Normative neuropsychological test performance: effects of age, education, gender and ethnicity

Normative data on neuropsychological test performance for a sample of 131 adults (ages 18-49) is presented. All subjects were native speakers of English screened for past or present medical, neurological and psychiatric disorders, including substance abuse. A broad-based battery including measures of intellectual skills, memory and learning, receptive and expressive language, auditory and visual information processing and attention, sensory processing, motor skills, and self-reported anxiety and depression was administered. Means, standard deviations and percentile rankings for all tests are reported. Regression analyses were computed to consider the concurrent influence of sociodemographic factors on all tests. Significant effects of age (M=27.1 yrs), education (M=14.6 yrs), gender (58% male), and ethnicity (62% white) were observed for relatively few test scores. Younger age at testing was associated with better continuous performance test scores. Higher education levels were associated with higher vocabulary and reading scores. Males had higher WAIS-R Information scores and faster Finger Tapping scores compared to females Ethnicity was associated with Full-scale IQ, and additional tests with a verbal component, e.g., Boston Naming Tests, and non-verbal component, e.g., Drawing Tests. We conclude that sociodemographic factors infrequently account for more than 10% of the variance for many neuropsychological test scores.

Effectiveness of an attention- and memory-training program on neuropsychological deficits in schizophrenia

The effect of two cognitive remediation procedures developed for closed head injury, Attention Process Training (APT) and Prospective Memory Training (PROMT), on neuropsychological deficits in schizophrenia was investigated. Six patients with schizophrenia, varying in baseline intellectual function and symptoms, were studied; three in a remediation condition and three in a nonremediated control condition. Results were evaluated individually for each of the three treated patients. Two of three remediation-treated subjects showed marked improvement on tests of sustained and divided attention. Untreated patients showed little evidence of change in neuropsychological test performance across a similar time interval, when tested on a subset of the measures administered to remediation-treated patients. The results of this study are discussed with a view toward future studies using larger sample sizes with homogeneous subject populations.

Striatal dopamine transporters and cognitive functioning in healthy men and women

OBJECTIVE

There is growing interest in distinguishing the biological bases of sex differences in behavior from environmental influences. Sex hormone levels seem to be related to some cognitive abilities, particularly memory, and the dopaminergic system participates in the mediation of memory. The dopamine transporter is the primary indicator of dopaminergic tone. This study investigated the relationship between cognition and dopamine transporter availability in healthy men and women.

METHOD

Dopamine transporter levels were measured with a technetium-99m radiolabeled analog of cocaine, TRODAT-1, in 66 healthy volunteers (30 men and 36 women). A neuropsychological battery designed to target functions associated with dopaminergic activity was administered during the uptake interval between the radiopharmaceutical injection and image acquisition.

RESULTS

Women and younger participants had higher dopamine availability in the caudate nucleus, and these groups also performed better on verbal learning tasks. Furthermore, dopamine transporter availability was correlated with learning performance within groups. Relationships between dopamine availability in the caudate and putamen and executive and motor functioning were observed in women, but not in men.

CONCLUSIONS

The results provide further evidence for age effects and sex differences in the neuromodulatory influences of dopamine on behavior in humans.

Cognitive impairment and functional status in elderly institutionalized patients with schizophrenia

OBJECTIVE

The relationship of cognitive impairment to functional status in older adults with schizophrenia was investigated.

PATIENTS

Ninety-three psychiatric inpatients with schizophrenia between the ages of 65 and 88 years. Two subsets of this sample, consisting of 48 and 24 patients, were studied with a greater number of assessment instruments.

MEASURES

The Mini-Mental State Examination (MMSE) was used for brief assessment of overall cognitive functioning, and the Psychogeriatric Dependency Rating Scale (PGDRS) was administered to assess functional status. The cognitive test battery from the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) and/or an expanded neuropsychological battery, was given to a subset of the patients.

