Functional brain imaging and aging in schizophrenia

The Emerging Roles for Telomerase in the Central Nervous System

Telomerase, a specialized ribonucleoprotein enzyme complex, maintains telomere length at the 3′ end of chromosomes, and functions importantly in stem cells, cancer and aging. Telomerase exists in neural stem cells (NSCs) and neural progenitor cells (NPCs), at a high level in the developing and adult brains of humans and rodents. Increasing studies have demonstrated that telomerase in NSCs/NPCs plays important roles in cell proliferation, neuronal differentiation, neuronal survival and neuritogenesis. In addition, recent works have shown that telomerase reverse transcriptase (TERT) can protect newborn neurons from apoptosis and excitotoxicity. However, to date, the link between telomerase and diseases in the central nervous system (CNS) is not well reviewed. Here, we analyze the evidence and summarize the important roles of telomerase in the CNS. Understanding the roles of telomerase in the nervous system is not only important to gain further insight into the process of the neural cell life cycle but would also provide novel therapeutic applications in CNS diseases such as neurodegenerative condition, mood disorders, aging and other ailments.

Disconnectivity between Dorsal Raphe Nucleus and Posterior Cingulate Cortex in Later Life Depression

The dorsal raphe nucleus (DRN) has been repeatedly implicated as having a significant relationship with depression, along with its serotoninergic innervation. However, functional connectivity of the DRN in depression is not well understood. The current study aimed to isolate functional connectivity of the DRN distinct in later life depression (LLD) compared to a healthy age-matched population. Resting state functional magnetic resonance imaging (rsfMRI) data from 95 participants (33 LLD and 62 healthy) were collected to examine functional connectivity from the DRN to the whole brain in voxel-wise fashion. The posterior cingulate cortex (PCC) bilaterally showed significantly smaller connectivity in the LLD group than the control group. The DRN to PCC connectivity did not show any association with the depressive status. The findings implicate that the LLD involves disruption of serotoninergic input to the PCC, which has been suggested to be a part of the reduced default mode network in depression.

Similar age-related decline in cortical activity over frontotemporal regions in schizophrenia: a multichannel near-infrared spectroscopy study

OBJECTIVES

Although recent studies have demonstrated that patients with schizophrenia and healthy controls did not differ in the speed of age-related decline in cortical thickness and performances on cognitive tests, hemodynamic changes assessed by functional neuroimaging remain unclear. This study investigated age effects on regional brain cortical activity to determine whether there is similar age-related decline in cortical activity as those observed in cortical thickness and cognitive test performance.

METHOD

A total of 109 patients with schizophrenia (age range: 16-59 y) and 106 healthy controls (age range: 16-59 y) underwent near-infrared spectroscopy (NIRS) while performing a verbal fluency test (VFT). Group comparison of cortical activity was examined using 2-tailed t tests, adopting the false discovery rate method. The relationship between age and cortical activity was investigated using correlational and multiple regression analyses, adjusting for potential confounding variables. A 2-way ANOVA was conducted to investigate differences in the age effects between diagnostic groups.

RESULTS

The patient group exhibited significantly decreased cortical activity in several regions of the frontotemporal cortices. However, slopes of age-dependent decreases in cortical activity were similar between patients and healthy individuals at the bilateral frontotemporal regions.

CONCLUSIONS

Our study showed no significant between-group differences in the age-related decline in cortical activity, as measured by NIRS, over the frontotemporal regions during a VFT. The results of our study may indicate a decrease in cortical activity in a relatively limited period around illness onset rather than continuously progressing over the course of the illness.

Do schizophrenia patients age early?

The etiopathogenesis of schizophrenia is poorly understood. Within the proposed "neurodegeneration paradigm", observations have been put forth for "accelerated aging" in this disorder. This proposition is largely based on the neuroscience research that demonstrates progressive changes in brain as well as other systemic abnormalities supportive of faster aging process in patients with this disorder. In this review, we have summarized the literature related to the concept of early aging in schizophrenia. These studies include P300 abnormalities & visual motion discrimination, neuroimaging findings, telomere dynamics as well as neuropathology of related brain regions. We also propose a role of vitamin D, neuroimmunological changes and elevated oxidative stress as well as mitochondrial dysfunction in addition to the above factors with 'vitamin-D deficiency' as the central paradox. Put together, the evidence supporting early aging in schizophrenia is compelling and this requires further systematic studies.

