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Biomedical subjects

C Shagass

Publications and source records attributed to C Shagass.

At least 37 records · Page 2Linked to original sources
PubMed1984

Psychiatric drugs and the somatosensory P400 wave.

The effects of antipsychotic and antidepressant medications on the somatosensory evoked potential (SEP) late wave (P400) were investigated in a diagnostically heterogeneous group of 51 psychiatric patients. SEPs were recorded from five scalp locations while subjects counted electrical stimuli to one of four randomly stimulated fingers. In seven subjects, tested both on and off medication, no significant drug effects were observed. P400 amplitudes of 14 patients being treated with antipsychotic medication were greater than those of unmedicated patients matched for age, sex, and diagnosis. P400 amplitudes did not differ between eight patients being treated with antidepressants and eight unmedicated matched patients. Accuracy in stimulus counting (index of task performance) was significantly correlated with P400 amplitude; more accurate counting was associated with higher P400 amplitude. When 14 medicated and 14 unmedicated subjects, matched for task performance, age, sex, and approximate diagnoses, were compared, P400 amplitude did not differ. These findings suggest that higher P400 amplitudes associated with medication probably reflected improved task performance with medication, rather than a direct action of the drugs on P400. The results suggest the conclusion that lower P400 amplitude in psychosis is not secondary to psychiatric drugs.

Adult↗
PubMed1984

Psychiatric diagnostic discriminations with combinations of quantitative EEG variables.

The possible psychiatric diagnostic utility of certain quantitative EEG measures was evaluated by further analysis of previously reported data from 242 unmedicated patients and 94 non-patients. Time series of amplitude, frequency and wave symmetry measures for 12-lead EEGs (eyes closed and open) were factor analyzed across leads. Factor scores meeting specified criteria in multivariate analyses were entered into discriminant analyses comparing pairs of the following groups: non-patients, neurotics, personality disorders, overt schizophrenics, latent schizophrenics, major depressives and manics. The following discriminations were obtained with at least 50 per cent sensitivity, and diagnostic confidence rates from 69 to 92 per cent: (a) non-psychotic patients (neuroses, personality disorders) from overt schizophrenics, latent schizophrenics or manics; (b) major depressives from latent schizophrenics or manics; (c) non-patients from schizophrenics (overt and latent), depressives or manics. Most discriminations were replicable in split-half analyses. Possible utility of EEG measures in differential diagnosis is supported.

Adolescent↗
PubMed1984

Distinctive somatosensory evoked potential features in obsessive-compulsive disorder.

The purpose was to determine whether obsessive-compulsive disorder (OC) is associated with a distinctive pattern of somatosensory evoked potential (SEP) measurements, based on amplitudes of the N60 (negativity 60 msec poststimulus), P90, and N130 peaks. Previously, we found higher N60 amplitudes in 14 OC patients than in controls or other neurotics. Here, SEPs of the same 14 OCs were compared with those of 28 other neurotics, 99 nonpatients, 49 chronic schizophrenics, 27 "other" schizophrenics, 20 DSM-II latent schizophrenics, and 42 major depressives. Utilizing all available subjects, each peak amplitude was factor analyzed across 14 leads; the resulting factor scores were compared between OCs and every other group. The factor scores of OCs differed from those of all other groups, and patterns of factor score differences were similar in all comparisons. Most discriminations were replicable in split-half analyses. OC appears to be associated with a relatively distinctive pattern of middle latency SEP peak amplitude measurements.

Adult↗
PubMed1983

Failure to replicate evoked potential observations suggesting corpus callosum dysfunction in schizophrenia.

Somatosensory potentials (SEPs) evoked by vibrotactile finger stimulation have been reported to be the same in both hemispheres in schizophrenics, whereas they are asymmetrical in normals, with the contralateral hemisphere leading the ipsilateral (Jones and Miller, 1981). These findings were taken to indicate that the corpus callosum is nonfunctional in schizophrenics. To attempt replication of these results, vibrotactile SEPs of 6 schizophrenics and 6 normal controls were recorded with both bipolar and monopolar derivations. Asymmetrical bipolar SEPs were obtained in both schizophrenics and controls; previous observations of schizophrenic-control differences were not replicated. Acceptable evidence of ipsilateral early SEPs was not obtained; the test procedure seems inappropriate for measuring callosal conduction time.

