Callosal transfer in schizophrenia: Too much or too little?

Evidence from diverse sources has pointed to an abnormality in callosal transfer in schizophrenia. To examine this further, a test was devised that measures Stroop interference and facilitation within and between the cerebral hemispheres. 46 heterogeneous schizophrenic patients were tested, and it was found that lateralized Stroop effects were equivalent in the left and right hemispheres and did not differ from normal or psychiatric (affective disorder) control Ss. In control Ss, Stroop effects that required interhemispheric transfer of coded information were reduced relative to those requiring intrahemispheric transfer, whereas among schizophrenic Ss, greater Stroop effects were found in the interhemispheric condition, presumably reflecting increased callosal connectivity. An index of callosal transfer did not correlate with gender, age, or IQ in any of the groups, nor did it relate to clinical characteristics in the schizophrenic Ss. The results support a specific functional abnormality of excessive callosal transfer in schizophrenia, though its role in pathogenesis remains unspecified. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contributions of frontal system dysfunction to memory and perceptual abilities in Parkinson's disease.

Tested (1) the hypothesis that Parkinson's disease (PD), thought to result in disturbed neuronal outflow from the striatum, leads to circumscribed deficits in cognitive functions presumed to be dependent on the functional integrity of the frontal lobes and (2) whether such deficits could account for previously reported memory and visuoperceptual difficulties in PD. 19 nondemented PD patients were demographically matched to 19 normal elderly control Ss. Three categories of tests were given: (1) tests sensitive to frontal system dysfunction, (2) tests of learning and memory, and (3) tests of visuoperceptual and visuoconstructive skills. Nondemented PD patients demonstrated selective deficits on frontal system tasks; tests of learning and memory and of visuoperceptual and visuoconstructive skill were not significantly impaired once performance on the frontal related tasks was statistically covaried. Results are consistent with the striatofrontal outflow model of neuropsychological impairment in nondemented PD patients. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Experimental and clinical neuropsychological measures of prefrontal dysfunction in schizophrenia.

Eighteen chronic schizophrenia patients and 14 controls were given tests that have been linked primarily to ventral (orbitofrontal) or to dorsolateral prefrontal dysfunctions in neurological patients and in nonhuman animal Ss having discrete frontal lesions. Schizophrenia patients were significantly impaired on object alternation and delayed alternation tasks but not on classical delayed response (DR). Schizophrenia patients performed well on the classical version of the DR task and their DR performance correlated significantly with measures of sustained attention. Future research is needed to interpret the contributions of attention, interference, and memory load to neuropsychological performance in schizophrenia. Additional studies are required to determine whether the frontal deficits reflect diffuse brain damage, circumscribed prefrontal damage, or damage in other brain regions having prefrontal connections. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cognitive resources and dual-task interference effects at retrieval in normal people: The role of the frontal lobes and medial temporal cortex.

Conducted 3 experiments to examine the hypothesis that concurrent secondary tasks at retrieval will interfere more with long-term, episodic memory functions involving the frontal lobes than those involving the medial temporal lobes hippocampus (MTL/H). The rationale is that strategic retrieval processes mediated by the frontal lobes place greater demands on cognitive resources than do relatively automatic associative retrieval processes (ecphory) mediated by the temporal lobes. In Exps 1 and 2, sequential finger tapping was performed at encoding, at retrieval, at both, or at neither. Recall of a categorized list of 16 words from the California Verbal Learning Test in Exp 1, and release from proactive inhibition (PI) in Exp 2, both being tests that involve the frontal lobes, were impaired if normal Ss tapped at both encoding and retrieval. Concurrent tapping had little effect on rate of learning in Exp 1 and on total words recalled during the buildup of PI in Exp 2, both of which are indices that are affected more by MTL/H than by frontal lesions. In Exp 3, tapping by normal Ss affected letter fluency, a test more sensitive to frontal lobe than temporal lobe damage, but not category fluency, for which the reverse is true. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparison of the contributions of the frontal and parietal association cortex to spatial localization in rats.