RESULTS

In the overall sample, patients with greater global cognitive impairment had higher levels of rated impairment on the individual items that comprised the Orientation and Physical, but not Behavior, subscales of the PGDRS. Furthermore, in the two subsamples, specific neuropsychological measures of problem-solving, word list learning, naming and constructional praxis were related to overall measures of outcome.

CONCLUSIONS

Neuropsychological deficit and psychosocial outcome are multi-dimensional entities that relate to one another in complex ways.

Depression in schizophrenia: II. MRI and PET findings

BACKGROUND

Despite consistent descriptions of depressive symptoms in schizophrenia, little is known about their neurobiology. The purpose of this study was to examine the association of depression in schizophrenia with measures of brain anatomy and metabolism.

METHODS

Seventy-nine patients were grouped according to their ratings on the Hamilton Depression Rating Scale (HDRS): > or = 18 was the cutoff between the "high" and "low" depression groups. All patients underwent clinical and magnetic resonance imaging (MRI) evaluation, and a subsample of 37 underwent 2-fluoro-2-deoxy-D-glucose-positron emission tomography (FDG-PET) measurements of cerebral glucose metabolism.

RESULTS

The high depression group had larger bilateral temporal lobe volumes and decreased laterality (left minus right of metabolism in the anterior cingulate).

CONCLUSIONS

The neurobiology of depression in schizophrenia thus seems to share features with major depression due to other disease states.

Lateralized changes in regional cerebral blood flow during performance of verbal and facial recognition tasks: correlations with performance and "effort"

Functional neuroimaging has been used to investigate neural substrates of mnemonic processes, and cerebral blood flow (CBF) measures have been sensitive to activation with memory tasks. Studies of memory with two-dimensional 133Xenon clearance techniques found that word and face recognition tasks produced contralateral CBF changes in mid-temporal cortical regions. This study replicated the activation paradigm, expanding to the three-dimensional resolution of positron emission tomography (PET). Word and face recognition, and a control baseline task were administered to 19 healthy right-handed volunteers (11 men, 8 women) during successive 10 min PET 15O-water measures of CBF. Quantitative CBF rates were calculated with the arterial input function and the equilibrium model. Redistributions of blood flow were compared across tasks-using both absolute and relative (region/ whole brain) CBF. Replicating the 133Xenon clearance findings, CBF was "appropriately" lateralized during task performance (left-right for words > left-right for faces) in the mid-temporal region. Contrary to predictions, the recognition tasks did not activate expected mesolimbic or prefrontal areas. The task-induced CBF changes also correlated with performance. Bilateral CBF in mid-temporal and parahippocampal gyrus regions of interest correlated with the ability to correctly identify word targets (sensitivity). Left-lateralized CBF in the amygdala and hippocampus correlated with better word sensitivity as well as specificity (ability to correctly reject foils). Complementally, right-lateralized CBF in the parahippocampal gyrus correlated with better face specificity performance. In addition, left-lateralized CBF in the amygdala and right-lateralized CBF in the parahippocampal gyrus and hippocampus correlated with "mental effort" indices (task performance relative to basal ability) for word and face memory tasks, respectively. Thus, whereas this recognition task showed the expected lateralized increase in the mid-temporal region and not in frontal and limbic areas, lateralized activation in some of these areas was associated with better performance. Exploratory analyses on other regions showed lateralized changes in one additional temporal region, the occipital-temporal, and several limbic regions.