Aging effects on regional brain structural changes in schizophrenia

BACKGROUND

Although mostly conceptualized as a neurodevelopmental disorder, there is an increasing interest in progressive changes of cognitive deficits and brain structure and function in schizophrenia across the life span.

METHODS

In this study, we investigated age-related changes in regional gray matter using voxel-based morphometry in a sample of 99 patients (age range 18-65 years) with Diagnostic and Statistical Manual of Mental Disorders-IV schizophrenia and 113 healthy controls (age range 19-59 years) using a cross-sectional design.

RESULTS

We found steeper age-related decline in gray matter in patients in a cluster comprising the left superior temporal cortex and adjacent inferior parietal lobule. We then divided the schizophrenia sample in 3 subgroups based on a 3-factor model of psychopathology ratings. Age-related changes were markedly different in each of the 3 subgroups (compared with healthy controls). While patients with predominantly paranoid symptoms showed stronger age-related progression in the left superior temporal cortex and right inferior frontal gyrus, those of the disorganized subgroup had stronger gray matter loss in the left lateral cerebellum, while the predominantly negative subgroup showed minor effects in the left superior temporal gyrus.

CONCLUSIONS

Our findings show that differences in brain structural changes associated with aging diverge between schizophrenia patients and healthy subjects and that different subgroups within a patient sample might be at higher risk of age-related regional gray matter loss.

Anterior and posterior cingulate cortex volume in healthy adults: effects of aging and gender differences

The cingulate cortex frequently shows gray matter loss with age as well as gender differences in structure and function, but little is known about whether individual cingulate Brodmann areas show gender-specific patterns of age-related volume decline. This study examined age-related changes, gender differences, and the interaction of age and gender in the relative volume of cingulate gray matter in areas 25, 24, 31, 23, and 29, over seven decades of adulthood. Participants included healthy, age-matched men and women, aged 20-87 (n=70). Main findings were as follows: (1) The whole cingulate showed significant age-related volume declines (averaging 5.54% decline between decades, 20s-80s). Each of the five cingulate areas also showed a significant decline with age, and individual areas showed different patterns of decline across the decades: Smaller volume with age was most evident in area 31, followed by 25 and 24. (2) Women had relatively larger cingulate gray matter volume than men overall and in area 24. (3) Men and women showed different patterns of age-related volume decline in area 31, at midlife and late in life. By delineating normal gender differences and age-related morphometric changes in the cingulate cortex over seven decades of adulthood, this study improves the baseline for comparison with structural irregularities in the cingulate cortex associated with psychopathology. The Brodmann area-based approach also facilitates comparisons across studies that aim to draw inferences between age- and gender-related structural differences in the cingulate gyrus and corresponding differences in cingulate function.

Global assessment of psychosocial functioning and predictors of outcome in schizophrenia

OBJECTIVE

This study identified predictors of psychosocial outcome in schizophrenia.

METHOD

A mixed group of patients diagnosed with schizophrenia were assessed as part of a routine clinical evaluation. A linear regression analysis was conducted in order to examine the effect of duration of untreated illness, number of previous hospitalisations, history of psychotic episodes and age at illness onset on patients' functioning, as assessed with the Global Assessment of Functioning (GAF) scale.

RESULTS

Number of previous psychotic episodes as well as duration of untreated illness were the strongest predictors of patients' levels of functioning amongst all main outcome measures. Older age at illness onset also predicted poorer functioning. Limitations. A principal limitation of our study is that our sample included predominantly Caucasian males; therefore, any extrapolation to other groups may remain speculative.

CONCLUSIONS

Our preliminary results suggest that psychosocial outcome in schizophrenia may be affected by different factors. Longer history of psychotic episodes emerged as the most significant determinant of poorer outcome while longer duration of untreated illness and older age at illness onset were also associated with detrimental effects. Our findings may reflect the combined influences of neurodevelopmental abnormalities, exposure to psychotropic medication and psychosocial interventions as well as the vicissitudes of natural aging processes embedded in a chronic mental illness.

Decreased default mode neural modulation with age in schizophrenia

OBJECTIVE

Previous studies have shown that patients with schizophrenia have less modulation of the task-positive and default mode neural networks during novelty detection. The diminished modulation may be interpreted as less functional activation of the task-positive network and less functional deactivation of the default mode network. The relationship between network modulation and age has not been assessed in patients with a long duration of illness.

