Differential effects of D2- and D4-blocking neuroleptics on the procedural learning of schizophrenic patients

Common and distinct neural effects of risperidone and olanzapine during procedural learning in schizophrenia: a randomised longitudinal fMRI study

RATIONALE

Most cognitive domains show only minimal improvement following typical or atypical antipsychotic treatments in schizophrenia, and some may even worsen. One domain that may worsen is procedural learning, an implicit memory function relying mainly on the integrity of the fronto-striatal system.

OBJECTIVES

We investigated whether switching to atypical antipsychotics would improve procedural learning and task-related neural activation in patients on typical antipsychotics. Furthermore, we explored the differential effects of the atypical antipsychotics risperidone and olanzapine.

METHODS

Thirty schizophrenia patients underwent functional magnetic resonance imaging during a 5-min procedural (sequence) learning task on two occasions: at baseline and 7-8 weeks later. Of 30 patients, 10 remained on typical antipsychotics, and 20 were switched randomly in equal numbers to receive either olanzapine (10-20 mg) or risperidone (4-8 mg) for 7-8 weeks.

RESULTS

At baseline, patients (all on typical antipsychotics) showed no procedural learning. At follow-up, patients who remained on typical antipsychotics continued to show a lack of procedural learning, whereas those switched to atypical antipsychotics displayed significant procedural learning (p = 0.001) and increased activation in the superior-middle frontal gyrus, anterior cingulate and striatum (cluster-corrected p < 0.05). These neural effects were present as a linear increase over five successive 30-s blocks of sequenced trials. A switch to either risperidone or olanzapine resulted in comparable performance but with both overlapping and distinct task-related activations.

CONCLUSIONS

Atypical antipsychotics restore procedural learning deficits and associated neural activity in schizophrenia. Furthermore, different atypical antipsychotics produce idiosyncratic task-related neural activations, and this specificity may contribute to their differential long-term clinical profiles.

Cerebellar-motor dysfunction in schizophrenia and psychosis-risk: the importance of regional cerebellar analysis approaches

Motor abnormalities in individuals with schizophrenia and those at-risk for psychosis are well documented. An accumulating body of work has also highlighted motor abnormalities related to cerebellar dysfunction in schizophrenia including eye-blink conditioning, timing, postural control, and motor learning. We have also recently found evidence for motor dysfunction in individuals at ultra high-risk for psychosis (1-3). This is particularly relevant as the cerebellum is thought to be central to the cognitive dysmetria model of schizophrenia, and these overt motor signs may point to more general cerebellar dysfunction in the etiology of psychotic disorders. While studies have provided evidence indicative of motor cerebellar dysfunction in at-risk populations and in schizophrenia, findings with respect to the cerebellum have been mixed. One factor potentially contributing to these mixed results is the whole-structure approach taken when investigating the cerebellum. In non-human primates, there are distinct closed-loop circuits between the cerebellum, thalamus, and brain with motor and non-motor cortical regions. Recent human neuroimaging has supported this finding and indicates that there is a cerebellar functional topography (4), and this information is being missed with whole-structure approaches. Here, we review cerebellar-motor dysfunction in individuals with schizophrenia and those at-risk for psychosis. We also discuss cerebellar abnormalities in psychosis, and the cerebellar functional topography. Because of the segregated functional regions of the cerebellum, we propose that it is important to look at the structure regionally in order to better understand its role in motor dysfunction in these populations. This is analogous to approaches taken with the basal ganglia, where each region is considered separately. Such an approach is necessary to better understand cerebellar pathophysiology on a macro-structural level with respect to the pathogenesis of psychosis.

More than just tapping: index finger-tapping measures procedural learning in schizophrenia

BACKGROUND

Finger-tapping has been widely studied using behavioral and neuroimaging paradigms. Evidence supports the use of finger-tapping as an endophenotype in schizophrenia, but its relationship with motor procedural learning remains unexplored. To our knowledge, this study presents the first use of index finger-tapping to study procedural learning in individuals with schizophrenia or schizoaffective disorder (SCZ/SZA) as compared to healthy controls.

