Cognitive functioning in the schizophrenia prodrome

The dopamine hypothesis of schizophrenia: version III--the final common pathway

The dopamine hypothesis of schizophrenia has been one of the most enduring ideas in psychiatry. Initially, the emphasis was on a role of hyperdopaminergia in the etiology of schizophrenia (version I), but it was subsequently reconceptualized to specify subcortical hyperdopaminergia with prefrontal hypodopaminergia (version II). However, these hypotheses focused too narrowly on dopamine itself, conflated psychosis and schizophrenia, and predated advances in the genetics, molecular biology, and imaging research in schizophrenia. Since version II, there have been over 6700 articles about dopamine and schizophrenia. We selectively review these data to provide an overview of the 5 critical streams of new evidence: neurochemical imaging studies, genetic evidence, findings on environmental risk factors, research into the extended phenotype, and animal studies. We synthesize this evidence into a new dopamine hypothesis of schizophrenia-version III: the final common pathway. This hypothesis seeks to be comprehensive in providing a framework that links risk factors, including pregnancy and obstetric complications, stress and trauma, drug use, and genes, to increased presynaptic striatal dopaminergic function. It explains how a complex array of pathological, positron emission tomography, magnetic resonance imaging, and other findings, such as frontotemporal structural and functional abnormalities and cognitive impairments, may converge neurochemically to cause psychosis through aberrant salience and lead to a diagnosis of schizophrenia. The hypothesis has one major implication for treatment approaches. Current treatments are acting downstream of the critical neurotransmitter abnormality. Future drug development and research into etiopathogenesis should focus on identifying and manipulating the upstream factors that converge on the dopaminergic funnel point.

Ameliorating prefrontal cortical dysfunction in mental illness: inhibition of phosphotidyl inositol-protein kinase C signaling

BACKGROUND

Bipolar disorder and schizophrenia are associated with profound dysfunction of the prefrontal cortex (PFC), with bipolar disorder most associated with changes in ventromedial PFC and schizophrenia more associated with changes in dorsolateral PFC.

DISCUSSION

Recent genetic and biochemical studies have also linked these illnesses to disinhibition of phosphotidyl inositol-protein kinase C signaling. For example, DAG kinase eta, an enzyme that metabolizes DAG and thus reduces protein kinase C activity, is the gene most altered in bipolar disorder. Similarly, regulator of G protein signaling 4 is the molecule most altered in the PFC of patients with schizophrenia, and this molecule normally serves to inhibit Gq signaling. Animal studies have shown that high levels of phosphotidyl inositol-protein kinase C signaling in the PFC markedly impair PFC function at the behavioral and cellular levels. Most importantly, many effective medications for bipolar disorder and schizophrenia inhibit phosphotidyl inositol-protein kinase C signaling, either through intracellular actions (lithium, valproate) or through extracellular blockade of receptors coupled to this pathway (5HT2 receptors and alpha-1 adrenoceptors). Recent data suggest that lithium and valproate can protect gray matter in patients with bipolar disorder. These findings encourage the development of protein kinase C inhibitors for the treatment of mental illness.

Use of Palm computer as an adjunct to cognitive-behavioural therapy with an ultra-high-risk patient: a case report

AIM

Recently, attempts have been made to develop cognitive-behaviour therapy (CBT) treatment models to target negative symptoms in individuals with schizophrenia, as well as individuals at ultra-high risk (UHR) for psychosis. Successful CBT treatment is founded on active patient participation including completion of homework assignments such as daily logs of activities and experiences. However, these very negative symptoms may themselves hinder the rate of homework assignment completion. We describe a case report of using experience sampling method with a Palm computer as an adjunct to CBT with a female patient at UHR status with predominantly negative symptoms. Our aim was to assess the feasibility and effectiveness of this methodology to improve homework completion and overcome treatment barriers associated with negative symptoms.

METHODS

Over the course of treatment, the patient was provided with a Palm computer to carry with her throughout her daily activities. The Palm computer was pre-programmed to beep randomly 10 times per day (10 a.m.-12 a.m.) over each three-day assessment period to elicit information on daily functioning.

