Replication of an evoked potential study of lateralized hemispheric dysfunction in schizophrenics

Visual (VEP) and auditory (AEP) evoked potentials (EPs) were measured to replicate previous findings concerning lateralized hemispheric dysfunction in chronic schizophrenic patients in a new sample. Measures of EP waveform stability (Zr') showed greater hemispheric asymmetry in 26 unmedicated chronic schizophrenics than in 26 matched nonpatients, and relatively lower left and right hemisphere values in schizophrenics. Similar hemispheric differences were not found between medicated patients and matched nonpatients; medication was associated with higher left and lower right hemisphere stability. EP amplitudes were lower with medications, the lowest amplitudes found in patients receiving nonphenothiazine or nonpiperazines as opposed to phenothiazine-piperazine drugs. Medications were associated with amplitude asymmetries not observed in unmedicated patients. This study confirms greater than normal hemispheric asymmetry of VEP and AEP waveshape stability measures in chronic schizophrenics, and lower left than right hemisphere stability suggesting left hemisphere dysfunction. Alteration of EP asymmetries by antipsychotic medications suggests that medication effects may obscure evidence of lateralized dysfunction in schizophrenics.     

Neuropsychological functioning of first-episode schizophreniform patients.

OBJECTIVE AND METHOD: This study compared 32 consecutively admitted first-episode schizophreniform patients, 26 patients with chronic schizophrenia according to the DSM-III-R criteria, and 25 normal comparison subjects on a comprehensive battery of neuropsychological tests to determine the degree of cognitive impairment existing at the onset of schizophrenic illness. Patients were tested within 2 weeks of admission to the hospital, after their medication had been stabilized. RESULTS: With age and education controlled, the first-episode and chronic patients performed significantly worse than the normal subjects on neuropsychological summary measures of executive function, verbal memory, spatial memory, concentration/speed, and global cognitive function and on left and right hemisphere function scales. The first-episode patients were as cognitively impaired as the chronic patients on all summary scales and many of the individual tests. Both groups showed relatively greater left than right hemisphere dysfunction. CONCLUSIONS: These findings suggest that substantial cognitive deficits, comparable to those of chronic patients, are present early in the course of psychotic illness.     

Neuropsychological dysfunction in schizophrenia. Relation to associative thought disorder

Recent evidence suggests that cerebral atrophy with cognitive deficits is associated with negative schizophrenic symptoms, including poverty of speech and speech content. This report investigates the relationship between specific measures of neuropsychological dysfunction and four major indices of associative thought disorder in schizophrenia, to ascertain whether neuropsychologically impaired schizophrenics show more associative disturbance than neuropsychologically intact schizophrenics. Twenty neuropsychologically intact and 12 impaired schizophrenics, rigorously diagnosed by the Research Diagnostic Criteria, were administered the Luria-Nebraska Neuropsychological Battery. These two groups of schizophrenics were compared on a continuous word-association test, which included two nonverbal and two verbal measures of associative disturbance. The neuropsychologically impaired schizophrenics had slower reaction times (p less than .05), but did not differ from the neuropsychologically intact schizophrenics on the verbal measures. Results indicated a stronger relationship between neuropsychological functions and the nonverbal dimensions (p less than .02), than with the verbal measures. This challenges the assumption that a left hemisphere abnormality in schizophrenia is particularly associated with cognitive disturbance, and suggests that neuropsychologically impaired schizophrenics may show greater potential for negative schizophrenic symptoms.     

Are schizophrenic men at higher risk for developmental deficits than schizophrenic women? Implications for adult neuropsychological functions

This study tested the hypothesis that schizophrenic men would be at a greater risk than schizophrenic women for exhibiting a history of developmental problems in childhood and would exhibit more neuropsychological deficits as adults. The study was a secondary analysis of data that were collected in 1981–83. The sample consisted of 49 DSM-III schizophrenic patients (57% male/43%female), who were generally in the early stages of the disorder. All subjects received a neurodevelopmental and clinical/diagnostic interview and a neuropsychological battery of tests, including measures of intelligence, abstract reasoning, memory, sustained attention, executive function, language skills, and motor ability. Latent class analysis was used to identify gender differences in subclasses of schizophrenia. The groups were then compared on neuropsychological function. Results indicated that schizophrenics with histories of early developmental problems exhibited significantly more neuropsychological dysfunction as adults than did other schizophrenics, and they were more likely to be men. Impairment in this group was evident in the areas of verbal ability, attention, abstraction, motor function, and verbal and nonverbal learning and memory, with verbal tasks being relatively more impaired.     