METHOD

Seventeen patients with schizophrenia (age range, from 34 to 60 years) with minimum disorder duration of 15 years and 28 demographically similar comparison subjects (age range, from 36 to 58 years) from the Mind Clinical Imaging Consortium database completed the auditory oddball discrimination task. Independent component analysis identified temporally cohesive but spatially distributed neural networks.

RESULTS

Group membership (F[1, 41] = 7.17, p = 0.011) and the interaction of group and age (F[1, 41] = 6.92, p = 0.012) affected the modulation of the anterior default mode network. Duration of illness was also significantly related to the modulation of the anterior default mode network (t[2, 15] = 2.24, p <0.042). These results were selective for the anterior default mode network and were not replicated with the posterior default mode network.

CONCLUSIONS

These findings show evidence of changes in the temporal modulation of the anterior default mode network with age and duration of illness in patients with schizophrenia. The loss of negative modulation of the anterior default mode network suggests that neural functions in schizophrenia may not be "static" later in the disease course.

Schizophrenia patients lack normal positive correlation between age and brain response during verbal learning

OBJECTIVE

To investigate the differences in the relationship of age to brain function among individuals with schizophrenia and a healthy comparison group. The authors hypothesized that the correlation with age would be more strongly negative among schizophrenia patients, particularly in the frontal cortex.

DESIGN

Cross-sectional measures of functional MRI (fMRI) brain response were correlated with age in both groups.

SETTING

Participants came to university research facilities for testing.

PARTICIPANTS

The authors analyzed data from 30 patients with Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition schizophrenia or schizoaffective disorder ranging in age from 25 to 68 years and 14 healthy comparison participants ranging in age from 21 to 70 years.

MEASUREMENTS

Brain response during word pair learning was measured with fMRI in each voxel of the brain. This measure was correlated with age within each group and the correlations were compared across groups in regions of interest determined a priori and based on a whole-brain analysis. In exploratory analyses, the authors examined the interaction of task performance with age and study group.

RESULTS

The correlations between age and brain response were more positive in the healthy group than in the schizophrenia group in several regions, including right lateral prefrontal cortex and clusters in midline precuneus and right superior temporal gyrus. Interactions with task performance suggest that age effects on brain function relate differently to cognitive output in patients and comparison participants.

CONCLUSIONS

There is no strong evidence that functional brain response during learning changes significantly with age among schizophrenia patients, in contrast to findings of positive associations with age among healthy individuals.

Telomerase levels in schizophrenia: a preliminary study

We previously demonstrated that telomere length was markedly reduced in peripheral blood lymphocytes from individuals with schizophrenia. Since reduced telomere length can be caused by decreased telomerase activity, we quantitated basal telomerase activity in peripheral blood lymphocytes derived from individuals with schizophrenia (n=53), unaffected relatives (n=31) and unrelated controls (n=59). Telomerase activity varied greatly among individuals, suggesting that this enzymatic activity is affected by various factors. We observed a nominally significant decrease in telomerase activity among individuals with schizophrenia compared to unaffected individuals (unaffected relatives and unrelated controls). Further studies are needed to investigate the role of telomerase in schizophrenia.

Effects of sex and normal aging on regional brain activation during verbal memory performance

This study examined the main and interactive effects of age and sex on relative glucose metabolic rate (rGMR) within gray matter of 39 cortical Brodmann areas (BAs) and the cingulate gyrus using (18)FDG-PET during a verbal memory task in 70 healthy normal adults, aged 20-87 years. Women showed significantly greater age-related rGMR decline in left cingulate gyrus than men (BAs 25, 24, 23, 31, 29). Both groups showed a decline in the anterior cingulate--a neuroanatomical structure that mediates effective cognitive-emotional interactions (BAs 32, 24, 25), while the other frontal regions did not show substantial decline. No sex differences in rGMR were identified within temporal, parietal and occipital lobes. Sex differences were observed for rGMR within subcomponents of the cingulate gyrus with men higher in BA25 and BA29, but lower in BA24 and BA 23 compared to women. For men, better memory performance was associated with greater rGMR in BA24, whereas in women better performance was associated with orbitofrontal-BA12. These results suggest that both age-related metabolic decline and sex differences within frontal regions are more marked in medial frontal and cingulate areas, consistent with some age-related patterns of affective and cognitive change.