METHODS

A computerized index finger-tapping test was administered to 1169 SCZ/SZA patients (62% male, 88% right-handed), and 689 healthy controls (40% male, 93% right-handed). Number of taps per trial and learning slopes across trials for the dominant and non-dominant hands were examined for motor speed and procedural learning, respectively.

RESULTS

Both healthy controls and SCZ/SZA patients demonstrated procedural learning for their dominant hand but not for their non-dominant hand. In addition, patients showed a greater capacity for procedural learning even though they demonstrated more variability in procedural learning compared to healthy controls. Left-handers of both groups performed better than right-handers and had less variability in mean number of taps between non-dominant and dominant hands. Males also had less variability in mean tap count between dominant and non-dominant hands than females. As expected, patients had a lower mean number of taps than healthy controls, males outperformed females and dominant-hand trials had more mean taps than non-dominant hand trials in both groups.

CONCLUSIONS

The index finger-tapping test can measure both motor speed and procedural learning, and motor procedural learning may be intact in SCZ/SZA patients.

Modulatory influence of dopamine receptors on consolidation of object recognition memory

The role of dopamine receptors in regulating the formation of recognition memory remains poorly understood. Here we show the effects of systemic administration of dopamine receptor agonists and antagonists on the formation of memory for novel object recognition in rats. In Experiment I, rats received an intraperitoneal (i.p.) injection of vehicle, the selective D1 receptor agonist SKF38393 (1.0 and 5.0mg/kg), or the D2 receptor agonist quinpirole (1.0 and 5.0mg/kg) immediately after training. In Experiment II, rats received an injection of vehicle, the dopamine receptor antagonist SCH23390 (0.1 and 0.05 mg/kg), or the D2 receptor antagonist raclopride (0.5 and 0.1mg/kg) before training, followed by an injection of vehicle or the nonselective dopamine receptor agonist apomorphine (0.05 mg/kg) immediately after training. SKF38393 at 5mg/kg produced an enhancement of novel object recognition memory measured at both 24 and 72 h after training, whereas the dose of 10mg/kg impaired 24-h retention. Posttraining administration of quinpirole did not affect 24-h retention. Apomorphine enhanced memory in rats given pretraining raclopride, suggesting that the effect was mediated by selective activation of D1 receptors. The results indicate that activation of D1 receptors can enhance recognition memory consolidation. Importantly, pharmacological activation of D1 receptors enhanced novel object recognition memory even under conditions in which control rats showed significant retention.

Motor sequence learning in primate: role of the D2 receptor in movement chunking during consolidation

Motor learning disturbances have been shown in diseases involving dopamine insufficiency such as Parkinson's disease and schizophrenic patients under antipsychotic drug treatment. In non-human primates, motor learning deficits have also been observed following systemic administration of raclopride, a selective D2-receptor antagonist. These deficits were characterized by persistent fluctuations of performance from trial to trial, and were described as difficulties in consolidating movements following a learning period. Moreover, it has been suggested that these raclopride-induced fluctuations can result from impediments in grouping separate movements into one fluent sequence. In the present study, we explore the hypothesis that such fluctuations during movement consolidation can be prevented through the use of sumanirole - a highly selective D2 agonist - if administered before raclopride. Two monkeys were trained to execute a well known sequence of movements, which was later recalled under three pharmacological conditions: (1) no drug, (2) raclopride, and (3) sumanirole+raclopride. The same three pharmacological conditions were repeated with the two monkeys, trained this time to learn new sequences of movements. Results show that raclopride has no deleterious effect on the well known sequence, nor the sumanirole+raclopride co-administration. However, results on the new sequence to be learned revealed continuous fluctuations of performances in the raclopride condition, but not in the sumanirole+raclopride condition. These fluctuations occurred concurrently with a difficulty in merging separate movement components, known as a "chunking deficit". D2 receptors seem therefore to be involved in the consolidation of new motor skills, and this might involve the chunking of separate movements into integrated motor sequences.

