Changes in regional cerebral blood flow due to cognitive activation among patients with schizophrenia

The Possible Link between GABAergic Dysfunction and Cognitive Decline in a Patient with Idiopathic Hypoparathyroidism

Idiopathic hypoparathyroidism (IHP) is accompanied by cognitive impairment. We report the case of a 70-year-old IHP patient with cognitive disturbance. Brain computed tomography showed bilateral calcification in basal ganglia, thalamus, and cerebellum. Neuropsychological assessment revealed low scores for intelligence, memory, and perseverative errors. Brain positron emission tomography showed a significant reduction in [(18)F]-Fludeoxyglucose (FDG) uptake in bilateral frontal, left temporal and parietal cortices, along with a marked reduction in [(11)C]-flumazenil binding in left frontal, temporal, parietal, and bilateral cerebellum. These findings suggest cognitive impairment in IHP may be ascribed to GABAergic dysfunction, thus leading to, or coexisting with, cerebral hypometabolism.

Brain perfusion single photon emission computed tomography in major psychiatric disorders: From basics to clinical practice

Brain single photon emission computed tomography (SPECT) is a well-established and reliable method to assess brain function through measurement of regional cerebral blood flow (rCBF). It can be used to define a patient's pathophysiological status when neurological or psychiatric symptoms cannot be explained by anatomical neuroimaging findings. Though there is ample evidence validating brain SPECT as a technique to track human behavior and correlating psychiatric disorders with dysfunction of specific brain regions, only few psychiatrists have adopted brain SPECT in routine clinical practice. It can be utilized to evaluate the involvement of brain regions in a particular patient, to individualize treatment on basis of SPECT findings, to monitor the treatment response and modify treatment, if necessary. In this article, we have reviewed the available studies in this regard from existing literature and tried to present the evidence for establishing the clinical role of brain SPECT in major psychiatric illnesses.

Autonomic regulation predicts performance on Wisconsin Card Sorting Test (WCST) in adults with schizophrenia

Although executive functions have been associated with autonomic regulatory capacity in healthy adults, there appear to be no reports of these relations in adults with schizophrenia to date. We tested whether baseline autonomic regulation was associated with performance on the Wisconsin Card Sorting Test (WCST) in a group of 42 stable community outpatients with schizophrenia. Patients exhibited faster resting heart rates and lower respiratory sinus arrhythmia (RSA) than age-matched controls, consistent with previous research. Patients also completed relatively few WCST categories and made many perseverative errors, replicating prior studies. Within the patient group, relatively better WCST performance was associated with slower resting heart rate and higher RSA, suggesting that inefficient executive and autonomic functioning in schizophrenia may be linked. WCST performance and autonomic regulatory capacity were further reduced in a subset of patients receiving clozapine, but relations between WCST performance and autonomic regulatory parameters did not differ from those of other patients. Findings extend the neurovisceral integration model of autonomic regulation to adults with schizophrenia and attest to the reliability of the model.

DHA-rich oil modulates the cerebral haemodynamic response to cognitive tasks in healthy young adults: a near IR spectroscopy pilot study

The impact of dietary n-3 PUFA on behavioural outcomes has been widely researched; however, very little attention has been given to their impact on brain functioning in physiological terms. A total of twenty-two healthy adults took part in this double-blind, placebo-controlled study, wherein the cerebral haemodynamic effects of 12 weeks of daily dietary supplementation with either 1 g DHA-rich or 1 g EPA-rich fish oil (FO) or placebo (1 g olive oil) were assessed. Relative changes in the concentration of oxygenated Hb (oxy-Hb) and deoxygenated Hb were assessed in the prefrontal cortex using near IR spectroscopy (NIRS) during the performance of four computerised cognitive tasks. Supplementation with DHA-rich FO, in comparison with placebo, resulted in a significant increase in the concentrations of oxy-Hb and total levels of Hb, indicative of increased cerebral blood flow (CBF), during the cognitive tasks. In comparison, no effect on CBF was observed following supplementation with EPA-rich FO, where concentration changes in the chromophores followed the same pattern as placebo. These encouraging pilot data warrant further application of NIRS in this area.