Vulnerability to tardive dyskinesia development in schizophrenia: an FDG-PET study of cerebral metabolism

An understanding of the development of tardive dyskinesia (TD) may require prospective studies assessing the relationship of brain function measures to behavior. This study was undertaken to determine whether predisposition to the development of TD is related to abnormalities of cerebral 18F-labeled 2-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) measures in schizophrenia. A group of 42 patients without TD underwent FDG PET scanning for measuring cerebral metabolism as well as neuropsychological evaluation and magnetic resonance imaging. Patients were assessed longitudinally for TD development. Eight patients developed TD within 3 years. They were matched to eight patients without TD. Glucose metabolic rates and region/ whole brain ratios were examined in 38 regions of interest per hemisphere. Whole brain metabolism did not differ between the two groups. However, relative hypermetabolism in temporolimbic, brainstem, and cerebellar regions and hypoactivity in parietal and cingulate gyrus were found in the patients who later developed TD in contrast to those who did not. The groups were matched on clinical measures and had similar neuropsychological and neuroanatomic testing results. Thus, differences in the metabolic activity of specific brain regions are associated with vulnerability to TD development.

Relationships between verbal memory performance and the cerebral distribution of fluorodeoxyglucose in patients with schizophrenia

Quantitative resting fluorodeoxyglucose-positron emission tomography scans were performed on 42 patients with schizophrenia. Magnetic resonance imaging-based regions of interest were transposed onto the corresponding positron emission tomography images. Region to whole brain ratios were calculated from the mean regional activity per pixel across both hemispheres (left plus right). Laterality scores were calculated from the difference between the mean activity in homotopic regions of the two hemispheres (left minus right). Subjects were tested contemporaneously with the Logical Memory subtest of the Wechsler Memory Scale. The subtest was scored with modified criteria to provide information about verbal recall, perseverations, and other components of verbal memory. Deficits in recall were associated with increased metabolism in selected regions of the left hemisphere that are known to mediate aspects of verbal memory. The findings support hypotheses suggesting that the left hemisphere is functionally overactive in schizophrenia.

Cerebral blood flow changes in limbic regions induced by unsolvable anagram tasks

OBJECTIVE

The study addressed the question of whether unsolvable as opposed to solvable cognitive problems activate discrete neuronal systems in the human brain.

METHOD

Twelve healthy humans tried to solve unsolvable anagrams. Solvable anagrams and a resting baseline after each anagram task served as control conditions in a within-subject design. Activation was measured with the equilibrium infusion method by using 15O-labeled water and positron emission tomography, with absolute quantitation of anatomically defined regional cerebral blood flow (CBF).

RESULTS

Compared to rest, both anagram tasks increased activity in frontal and temporal regions. The soluble task condition increased hippocampal activation and decreased mammillary bodies activity, while unsolvable anagrams were associated with increased CBF to the mamillary bodies and amygdala and decreased hippocampal activity.

CONCLUSIONS

A limbic network integrating negative emotion and cognition seems reflected in reciprocal diencephalic and limbic activation with solvable and unsolvable anagrams. Since unsolvable anagrams have been used to induce learned helplessness in humans, this finding may provide an initial step toward clarifying its neural substrate.

Mood effects on limbic blood flow correlate with emotional self-rating: a PET study with oxygen-15 labeled water

Positron emission tomography was used to study the effects of experimentally controlled mood states on cerebral blood flow (CBF), measured with the quantitative equilibrium infusion method and 15O-labeled water. Twenty-seven brain regions in each hemisphere were assessed in 16 normal subjects. CBF and heart rate were measured during happy and sad mood induction, and during two nonemotional control conditions: sex differentiation and resting baseline. Valence-specific effects of mood on CBF were obtained for subcortical, but not for frontal-temporal or control regions. CBF increased in left amygdala and decreased in right amygdala during sad mood relative to the averaged control conditions. These changes correlated with shifts toward negative affect. Correlations were opposite for subcortical (negative affect associated with lower left hemispheric CBF) compared with frontal-temporal cortical regions. Results support limbic involvement in regulating emotional states and suggest some reciprocity between subcortical and frontal-temporal regulation of emotional experience.

Resting cerebral glucose metabolism in first-episode and previously treated patients with schizophrenia relates to clinical features

BACKGROUND

Functional neuroimaging can elucidate brain dysfunction in schizophrenia. The frontal, temporolimbic, and diencephalic regions have been implicated. There is a lack of prospective samples of first-episode and previously treated patients followed up longitudinally.