Sensorimotor adaptation in Parkinson's disease: evidence for a dopamine dependent remapping disturbance

Sensorimotor adaptation is thought to involve a remapping of the kinematic and kinetic parameters associated with movements performed within a changing environment. Patients with Parkinson's disease (PD) are known to be affected on this type of learning process, although the specific role of dopamine depletion in these deficits has not yet been elucidated. The present study was an attempt to clarify whether dopamine depletion in PD may directly affect the capacity to internally reorganize the visuomotor remapping of a distorted environment. Fourteen PD patients were tested twice, while they were treated and while they were withdrawn from their regular levodopa treatment. Fourteen control subjects were also enrolled and tested twice. Two parallel forms of the Computed Mirror Pointing Task (CMPT), requiring making a reaching movement in a visually transformed environment (mirror inversion), were administered to each participant. Each of them had to perform 40 trials at each of the 2 testing sessions. At each trial, sensorimotor adaptation was evaluated by the initial direction angle (IDA), which reflects the direction of movement before any visually guided readjustment. Results revealed no IDA difference at baseline, between control subject and PD patients, whether they were treated or not. In all group, IDA values at that time were large, reflecting a tendency to make movements according to the real life visuomotor mapping (based on the natural direct vision). However, striking differences appeared during sensorimotor learning, in that IDA reduction along trials was poorer in patient not treated with levodopa than both control subjects and the same PD patient treated with levodopa. No difference was observed between the treated PD patients and control subjects. Given that IDA is thought to reflect the internal representation of the visuomotor mapping, it is concluded that dopamine depletion in PD would affects sensorimotor adaptation, in that it facilitates old and poorly adapted movements (real life mapping), instead of new and more adapted ones (mirror transformed mapping).

Raclopride-induced motor consolidation impairment in primates: role of the dopamine type-2 receptor in movement chunking into integrated sequences

Results obtained in patients with schizophrenia have shown that antipsychotic drugs may induce motor learning deficits correlated with the striatal type-2 dopamine receptors (D(2)R) occupancy. Other findings suggest that the role of the striatum in motor learning could be related to a process of "chunking" discrete movements into motor sequences. We therefore hypothesized that a D(2)R blocking substance, such as raclopride, would affect motor learning by specifically disrupting the grouping of movements into sequences. Two monkeys were first trained to perform a baseline-overlearned sequence (Seq. A) drug free. Then, a new sequence was learned (Seq. B) and the overlearned sequence was recalled OFF-drug (Seq. A recall OFF-drug). The effect of raclopride was then assessed on the learning of a third sequence (Seq. C), and on the recall of the overlearned sequence (Seq. A recall ON-drug). Results showed that performance related to the overlearned sequence remained the same in the three experimental conditions (Seq. A, Seq. A recall OFF-drug, Seq. A recall ON-drug), whether the primates received raclopride or not. On the other hand, new sequence learning was significantly affected during raclopride treatment (Seq. C), when compared with new sequence learning without the effect of any drug (Seq. B). Raclopride-induced disturbances consisted in performance fluctuations, which persisted even after many days of trials, and prevented the monkeys from reaching a stable level of performance. Further analyses also showed that these fluctuations appeared to be related to monkeys' inability to group movements into single flowing motor sequences. The results of our study suggest that dopamine is involved in the stabilization or consolidation of motor performances, and that this function would involve a chunking of movements into well-integrated sequences.

Dissociating medication effects from learning and practice effects in a neurocognitive study of schizophrenia: Olanzapine versus haloperidol

OBJECTIVE

To contrast the effect of a typical antipsychotic (haloperidol) and an atypical antipsychotic (olanzapine) on neurocognitive functioning in schizophrenia when learning and practice (LP) effects are controlled.

METHODS

Two groups of participants were recruited, 27 schizophrenia patients in their first 5 years of illness and 13 normal controls. Prior to double-blind randomisation, all subjects were assessed on four occasions within 5 days (prerandomisation period) on the same neurocognitive battery. Repeated assessment prior to randomisation was chosen as a method to control for LP effects. Patients were then randomised to 56 days of treatment with haloperidol or olanzapine (postrandomisation). All subjects were assessed on neurocognitive measures at Days 28 and 56.

RESULTS

LP effects were present during the prerandomisation period on motor tasks, verbal and visual short-term memory, attention, and on a measure of verbal working memory. There were no changes in performance for patients randomised to treatment with olanzapine or haloperidol or the normal control group during the postrandomisation period.