Compared 15 rats with lesions of the medial frontal, orbital frontal, or parietal cortex with 5 rats with complete removal of the neocortex and 5 normal controls on 3 spatial tasks: Morris water task, radial arm maze, and spatial reversals in a Grice box. Decortication produced severe impairments in the acquisition of all 3 tasks. Ss with parietal cortex lesions were relatively unimpaired at any of the tasks, although they had a significant deficit on the spatial reversal task and had a short-term memory impairment on the radial arm maze. In contrast, Ss with medial frontal lesions had a significant, but relatively mild, impairment on the radial arm maze and were poor at learning the water task. Ss with orbital frontal lesions were nearly as impaired on the radial arm maze and water task as decorticate Ss. Results suggest that the frontal and parietal cortex of rats play different roles in the control of spatial orientation but do not support the view that egocentric and allocentric spatial orientation are related to frontal and parietal mechanisms, respectively. In addition, results suggest that the frontal cortex plays a larger role in the control of spatially guided behavior than has been previously recognized and that both the medial frontal and the orbital frontal cortex play a dissociable role in the control of spatial orientation. (60 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Priming effects in schizophrenia: Associative interference and facilitation as a function of visual context.

Irrelevant stimuli that flank a fixated target may cause either facilitation or interference with target classification. 20 schizophrenic patients, 20 depressed control patients, and 20 normal control Ss were compared on a flanker priming task that involved the linear display of a target surrounded by 2 flanking letters or digits. Choice reaction time (RT) between letter and digit targets was examined as a function of flanker condition and onset asynchrony between flankers and target. Facilitative priming occurred only with prior exposure of flankers compatible with the response required and was greater in degree with schizophrenic and depressed than with normal Ss. Interference from flankers incompatible with the response required occurred less among schizophrenics than among other groups. Several different processes may be involved in the inhibition of irrelevant information by schizophrenics. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An application of prefrontal cortex function theory to cognitive aging.

The purpose of this review is to extend the existing application of the frontal lobe hypothesis of cognitive aging beyond the limited work on inhibitory control (F. N. Dempster, see record 1992-22951-001) to include memory processes supported by the prefrontal cortex. To establish a background for this analysis, I review existing models of prefrontal cortex function and present a synthesized model that includes a general function of temporal integration, supported by 4 specific processes: prospective memory, retrospective memory, interference control, and inhibition of prepotent responses. I found the frontal lobe hypothesis to perform well, with the exception of an inability to account for age-related declines in item recall and recognition memory, possibly a result of age-related declines in medial temporal function. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contextual constraint and schizophrenic language.

Compared 16 hospitalized schizophrenic patients and 16 nonpsychiatric patients for the degree of facilitation of contextual constraint in memory. Ss were matched for intelligence, age, education, duration of illness, and socioeconomic level. All Ss listened to 4 taped word passages of different linguistic structure: normal and anomalous sentences, and semantically related and random word-strings. Ss differed in recall on all conditions, with the greatest difference between S groups occurring on normal sentences. Both S groups showed greater recall on passages emphasizing semantic components than on those with syntactic. Results suggest that the schizophrenic difficulty in communication may be influenced by lack of memory facilitation due to contextual constraints. (24 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prospective memory: A neuropsychological study.

To examine the neuropsychology of prospective remembering, older adults were divided preexperimentally into 4 groups on the basis of their scores on 2 composite measures: one assessing frontal lobe function and the other assessing medial temporal lobe function. The groups reflected the factorial combination of high and low functioning for each neuropsychological system, and they were tested on an event-based laboratory prospective memory task. High-functioning frontal participants showed better prospective remembering than low-functioning frontal participants. There was no significant difference in prospective memory performance attributable to medial temporal functioning. The results support the theoretical notion that frontal lobe processes play a key role in prospective remembering. Discussion focuses on the particular components of prospective memory performance that frontal lobes might mediate. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Direct measurement of differential cognitive deficit in acute schizophrenia.

This is a longitudinal study in which 11 standardized tests of cognitive function were administered to 20,000 normal Ss and at a later point in time readministered to those Ss of the original group (N=15) who became schizophrenic and were hospitalized. The tests were also readministered to part of the original group (N=40) who, at the same point in time, were still normal. The results, which revealed significant differential deficit on 5 of the measures, suggest that lack of motivation to reach out and actively manipulate stimuli or experience new learning produced the differences observed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A test of Chapman's theory of schizophrenic thought disorder.

Tested the validity of L. J. Chapman's (1964) theory of schizophrenic thought disorder. The vocabulary test from the Shipley-Institute of Living Scale for Measuring Intellectual Impairment served as the control task, and the multiple-choice vocabulary test used by T. B. Boland and L. J. Chapman (see record 1972-03368-001) to disclose a schizophrenic deficit related to thought disorder served as the experimental task. Two groups of 97 hospitalized psychiatric patients, one group classified as schizophrenic and the other as psychiatric controls, served as Ss. Both groups performed below the normal level reported by Boland and Chapman but somewhat above the mean level of the chronic schizophrenics they tested. The schizophrenic group in this study did not perform differently from the psychiatric controls on the experimental task. Results indicate that some factor other than schizophrenic thought disorder was being measured by the experimental task. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hippocampal and prefrontal cortex contributions to learning and memory: Analysis of lesion and aging effects on maze learning in rats.