Changes in glucose metabolism due to aging and gender-related differences in the healthy human brain

Using [(18)F]fluoro-deoxy-glucose-PET, we studied relative metabolic changes due to age- and gender-related differences in the brain of 126 healthy subjects from their twenties to seventies. We used a data-extraction technique, the three-dimensional stereotactic surface projections (3D-SSP) method, to measure metabolic changes with fewer effects of regional anatomic variances. Simple regression analysis revealed significant age-related increases in relative metabolic values in the parahippocampal and amygdala regions in both sexes in their twenties to forties, and significant age-related decreases in both sexes in their fifties to seventies. Relative values in the frontal lobe showed significant age-related decreases in both sexes in their twenties to forties, but these effects were not seen in subjects in their fifties to seventies. Significant gender differences in correlation coefficients of relative values with age were shown in the parahippocampal, primary sensorimotor, temporal, thalamus and vermis regions in subjects in their 20s to 40s, but disappeared in subjects in their twenties to forties, but were not apparent in subjects in their fifties to seventies except in the vermis. Males in their twenties to sixties and females in their fifties showed significant laterality in relative values in the temporal lobes. Our study demonstrated age- and gender-related differences in glucose metabolism in healthy subjects.

Serotonin1A receptors in the pathophysiology of schizophrenia: development of novel cognition-enhancing therapeutics

Serotonin (5-HT) receptors have been suggested to play key roles in psychosis, cognition, and mood via influence on neurotransmitters, synaptic integrity, and neural plasticity. Specifically, genetic evidence indicates that 5-HT(1A), 5-HT(2A), and 5-HT(2C) receptor single-nucleotide polymorphisms (SNPs) are related to psychotic symptoms, cognitive disturbances, and treatment response in schizophrenia. Data from animal research suggest the role of 5-HT in cognition via its influence on dopaminergic, cholinergic, glutamatergic, and GABAergic function. This article provides up-to-date findings on the role of 5-HT receptors in endophenotypic variations in schizophrenia and the development of newer cognition-enhancing medications, based on basic science and clinical evidence. Imaging genetics studies on associations of polymorphisms of several 5-HT receptor subtypes with brain structure, function, and metabolism suggest a role for the prefrontal cortex and the parahippocampal gyrus in cognitive impairments of schizophrenia. Data from animal experiments to determine the effect of agonists/antagonists at 5-HT(1A), 5-HT(2A), and 5-HT(2C) receptors on behavioral performance in animal models of schizophrenia based on the glutamatergic hypothesis provide useful information. For this purpose, standard as well as novel cognitive tasks provide a measure of memory/information processing and social interaction. In order to scrutinize mixed evidence for the ability of 5-HT(1A) agonists/antagonists to improve cognition, behavioral data in various paradigms from transgenic mice overexpressing 5-HT(1A) receptors provide valuable insights. Clinical trials reporting the advantage of 5-HT(1A) partial agonists add to efforts to shape pharmacologic perspectives concerning cognitive enhancement in schizophrenia by developing novel compounds acting on 5-HT receptors. Overall, these lines of evidence from translational research will facilitate the development of newer pharmacologic strategies for the treatment of cognitive disturbances of schizophrenia.

Patterns of anterior cingulate activation in schizophrenia: a selective review

BACKGROUND

Anterior cingulate cortex (ACC) dysfunction is implicated in schizophrenia by numerous strands of scientific investigation. Functional neuroimaging studies of the ACC in schizophrenia have shown task-related hypo-activation, hyper-activation, and normal activation relative to comparison subjects. Interpreting these results and explaining their inconsistencies has been hindered by our ignorance of the healthy ACC's function. This review aims to clarify the site and magnitude of ACC activations in schizophrenia, and sources of their variation.

METHOD

48 studies of mnemonic and executive task-related activations in schizophrenia using both positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) were analyzed.

RESULTS

Abnormal activations in schizophrenia were not restricted to the "cognitive" part of the ACC. Hypoactivations were most common, and were found in all types of tasks. Hyperac-tivations when found, were largely in n-back tasks.

CONCLUSIONS

Hypoactivations cannot be explained by poor performance, more demanding control conditions or chronicity of illness alone. Patients on anti-psychotic medication tended to show both greater ACC activation and better performance, although whether this is directly due to their medication or the resultant reduction in symptoms is unclear. The relationship between ACC rCBF and task performance is not straightforward. Future research should better control confounding factors and incorporate different levels of difficulty.

