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Biomedical subjects

C Shagass

Publications and source records attributed to C Shagass.

At least 55 records · Page 3Linked to original sources
PubMed1979

Correlations between psychiatric diagnosis and some quantitative EEG variables.

Several methods of quantitative analysis were applied to the left parietal 'resting' EEGs of 48 nonpatient controls and 90 undrugged psychiatric inpatients. Patient and control groups, matched for age and sex, differed as follows: (a) Mean frequency was lower and frequency variability was greater in the total patient group than in controls. (b) Mean amplitude was higher and mean frequency lower in chronic schizophrenics than in controls; the amplitude differences were contributed mainly by female patients. (c) Amplitude and frequency means of nonpsychotic patients were intermediate between those of chronic schizophrenics and controls. (d) Mean amplitudes were greater and frequency variability was less in neurotics than in controls.

Adult↗
PubMed1979

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.

Acoustic Stimulation↗
PubMed1978

Evoked potential correlates of psychosis.

Evoked potential (EP) correlates of several psychiatric disorders were investigated by applying a comprehensive EP procedure to 102 psychiatric patients and 28 nonpatients. EPs to left and right median nerve shocks, visual pattern flashes, and auditory clicks were recorded from one EOG and 14 monopolar scalp derivations. Nine age- and sex-matched groups were compared to yield the following main results: (i) EPs of overtly psychotic patients (schizophrenics, depressives, manics) differed markedly from normal, while those of patients without overt psychosis (neurotics, personality disorders, latent schizophrenics) did not; in the overtly psychotic, later EP events (100 msec or more poststimulus) were attenuated. (ii) EPs of neurotic depressives differed greatly from those of psychotic depressives. (iii) A somatosensory negative peak occurring 60-msec poststimulus (N60) was more posteriorly distributed in chronic schizophrenics (paranoid, undifferentiated) than in any other subject group. The attenuated later EP activity associated with overt psychosis was interpreted as a concomitant of cognitive (attention?) impairment, rather than of emotional disturbance.

Acoustic Stimulation↗
PubMed1978

Pattern evoked potential measurements suggesting lateralized hemispheric dysfunction in chronic schizophrenics.

Visual evoked potentials (VEP) were measured to obtain evidence concerning possible lateralized hemispheric dysfunction in schizophrenia. The main results are based on the spatial distribution (12 electrodes) of a measure of VEP wave form stability over time. Subjects were 86 psychiatric inpatients and 33 nonpatients; these were grouped in three ways to permit comparisons of various age- and sex-matched diagnostic classes. Main findings were: (i) VEP wave form stability was generally lower in all types of schizophrenia than in nonpatients, nonpsychotic patients and, probably, psychotic depressives. (ii) VEP stability differed more between the hemispheres in schizophrenics and psychotic depressives than in nonpsychotic subjects; in schizophrenics, left hemisphere stability was lower than normal, whereas it was normal in psychotic depressives. (iii) VEP stability differences between the hemispheres were also greater than normal in latent schizophrenics, with less stability on the left. The results provide a direct demonstration of a left hemisphere involvement in schizophrenic dysfunction.

Adolescent↗
PubMed1977

EEG and evoked potential approaches to the study of neuropeptides.

EEG and event related potential (ERP) phenomena were considered here from the standpoint of possible applications to investigations of the central effects of neuropeptides in man. These electrophysiological phenomena were viewed from the standpoint that they provide an accessible intermediate level of observation between behavior and detailed neuronal events. Several general methodological issues were discussed. An attempt was made to describe the EEG and ERP phenomena that may be pertinent to future neuropeptide studies and to consider their functional significance. Available data concerning electrophysiological effects of neuropeptides were also discussed. Suggestions for future research were made, which emphasized comprehensive recording of EEG and ERP phenomena to permit examination of the patterning of electrocerebral events.

Acoustic Stimulation↗
PubMed1977

Evoked potentials of schizophrenics in several sensory modalities.