Adult↗
PubMed1983

Rheoencephalographic concomitants of cognitive engagement in nonpatients and schizophrenics. An exploratory study.

Noninvasive cranial impedance plethysmographic, or rheoencephalography (REG), characteristics are reported to be well correlated with cerebral blood flow. This paper reports an exploratory study, in which we recorded REGs from four locations over each hemisphere in 16 nonpatients and 16 medicated schizophrenics under four conditions: eyes closed, eyes open, and following performance of the Seashore Rhythms and Wisconsin Sorting Tests. REG (Jacquy F index) values were greater anteriorly than posteriorly under all conditions. F index differed regionally between card sorting and eyes open conditions. With card sorting, F values of nonpatients increased more in the left than right hemisphere; schizophrenics showed the reverse hemispheric effect. Card sorting performance scores were positively correlated with regional F index changes in nonpatients, but not in schizophrenics. The results suggest that the REG may reflect regional cerebral effects associated with cognition and psychopathology.

Adult↗
PubMed1982

Relationships between psychiatric diagnosis and some quantitative EEG variables.

Psychiatric diagnostic correlates of EEG measures were investigated in 242 unmedicated patients and 94 nonpatients. Computer analysis of eyes-open and eyes-closed EEGs (12 leads) provided time series of amplitude, frequency, and wave-symmetry measures; mean levels and temporal variability indexes were also factor analyzed across leads. Comparisons between various age- and sex-matched groups disclosed numerous differences. Compared with those of nonpatients, schizophrenics' EEGs showed lower amplitude variability, greater frequency variability, greater wave symmetry, and less reactivity to eye opening. The EEGs of schizophrenic subgroups, including latent schizophrenics, were similar and also like those of manics. The EEGs of manics and major depressives differed markedly. The EEGs of subjects with personality disorders and schizophrenics differed from nonpatients in opposite directions. Groups could be classed according to the level of EEG activation: high included manics and schizophrenics; normal, nonpatients and neurotics; and low, major depressives and those with personality disorders.

Adolescent↗
PubMed1982

Somatosensory evoked potentials in Huntington's disease.

Scalp recorded somatosensory evoked potentials (SEPs) elicited by left and right median nerve stimulation were obtained in 21 patients with Huntington's disease (HD), 14 individuals at risk (AR) for HD, and 21 non-patient controls matched for age and sex. Although SEP abnormalities were not uniform in the HD group, no HD patient had SEPs that conformed fully to the normal configuration with respect to peak latencies, presence of all components and spatial distribution. The most common abnormality was non-specific in nature, consisting of amplitude reduction or virtual abscence of components after 100 msec. More specific deviations were noted in the early SEP events. In half of the HD patients, peak P30 seemed to occur at approximately 45 msec poststimulus; this peak could have been taken as the normal P45 had it not reversed in phase between the central and frontal leads. In these cases peak P45 prepared to be missing. Peak N20 latency values were longer in the HD group than in the non-patient controls, whereas the P15 latencies did not differ significantly. The conduction time between P15 and N20 was significantly longer in HD patients than the non-patient controls. SEPs of the majority of the ARs were similar to those of the non-patients controls in terms of overall configuration, although mean amplitudes were generally lower for ARs than non-patient controls and 4 ARs exhibited prolonged P15-N20 latency differences.

Adult↗
PubMed1982

Influence of antipsychotic and antidepressant drugs on evoked potential correlates of psychosis.

This study aimed to (i) determine the changes in evoked potentials (EPs) associated with hospital treatment involving either antipsychotic (AP) drugs, tricyclic (TTR) drugs, or no medication (NM); (ii) determine which EP changes may be direct drug effects; (iii) evaluate effects of testing patients receiving AP and TR drugs on psychiatric correlates of EPs. Somatosensory (SEP) to left and right median nerve stimuli, visual (VEP), and auditory (AEP) EPs were recorded from one eye and 14 scalp leads. Patients were tested before and during AP (N = 28), TR (N = 10), or NM (N = 15) treatments; results of 35 age- and sex-matched nonpatients were compared with predrug and drug test results of 35 patients. Main findings included (i) with AP and TR drugs, SEP peak P30 amplitude tended to decrease and SEP N130 to increase; (ii) with AP drugs and NM, VEP amplitudes decreased; (iii) AEP amplitudes increased with AP drugs; (iv) changes in amplitude measures did not differ significantly between AP, TR, and NM treatments; (v) marked later SEP amplitude differences between patients and nonpatients were about the same for pretreatment and drug tests; (vi) patient-control differences were greater with drugs for VEPs and less with drugs for AEPs. It was concluded that later SEP amplitude correlates of psychopathology are little influenced by AP and TR drugs, but that VEP and AEP results are modified.

