"sample of the Mental State Hospital and in male patients. With respect to schizophrenic subtype few differences could be demonstrated with drug dependence being more common in patients with paranoid schizophrenia. The MALT proved to be a valuable screening instrument for alcohol abuse in schizophrenics with both a high specificity and sensitivity. "Dual diagnosis" schizophrenics had a significantly higher rate of suicide attempts and were less likely to be married. Possible clinical implications of these findings are discussed.

Double-blind cross-over study of phosphatidylserine vs. placebo in patients with early dementia of the Alzheimer type

Thirty-three patients with mild primary degenerative dementia according to DSM-III (MMS between 15 and 27) took part in a double-blind cross-over study of phosphatidylserine (Fidia, 300 mg/d) versus placebo. Both treatment phases lasted for 8 weeks with an 8 week washout phase in between and a 4 week washout phase before treatment phase one. Clinical global improvement ratings showed significantly more patients improving under BC-PS than under placebo during treatment phase one. The improvement carried over to the following wash-out and treatment phases. There were no significant improvements in GBS dementia rating scale, psychometric tests or P300-latency. 16-channel EEG mapping findings indicated that the patients initially showed higher power values in all frequency bands (except alpha), when compared to a younger, healthy control group. BC-PS reduced the higher power values compared to placebo, shifting EEG power more towards the normal level.

Sensory gating in normals and schizophrenics: a failure to find strong P50 suppression in normals

In a series of investigations, suppression of the auditory-evoked P50 potential to the second of two paired clicks presented 500 msec apart has been shown to be absent in schizophrenic patients, whereas normals suppress their second response to less than 20% of the first response. The phenomenon has been discussed as a possible trait marker for schizophrenia. The present study with 19 schizophrenics and 23 healthy control subjects was intended as an extended replication of the phenomenon using different stimulus parameters and a slightly different method of measuring P50 amplitudes. Replication was unsuccessful, revealing only weak suppression scores in normal subjects not significantly superior to schizophrenics. Retest sessions yielded generally stronger P50 suppression suggesting that the stability of the measure over time is questionable. The methodological changes are discussed as possible sources of this failure to replicate. It is concluded that the conditions under which P50-suppression occurs should be better clarified in order to facilitate replication.

Cognitive determinants of the postimperative negative variation

This study examined cognitive determinants of the postimperative negative variation (PINV), a slow brain potential observable after the onset of an imperative stimulus in a forewarned reaction time task. Controllability of the aversive imperative stimulus by a motor reaction and predictability of the contingency were varied in a factorial design. The exogenous portion of the slow negative wave was assessed in a passive listening condition using tones of the same quality as the imperative stimuli, but presented without forewarning. Results show that PINV not only occurs when control is absent but also during unpredictably gained control. Similarly, unpredictable lack of control yields a more negative potential than continual helplessness. Negativity elicited by the aversive tone alone was not significantly different from PINV during predictable lack of control. The order of conditions, which was manipulated between groups, did not affect amplitudes. It was concluded that contingency change is a crucial cognitive determinant of the PINV, whereas the effect of lack of control is difficult to differentiate from the sensory influence of the acoustic stimulation.