Abnormal glucose metabolism in the anterior cingulate cortex in patients with schizophrenia

Changes in glucose metabolism were studied in the brains of schizophrenic patients treated with neuroleptics, using [(18)F]fluoro-deoxy-glucose positron emission tomography (FDG-PET). Fourteen male and eight female patients in their thirties and forties were studied in a resting state. Data from FDG-PET were processed with an anatomic standardization method, three-dimensional stereotactic surface projections (3D-SSP), which provided relative glucose metabolic values that mitigated the contamination of brain atrophy. Z-score maps indicating metabolic differences between the patient and control groups were also acquired. Metabolic values in 19 regions were evaluated in the right and left hemispheres. Patients showed decreased values in the frontal cortex, primary sensory regions and anterior cingulate cortex, more in the rostral affective subdivision than the dorsal cognitive subdivision in both hemispheres, and increased metabolic values in left and right basal ganglia, left temporal and right medial parietal regions. Values were more decreased in both anterior cingulate regions, and more increased in the right thalamus in male than female patients, suggesting gender-related dysfunction in the anterior cingulate and thalamus in schizophrenia. FDG-PET demonstrated that schizophrenia may be a disorder with a dysfunction of fronto-striatal-thalamic circuitry including the cingulate cortex.

Regional axonal abnormalities in first episode schizophrenia: preliminary evidence based on high b-value diffusion-weighted imaging

Connectivity has been implicated as a major source of brain abnormality in schizophrenia. The current study focused on first episode schizophrenia to identify possible early pathology in axonal structure. First episode schizophrenic patients and healthy controls were scanned in a 1.5-Tesla scanner during which high b-value diffusion-weighted imaging (DWI) was acquired. Histogram analysis revealed a decrease in overall white matter (WM) tissue, indicating relative axonal abnormality in the schizophrenic group. Subsequent analysis found that this effect was contributed mainly by anterior-prefrontal bundles. Moreover, negative correlations were found between positive and negative symptom severity and whole head WM displacement peak value, implying an overall lesser degree of WM integrity is associated with greater symptom severity. These preliminary results suggest that WM abnormality, as measured by high b-value DWI, is already a significant pathological brain marker in early stage of schizophrenia.

Review of longitudinal functional neuroimaging studies of drug treatments in patients with schizophrenia

We systematically reviewed twenty-one functional neuroimaging studies that used longitudinal designs to investigate the effects of medication treatments on brain functioning among patients with schizophrenia. The studies reviewed were comprised of functional magnetic resonance imaging and positron emission tomography research using a baseline and at least one follow-up. The present review summarizes the different effects of medication and disease status on brain function, with attention to functional normalization, specific drug effects, and comparisons of typical versus atypical antipsychotics. Particular emphasis is given to methodological limitations in the existing literature, including lack of reliability data, clinical heterogeneity among studies, and inadequate study designs and statistics. Suggestions are made for improving future longitudinal neuroimaging studies of treatment effects in schizophrenia.

Anterior cingulate dysfunction during choice anticipation in schizophrenia

The anterior cingulate cortex (ACGC) participates in selective attention, working memory (WM), anticipation, and behavioral monitoring. Subjects with schizophrenia exhibit deficits in these mechanisms during selective attention and WM tasks. However, ACGC dysfunctions have not been specifically investigated during behavioral anticipation, whose deficits may relate to salient schizophrenic features such as foresight abnormalities and impaired social functioning and behavior. We thus studied ACGC function in relation to two aspects of WM, remembering information and anticipating responses, in control and schizophrenic subjects. We measured brain activation in eight subjects with schizophrenia and eight healthy volunteers using functional magnetic resonance imaging. All subjects performed stimulus-response delay tasks with color dots or facial expression diagrams as cues and either 50% or 100% response predictability, which emphasized demands on remembering the cues or anticipating the response for correct performance, respectively. We found a double dissociation of ACGC activation between subject groups and task type. In controls, the ACGC became intensely activated during response anticipation (more extensively and bilaterally when the cues were colors than when they were facial diagrams) but remained at resting activity levels during remembering. In schizophrenic patients, significant ACGC activation was seen only when remembering a percept (more extensively and bilaterally when it was a facial diagram than when it was a color) but not when anticipating a response. These results reveal an ACGC dysfunction during choice anticipation in schizophrenia and suggest that it might underlie the foresight deficits seen in schizophrenic patients.