Adolescent↗
PubMed1982

Psychotropic drugs and evoked potentials.

Effects of antipsychotic and antidepressant drugs and lithium carbonate (Li) on somatosensory, visual and auditory EPs were studied in psychiatric patients under treatment with those agents. A comparison group of patients treated without medication was also examined. The no medication group showed fewer EP changes on retest than the drug-treated groups. The effects of Li were greater than, and differed from, those of antipsychotics and antidepressants. EP changes with antipsychotics and antidepressants were relatively small and in the direction of normalization; these findings indicate that the pre-treatment EP differences from normal found in psychotic patients are probably not secondary to previous treatment with these drugs.

Antipsychotic Agents↗
PubMed1981

Neurophysiological evidence for different types of depression.

A brief, selective review of a broad range of evidence bearing upon biological distinctions between neurotic and psychotic forms of depression is presented. It includes a somewhat detailed presentation of clinical neurophysiological findings obtained in the author's laboratory over three decades of research. The available evidence is taken to support the discontinuity position of the continuity-discontinuity controversy about neurotic vs psychotic depression. It is concluded that more than one process underlies clinical depression, and that there may be several kinds of depressive disorders.

Affective Disorders, Psychotic↗
PubMed1981

The attention-related somatosensory evoked potential late positive wave in psychiatric patients.

Somatosensory evoked potential (SEP) late waves (P400) associated with selective attention were elicited by having subjects count electrical stimuli to one of four randomly stimulated fingers. P400 amplitude was lower in a diagnostically heterogeneous group of 20 psychiatric patients than in 16 nonpatients. Among patients, a general psychopathology factor derived from the Millon Clinical Multiaxial Inventory was significantly correlated with a factor accounting for most of the P400 amplitude variance. In psychiatric patients, attention-related late activity amplitude is apparently reduced from normal in evoked potentials of all modalities; degree of reduction appears quantitatively related to level of psychopathology.

Adolescent↗
PubMed1981

Cerebral evoked potential changes produced by treatment with lithium carbonate.

To confirm and extend previous findings concerning evoked potential (EP) changes produced by lithium carbonate (Li), 12 depressive patients were studied while on placebo and on therapeutic doses of Li. Four kinds of EPs were recorded from 14 leads: somatosensory (SEP) to left (LSEP) and right (RSEP) median nerve stimuli; visual (VEP) to a checkerboard flash; auditory (AEP) to binaural click. Plasma and erythrocyte (RBC) Li levels and Hamilton Depression ratings were obtained. Li produced a number of amplitude changes in EPs of all sensory modalities, while there were few latency changes; in general, amplitudes of positive components were increased, while negative component amplitudes were reduced. The spatial distributions of EP peaks were mainly unaltered by Li. The amount of EP amplitude change with Li tended to be correlated with plasma and RBC Li levels. No convincing correlations were found between alterations in EPs and depression ratings. The nature of the EP changes with Li was generally not concordant with normalization of the deviant EP characteristics found in depressives. The findings indicate that Li produces more widespread CNS changes than suggested by previous reports; it appears that these tend to be related to Li levels, but not to the therapeutic effects of Li.

Adult↗
PubMed1981

Intelligence as a factor in evoked potential studies of psychopathology. I. Comparison of low and high IQ subjects.

To evaluate possible influences of differences in intelligence on evoked potential (EP) relations to psychopathology, EPs of subjects with high and low scores on Raven's Progressive Matrices were compared. EPs to left median nerve (LSEP), right median nerve (RSEP), visual (VEP), and auditory (AEP) stimul were recorded from 15 leads. EPs of age- and sex-matched high and low IQ nonpatients (7 of each) and psychiatric patients (40 of each) were compared with respect to group mean EPs, amplitude, latency, and wave-shape stability measures; high and low IQ patients were also matched for diagnosis. Certain differences between high and low IQ subjects were common to both patients and nonpatients; lower IQ was associated with (i) higher early (before 100 msec) LSEP and RSEP amplitudes; (ii) lower later LSEP amplitudes; (iii) less late epoch LSEP wave-shape stability; (iv) less VEP wave-shape stability. Since these EP characteristics resemble deviations from normal reported for psychotics, intelligence differences could account for part, but by no means all, of the psychopathology-related EP differences. The relationship to IQ of the EP contour length ("string") measure, reported by Hendrickson and Hendrickson to be highly correlated with IQ, was also assessed; results were negative.

