Phenothiazine effects in chronic schizophrenia

Impairment of willed actions and use of advance information for movement preparation in schizophrenia

OBJECTIVES

To assess willed actions in patients with schizophrenia using reaction time (RT) tasks that differ in the degree to which they involve volitionally controlled versus stimulus driven responses.

METHODS

Ten patients diagnosed with schizophrenia and 13 normal controls of comparable age were tested. Subjects performed a visual simple RT (SRT), an uncued four choice reaction time (CRT), and a fully cued four choice RT task. A stimulus 1(S1)-stimulus 2(S2) paradigm was used. The warning signal/precue (S1) preceded the imperative stimulus (S2) by either 0 (no warning signal or precue) 200, 800, 1600, or 3200 ms.

RESULTS

The patients with schizophrenia had significantly slower RTs and movement times than normal subjects across all RT tasks. The unwarned SRT trials were significantly faster than the uncued CRT trials for both groups. For both groups, fully cued CRTs were significantly faster than the uncued CRTs. However, the S1-S2 interval had a differential effect on CRTs in the two groups. For the normal subjects fully cued CRTs and SRTs were equivalent when S1-S2 intervals were 800 ms or longer. A similar pattern of effects was not seen in the patients with schizophrenia, for whom the fully cued CRT were unexpectedly equivalent to SRT for the 200 ms interval and expectedly for the 1600 ms S1-S2 interval, but not the 3200 or 800 ms intervals.

CONCLUSIONS

Patients with schizophrenia were able to use advance information inherent in SRT or provided by the precue in fully cued CRT to speed up RT relative to uncued CRT. However, in the latter task, in which the volitional demands of preprogramming are higher since a different response has to be prepared on each trial, patients showed some unusual and inconsistent interval effects suggesting instability of attentional set. It is possible that future studies using RT tasks with higher volitional demands in patients with predominance of negative signs may disclose greater deficits in willed action in schizophrenia.

Risperidone vs. haloperidol on reaction time, manual dexterity, and motor learning in treatment-resistant schizophrenia patients

BACKGROUND

The present study compared the effects of risperidone vs. haloperidol on reaction time, manual dexterity, and two types of motor learning in a sample of treatment-resistant schizophrenia patients.

METHODS

Fifty-six DSM-III-R diagnosed schizophrenia inpatients participated in a randomized, double-blind comparison of risperidone vs. haloperidol. Measures of reaction time, manual dexterity, motor sequence learning, and gross motor learning were administered at baseline, after 4 weeks of fixed-dose medication, and after 4 weeks of flexible-dose medication.

RESULTS

The results indicated that patients receiving risperidone showed greater improvement in reaction time and manual dexterity than patients receiving haloperidol. After covarying symptom changes and movement disorder ratings, the results remained significant. The two treatment groups did not differ on either measure of motor learning.

CONCLUSIONS

The differences in performance in reaction time and manual dexterity may be due to a specific beneficial effect of risperidone, as opposed to a general reduction in extrapyramidal symptom liability, compared to haloperidol.

The clinical relevance of an auditory attention task (PAT) in a longitudinal study of chronic schizophrenia, with placebo substitution for chlorpromazine

A new auditory attention task (PAT) is described. The test comprises four different subtest combinations (diotic/dichotic, slow/fast) each of 5 min duration. Omission and commission errors are combined by an index of errors (IE). The PAT was given fortnightly to 20 chronic schizophrenic inpatients for more than one year. Independent psychiatrists rated the patients according to the Brief Psychiatric Rating Scale and a Global Rating Scale. All measures yielded significant test-retest reliabilities. The patients were stabilized on individualized doses of chlorpromazine (CPZ) and randomized to two groups. Placebo was substituted for CPZ during 10 weeks, according to a double-blind cross-over design. Significant deterioration under placebo was detected by all three methods, but the PAT was the most sensitive to change. The PAT mean score (M IE) was correlated with both rating scales. Unlike the rating scales, it also correctly ordered the twenty patients along a dimension which measured the severity of illness and 'predicted' hospital discharge.

The effect of neuroleptics on cognitive and psychomotor function

There has been great variability and inconsistency in the reported effects of neuroleptic drugs on cognitive and psychomotor function in both patients and normal controls. Experimental design rather than any particular cognitive or psychomotor test appears to have determined the sensitivity of detection of neuroleptic drug effects. In general, sedative phenothiazines have been found to depress psychomotor function and sustained attention, but higher cognitive functions are relatively unaffected. In the majority of studies of schizophrenic patients, both cognitive function and attention improve with neuroleptic treatment, in parallel with clinical recovery. Negative symptoms are not increased and usually show slight improvement with neuroleptic treatment. Controls are more sensitive than schizophrenic patients to neuroleptic drug-induced impairments. Tolerance has been seen in patients but has not been demonstrated in normal volunteers. The way in which neuroleptics produce their beneficial effects in patients remains unknown. Three main hypotheses to replace early arousal theories are proposed: normalisation of attention, facilitated indirectly by suppression of 'released' limbic dopamine hyperactivity; normalisation of asymmetrical temporohippocampal function; or direct improvement of attentional processing. Studies of the effects of new antipsychotic drugs with selective actions and the development of more reliable and selective tests of psychomotor and cognitive functions are required.