RESULTS

The use of the Palm computer was acceptable to the patient and resulted in a substantial increase in homework completion. This methodology resulted in rich information about the patients' daily functioning and patterns of improvement during treatment. The experience sampling method data were also successfully used in the application of treatment interventions.

CONCLUSION

The findings support the feasibility and effectiveness of using Palm computers as adjunct to CBT with UHR individuals with predominantly negative symptoms. The implications for treatment and future research directions are discussed.

Neuropsychological course in the prodrome and first episode of psychosis: findings from the PRIME North America Double Blind Treatment Study

OBJECTIVE

There is uncertainty regarding the onset timing of the cognitive deficiencies of schizophrenia. We investigated whether conversion to psychosis and/or olanzapine altered the neuropsychological course of subjects within the first-ever double blind medication study of the putative schizophrenia first episode prodrome.

METHOD

Sixty participants in a double blind trial of olanzapine as a treatment for putative prodromal states were assessed at entry (pre-randomization), and again at 6 and 12 months (if they remained non-psychotic), or at any of these points prior to psychosis followed by post-psychosis and 6 months post-psychosis assessments.

RESULTS

Participants who converted to psychosis did not differ from placebo non-converters in pre-randomization global neuropsychological status. Early converters did not differ from later converters in entry neuropsychological status. Subjects who converted after 6 months did not show neuropsychological declines during the initial, pre-psychosis, 6 months. Neuropsychological course did not differ between converters to psychosis and non-converters, or between olanzapine and placebo-assigned subjects.

CONCLUSIONS

Neither the onset of frank psychosis nor olanzapine treatment of the prodrome significantly alters neuropsychological course in persons considered to be at high risk at their initial (pre-psychosis) assessment. These findings suggest that the neuropsychological deficiencies associated with psychotic conditions largely pre-exist the first frank psychotic episode.

Working memory in schizophrenia: an EEG study using power spectrum and coherence analysis to estimate cortical activation and network behavior

This study examined regional cortical activations and cortico-cortical connectivity in a group of 20 high-functioning patients with schizophrenia and 20 healthy controls matched for age and sex during a 0- and a 2-back working memory (WM) task. An earlier study comparing schizophrenia patients with education level-matched healthy controls revealed less "optimally" organized network during the 2-back task, whereas a second study with healthy volunteers had suggested that the degree of cortical organization may be inversely proportional to educational level (less optimal functional connectivity in better educated individuals interpreted as the result of higher efficiency). In the present study, both groups succeeded in the 2-back WM task although healthy individuals had generally attained a higher level of education. First absolute power spectrum of the different frequency bands corresponding to the electrodes of each lobe was calculated. Then the mean values of coherence were calculated as an index of the average synchronization to construct graphs in order to characterize local and large scale topological patterns of cortico-cortical connectivity. The power spectra analyses showed signs of hypofrontality in schizophrenics with an asymmetry. Additionally, differences between the groups with greater changes during WM in healthy individuals were visible in all lobes more on the left side. The graph parameter results indicated decreased small-world architecture i.e. less optimal cortico-cortical functional organization in patients as compared to controls. These findings are consistent with the notion of aberrant neural organization in schizophrenics which is nevertheless sufficient in supporting adequate task performance.

Genetic variation in the schizophrenia-risk gene neuregulin1 correlates with differences in frontal brain activation in a working memory task in healthy individuals

Working memory dysfunctions are a prominent feature in schizophrenia. These impairments have been linked to alterations in prefrontal brain activation with studies reporting hypo- and hyperactivations. Since schizophrenia has a high heritability, it is of interest whether susceptibility genes modulate working memory and its neural correlates. The aim of the present study was to test the influence of the NRG1 schizophrenia susceptibility gene on working memory and its neural correlates in healthy subjects. 429 healthy individuals performed a verbal and a spatial working memory task. A subsample of 85 subjects performed a 2-back version of the Continuous Performance Test (CPT) in a functional MRI study. The NRG1 SNP8NRG221533 (rs35753505) carrier status was determined and correlated with working memory performance and brain activation. There were no effects of genetic status on behavioural performance in the working memory tasks in the 429 subjects and in the fMRI task (n=85). A linear effect of NRG1 SNP8NRG221533 carrier status on neuronal activation emerged in the fMRI experiment. Hyperactivation of the superior frontal gyrus (BA 10) was correlated with the number of risk alleles. The fMRI data suggest that performance measures between groups did not differ due to a compensational activation of BA 10 in risk-allele carriers. Our results are in line with functional imaging studies in patients with schizophrenia, which also showed a differential activation in lateral prefrontal areas.