Amphetamine-related improvement in executive function in patients with chronic schizophrenia is modulated by practice effects

BACKGROUND

Amelioration of cognitive impairment is an important treatment goal for a broad range of neuropsychiatric disorders, including schizophrenia. One critical issue in clinical trial design is the extent to which repeated exposure to cognitive tests (i.e., practice effects) may lead to improvement in performance on the cognitive tests in the absence of any true treatment effect. The current study examined the extent to which practice effects on a measure of executive function may influence the sensitivity of that task to detecting the cognitive-enhancing effects of a single acute dose of d-amphetamine in individuals with chronic schizophrenia.

METHODS

Twenty-four men with chronic schizophrenia were randomized to receive a constant or random/matched alternate form version of a hidden maze learning measure of executive function (Groton Maze Learning Test; GMLT) on four separate occasions in one month. They also completed a measure of psychomotor speed. Using a double-blind, placebo-controlled, parallel groups design, cognitive function following administration of a single dose of d-amphetamine (20mg p.o) or placebo was then assessed.

RESULTS

The group who received the constant-pathway version of the GMLT showed a large practice effect (d = 2.05) over four practice sessions. Consequently, they did not evidence any improvement on the GMLT following d-amphetamine administration. In contrast, the group who received the random/matched alternate version of the GMLT showed a statistically significant and large effect size (d = .84) improvement on this measure. Both groups showed d-amphetamine-related improvement on a measure of psychomotor speed.

CONCLUSIONS

Results of this study suggest that practice effects associated with repeated exposure to a cognitive test could obscure the sensitivity of the test to detecting true treatment-related cognitive improvement.

Neural correlates of set-shifting: decomposing executive functions in schizophrenia

BACKGROUND

Although there is considerable evidence that patients with schizophrenia have impaired executive functions, the neural mechanisms underlying these deficits are unclear. Generation and selection is one of the basic mechanisms of executive functioning. We investigated the neural correlates of this mechanism by means of functional magnetic resonance imaging (fMRI) in patients with schizophrenia and healthy controls.

METHODS

We used the Wisconsin Card Sorting Test (WCST) in an event-related fMRI study to analyze neural activation patterns during the distinct components of the WCST in 36 patients with schizophrenia and 28 controls. We focused our analyses on the process of set-shifting. After participants received negative feedback, they had to generate and decide on a new sorting rule.

RESULTS

A widespread activation pattern encompassing the inferior and middle frontal gyrus, parietal, temporal and occipital cortices, anterior cingulate cortex (ACC), supplementary motor area, insula, caudate, thalamus and brainstem was observed in patients with schizophrenia after negative versus positive feedback, whereas in healthy controls, significant activation clusters were more confined to the cortical areas. Significantly increased activation in the rostral ACC after negative feedback and in the dorsal ACC during matching after negative feedback were observed in schizophrenia patients compared with controls. Controls showed activation in the bilateral dorsolateral prefrontal cortex (Brodmann area 46), whereas schizophrenia patients showed activation in the right dorsolateral prefrontal cortex only.

LIMITATIONS

All patients were taking neuroleptic medication, which has an impact on cognitive function as well as on dopaminergic and serotonergic prefrontal metabolism.

CONCLUSION

Our data suggest that, in patients with schizophrenia, set-shifting is associated with increased activation in the rostral and dorsal ACC, reflecting higher emotional and cognitive demands, respectively.

Use of an acute challenge with d-amphetamine to model cognitive improvement in chronic schizophrenia

There is general agreement that pharmacologic improvement of cognition in chronic schizophrenia is a worthwhile therapeutic goal. Accordingly, there has been careful consideration about how neuropsychological methods can be used to detect improvement in cognition in people with schizophrenia. However, little data are available on the nature and magnitude of cognitive improvement that can occur with adjunctive therapeutic interventions.This double-blind, placebo-controlled crossover study examined the nature and magnitude of cognitive enhancement associated with a single-dose administration of d-amphetamine in 32 adult men with schizophrenia using a set of tasks developed specifically for detecting treatment-related change in cognitive function. Relative to placebo, acute d-amphetamine administration was associated with clinically meaningful improvement on measures of executive function and visual attention and vigilance, and with modest improvements on a measure of speed of processing. These results suggest that a brief computerized cognitive test battery designed for repeat administration, in combination with a statistical approach that emphasizes individual-level change, provides a sensitive approach to detecting the effect of cognitive-enhancing medications in people with chronic schizophrenia.