This is the initial report of results obtained by a comprehensive approach to investigation of evoked potential (EP) characteristics of psychiatric patients. EP to left and right medion nerve, visual (checkerboard flash), and auditory (click) stimuli were obtained for 14 monopolar scalp and one EOG derivation in 32 schizophrenics and 16 nonpatients, matched for age and sex. Results showed amplitude attenuation of EP events 100 msec poststimulus or later in the patients' EPs of all modalities and in most lead locations. Attenuation of later EP events thus appears to be a general characteristic of schizophrenia. Comparisons of chronic paranoid and undifferentiated with other patient subtypes revealed a relatively specific correlate of the chronic subgroup, increased negativity of a negative somatosensory peak occurring 60 msec poststimulus (N60) at contralateral central leads.

Acoustic Stimulation↗
PubMed1977

Can callosal speed of transmission be inferred from verbal reaction times?

Filbey and Gazzaniga (1969) found that verbal reaction times were shorter to right than to left visual field stimuli. They interpreted this reaction time difference (30 to 40 msec) to reflect callosal transmission time, i.e., the delay required for information received in the right hemisphere to be acted upon by the verbal left hemisphere. We have performed four verbal reaction time experiments with normal subjects, utilizing differing hemifield stimulus presentations and task requirements. Stimuli were: small lights (light-emitting diodes); checkerboard pattern briefly flashed; small circles; consonant-vowel-consonant triads, either meaningful or nonsense. Contrary to Filbey and Gazzaniga's observations, we found no difference between verbal reaction times to left and right half-field presentations, or a significantly shorter reaction time with left-field presentations, depending upon experimental conditions. Faster reaction times with left-field stimuli were found in left-handed as well as right-handed subjects. Our data indicate that it may be premature to infer callosal speed of transmission from verbal reaction times to half-field stimuli. The paradoxical finding of faster verbal reactions to right hemisphere visual inputs does not appear to be related to handedness, and it occurs with meaningful stimuli; this finding remains unexplained.

Corpus Callosum↗
PubMed1976

Electrophysiological effects of triiodothyronine and propranolol.

The effects of triiodothyronine (T3), T3 combined with propranolol, and propranolol alone on somatosensory evoked responses (SER) and EEG were studied in 2 groups each of 6 male volunteer subjects. The following results were obtained: (1) T3 increased SER amplitude during the first 100 ms after stimulus. (2) Addition of propranolol eliminated the SER amplitude increase resulting from T3 administration. (3) Neither T3 nor T3 plus propranolol significantly altered the mean level or the temporal variability of EEG amplitude and frequency. (4) There were no significant effects of propranolol alone on SER and EEG measures.

Adult↗
PubMed1976

Eye-tracking performance and engagement of attention.

Eye-tracking dysfunction has previously been demonstrated in psychotic patients. To investigate possible influences on this finding of factors related to attention, subjects were required to read numbers while tracking an oscillating pendulum or a pendulum-like target displayed on an oscilloscope tube. Subjects for the pendulum task were 16 nonpatients and 21 patients; 10 nonpatients and 14 patients performed the other task. Introduction of the number-reading maneuver greatly improved tracking performance in both tasks in patients and nonpatients. The results indicate that poor eye-tracking can be improved by facilitating attentional effort; it is suggested that the number-reading maneuver improved tracking by providing extra feedback cues. The poorer the base line performance, the greater the improvement. However, differences between patients and nonpatients were not abolished with number reading.

Adolescent↗
PubMed1976

Spatial distribution of potentials evoked by half-field pattern-reversal and pattern-onset stimuli.