CONCLUSIONS

Once LP effects are controlled, olanzapine and haloperidol do not affect performance on measures of motor functioning, verbal short-term memory, attention, verbal working memory, reaction time, visuospatial short-term memory, and visual working memory beyond that observed from LP effects.

A meta-analysis of cognitive change with haloperidol in clinical trials of atypical antipsychotics: dose effects and comparison to practice effects

Prospective, double-blind, randomized trials comparing atypical antipsychotic drugs (APDs) to typical APDs, such as haloperidol, indicate that atypical APDs provide a modest benefit to cognitive function in schizophrenia. However, the validity of this inference has been contested by suggestions that the cognitive improvements observed with atypical APDs reflect practice effects associated with repeated testing on the same neuropsychological instruments, or an avoidance of a deleterious effect of haloperidol on cognitive function that might be dose related. These alternate hypotheses were assessed by meta-analyses that 1) examined the relationship between cognitive change and dose of haloperidol within the control arms of prospective atypical vs. typical APD clinical trials; and 2) compared the magnitude of change observed within the haloperidol arms of these studies to estimated practice effects for several commonly used neuropsychological measures. The results indicate that overall cognitive performance improves while on haloperidol. Studies that used a low dose of haloperidol (<10 mg) did not yield larger effect sizes for overall cognitive function or specific neuropsychological measures than studies that used a high dose (>10 mg), although doses greater than 24 mg appear to have deleterious effects. For two of the six neuropsychological tests examined (digit symbol substitution and verbal fluency) the magnitude of change observed was significantly less than practice effects. The results indicate that although haloperidol may cause deleterious effects at very high doses, or in specific cognitive domains, these effects are not likely to explain the broader range of cognitive improvements observed with atypical APDs.

Procedural learning in schizophrenia investigated with functional magnetic resonance imaging

A cerebral basis for the acquisition and retention of procedural knowledge in schizophrenia was examined with 1.5 T functional MRI during an embedded sequence Serial Reaction Time Task (SRTT) in 10 chronic medicated patients and 15 healthy controls. Comparable procedural learning was observed in both groups, suggesting that the impairment reported in previous schizophrenia samples may not be robust. Consistent with previous fMRI reports, procedural learning in the control group was associated with activity in the dorsal striatum, anterior cingulate, parietal cortex and frontal cortex. Greater procedural learning related activity was observed in the control relative to the schizophrenia group in the bilateral frontal, left parietal and bilateral caudate regions. Patients did not activate frontal or parietal areas while responding to the embedded sequence within the SRTT, but greater activation during procedural learning was observed relative to the control sample in the right anterior cingulate, left globus pallidus and the right superior temporal gyrus. Thus, despite comparable instantiation of procedural learning in schizophrenia, the cerebral activation associated with this cognitive skill was abnormal. The paucity of activity in bilateral frontal cortex, left parietal cortex and bilateral caudate nucleus may represent cerebral dysfunction associated with schizophrenia, whereas the hyperactivation of the right superior temporal gyrus, the right anterior cingulate cortex and the left globus pallidus may represent a compensatory cerebral action capable of facilitating near-normal task performance. The results are thus consistent with a neurodevelopmental pathology impinging on fronto-subcortical circuitry.

State-dependent implicit learning deficit in schizophrenia: evidence from 20-month follow-up

Previous research has confirmed stable explicit memory deficits in schizophrenia across disease states. However, little is known about the implicit learning capabilities of individuals with schizophrenia across the course of illness. The current study assessed procedural learning in 19 schizophrenia subjects (DSM-IV criteria) and 19 matched controls using the Serial Reaction-Time Task (SRTT). The severity of negative, positive and disorganized symptoms was assessed using the Scales for the Assessment of Positive and Negative Symptoms. A sub-sample of 11 schizophrenia subjects and 11 controls was reassessed 20 months later when symptoms in the schizophrenia subjects had largely remitted. Schizophrenia subjects were severely impaired on sequence-specific procedural learning during an acute episode. This deficit could not be explained by a general memory or processing speed impairment. Impaired implicit learning scores were significantly related to higher ratings of disorganized symptoms. However, 20 months later, when acute symptoms had remitted, the performance of the schizophrenia subjects on procedural learning had normalized. Our findings might share a conceptual overlap with previous reports of a reduced ability of schizophrenia subjects during an acute episode to adapt ongoing perceptual and behavioral programs to previously experienced regularities in their environment.