Thalamic dysfunction in schizophrenia: neurochemical, neuropathological, and in vivo imaging abnormalities

While abnormalities of the prefrontal cortex and temporal lobe structures have typically been associated with the pathophysiology of schizophrenia, recent findings implicate thalamic dysfunction in this illness as well. The thalamus plays a critical role in processing and integrating sensory information relevant to emotional and cognitive functions. Neuropathological and in vivo imaging studies in schizophrenia have identified several structural and metabolic abnormalities in the thalamus, which may contribute to a deficit in sensory processing and be related to psychotic symptomatology. In addition to these postmortem and in vivo imaging studies indicating structural and metabolic changes in the thalamus in schizophrenia, more recent studies have examined the neurochemical substrates that accompany these changes. Much of this work to date has focused on glutamatergic abnormalities in the thalamus, in part because it is a predominant neurotransmitter used in the thalamus, and because glutamatergic dysfunction has been hypothesized to be involved in schizophrenia. Several studies, however, have also examined markers of gamma-aminobutyric acid (GABA) and dopaminergic neurotransmission in the thalamus in schizophrenia. We review these neurochemical findings, as well as the growing body of postmortem and in vivo imaging evidence that supports the hypothesis of thalamic dysfunction in schizophrenia.

Quantification of frontal and temporal lobe brain-imaging findings in schizophrenia: a meta-analysis

Magnetic resonance imaging (MRI) and positron emission tomography (PET) studies of the frontal and temporal lobes in schizophrenia patients and healthy controls have proliferated over the past 2 decades, but there have been relatively few attempts to quantify the evidence. In this meta-analytic review, 155 studies on frontal and temporal lobe neurobiology were synthesized, reflecting results from 4043 schizophrenia patients and 3977 normal controls. Cohen's d was used to quantify case-control differences, and moderator variable analysis indexed the relation of sample and imaging characteristics to the magnitude of these differences. Frontal metabolic and blood flow deficiencies in conjunction with cognitive activation tasks ("hypofrontality") emerged as the strongest body of evidence, demonstrating abnormalities that distinguish approximately half of schizophrenia patients from healthy people. Most case-control comparisons with structural and functional imaging yield small and in many cases unstable findings. Technical scanning parameters like slice thickness and magnet strength did not vary with case-control differences consistently across the meta-analyses. However, patient sample characteristics including sample size, handedness and gender composition emerged frequently as moderators of brain-imaging effect sizes.

Electrophysiological signs of reduced prefrontal response control in schizophrenic patients

The prefrontal cortex is considered as a brain region important in the etiopathogenesis of schizophrenic disorders. Based on converging results from different research areas, the prefrontal cortex is regarded as the anatomical and functional representation of response control under physiological conditions. In previous studies, a robust electrophysiological marker for the investigation of response control in healthy control subjects was validated. This parameter was termed NoGo anteriorisation and consists of a more anterior peak of the event-related potentials during the inhibition of a prepared motor response (NoGo condition within the Continuous Performance Test) than during its execution (Go condition). The present study investigated these brain electrical correlates of response control in 19 schizophrenic patients and 19 age- and sex-matched healthy subjects. Compared to control subjects, the event-related potentials in schizophrenic patients were located more anterior in the Go condition and, as a trend, more posterior in the NoGo condition. The NoGo anteriorisation was strongly reduced in the schizophrenic group. On a qualitative level, the NoGo anteriorisation was present in all control subjects, but not in eight of the 19 patients. The results were interpreted as an indication of a disturbed prefrontal response control in schizophrenic patients. Further studies will clarify whether this method may be useful as a global test of hypofrontality in different groups of chronic schizophrenias, or as a quantifiable measure of an affected response control system, especially in catatonic subgroups.

Age and neuropsychologic function in schizophrenia: a decline in executive abilities beyond that observed in healthy volunteers

BACKGROUND

Kraepelin originally conceptualized schizophrenia as a degenerative brain disorder. It remains unclear whether the illness is characterized by a static encephalopathy or a deterioration of brain function, or periods of each condition. Assessments of cognitive function, as measured by neuropsychologic assessment, can provide additional insight into this question. Few studies of patients with schizophrenia have investigated the effect of aging on executive functions, in an extensive neuropsychologic battery across a wide age range, compared to healthy volunteers.