Young adult rats with bilateral lesions to the hippocampus or prefrontal cortex, young operated controls, and normal old rats were tested on two complex mazes in the Hebb–Williams series. Approximately half the animals were previously trained on one of the mazes; the remainder received no previous training. The trained hippocampal rats showed sparing of memory for the general skill of maze learning but poor recall of the specific maze on which they had been previously trained. The opposite pattern was observed in trained prefrontal rats. In contrast, the aged rats' memory for maze-specific and maze-general information was impaired. The results confirmed the importance of the hippocampus for recalling highly specific information and pointed to a possible role for the frontal lobes in learning and remembering nonspecific skill-related information. The generalized deficit of the aged rats indicates that both types of memory were compromised and offers further evidence of frontal lobe and hippocampal dysfunction in normal aging. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of psychopathology on visual discrimination.

"Perceptual and motor aspects of the Bender-Gestalt Test performance were compared for 4 groups of Ss: 10 student nurses, 10 acute schizophrenic patients, 10 chronic schizophrenic patients, and 10 patients hospitalized for neurological reasons… . After the Ss had obtained equal experiences with the Bender designs by reproducing them under memory and copy conditions, a perceptual multiple-choice test was administered under memory and matching conditions. Results indicate that there are marked differences in perceptual accuracy between the 4 groups: the control population was most accurate, with the acute schizophrenic, chronic schizophrenic, and neurological patients less proficient in that order." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Clinical and neurocognitive aspects of source monitoring errors in schizophrenia

OBJECTIVE: Source monitoring, an aspect of memory that involves judgments about the origin of information, has been found to be more prone to errors in schizophrenic subjects than in normal persons. To examine the precise nature of such errors and their relationship to clinical and neurocognitive variables, the authors compared schizophrenic and normal subjects. METHOD: Schizophrenic subjects who had been medication free for 1 week (N = 26) and demographically matched normal subjects (N = 21) performed a source monitoring task and were assessed on current psychiatric symptoms, IQ, and frontal lobe functioning. RESULTS: The schizophrenic subjects had normal recognition memory of target words (recognition hits) and a normal generation effect but made more errors than the comparison subjects in identifying the source of target words. Specifically, the schizophrenic subjects made more errors in remembering the source of new and self-generated items, and they tended to attribute items to an external source. In 11 retested subjects, these errors were stable and independent from medication status after a 2-year interval. Secondary analyses suggested that certain source monitoring errors may be associated with hostility and lower IQ. When the effect of IQ was controlled, correlations with frontal dysfunction were not significant. CONCLUSIONS: Schizophrenic subjects make significantly more source monitoring errors than normal subjects, but not because of problems with recognition memory hits or with the generation effect. This tendency may be trait like and may be related to hostility. Lower IQ in schizophrenia plays a partial role in these errors, but frontal dysfunction does not.     

Cognitive controls and psychopathology.

Studied 90 psychiatric inpatients (nonpsychotic, nonschizophrenic psychotic, schizophrenic) and 35 normal controls to (a) determine whether some of the traditional cognitive controls could be isolated in these patients and (b) evaluate whether various diagnostic groups differed from each other and from normals in terms of these congitive controls. Ss were administered a battery of cognitive control tasks (e.g., the Phillips Scale of Premorbid Adjustment, WAIS, and Rorschach tests). With age, socioeconomic status, and verbal IQ as covariates, the factor structure for the total group was similar to that reported in other studies of cognitive control organization in the normal population. Schizophrenic and other psychiatric patients were not characterized by distinctly different organizations of cognitive controls. Although patients showed specific areas of cognitive dysfunctions, these seemed to be related to degree of disorganization. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Empirical test of the "levels" hypothesis with five projective techniques.