The effect of verbalization strategy on Wisconsin Card Sorting Test performance in schizophrenic patients receiving classical or atypical antipsychotics

BACKGROUND

A number of reports showed en encouraging remediation in some patients' executive deficits thanks to the use of 'information processing strategies'. Moreover the impact of antipsychotics on cognitive functions of the schizophrenics is an important issue, especially if an integrated psychosocial treatment is needed. The aim of this paper is to evaluate different executive performance and response to verbalization, a strategy of the Wisconsin Card Sorting Test (WCST) remediation, in subjects on classical vs atypical antipsychotic (AP) treatment.

METHODS

Sixty-three schizophrenic subjects undertook the WCST under standard and modified (verbalization) administration. Subjects were stratified by the kind of WCST response (i.e. good, poor and remediable) and AP treatment (i.e. atypical vs. classical).

RESULTS

Subjects on atypical APs showed a better performance than those on classical ones. More poor performers who did not remediate were seen in the sample with classical Aps while subjects who remediated the performance were seen in the subgroup with atypical APs only. An increase of perseverative and total errors was seen in poor performers subjects on classical APs.

CONCLUSION

Subjects on atypicals showed a better cognitive pattern in terms of WCST performance. Since the naturalistic assignment of medication we cannot draw conclusions about its effect on cognitive performance and its interaction with cognitive remediation potential. However the data lead us to hypothesize that subjects with potential room for remediation did so with the atypical APs.

Executive function assessment of patients with schizophrenic disorder residual type in olanzapine treatment: an open study

Cognitive deficits are a fundamental feature of the schizophrenic disorder, but the effect of antipsychotic treatment is still debated. The study assesses the effect of olanzapine on neurocognitive functioning and symptomatology of patients with schizophrenic disorder residual type. Executive function evaluation by the Wisconsin card sorting test (WCST) was performed on 39 patients treated with olanzapine (5-20 mg/day); the efficacy of drug in improving symptomatology, safety and quality of life was also evaluated. After 7 months of treatment, the mean number of WCST categories tended to increase. Correct responses increased with a statistically significant change from the baseline. The total and unique errors decreased significantly. At all post-baseline visits a decrease from baseline in the PANSS total, positive and negative scores was seen. The proportion of patients with less severe illness (CGI), increased over the course of the study with a corresponding decrease of patients with more severe illness. The quality of life scores also tended to improve during treatment. The Simpson Angus scale, Barnes-akathisia and abnormal involuntary movement scale scores decreased consistently. The most common treatment emergent drug related adverse events were weight gain, insomnia, agitation and anxiety. Neurocognitive functioning in terms of executive performance and symptomatology improved in people with schizophrenia residual type.

Procedural learning in schizophrenia can reflect the pharmacologic properties of the antipsychotic treatments

BACKGROUND

Conventional and atypical antipsychotics have different affinities for D2 receptors, and these receptors are principally located in the striatum. Given that this cerebral structure was previously found to play a major role in procedural learning, the antipsychotic treatment in schizophrenia may be determinant for the procedural learning profile of these patients.

OBJECTIVE

The current study was aimed at verifying whether procedural learning differs in patients with schizophrenia treated with conventional antipsychotics and patients treated with atypical antipsychotics.

METHOD

Forty-five patients with schizophrenia were divided into 3 different groups according to their pharmacologic treatment: (1) haloperidol, a classical neuroleptic with high D2 receptor affinity; (2) clozapine, an atypical neuroleptic with practically no D2 receptor affinity; and (3) risperidone, an atypical neuroleptic that nevertheless shows high D2 receptor affinity. Patients were compared to 35 control subjects on a visuomotor procedural learning task (mirror drawing).