Anhedonia and ambivalence in schizophrenic patients with fronto-cerebellar metabolic abnormalities: a fluoro-d-glucose positron emission tomography study

OBJECTIVE

Prefrontal and cerebellar abnormalities have been associated with higher cognitive deficits in schizophrenia. The current study aimed to show whether or not schizophrenic patients with fronto-cerebellar functional abnormalities show more anhedonia or ambivalence.

METHODS

Regional cerebral metabolic activity was measured using fluoro-D-glucose positron emission tomography and was compared between 24 patients with chronic schizophrenia and 22 healthy normal volunteers. The existence of regional prefrontal hypofunction and regional cerebellar hyperfunction was investigated in each patient. Demographic and clinical variables including the emotional self-report scales were compared between the subgroups of the patients categorized according to the existence and the absence of the regional dysfunctions.

RESULTS

Comparisons between each patient and the total normal controls revealed that 14 of the total twenty-four patients had regional hypofrontal functions, whereas 11 patients had regional hypercerebellar functions. Patients with prefrontal hypofunction showed more severe anhedonia than those without prefrontal hypofunction, whereas patients with cerebellar hyperfunction compared to those without cerebellar hyperfunction had more severe ambivalence.

CONCLUSION

It seems that fronto-cerebellar abnormalities may be associated with cardinal emotional features of schizophrenia, such as anhedonia and ambivalence.

Is schizophrenia the price of human central nervous system complexity?

The purpose of the present study was to determine if there is evidence to support the hypothesis that schizophrenia is a human-specific disorder associated with the need for highly complex central nervous system (CNS) development. A review was therefore undertaken of published literature relevant to the identification of human-specific CNS development. There was no clear evidence found at the macroscopic, microscopic or molecular level that suggests unique changes have occurred in the evolution of the human CNS. Rather, highly significant changes in the size of the frontal lobe, increases in numbers of specific cell types, changes in gene expression and changes in genome sequence all seem to be involved in the evolution of the human CNS. Human-specific changes in CNS development are wide ranging. The modification in CNS structure and function that has resulted from these changes affects many pathways and behaviours that appear to be also affected in subjects with schizophrenia. Therefore there is evidence to support the hypothesis that schizophrenia is a disease that develops because of derangements to human-specific CNS functions that have emerged since our species diverged from non-human primates.

The application of computerized WCST and long-term evoked potentials for schizophrenia analysis

The purpose of this study is to characterize the cognitive functions of schizophrenic patients using different auditory and visual event-related potentials (ERPs) based on Wisconsin card sorting test (WCST). From the experimental results, it is indicated that there is a slowness of automatic cognitive processing and controlled cognitive processing during WCST in comparison with ERPs for schizophrenic patients.

The effects of clozapine on cognitive function and regional cerebral blood flow in the negative symptom profile schizophrenia

OBJECTIVE

Cognitive function and regional cerebral blood flow (rCBF) were studied in negative symptom profile schizophrenic patients by using WCST and SPECT.

METHODS

Twenty-one schizophrenic patients who matched the criteria of Andreason's negative symptom profile received SPECT and WCST, and then were treated with clozapine for 8 consecutive weeks. There were 28 and 12 normal subjects as the control groups of WCST and SPECT, respectively.

RESULTS

Compared with controls, significantly poorer performance on total trials of category (TT), persevering errors (PE), and non-persevering errors (NPE) of WCST were found in schizophrenia (p < 0.05). The total score of the scale for assessment negative symptoms (SANS) was significantly related with poor TT (r = 0.45, p < 0.01) and PE performance (r = 0.45, p < 0.01). The poor TT, PE, and NPE tasks of WCST and SANS scores in the negative schizophrenic patients were significantly improved through clozapine treatment (p < 0.05). The schizophrenic patients had a significantly lower rCBF in bilateral frontal and temporal lobes and lower change rate of rCBF in bilateral frontal lobes during WCST compared to normal controls (p < 0.05).