Tested the "levels" hypothesis that there is an inverse relationship between the degree of stimulus structure in a test and the level of personality impulse-control system being tapped by the test, for 20 normal and 20 psychiatric Ss. As predicted, an inverse relationship between pathology and stimulus structure over 5 tests (from low-high structure Draw-a-Person, Rorschach, TAT, Rotter Incomplete Sentence Blank, and Bender-Gestalt) was found for normals. Contrary to hypothesis, no such relationship appeared for psychiatric Ss. Other hypotheses that psychiatric Ss manifest more projection and more pathology than normals, and that there is a significant correlation between pathology and projection for every test for each group were confirmed. A new theory of projection of pathology as a function of the stimulus structure of tests is proposed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Immediate versus delayed visual memory task performance among schizophrenic patients and normal control subjects

In an exploratory study, 10 schizophrenic patients and 10 normal control subjects performed immediate and delayed memory tasks, which were variants of previously developed continuous performance tests. Both tasks required participants to identify five-digit numbers which were repeated. Numbers were presented in series for 500 ms each and separated by a 500-ms time-out period. In the immediate memory task, subjects were to respond if a number was identical to the one that had immediately preceded it. The delayed memory task differed from the first task in that a longer delay (3.5 s) between stimuli was introduced, and during this delay distracter stimuli appeared. While normal control subjects performed accurately on both tasks (exceeding 80% correct detections), schizophrenic patients performed poorly, performing worse on the delayed memory task than on the immediate memory task. Rates of commission errors (responses made to similar, but not identical numbers) were nearly equal between groups on the immediate memory task, but on the delayed memory task normal control subjects made relatively more commission errors while schizophrenic patients made fewer commission errors. No differences in response latencies were observed between subject groups or tasks. This paradigm may prove useful in discriminating subtle differences in immediate and delayed memory capability among psychiatric populations and normal control subjects.     

Reversal shift preferences in process and reactive schizophrenic, brain-damaged, and control group patients.

Compared process and reactive schizophrenic, brain-damaged, and normal control groups (n = 34 each) in frequency of reversal shifts in discrimination learning using the optional-shift paradigm. The main hypothesis that reactive schizophrenics, like normal adults, would show a stronger preference for reversal shifts than would process Ss was supported. Results show that significantly more reactive (68%) than process (44%) Ss made reversal shifts. Significantly more brain-damaged and reactive schizophrenic Ss showed reversal shift preferences when color was learned initially rather than form, while such initial concept preferences were not found in the process schizophrenic or normal control Ss. Previous findings in discrimination learning with pathological groups are discussed in the context of these findings. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A test-retest study of cerebral blood flow during somatosensory stimulation in depressed patients with schizophrenia and major depression

Six depressed patients with schizophrenia and 6 depressed patients with major depression were investigated before and during somatosensory stimulation (SS) with Tc-99m HMPAO SPECT. 8 controls were investigated only under resting conditions. The results can be summarized as follows: 1. Both psychiatric patient groups were hypofrontal (dorsolateral prefrontal cortex) compared to controls. 2. Hypofrontality was further enhanced by SS, significantly only in affective psychoses in the right inferior frontal lobe and in the right frontal hemisphere in total, in schizophrenia in the left dorsolateral prefrontal cortex. 3. Within the frontal lobes different regions were affected by SS in the two diagnostic groups. 4. In the right inferior parietal lobe SS response was significantly different in the two illnesses with schizophrenia showing a relative decrease, affective psychoses showing a relative increase of activity. 5. SS produced an increase of cerebral blood flow in subcortical regions (statistically significant contralateral to SS in thalamus and basal ganglia, ipsilateral to SS in cerebellum), a pattern which was common to all psychiatric patients. 6. Somatosensory cortex flow was not changed by SS. In conclusion, we could not fully confirm our hypotheses that similar blood flow abnormalities in different illnesses during SS are only caused by similarities in depressive psychopathology. Instead, depressed patients with schizophrenia were different from depressed patients with major depression in showing decreased activity in interrelating brain regions participating in an attentional network.     

Structural cerebral pathology in schizophrenia: regional or diffuse?

Is brain pathology in schizophrenia topographically distinct? If so, are the putative regional changes unique to the disorder? To address these questions, 56 chronic schizophrenic Ss were compared with 16 psychiatric control Ss with mood disorders and with 31 healthy volunteers on multiple-volume measures of regional cerebral atrophy obtained with computed tomography. Generalized cortical and subcortical enlargement of spaces filled with cerebrospinal fluid sparing only the occipitoparietal cortex was found in the schizophrenic Ss compared with normal control Ss. Statistically significant differences in the extent of perisylvian atrophy were noted between schizophrenic Ss and patients with mood disorders: Schizophrenic Ss evidenced greater dilation of perisylvian fissures and sulci. The implications of the results for future research and for recent theories on the etiology of schizophrenia are discussed.