Adolescent↗
PubMed1981

Intelligence as a factor in evoked potential studies of psychopathology. II. Correlations between treatment-associated changes in IQ and evoked potentials.

The first report of this series indicated that evoked potential (EP) characteristics previously shown to correlate with psychopathology differed between subjects with high and low intelligence test scores (IQ). This paper reports the results of an attempt to determine if these IQ-EP relationships could result from variations in clinical state, rather than from differences between groups in trait IQ. Two patient groups were selected on the basis of the shifts in their Raven Progressive Matrices scores from first test to retest: (i) increase of 17-46 percentile points; (ii) decrease of 5 to 30 points. Their somatosensory, visual, and auditory EPs were compared in several ways to determine if the EP changes on retest were correlated with the IQ changes, as predicted from the state hypothesis. The results did not confirm the predictions, suggesting that the previous findings reflected differences in trait IQ.

Adolescent↗
PubMed1981

Confirmation of deviant EEG-evoked potential relationships in the neuroses.

A previous study of relationships between EEG and somatosensory evoked potential (SEP) measurements in psychiatric patients showed correlations between EEG and SEP amplitudes to be negative in nine neurotic patients and positive in nine age- and sex-matched nonpatients. The present study attempted to replicate this finding in 35 neurotics and 35 age- and sex-matched nonpatients. Data involved amplitudes of SEPs to right median nerve stimuli from frontal, central, and parietal leads and central and parietal EEG amplitudes (eyes open and closed), both obtained in the context of our comprehensive EP recording procedure. Correlations between SEP and EEG amplitudes in controls were generally positive, while those in patients tended to be negative or close to zero. No specific neurosis group differed from the others. The results confirm the previous finding in showing absence of normal EEG-SEP amplitude relationships in neurotic disorders.

Adult↗
PubMed1980

Topography of sensory evoked potentials in depressive disorders.

This study investigated differences in evoked potential (EP) topography between psychotic depressives, nonpatient controls, chronic schizophrenics, and neurotic depressives. Somatosensory (SEP), visual, and auditory EPs were recorded from 14 scalp leads. Locations (latencies) of consecutive EP peaks in a given subject were identified visually in key leads; these latencies were used for computer measurements of amplitude in all leads. Four sets of age- and sex-matched groups were compared by multivariate profile analysis. Amplitude differences between groups agreed well with findings obtained by comparing group sum EPs, indicating convergence between the two measurement methods. Topographic differences involved mainly SEP peaks. Distributions of SEP peaks P90 (positivity at 90 msec), N130, and P290 showed more posterior maxima in psychotic depressives than controls, while P185 was maximal more anteriorly in depressives. Distribution of SEP peaks N20, N60, N130, and P185 differed between psychotic depressives and chronic schizophrenics. The topographic approach appears to provide new EP information of pyschiatric relevance.

Adolescent↗
PubMed1979

Temporal variability of somatosensory, visual, and auditory evoked potentials in schizophrenia.

Previous findings in chronic schizophrenics showed greater than normal somatosensory evoked potential (SEP) waveshape stability before 100-ms after stimulus and reduced stability after 100 ms. To confirm and extend these findings, EPs to left and right median nerve stimuli, visual pattern flashes (VEPs), and auditory clicks (AEPs) were recorded from 14 locations in 86 patients and 33 controls. Three sets of analyses compared different patient groups with age- and sex-matched controls. The results confirmed previous SEP findings in chronic schizophrenics; no other subject group displayed the combination of high early and low late SEP stability. The SEP results did not generalize to VEPs and AEPs. Lead location was important for group differences. In overt schizophrenics, late epoch stability was low in all EPs. The results suggest certain limitations to the hypothesis of an impaired subcortical filtering mechanism in chronic schizophrenics.

Adolescent↗