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Biomedical subjects

R Alliger

Publications and source records attributed to R Alliger.

8 recordsLinked to original sources
PubMed1995

Symptoms of schizophrenia. Methods, meanings, and mechanisms.

BACKGROUND: The "group of schizophrenias," normally referred to with a single nominative, is phenomenologically heterogeneous. Its symptoms represent multiple psychological domains, including perception, inferential thinking, language, attention, social interaction, emotion expression, and volition. Studies of psychopathology have simplified this complex array in several ways, one of which is a subdivision into positive and negative symptoms. METHODS: This study examined the positive vs negative distinction in a sample of 243 patients with schizophrenia or schizophreniform disorder who were evaluated with the Scale for the Assessment of Negative Symptoms and the Scale for the Assessment of Positive Symptoms. A two-stage factor analysis was applied, beginning with a principal components analysis applying varimax rotation, followed by an extension analysis. The purpose of these analyses was to evaluate the correlational relationships of the various symptoms of schizophrenia. RESULTS: The results confirmed previous reports by our group and others suggesting that the symptoms of schizophrenia fall into three natural dimensions, as assessed by the correlational interrelationships: positive symptoms subdivide into psychotic and disorganized dimensions, while a third negative dimension also emerges. CONCLUSION: Because these dimensions have impressive consistency across studies, future work must examine their relationship to clinically relevant concepts such as prognosis or etiology and examine four different aspects: longitudinal course, neural mechanisms, relationship to treatment, and interrelationships in other pathological conditions.

Age of Onset↗
PubMed1994

Further evidence for olfactory identification deficits in schizophrenia.

Forty-seven schizophrenic patients and 36 normal controls, matched for smoking history, were administered the University of Pennsylvania Smell Identification Test (UPSIT) and the Picture Identification Test (PIT). Amongst subjects successfully completing the PIT, non-smoking schizophrenic patients had significantly lower UPSIT scores than non-smoking controls. Smoking history and diagnosis did not interact to produce any pronounced effect. No significant gender difference was found. These results suggest schizophrenics display decreased olfactory identification even if likely confounders are adequately controlled.

Adolescent↗
PubMed1993

The neuropsychology of the prefrontal cortex.

Single photon emission computed tomography with the xenon inhalation technique is used to compare activation of regional cerebral blood flow in frontal brain regions during the performance of four widely used neuropsychological tests: the Continuous Performance Test, the Wisconsin Card Sorting Test, the Tower of London, and Porteus Mazes. Healthy normal volunteers performing these tasks show significant increases in frontal regions during the Continuous Performance Test, the Wisconsin Card Sorting Test, and the Tower of London, but not the Porteus Mazes. Activation produced by the Continuous Performance Test and the Tower of London are mesial and bilateral and may reflect stimulation of midline attentional circuits. The Wisconsin Card Sorting Test produces a left dorsolateral area of prefrontal activation. These findings indicate that regional activation of the frontal lobes occurs in response to cognitive challenges produced through performance of standard neuropsychological tests.

Adult↗
PubMed1993

Intelligence and brain structure in normal individuals.

OBJECTIVE: This study was designed to evaluate the relation between intelligence and a variety of measures of brain structure. METHOD: Magnetic resonance imaging scans were used to measure the volume of the intracranial cavity, cerebral hemispheres, lateral ventricles, temporal lobes, hippocampus, caudate, and cerebellum, as well as the overall volume of gray matter, white matter, and CSF, in 67 healthy, normal volunteers. Intelligence was measured with the Wechsler Adult Intelligence Scale--Revised. RESULTS: Full-scale IQ was found to be significantly correlated with intracranial, cerebral, temporal lobe, hippocampal, and cerebellar volume but not with caudate and lateral ventricle volume. There were also significant correlations of full-scale, verbal, and performance IQ with overall gray matter volume but not with white matter or CSF volume. Gender differences were noted in the pattern and number of correlations between the volume of the brain and its subregions and full-scale, verbal, and performance IQ. CONCLUSIONS: The results suggest that the size of some cerebral structures may account for a significant, but modest, proportion of the variance in human intelligence.

Brain↗
PubMed1992

Hypofrontality in neuroleptic-naive patients and in patients with chronic schizophrenia. Assessment with xenon 133 single-photon emission computed tomography and the Tower of London.

The "hypofrontality hypothesis" has been supported by many neuroimaging studies, but not all, perhaps because of heterogeneity of samples. The present study examined three different samples that permitted assessment of a variety of confounders, such as effects of long-term treatment, chronicity of illness, and presenting phenomenology: (1) 13 neuroleptic-naive schizophrenic patients, (2) 23 nonnaive schizophrenic patients who had been relatively chronically ill but were medication free for at least 3 weeks, and (3) 15 healthy normal volunteers. Regional cerebral blood flow was measured using single-photon emission computed tomography with xenon 133 as the tracer. The control condition consisted of looking at undulating colored shapes on a video monitor, while the experimental task was the Tower of London. We observed the Tower of London to be a relatively specific stimulant of the left mesial frontal cortex (probably including parts of the cingulate gyrus) in healthy normal volunteers. Both the neuroleptic-naive and the nonnaive patients lacked this area of activation, as well as a related one in the right parietal cortex (representing the circuitry specifically activated by the Tower of London). Decreased activation occurred only in the patients with high scores for negative symptoms. These results suggest that hypofrontality is related to negative symptoms and is not a long-term effect of neuroleptic treatment or of chronicity of illness.

Adult↗
PubMed1992

Segmentation techniques for the classification of brain tissue using magnetic resonance imaging.

A technique is described for classifying brain tissue into three components: gray matter, white matter, and cerebrospinal fluid. This technique uses simultaneously registered proton density and T2-weighted images. Samples of each of the three types of tissue are identified on both image sets and used as "training classes"; these tissue samples are then used to generate a linear discriminant function, which is used to classify the remaining pixels in the image data set. Effects of varying the location and number of training classes have been explored; six pairs of training classes have been found to yield a suitable classification. Interrater and test-retest reliability have been examined and found to be good. Intrascanner and interscanner reproducibility has also been evaluated; classification rates are reproducible within the same individual when the same scanner is used, but in this study poor reproducibility occurs when the same individual is scanned on two different scanners. The validity of the technique has been tested by examining correlations between traced and segmented regions of interest, evaluating correlations with age, and conducting phantom studies, in addition to using visual inspection of the classified images as an indication of face validity. From all four perspectives, the method has been found to have good validity. Additional applications, strengths, and limitations are discussed.

Age Factors↗
PubMed1990

Ventricular abnormalities in affective disorder: clinical and demographic correlates.

Ventricle-brain ratio was measured by CT scan in 24 bipolar patients, 27 unipolar patients with major depression, 108 schizophrenic patients, and 75 normal control subjects. The male bipolar patients had significantly larger ventricles, but the depressive patients did not. The findings suggest the possibility that ventricular enlargement in bipolar patients is independent of age, as it appears to be in schizophrenia, whereas in depressed patients it may be related to the aging process. Ventricular enlargement in bipolar patients was not related to relevant clinical correlates, such as response to treatment, history of substance abuse, history of ECT, or cognitive impairment.

Adult↗