Temporal discrimination in schizophrenic and affective disorders: evidence for a dopamine-dependent internal clock

Performance in temporal discrimination of time intervals in the range of milliseconds was compared in 80 healthy subjects, 27 patients with schizophrenic disorders, 33 patients with major depression, 21 patients with dysthymic disorders. For schizophrenic patients as well as for patients with major depression, pronounced deficits in duration discrimination could be demonstrated as compared to the healthy control group (p less than .01). Patients with dysthymic disorders and schizophrenic patients differed significantly from the melancholic group (p less than .01 and p less than .05, respectively). The results are discussed on the basis of the assumption of an internal clock, implying that the clock rate is highest and therefore temporal resolution is best with healthy subjects. With psychiatric patients performance in temporal discrimination was impaired to a slowing down in clock rate and thus decreased temporal resolution. There is strong evidence that changes in clock rate depend on the effective level of dopamine. This leads to the conclusion that temporal discrimination thresholds may be seen as an indicator for deviations from the optimal level of dopaminergic activity in psychiatric patients. In addition, possible effects due to age and medication are discussed.

Voluntary motor performance in psychotic disorders: a replication study

Voluntary motor performance was used to investigate the hypothesis of a continuum of psychosis from depression through schizophrenia. 43 schizophrenic, 36 schizoaffective, 50 major depressive, 20 manic, and 25 nonpsychotic patient controls were tested for tapping speed, finger dexterity, hand grip strength, and neuropsychological motor performance. Sex was included as an independent variable, and the effects of psychotropic drugs were evaluated. A continuum of motor dysfunction from depression through schizophrenia was not obtained. A measure of current psychotic symptoms was not associated with motor or neuropsychological performance. Motor performance was significantly worse in schizophrenic, schizoaffective, and psychotic affective disorders, when compared to nonpsychotic affective disorders. In this final analysis, psychoticism was defined by history. The results are discussed in terms of the hypothesis that psychoticism is a trait that is independent of diagnosis.

Voluntary movement dysfunction in schizophrenics

Several aspects of fine motor control were compared in schizophrenics and two control populations. The motor behavior analyzed was a button-press response in a forced choice paradigm. Three areas of abnormality were seen in schizophrenics: first, the interval preceding the motor response was characterized by reduced motor steadiness prior to the button-press response; second, the motor response was made with excessive force (hyperdynamia); and third, the agonist-antagonist synchrony (motor reversal) was impaired. Schizophrenics on and off neuroleptics did not differ on any measure of motor control, but schizophrenics with clinically observed tardive dyskinesia were found to have significantly less steadiness prior to the motor response than other schizophrenics.

Performance of chronic schizophrenics on matched word and design recall tasks

Matched word and design recall tasks were constructed and used to assess the performance of chronic schizophrenics on neuroleptics alone and on both neuroleptic and anticholinergic drugs. The two groups of patients performed at an equally low level on both tasks, without evidence for a differential deficit. The tasks did, however, evoke a differential deficit in clustering performance for designs as opposed to words. Although clustering, which is based on recall, is not necessarily as well matched for words and designs as recall itself, this result suggests a lateralized dysfunction in brain structures related to use of mnemonic organization at retrieval.

Recall and recognition in mildly disturbed schizophrenics: the use of matched tasks

Unlike previous studies, this study shows that in controlled conditions non-chronic schizophrenics receiving neuroleptic medication show no disparity between recall and recognition. Patients receiving both neuroleptic and anticholinergic drugs show this disparity, performing less well on recall than on recognition. These patients also seem more severely disturbed. The importance of task matching, drugs and chronicity are discussed.

Decisional processing in paranoid and non-paranoid schizophrenics

40 schizophrenic subjects, divided into paranoid/non-paranoid categories and 14 normal controls were presented a task which involved making "same-different" judgments during random presentations of a series of visual comparison stimuli with a standard which represented the midpoint of the stimulus continuum. Using Sternberg's Choice RT paradigm for studying the locus of cognitive deficit, difficulty at the response-selection stage was manipulated while holding other stages constant. It was predicted that paranoids would have shorter RTs at easy decision points and longer RTs at difficult decision points relative to non-paranoids. The directions of the differences were as predicted but did not attain statistical significance. Both schizophrenic groups, compared to normals, made significantly fewer "same" responses on those trials where the comparison and standard were most similar.

Similarities and differences in encoding processes in chronic schizophrenics and normals

The encoding of visual stimuli was compared for 9 female chronic nonparanoid schizophrenics and 9 normals using the Sternberg paradigm. This paradigm allows an examination of several hypothetical stages in information processing using a reaction time measurement. Degradation level (degraded vs nondegraded), type faces of letter stimuli (varied versus constant type face), and order of degradation levels (mixed or constant level across a block of trials) were manipulated in order to examine differences in encoding process between the two groups. Results suggest two subprocesses in encoding, only one of which is defient in schizophrenics. Additional processing of encoded information at a memory stage may be comparable in normal schiziphrenics. Chronic schizophrenics are also more easily disrupted by the context of varying stimulus conditions such as mixing degradation levels and type faces. This finding suggests schizophrenic perseveration in encoding processes.

Drug-related test patterns of depressed patients

Several types of drugs reportedly have been useful in treating depressions, but the specific effects of these drugs on functioning remain unclear. Forty-nine hospitalized depressed patients were randomly assigned on a double-blind basis to an imipramine, chlorpromazine or placebo group. Psychological test performance was compared after 3 weeks of in-hospital drug treatment. Neither drug produced impairment on most measures of intellectual functioning. The results suggest imipramine may impair ability to assimilate and retain information, and that chlorpromazine may impair sustained attention. The differential effects were discussed in relation to symptoms, and to hypotheses about the relationship between arousal and chlorpromazine and between retardation and imipramine in the treatment of depression.