Kraepelin and psychotic prodromal conditions

When Emil Kraepelin combined the formerly distinct entities of dementia paranoides, catatonia and hebephrenia to form the concept of 'dementia praecox' in 1896, he was well aware that this new disease entity--first coined 'schizophrenia' by Eugen Bleuler in 1908--does not generally only start off with the first psychotic manifestation. Even in his original observations, the characteristic psychotic phenomena developed via transition sequences from rather uncharacteristic prodromal disturbances. Meanwhile an initial prodromal condition was shown for about 75% of first-episode psychosis patients, lasting 5 years on average, possessing pathological significance and leading to psychosocial disruptions. Whereas most symptoms of the initial prodromal condition appear to be rather unspecific and hard to distinguish from other psychiatric conditions especially depressive ones, some syndromes seem to enable an early detection and thus an indicated prevention. These are constituted by attenuated and/or transient psychotic symptoms on the one hand and certain cognitive-perceptive basic symptoms on the other. Whereas the former are thought to delineate an advanced prodromal state, the latter can occur early in course and even at the beginning of the transition sequence to first-rank symptoms. This review will outline the current state of the art of a phase specific early detection and intervention based on these syndromes.

Deficit of theory of mind in individuals at ultra-high-risk for schizophrenia

BACKGROUND

Although a deficit in social cognition is regarded as an early indicator of schizophrenia, few studies have investigated social cognition in ultra-high-risk (UHR) individuals.

METHODS

Our investigation involved subjects at UHR for psychosis (N=33) and an age- and IQ-matched healthy control (HC) group (N=36). Two types of theory of mind (ToM) tasks and a neuropsychological test battery were measured.

RESULTS

Compared to the HC group, the UHR group performed significantly worse for ToM tasks, with the effect size at an intermediate level (0.64-0.68). Furthermore, the UHR group showed impaired performance in the executive and working memory tests, but not verbal memory tests. These deficits for ToM tests observed in the UHR group were significantly correlated with set-shifting tasks.

CONCLUSIONS

Deficits in social cognition may be modest at the prodromal stage of schizophrenia and may be attributed to prefrontal dysfunction. To prevent or delay transition to psychosis, there is a need for specific preventive strategies targeting social functioning for the UHR group.

The empirical status of the ultra high-risk (prodromal) research paradigm

Given the growth of prodromal research in the past 15 years, the time seems right for assessing whether the ultra high-risk (UHR) research paradigm has delivered on its promise as an approach to identification of individuals at risk for imminent onset of psychosis and as a platform for studies assessing protective benefits of early interventions and for elucidating predictive markers. As demonstrated by the 8 articles on this theme in the present issue, the empirical basis of the prodromal research area has advanced significantly. While there is a lower risk for transition to psychosis in recent studies compared with initial studies, most recent studies still show a 30%-35% risk for psychosis within 1-2 years of follow-up, a rate that is substantially higher than the incidence rate of psychosis among transition age youth in the general population. Moreover, the means with which to improve this predictive equation is rapidly developing, enabled by the collaborative integration of data across multiple sites, the employment of multivariate risk algorithms, and a longitudinal perspective on symptoms, cognition, and functioning. All the initial intervention studies have produced encouraging findings, albeit with small sample sizes and relatively large attrition rates. Nevertheless, the findings in this issue, together with others like them appearing at an increasing rate in the world literature, indicate that the prodromal research area is increasing in maturity and sophistication, providing a useful heuristic for early detection and intervention in those at risk for psychosis.