CONCLUSIONS

Negative symptom profile schizophrenia has cognitive deficits and lower rCBF in bilateral frontal and temporal lobes, which suggests that negative symptom profile schizophrenic patients have hypofrontality. Clozapine can improve negative symptoms and improve cognitive dysfunction, although it cannot improve reduced rCBF in the frontal lobes.

The Wisconsin Card Sort Test and P300 responses to novel auditory stimuli in schizophrenic patients

The authors studied the relationship between performance on the Wisconsin Card Sort Test (WCST) and P300 activity in schizophrenics and normal controls. Fourteen male predominantly medicated schizophrenics and matched non-ill controls were administered the WCST and tests of temporal lobe (delayed verbal and spatial memory) and general intellectual functioning (Shipley). Patients were rated with negative and positive symptom scales extracted from the Brief Psychiatric Rating Scale. Subjects performed a tone discrimination task requiring identification of rare targets in both a standard oddball paradigm and a three-stimulus paradigm that included rare novel sounds. Reference independent data from 16 scalp electrodes yielded Global Field Power (GFP), from which P300 latency was determined. P300 amplitude measures included amplitude at this identified latency as well as amplitude integrated over a 100 ms time window centered over it. These amplitude measures were examined at six selected electrode locations. Schizophrenics produced smaller P300 responses that tended to be slower, but there were no group differences in the relationships between neuropsychological performance and P300 responses. Across diagnostic groups percent perseverative errors predicted lower integrated and peak P300 amplitude during the novel but not the standard oddball paradigm. The effect on integrated P300 amplitude was localized to anterior leads after novel stimuli. Negative symptoms predicted lower WCST performance, lower integrated P300 amplitude, and smaller GFP after novel stimuli. Positive symptoms predicted reduced overall GFP and specific but inconsistent reductions in parietal P300 amplitude. The results suggest relationships between dorsolateral prefrontal competence, P300 activity in response to stimulus novelty, and negative symptoms in schizophrenic patients, paralleling findings obtained from blood flow and other measures of brain activity.

Do schizophrenia patients make more perseverative than non-perseverative errors on the Wisconsin Card Sorting Test? A meta-analytic study

The Wisconsin Card Sorting Test (WCST) is widely used to explore executive functions in patients with schizophrenia. Among other findings, a higher number of perseverative errors has been suggested to implicate a deficit in task switching and inhibitory functions in schizophrenia. Many studies of patients with schizophrenia have focused on perseverative errors as the primary performance index in the WCST. However, do schizophrenia patients characteristically make more perseverative than non-perseverative errors compared with healthy controls? We reviewed the literature where schizophrenia patients were engaged in the WCST irrespective of the primary goal of the study. The results showed that while both schizophrenia patients and healthy participants made more perseverative than non-perseverative errors, the contrast between perseverative and non-perseverative errors is higher in schizophrenia patients only at a marginal level of significance. This result suggests that schizophrenia patients do make a comparable number of non-perseverative errors and cautions against simplistic interpretation of poor performance of schizophrenia patients in WCST as entirely resulting from impairment in set-shifting or inhibitory functions.

Hypofrontality in schizophrenia: a meta-analysis of functional imaging studies

OBJECTIVE

Hypofrontality is not a well-replicated finding in schizophrenia either at rest or under conditions of task activation.

METHOD

Studies comparing whole brain and frontal blood flow/metabolism in schizophrenic patients and normal controls were pooled. Voxel-based studies were also combined to examine the pattern of prefrontal activation in schizophrenia.

RESULTS

Whole brain flow/metabolism was reduced in schizophrenia to only a small extent. Resting and activation frontal flow/metabolism were both reduced with a medium effect size. Duration of illness significantly moderated resting hypofrontality, but the moderating effects of neuroleptic treatment were consistent with an influence on global flow/metabolism only. Pooling of voxel-based studies did not suggest an abnormal pattern of activation in schizophrenia.

CONCLUSION

Meta-analysis supports resting hypofrontality in schizophrenia. Task-activated hypofrontality is also supported, but there is little from voxel-based studies to suggest that this is associated with an altered pattern of regional functional architecture.