METHODS

Patients and controls (42 per group) were studied. Positron emission tomography with flurodeoxyglucose, cross-registered with magnetic resonance imaging, measured metabolism. Scales assessed clinical features, premorbid adjustment, and outcome.

RESULTS

There were no differences between groups in whole-brain metabolism or regional ratios or in anterior-posterior gradients, but left midtemporal metabolism was relatively higher in patients. This was pronounced in the negative and Schneiderian and absent in the paranoid subtypes. Higher metabolism and lower relative left hemispheric values were associated with better premorbid adjustment and outcome. A higher subcortical-cortical gradient was noted in first-episode patients.

CONCLUSIONS

There are no resting metabolic abnormalities in any brain region, but abnormal gradients are evident. These vary in subtypes, and laterality is associated with functioning. The results support the hypothesis of temporolimbic disturbance in schizophrenia that is all ready present at the onset of illness.

Sex differences in regional cerebral glucose metabolism during a resting state

Positron emission tomography was used to evaluate the regional distribution of cerebral glucose metabolism in 61 healthy adults at rest. Although the profile of metabolic activity was similar for men and women, some sex differences and hemispheric asymmetries were detectable. Men had relatively higher metabolism than women in temporal-limbic regions and cerebellum and relatively lower metabolism in cingulate regions. In both sexes, metabolism was relatively higher in left association cortices and the cingulate region and in right ventro-temporal limbic regions and their projections. These results are consistent with the hypothesis that differences in cognitive and emotional processing have biological substrates.

Neuropsychological deficits in neuroleptic naive patients with first-episode schizophrenia

BACKGROUND

Medication and chronicity have complicated past attempts to characterize the neuropsychological performance of patients with schizophrenia. There have been inconsistencies regarding the pattern, selectivity, and sources of observed deficits. Our objective was to comprehensively examine neuropsychological function in patients with schizophrenia who had never been exposed to neuroleptic medication, and who were experiencing their first episode (FE) of psychosis.

METHODS

Subjects were consecutive recruitments that included 37 patients with FE schizophrenia who were never exposed to neuroleptics. These subjects were compared with 65 unmedicated, previously treated (PT) patients and 131 healthy controls.

RESULTS

The patients groups had nearly identical profiles showing generalized impairment, particularly in verbal memory and learning, attention-vigilance, and speeded visual-motor processing and attention. Verbal memory and learning accounted for most of the variance between patients and controls and removing this effect substantially attenuated all other differences. By contrast, both the FE group and PT group continued to show highly significant deficits in verbal memory and learning after controlling for attention, abstraction, and all other functions. Some functions not typically implicated in schizophrenia (spatial cognition, fine motor speed, and visual memory) were more impaired in the PT group than in the FE group.

CONCLUSIONS

Verbal memory, as a primary neuropsychological deficit present early in the course of schizophrenia, implicates the left temporal-hippocampal system. Neuropsychological evaluations before treatment permit differentiation of primary deficits from changes secondary to medication or chronicity. This is essential for developing a neurobehavioral perspective on schizophrenia.

Neuropsychological function in schizophrenia. Selective impairment in memory and learning

Unmedicated schizophrenic patients (according to DSM-III-R criteria) (n = 36) and age-matched normal controls (n = 36), balanced for parental socioeconomic status, were administered a battery of standardized neuropsychological tests. Patients showed generalized impairment relative to controls and a selective deficit in memory and learning compared with other functions. Selective impairment was not found on tests related to frontal system function (abstraction, verbal fluency, and motor). The observed pattern is consistent with greater involvement of the temporal-hippocampal system, against the background of diffuse dysfunction. Although impairment in memory and learning has been reported, the selectivity and relative severity compared with other behavioral functions have not been recognized. The specificity of this profile merits further examination. These findings lend support to the hypothesized importance of the temporal-hippocampal region in understanding the pathophysiology of schizophrenia.