RESULTS

All patients were able to learn the task. However, those treated with haloperidol showed some degree of learning impairment, while those treated with clozapine or risperidone did not show this impairment. In addition, performance per se, regardless of the learning, was found to be affected in the haloperidol and risperidone, but not in the clozapine groups.

CONCLUSION

Procedural learning in schizophrenia may be differentially affected, depending on the pharmacologic profiles of the antipsychotics used for the treatment of this illness.

A meta-analysis and critical review of the effects of conventional neuroleptic treatment on cognition in schizophrenia: opening a closed book

BACKGROUND

In recent years, numerous studies have examined whether new-generation antipsychotic agents impact cognitive impairment in patients with schizophrenia when compared with conventional antipsychotic treatment. The working assumption of such studies, supported by narrative reviews, is that the conventional antipsychotic medications have little or no effect on cognition. The studies concerning the effects of conventional neuroleptics on cognition, however, have never been analyzed quantitatively. In this meta-analysis, we revisit the question of whether typical agents might have enhancing effects on cognition.

METHODS

The meta-analysis included studies that 1) compared the effects of typical neuroleptic agents with those of placebo or no medication on cognition; 2) examined adult patients identified as having schizophrenia; and 3) produced adequate data to estimate an effect size. Studies were identified by searches of computerized literature databases and by cross-referencing included studies. The effect size calculated was d, the difference between the means in cognitive measures of patients with schizophrenia taking and not taking conventional neuroleptic medication, divided by the pooled SD. Critically, when multiple measures were reported in a single article, effect sizes were combined so as to minimize the possibility that one study had undue weight simply because of the number of cognitive outcome variables that it contained. These results were corrected for bias due to sample size, with each of the effect sizes weighted by the reciprocal of its variance. The final sample after exclusion of outliers comprised 208 effect sizes from 34 studies.

RESULTS

With a random-effects model, effect sizes from the primary studies were weighted according to sample size and averaged. The resulting mean effect size was.22 (95% confidence interval =.10,.34). The result is positive, in that the range did not include zero and was of low moderate size. No moderating effects of study design or patient qualities were found to be significant. With the same procedures, effect sizes for individual neurocognitive domains were computed. Effect sizes were generally in the.13-.29 range for the majority of cognitive functions, whereas motor function was impacted negatively (-.11). Unexpectedly, medication dose did not correlate with effect size.

CONCLUSIONS

Typical antipsychotic medication provides modest-to-moderate gains in multiple cognitive domains. Given unavoidable methodologic limitations of the primary studies, current findings suggest that the impact of conventional medication on cognitive function should be re-evaluated.

Procedural learning in schizophrenia after 6 months of double-blind treatment with olanzapine, risperidone, and haloperidol

RATIONALE

First generation antipsychotics induce extrapyramidal motor symptoms (EPS), presumably through dopamine D(2) receptor blockade at the dorsal striatum. This may also produce impairment of cognitive processes, such as procedural learning, that are dependent on this region. Haloperidol and, to a lesser extent, risperidone, are active in the dorsal striatum and may induce EPS and impairment of procedural learning. In contrast, the prototypical second-generation antipsychotic, clozapine, is less active in the dorsal striatum and does not induce EPS or impair procedural learning. Olanzapine is pharmacologically similar to clozapine and has a low incidence of EPS induction.

OBJECTIVES

To assess the hypothesis that olanzapine would not have a deleterious effect on procedural learning.

METHODS

Thirty-nine subjects with early phase schizophrenia were randomly assigned to double blind treatment with haloperidol, risperidone, or olanzapine. They were administered the Tower of Toronto test at an unmedicated baseline and again following 6 weeks and 6 months of treatment.

RESULTS

Procedural learning, defined as the improvement observed between two blocks of five trials of the Tower of Toronto, was preserved after 6 weeks of all three treatments but showed a substantial decline after 6 months of treatment with haloperidol or risperidone.

CONCLUSIONS

These data are consistent with the differential activity of the three medications in dorsal striatum structures and suggest that the advantages of olanzapine over haloperidol and risperidone in relation to extrapyramidal syndromes may also generalize to procedural learning. The results also suggest that the procedural learning disadvantages of haloperidol and risperidone accrue slowly but are apparent after 6 months of treatment.