Effects of localised cerebral lesions and dysphasia on verbal memory.

Twenty-nine patients with unilateral left hemisphere lesions, 22 patients with unilateral right hemisphere lesions, and 19 neurological control patients with extracerebral lesions were assessed on verbal memory recall and recognition tests and on a battery of language tests. The left hemisphere group was significantly impaired in memory and language skills. Significant verbal memory impairment was found both in the subgroup of left hemisphere lesion patients whose lesions involved the temporal lobe and in the subgroup whose lesions did not. However, no significant differences between these left hemisphere subgroups' levels of performance on memory tasks emerged, even when dysphasia was taken into account. This study, therefore, fails to support the notion of a specific anatomical correlate of verbal memory impairment within the left hemisphere. Dysphasic subjects were significantly impaired on verbal memory tasks but displayed the same pattern of sensitivity to the effects of word frequency and word concreteness on verbal memory as control subjects, suggesting that the verbal memory of the dysphasic subjects was quantitatively rather than qualitatively impaired. This impairment could not be attributed to deficits in the comprehension or expression of the memory test items, and it is, therefore, proposed that language disturbances may hinder the efficient use of such language based procedures as may subserve verbal memory.     

Emotional behavior in schizophrenia and one-sided brain damage--expression and verbalization of emotions. Cerebral hemispheric asymmetry. Part II

Emotional behaviour in non-chronic and chronic schizophrenic patients, right and left hemisphere-damaged patients and healthy people was observed. Similar type of emotional reactions have been recorded in schizophrenia and right hemisphere damage. This might suggest the similarity of localisation of the cerebral dysfunction in the two patient groups. The difficulties with catching verbal expressions and verbal humour might be associated with the frontal cortex dysfunction.     

Somatosensory and auditory evoked potential studies of functional differences between the cerebral hemispheres in psychosis.

Evidence of lateralized hemispheric dysfunction in schizophrenia was previously found with a measure of visual evoked potential (VEP) wave-shape stability. The purpose of this study was to determine whether the VEP findings would extend to the auditory and somatosensory modalities. Measures of wave-shape stability were computed for auditory (AEP) and somatosensory (SEP) evoked potentials, recorded from one EOG and 14 scalp leads. Subjects were 74 unmedicated patients (49 schizophrenics, 25 nonpsychotics) and 27 nonpatients; two sets of age- and sex-matched comparison groups were formed. Main findings were: (i) Overtly psychotic schizophrenics exhibited lower than normal stability in left hemisphere AEPs (15-100 msec poststimulus). (ii) Both overtly psychotic and latent schizophrenics showed lower than normal wave-form stability, bilaterally, in the later epoch of AEPs (101-450 msec poststimulus). (iii) A subgroup of overt schizophrenics (other than chronic paranoid or chronic undifferentiated) had lower than normal stability in SEPs (15-100 msec) evoked by right median nerve stimuli and recorded from the right (ipsilateral) hemisphere. It was concluded that only the AEP results augment the previous VEP evidence indicating left hemisphere involvement in schizophrenic dysfunction.     

Differences of cerebral lateralization among schizophrenic and depressed patients.