METHODS

We examined the interaction of aging and neuropsychologic function in schizophrenia through a cross-sectional study in patients (n = 87) and healthy control subjects (n = 94). Subjects were divided into three age groups (20-35, 36-49, and 50-75), and performance on an extensive neuropsychologic battery was evaluated.

RESULTS

Compared to control subjects, patients with schizophrenia demonstrated similar age-related declines across most neuropsychologic functions, with the exception of abstraction ability, in which significant evidence of a more accelerated decline was observed.

CONCLUSIONS

These results are consistent with previous reports indicating similar age effects on most aspects of cognition in patients with schizophrenia and healthy adults, but they support the hypothesis that a degenerative process may result in a more accelerated decline of some executive functions in older age in schizophrenia.

Neuropharmacology and receptor studies in the elderly

Functional brain imaging has provided unique and exciting opportunities to strengthen our knowledge of the biologic substrate of the aging brain and neuropsychiatric disorders. Positron emission tomography (PET) is a particularly powerful tool for quantifying the neurobiologic correlates of cognition, mood, and behavior. Initial PET studies of aging, psychiatric disorders, and neurodegenerative disease focused primarily on generalized physiologic parameters such as cerebral blood flow and metabolism, and early neuroreceptor imaging studies relied on relatively nonselective markers. New, selective receptor radioligands now offer a previously inaccessible means to investigate the dynamic relationships among neurochemistry, aging, and psychopathology in vivo. This approach has substantial advantages over peripheral (platelet and cerebrospinal fluid) markers, neuroendocrine challenge studies, animal models, and postmortem receptor binding assays. Advances in tracer kinetic modeling, magnetic resonance imaging facilitated PET image analysis, radiochemistry techniques, instrumentation, and image processing have helped pave the way for increased emphasis on functional imaging studies of neuropsychiatric disorders. The capability to correct PET image data for the confounding effect of cerebral atrophy permits relationships among age-related brain changes and neurobiologic disease mechanisms to be more accurately examined in the elderly.

Effects of age, medication, and illness duration on the N-acetyl aspartate signal of the anterior cingulate region in schizophrenia

The authors performed a MRSI study of the anterior cingulate gyrus in 19 schizophrenic patients under stable medication and 16 controls in order to corroborate previous findings of reduced NAA in the anterior cingulate region in schizophrenia. Furthermore, correlations between NAA in the anterior cingulate gyrus and age or illness duration have been determined. A decreased NAA signal was found in the anterior cingulate gyrus of patients compared to controls. Subdividing the patient group into two groups depending on medication revealed that the group of patients receiving a typical neuroleptic medication showed a lower mean NAA in comparison to the group of patients receiving atypical antipsychotic drugs. No significant group differences in the creatine and phosphocreatine signal or the signal from choline-containing compounds were found. The NAA signal significantly correlated with age, and therefore, individual NAA values were corrected for the age effect found in the control group. The age-corrected NAA signal in schizophrenia correlated significantly with the duration of illness. The detected correlations of NAA decrease with age and illness duration are consistent with recent imaging studies where progressing cortical atrophy in schizophrenia was found. Further studies will be needed to corroborate a possible favorable effect of atypical antipsychotics on the NAA signal.

Multimodal imaging in psychiatry: the electroencephalogram as a complement to other modalities

The use of different imaging modalities provides the clinician and researcher with different views of anatomy and physiology at unprecedented levels of detail. Multimodal imaging allows for noninvasive measurement of structure and function in humans during complex behavior, and thus provides information about the inner workings of the brain previously unavailable. The present paper examines the various imaging techniques available, and describes their application to the clinic-in the case of epilepsy-and to research-in the case of schizophrenia. Because the electroencephalogram has a dynamic response in milliseconds, it provides the best temporal sensitivity of functional measures of brain activity. When coupled with high-resolution magnetic resonance imaging measures of brain structure, this multimodal approach provides a powerful tool for understanding brain activity. Clinically, the use of multimodal imaging has provided greater precision in localization of the epileptogenic focus. For researchers attempting to determine the underlying causes of schizophrenia, the use of multimodal imaging has helped lead the field away from a specific lesion view to a more distributed system abnormality view of this disorder.