Basal ganglia N-acetylaspartate correlates with the performance in the procedural task 'Tower of Hanoi' of neuroleptic-naive schizophrenic patients

We tested the hypothesis that basal ganglia dysfunction may be related to procedural learning impairment in schizophrenia. We determined the N-acetylaspartate/choline (NAA/Cho) ratio in the left striatal area in 11 young first-episode antipsychotic-naive patients and matched controls. Procedural learning was assessed by the four-disk version of the Tower of Hanoi. Analysis of variance showed that the number of moves and the execution time had a significant group effect (P=0.02, P<0.0001, respectively). Correlation analysis between procedural learning and the NAA/Cho ratio showed a negative significant correlation only in patients, measured by both time (P=0.006) and by moves (P=0.001). In summary, we found that schizophrenic patients have impaired procedural learning, and that this impairment is related to basal ganglia metabolism.

Procedural learning in schizophrenia: a functional magnetic resonance imaging investigation

Procedural learning (PL) is a type of rule-based learning in which performance facilitation occurs with practice on task without the need for conscious awareness. Schizophrenic patients have often (though not invariably) been found to show impaired PL. We performed functional magnetic resonance imaging (fMRI) during a blocked, periodic sequence-learning task with groups of: (i) healthy subjects, and (ii) schizophrenic patients on conventional antipsychotics. Healthy subjects showed significant PL, but patients did not. In healthy subjects, PL was associated with increased activation in the striatum, thalamus, cerebellum, precuneus, medial frontal lobe, and cingulate gyrus. The power of activation in the thalamus, striatum, precuneus, cingulate gyrus and BA 6 was related to the magnitude of PL in these subjects. No regions, except the anterior inferior gyrus, were significantly activated in patients. The caudate nucleus, thalamus, precuneus, and sensorimotor regions were activated significantly differently between the two groups. The findings demonstrate the involvement of the striatum, cerebellum, thalamus, cingulate gyrus, precuneus, and sensorimotor regions in PL. Further fMRI studies of PL in normal subjects treated with conventional antipsychotics, drug naïve patients, and patients given atypical antipsychotics would help to clarify the roles of schizophrenic disease processes and antipsychotic medication in impaired PL and associated brain abnormalities in schizophrenia.

Social memory is impaired in neonatally ibotenic acid lesioned rats

Postnatal lesion with ibotenic acid in the ventral hippocampus produces several behavioural effects that resemble the symptoms of schizophrenia. In the present study, we tested neonatally lesioned 1-year-old Sprague-Dawley rats for their social memory. It was found that social memory is worsened in lesioned rats. Subchronic treatment with haloperidol (0.025 mg/kg body weight) partly ameliorated this impairment. It was suggested that social memory might be a useful paradigm to test clinically used and potential antipsychotic drugs for their effects on learning and memory processes.

Memory impairment in schizophrenia: perspectives from psychopathology and pharmacotherapy

OBJECTIVE

To describe the concept of memory impairment in schizophrenia and the clinical implications of this concept in terms of patient assessment and neuroleptic drug use.

METHOD

Narrative literature review.

RESULTS

Individuals suffering from schizophrenia normally exhibit some degree of memory impairment. Recent work in psychopathology indicates that the impairment is comprehensive, involving the sensory, short-term, and long-term memory stores. Memory impairment appears to be a primary symptom of the disease, and its underlying causes are likely organic. A number of medications, however (for example, traditional neuroleptics and drugs that have pronounced anticholinergic activity), may cause or exacerbate impairment. In particular, anticholinergic agents used to treat extrapyramidal symptoms, a common complication of neuroleptic drugs, appear to have a deleterious effect on memory.

CONCLUSIONS

Memory impairment is an important consideration in the clinical assessment and management of patients with schizophrenia. The use of atypical antipsychotics like risperidone appears to have no impact on memory function; because risperidone is associated with a low incidence of extrapyramidal side effects, it can obviate the need for anticholinergic medications-thus offering greater hope of nondebilitative intervention. The advent of medications that are safer (on cognition) could also lead to generally better outcomes by facilitating compliance with drug regimens and rehabilitation programs.