Conjugate lateral eye movements (LEMs) have been used as a measure of contralateral frontal hemisphere activation when individuals carry out reflective tasks. In a previous study, schizophrenics were noted to produce significantly more R-LEMs than controls suggesting that they use the left hemisphere in general more often than controls when initiating thought. More specifically, schizophrenics initiated thought on spatial emotional material in their left hemisphere more often than normals. In an effort to replicate these findings, the present study contrasted a new sample of 13 schizophrenics first with the original schizophrenic sample, and then with 13 psychotic depressives, and the original controls. In addition, other group comparisons are reported. The data obtained replicate the original findings of increased R-LEM (i.e., increased left hemisphere activity) and the excessive processing of spatial and to a lesser extent emotional material in the left hemisphere of schizophrenics. Psychotic depressives were found to initiate reflective tasks more often in their right hemisphere than either schizophrenic or the original sample of normal controls. Significant group differences among schizophrenics, normal controls, and psychotically depressed patients were obtained. The data are consistent with emerging concepts of a left hemisphere locus of disturbance in schizophrenia and right hemisphere disturbances in affective disorders.     

An analysis of the specificity and the syndromal correlates of verbal memory impairments in schizophrenia

It was investigated whether schizophrenic and depressive patients show a distinguishable mnestic profile. A further aim was to explore the psychopathological correlates of memory malperfomance in schizophrenic patients. For the present study, schizophrenic, depressive and healthy samples (n=25 each) were compared regarding their performance in the Rey Auditory Verbal Learning Test. Subjects' sociodemographic background variables were comparable except for age (entered as a covariate). Depressive and schizophrenic patients performed significantly worse than healthy controls regarding both short-term and long-term free recall as well as recognition. No differences occurred for two parameters reflecting proneness to interference. Negative schizophrenic symptomatology was strongly correlated with memory dysfunction before and after controlling for distractibility. The study supports previous research suggesting that memory impairments in schizophrenia are not an epiphenomenon of deficits in verbal fluency or an attentional impairment. The major deficit in both schizophrenic and depressive patients is inferred to be the capability to learn.     

Hemispheric function in disorganized type schizophrenia: performance on the quality extinction test.

We assessed hemisphere function in right-handed male chronic, disorganized type schizophrenic patients (N = 60, age range 18-45 years) using the Quality Extinction Test (QET), in comparison to 20 right-handed male healthy controls in the same age range. The QET analysis discriminated between the disorganized schizophrenic patients and the controls. QET results indicated that chronic schizophrenic patients were less sensitive to tactile stimuli in both hands as compared to controls. Furthermore, the sensitivity to tactile stimuli of the left hand was less than that of the right hand in the schizophrenic patients. In contrast, in the normal controls the sensitivity was similar in both hands. These results indicate possible right hemisphere dysfunction together with disturbance in interhemispheric transmission through the corpus callosum in chronic, disorganized type schizophrenic patients.     

Interhemispheric transfer of information and schizophrenia

Summary The interhemispheric transfer of stereognostic information was investigated in four groups of subjects: paranoid schizophrenics, non-paranoid schizophrenics, non-schizophrenic psychiatric patients, and normals. Previous work has raised the possibility that schizophrenia is characterised by a dysfunction of the corpus callosum, but there are several methodological problems associated with this research. A comparison of inter-manual and same-hand conditions on the experimental task revealed no evidence for impaired transfer of information in the schizophrenic groups. However, the performance of the non-paranoid schizophrenic group was markedly inferior to all other groups on the right hand/right hand no transfer condition, consistent with a left hemisphere dysfunction. Possible reasons for the failure to replicate previous findings are discussed.     

Personality and Neuropsychological Aspects of Temporal Lobe Epileptics and Schizophrenics

Abstract: The present study was designed to ascertain and explore whether distinct personality profiles and neuropsychological features characterized temporal lobe epilepsy (TLE) vs. schizophrenic patients (Sc). The subjects were 20 epileptics and 19 schizophrenics matched with an overall IQ. They underwent various personality and neuropsychological tests. These results showed that the personality of the left-TLE patients tended to be more sensitive, aggressive, hostile and emotionally labile than the right-TLE and Sc patients. Finally, the Sc patients showed poor performances in verbal and nonverbal delayed tasks, especially on the right visual hemifield ones. These results suggested that they have the frontal lobe dysfunction, especially of the left hemisphere.     