In vivo31P NMR spectroscopy shows an increase in glycerophosphorylcholine concentration without alterations in mitochondrial function in the prefrontal cortex of medicated schizophrenic patients at rest

The (31)P NMR localised method was used to study the metabolism of phospholipid and high energy phosphate in the prefrontal cortex. The spectra were taken from patients with schizophrenia (11 males) receiving neuroleptic medication, and were compared to normal controls (15 males). Their spectral intensities were analysed using a non-linear least-squares method with a prior knowledge of the fixed chemical shifts and linewidths, leading to further resolution into resonances of glycerophosphorylethanolamine (GPE), glycerophosphorylcholine (GPC), phosphorylethanolamine (PE) and phosphorylcholine (PC). The metabolite concentrations were calculated referring to the spectral intensities of phosphate phantoms with known concentrations. T1 values of phantom and cerebrum were estimated from a series of localised inversion recovery spectra to correct for the signal saturation effects. The schizophrenic patients showed an increased concentration of GPC but not GPE, PE or PC. Furthermore, no difference was observed regarding the concentration of high-energy phosphates such as phosphocreatine, inorganic phosphate and ATP. The patients did not show any differences in mitochondrial function such as phosphorylation potential and the ratio of the rate of ATP synthesis. Thus, an increase in GPC concentration in the prefrontal cortex could be characteristic of the pathophysiology of schizophrenia with mild negative symptoms.

Total length of nerve fibers in prefrontal and global white matter of chronic schizophrenics

It has been suggested that the dysfunction of the prefrontal cortex in schizophrenics is due to dysfunctional connections between the prefrontal cortex and more posterior structures. The present study uses a recent stereological method that allows quantitation of the myelinated nerve fibers in the brain white matter. As especially the prefrontal region is of interest in schizophrenics, the prefrontal white matter was quantitated separately. The total length of nerve fibers in post-mortem brains was estimated from eight male chronic schizophrenics and nine male controls (age-range: 40-81 years). Samples were taken systematically and randomly from both the entire white matter and selectively from the prefrontal white matter. The biopsies were rotated randomly before sectioning to avoid bias due to the anisotropic nature of nerve fibers. The fibers were counted at light microscopic level at about 10,000 x magnification and the fiber diameter of each counted fiber was measured to get the size distribution of the fibers. The schizophrenics had a total of 129,000 km myelinated fibers in the white matter and 25,700 km in the prefrontal white matter, which was non-significantly different from a total of 137,000 km in the entire white matter and 27,600 km in the prefrontal white matter in controls. The size distribution of the fibers in schizophrenics was within normal limits compared to controls. Our results do not show a larger loss of nerve fibers in neither the white matter globally or in the prefrontal white matter of schizophrenics.

The effect of melperone, an atypical antipsychotic drug, on cognitive function in schizophrenia

Melperone, a butyrophenone, has been shown to possess atypical antipsychotic properties, i.e. ability to produce an antipsychotic effect in man at doses that cause minimal extrapyramidal side effects. In addition, melperone shares the following with other atypical antipsychotic drugs: (1) effectiveness for ameliorating negative symptoms; (2) no prolactin elevation; and (3) effectiveness in the treatment of some patients with neuroleptic-resistant schizophrenia. Other atypical antipsychotic drugs have been reported to improve cognitive function. This study was performed to investigate the effect of melperone on cognitive function. Nineteen patients with schizophrenia or schizoaffective disorder, including 11 neuroleptic-resistant patients, were treated with melperone for 6 weeks. A comprehensive neurocognitive test battery and psychopathological ratings (Brief Psychiatric Rating Scale, BPRS) were administered at baseline and after 6 weeks of melperone treatment. Treatment with melperone was associated with improvement in executive function, as measured by the Wisconsin Card Sorting Test (WCST)-Categories and WCST-Percent Perseveration. On the other hand, visuospatial manipulation, as measured by the Wechsler Intelligent Scale for Children-Revised (WISC-R) Maze, worsened during melperone treatment. There were no significant changes in other domains of cognition, i.e. verbal learning and memory, verbal working memory, verbal fluency and sustained attention. Scores of WCST-Categories and Perseveration at 6 weeks were predicted from the relevant cognitive test scores at baseline and the change in BPRS Total and Positive scores. These results suggest the usefulness of melperone for facilitating work and social function in patients with schizophrenia. The differences in the cognition-enhancing abilities between melperone and clozapine are discussed.