Spatial distributions of visual potentials (VEPs) evoked by half-field checkerboard pattern-reversal and pattern-onset stimuli were studied in 13 subjects, using an 11 lead unipolar array. The main aim was to confirm findings, obtained by previous workers with bipolar recordings, that half-field pattern-reversal VEP's are confined to the contralateral hemisphere and that half-field pattern-onset VEPs are asymmetrical, with greater right hemisphere involvement. Pattern-reversal VEP's contained four consistent peaks, designated here by polarity and peak latency as: (a) P95, positivity contra-lateral and negativity ipsilateral to the field stimulated; (b) P125, predominantly ipsilateral positivity; (c) N165, predominantly ipsilateral negativity; (d) P225; predominantly midline positivity. Pattern-onset VEPs contained three consistent peaks: (a) P125, mainly contraleteral positivity; (B) N175, mainly contralateral negativity; (c) P225, midline positivity. Distributions of pattern-reversal and pattern-onset peaks resembled one another only for P225, suggesting different cortical representation for the other events of the two kinds of VEP. Bipolar pattern-reversal VEPs were largely contralateral, but unipolar recordings showed that this was due to steeper contralateral potential gradients, as ipislateral activity was widespread. Pattern-onset peaks did not differ in amplitude with respect to the half-field stimulated. Previously reported asymmetries were not confirmed. The P125 and N175 pattern-onset peaks were almost entirely restricted to the contralateral hemisphere, but the distributions by half-field were mirror-images of one another. Half-field pattern-onset stimuli could be used to investigate the responsiveness of each hemisphere, although differential hemispheric involvement was not shown. Several differences in amplitude and distribution resulted from varying the width of the vertical central dark strip.

Adolescent↗
PubMed1976

Application of factor analytic procedures to complex evoked potential measurements in psychiatric research.

Several factor analytic procedures were applied to data gathered with a modified somatosensory evoked potential (SEP) recovery function prodecure in 56 non-patients and 224 psychiatric inpatients. The data were analyzed for each option reflected in three main issues. (1) Which group should be used for calculating the basic factor structure--normals only or all subjects? (2) Should measurements be preadjusted for covariance with variables known to obscure events of interest? (3) Should varimax rotation be used, or are principal components sufficient? Using two criteria, interpretability of factors in relation to experimental design, and their ability to discriminate clinical groups, it appeared that: (1) choice of either population yielded similar results; (2) when measurements were pre-adjusted for covariance more interpretable factors, which also yielded clinical discriminations, were obtained by varimax rotations than by principal components, and (3) when data were not adjusted by covariance, principal component analysis produced a factor which, although less interpretable in relation to experimental design than the varimax factors, provided equivalent clinical discriminations.

Brain↗
PubMed1975

Psychiatric diagnosis and EEG-evoked response relationships.

This study was conducted to determine whether the patterning of EEG and somatosensory evoked response (SER) variables, as determined by the correlations between them, differs with respect to psychiatric diagnosis. Subjects were 43 nonpatients and 90 psychiatric inpatients. SER modified recovery function recordings provided 36 variables, reflecting amplitude and its variations with different stimulus conditions. A 10-min left parietal EEG was quantitatively analyzed to give mean amplitude and frequency and variability measures. Correlations between EEG and ER variables were compared both for unmatched groups of nonpatients, schizophrenics, psychotic depressions, and nonpsychotics and for smaller age and sex-matched diagnostic groups. The results revealed a number of correlation differences between clinical groups. The nature of the differences suggested diagnostic specificity for EEG-ER patterning, which may provide a new, psychiatrically relevant electrophysiological variable.

Adolescent↗
PubMed1975

EEG and evoked potentials in the psychoses.

EEG and evoked potential (ER) findings in schizophrenic and affective psychoses were selectively reviewed. Both groups of psychoses appear to differ from normal in a number of EEG and ER characteristics; however, diagnostic specificity was suggested by relatively few findings. More encouraging result with respect to specificity have been obtained by subtyping the psychotic groups, e.g., process versus reactive schizophrenic, unipolar versus bipolar depression. Methodologic issues and directions for future research were discussed.

Adjustment Disorders↗