Memory scanning and retrieval in affective disorders

Previous studies have consistently demonstrated unimpaired memory scanning and retrieval in schizophrenic patients. Using the choice-reaction time paradigm, this study assessed the speed of short-term memory processing for pictorial information in both unipolar and bipolar depressives by comparing it with that of schizophrenics. It was found that the processing rate is comparable between depressives and schizophrenics, between unipolar and bipolar depressives, and between depressives on medication and those not on medication. It was concluded, therefore, that the short-term memory scanning and retrieval processes are not impaired in depressive patients. The results further suggested that the depressives' slowness often found in simple reaction time tasks may result from a dysfunction in their stimulus encoding and/or response execution rather than in the central information-identification process.     

Personality and neuropsychological aspects of temporal lobe epileptics and schizophrenics

The present study was designed to ascertain and explore whether distinct personality profiles and neuropsychological features characterized temporal lobe epilepsy (TLE) vs. schizophrenic patients (Sc). The subjects were 20 epileptics and 19 schizophrenics matched with an overall IQ. They underwent various personality and neuropsychological tests. These results showed that the personality of the left-TLE patients tended to be more sensitive, aggressive, hostile and emotionally labile than the right-TLE and Sc patients. Finally, the Sc patients showed poor performance in verbal and nonverbal delayed tasks, especially on the right visual hemifield ones. These results suggested that they have the frontal lobe dysfunction, especially of the left hemisphere.     

A corpus callosal deficit in sequential analysis by schizophrenics

This preliminary study evaluated interhemispheric (i.e., corpus callosal) information processing by chronic schizophrenic and normal subjects. In right-handed normals the left hemisphere has been reported to be superior in temporal sequential analysis. Consequently temporal information presented to the right hemisphere requires time to cross to the left hemisphere for analysis. Measurement of hemispheric laterality and corpus callosal transfer time were evaluated by a two-pulse temporal discrimination task. Two dot stimuli were presented with decreasing temporal separation during bilateral and unilateral conditions. Subjects were required to judge perceived simultaneity and nonsimultaneity of dot onset. The results indicate that left hemisphere function in chronic schizophrenic and normal controls is superior to the right hemisphere in temporal analysis. Corpus callosal transfer time was significantly slower for chronic schizophrenics than for normal controls.     

Body side of motor symptom onset in Parkinson's disease is associated with memory performance.

The relation of body side of motor symptom onset in Parkinson's disease (PD) to memory measures associated with hemispheric dominance was examined. Fourteen patients with right body side motor symptom onset (RPD, inferred left hemisphere dysfunction) and 16 patients with left side onset (LPD, right hemisphere dysfunction) were administered measures of verbal (Hopkins Verbal Learning Test-Revised) and visual memory (Brief Visual Memory Test-Revised), that require similar task demands and are associated with left or right hemisphere dominance, respectively. The LPD group demonstrated poorer visual than verbal memory, both within group and in comparison to the RPD group. By contrast, the RPD group showed poorer verbal than visual memory within group. These findings suggest that side of motor symptom onset is associated with asymmetrical memory dysfunction.     

Problem-solving and spatial working memory in patients with schizophrenia and with focal frontal and temporal lobe lesions

Problem-solving ability was investigated in 25 DSM-IIIR schizophrenic (SC) patients using the Tower of Hanoi (TOH) task. Their performance was compared to that of: (1) 22 patients with neurosurgical unilateral prefrontal lesions, 11 left (LF) and 10 right hemisphere (RF); (2) 38 patients with unilateral temporal lobectomies, 19 left (LT) and 19 right (RT); and (3) 44 matched control subjects. Like the RT and LF group, the schizophrenics were significantly impaired on the TOH. The deficit shown by the schizophrenic group was equivalent whether or not the problems to be solved included goal-subgoal conflicts, unlike the LF group who were impaired specifically on these problems. The nature of the SC deficit was also distinct from that of the RT group, in that the problem-solving deficit remained after controlling for the effects of spatial memory performance. This study indicates, therefore, that neither focal frontal nor temporal lobe damage sustained in adult life is a sufficient explanation for the problem-solving deficits found in patients with schizophrenia.     

Late auditory magnetic sources may differ in the left hemisphere of schizophrenic patients. A preliminary report

We recorded magnetoencephalographic auditory evoked fields from the left and right hemispheres of six medicated, paranoid schizophrenic subjects and six normal controls. The magnetic field data were used in estimating the location, orientation, and depth of the source generating the 100-millisecond latency evoked field component (M100). The M100 latencies were slightly shorter than simultaneously recorded vertex electroencephalographic evoked potential N100 latencies, suggesting that magnetoencephalographic and electroencephalographic recordings were examining slightly different aspects of the source(s). The M100 sources demonstrated substantial interhemispheric asymmetry in normal controls, and were located more posteriorly, with more nearly vertical orientations, over the left hemisphere. The M100 sources in schizophrenics did not exhibit the same interhemispheric asymmetry. Left hemisphere source orientation differed significantly between normal controls and schizophrenics. Discriminant function analysis correctly classified normal controls and schizophrenics at 100% using the conservative jackknife procedure on the basis of left hemisphere orientation alone. Our findings, while preliminary, support altered left hemisphere function, or possibly structure, in this group of schizophrenic subjects, and suggest that magnetoencephalographic recordings may be a useful research method in this major mental illness.     

Schizophrenics show spatial working memory deficits.

The present study demonstrates that schizophrenics are impaired on spatial delayed-response tasks, analogous to those that have been used to assess the working memory function of the dorsolateral prefrontal cortex in rhesus monkeys. Schizophrenic patients and two control groups, normal subjects and bipolar psychiatric patients, were tested on the oculomotor version of the memory task, a haptic version of the same task, and two control tasks: a sensory task that did not require working memory and a digit span test. The schizophrenic patients showed marked deficits relative to the two control groups in both the oculomotor and haptic delayed-response tasks. They were not, however, impaired on the digit span test, which taps verbal working memory as well as voluntary attention, and on the sensory control task, in which their responses were guided by external cues rather than by spatial working memory. These findings provide direct evidence that schizophrenics suffer a loss in representational processing and that this deficit is modality independent. These data on spatial working memory add to the growing evidence for involvement of the dorsolateral prefrontal cortex in schizophrenic disease.     

Affective-prosodic deficits in schizophrenia: comparison to patients with brain damage and relation to schizophrenic symptoms [corrected

OBJECTIVE: Although affective prosody seems to be a dominant and lateralised communication function of the right hemisphere, focal lesions of either hemisphere may cause problems with its modulation. When impairment occurs after brain damage, the profiles of affective-prosodic disturbances differ depending on the hemisphere injured. Patients with left brain damage (LBD) improve their performance whereas patients with right brain damage (RBD) do not when the verbal-articulatory demands of the test stimuli are reduced systematically. One of the major arguments for a right hemispheric contribution to schizophrenia has been the documentation of affective prosodic deficits under the assumption that these abnormalities reflect right hemispheric dysfunction. Thus, an essential question to resolve is whether the profile of affective prosodic disturbances in schizophrenia is similar to LBD or RBD, or represents a unique variation. METHODS: Data were collected from four subject groups: 45 chronic, medication-stabilised, schizophrenic patients, 10 patients with focal LBD, nine patients with focal RBD, and 19 controls. All groups were tested on the aprosodia battery, which uses stimuli having incrementally reduced verbal-articulatory demands. Schizophrenic and aphasic symptoms were evaluated using standard assessment tools. RESULTS: For patients with impaired performance on the aprosodia battery, schizophrenic patients were statistically identical to patients with RBD and robustly different from those with LBD. Thirty eight schizophrenic patients (84.4%) were found to have some type of affective prosodic deficit with the predominant pattern indicating, at minimum, right posterior sylvian dysfunction (57.8%). When schizophrenic symptoms and aprosodic deficits were examined using a principal component analysis, affective comprehension and repetition loaded uniquely as separate factors. CONCLUSIONS: The profile of affective-prosodic deficits found in impaired schizophrenic patients is characteristic of RBD, supporting the concept that schizophrenia is a bihemispheric disease process. These deficits may also represent cardinal symptoms of schizophrenia as they are highly prevalent and, except for spontaneous affective prosody, are not associated statistically with traditional clusters of schizophrenic symptoms.