Biomedical subjects

R A Roemer

Publications and source records attributed to R A Roemer.

At least 19 recordsLinked to original sources

PubMed1999

Alcohol-induced depersonalization.

BACKGROUND: A case of alcohol-induced depersonalization disorder is presented. The subject had experienced several depersonalization states following the consumption of alcohol rather than from a psychogenic etiology, and the episodes were transient, not chronic. METHODS: Three quantitative EEG (QEEG) studies were performed on the subject, one during the index depersonalization episode and two subsequent studies when the subject was clinically asymptomatic. RESULTS: Slow wave activity (relative theta power) was significantly increased when symptomatic. This slowing was still present over the occiput 3 days after the symptoms had remitted but was absent 17 days after symptoms had ameliorated. CONCLUSIONS: The time course of EEG slowing suggests a metabolic encephalopathy, a condition which likely contributes to the manifestations of depersonalization syndrome.

Adult↗

PubMed1996

A method to estimate in vivo D2 receptor occupancy by antipsychotic drugs.

A computational method is presented to estimate in vivo receptor occupancies of frequently used antipsychotic medications, which may provide a way to determine their central nervous system (CNS) effects in humans. The method can be used to estimate occupancies of several receptor types based on the daily dose of antipsychotic medication. Estimates of D2 receptor occupancy by haloperidol based on this equation were compared with those yielded by positron emission tomography (PET) measures in humans for the same compounds and dosages: the results of this comparison validated the approach.

Antipsychotic Agents↗

PubMed1996

The peak latency of orbital presaccadic spike potential with horizontal eye movements.

PURPOSE: To investigate the peak latency of the orbital presaccadic spike potential (SP) with horizontal eye movement in normals. METHODS: Orbital SP was recorded in 28 normal subjects from 8 electrodes around the eyes with Pz as the reference while performing 5 degrees, 10 degrees, 20 degrees, 30 degrees and 40 degrees horizontal saccades to visual targets. SP peak latency was measured from SP onset to SP peak on averaged data aligned on SP peak. RESULTS: Significant main effects on SP peak latency are found for saccade size (P < 0.01), saccade direction (P < 0.01) and electrode site (P < 0.05). No significant main effect on SP peak latency is found for eye (P > 0.05). SP peak latency increases with increasing saccade size from 5 degrees to 40 degrees. SP peak latency is longer with saccades back to center than away from center, and with abducting saccades than with adducting saccades. SP peak latency differs at the electrode sites with an order from shorter to longer as follows: inner canthus (IC); inferior orbit (IO); outer canthus (OC); superior orbit (SO). CONCLUSIONS: The effects on the peak latency of orbital SP can be explained by the saccade dynamic property, volume conduction as well as physiologic and anatomic factors of the eyes and orbits. The peak latency of orbital SP can be used to reflect the temporal characteristics of ocular motor units controlling saccadic eye movement.

Adolescent↗

PubMed1995

Quantitative electroencephalographic analyses in cocaine-preferring polysubstance abusers during abstinence.

Quantitative electroencephalographic (QEEG) analyses are presented for a group of 90 subjects recovering from polysubstance abuse (median = 90 days abstinent) who preferentially used cocaine. QEEGs showed significant decreases from normal in both absolute and relative delta power and decreased theta power in both absolute and relative power. Significantly increased relative but not absolute alpha and beta power was found. Asymmetry of frontal delta, theta, and alpha power differed from normal with right power greater than left. Globally, reduced interhemispheric coherence was found in delta and theta bands and frontally in the beta band. An atypical EEG pattern was observed in about half of the subjects. This was a paroxysmal-like EEG alpha pattern reminiscent of vertex waves typically associated with drowsiness but lacking the waxing and waning of alpha and the slow lateral eye drift associated with drowsiness.

Adult↗

PubMed1995

The effects of time point alignment on the amplitude of averaged orbital presaccadic spike potential (SP).

Effects of two time-point selection averaging techniques on orbital SP amplitude were studied on 10 normal subjects performing horizontal saccades. One technique involved averaging from the SP peak, another technique involved averaging from the saccadic onset. The time-point selection methods only affected the magnitude of SP amplitude but did not interact with experimental conditions. Repeated measures analysis of variance showed that SP amplitudes were higher in data aligned on SP peak than those aligned on saccadic onset (P < 0.01). No significant second order (saccade by degree) or third order (saccade by direction) interactions involving averaging method were found (P > 0.05).

Adolescent↗

PubMed1992

Quantitative EEG in elderly depressives.

Thirty-one elderly depressive patients were evaluated with topographic, quantitative EEG using relative measures, absolute measures, and computations of interhemispheric asymmetry and interhemispheric coherence in four frequency bands: delta, theta, alpha and beta. Patients were found to have lower than normal delta, higher than normal theta, higher than normal alpha and lower than normal beta values. EEG values were greater over the left than the right hemisphere in theta, alpha and beta bands. Lower than normal anterior interhemispheric coherence was found in all four frequency bands.

Aged↗

PubMed1992

Evoked potential topography in major depression. I. Comparisons with nonpatients and schizophrenics.

This study compared evoked potential (EP) topography in major depression (MD), schizophrenia and nonpatient controls. EPs to four kinds of stimuli were recorded from 15 locations. Patients were 69 MDs and 52 schizophrenics, currently unmedicated. EP waveforms of 195 controls were subjected to principal component factor analysis (PCA). The structures of 32 factors so extracted have been shown to encompass the data space of disparate groups; they were used to compute factor scores for all subjects. Age- and gender-matched groups were compared. Factor scores were normalized across leads (Z-transform) to distinguish between topographic and mean level differences. Topographic differences (P < 0.05) between MD and controls were demonstrated for scores of 8 factors, with 2 others at P = 0.053. Unlike those for schizophrenia/control comparisons, these topographic differences did not converge regionally in MD. EP findings were not related to duration of withdrawal from drugs. There were few differences between bipolar and unipolar patients. Topographies of 5 factors differed between MDs and schizophrenics; these involved all modalities and reflected long latency, cognition-related events, such as P300. These topographic differences were antero-posterior (AP); values were greater posteriorly in MDs and anteriorly in schizophrenics. Deviant AP gradients appear specific to MD; gradients were similar in schizophrenics and controls.

Adolescent↗

PubMed1992

Evoked potential topography in major depression. II. Comparisons between subgroups.

Brief Psychiatric Rating Scale (BPRS) ratings of 69 patients with major depression (MD) were employed in an attempt to define subgroups of MD with more homogeneous evoked potential (EP) findings than the MD group as a whole. Correlations were computed between 6 BPRS ratings and scores for 32 EP factors; 14 correlations were significant. These indicated mainly that EP values were related to severity of depression. When age- and gender-matched groups of MDs with above- and below-median depressive mood (D) ratings were compared with controls, 3 of the 10 factors differing significantly between groups gave evidence of two different subgroups of MD. EPs of these subgroups differed from those of controls in opposite directions. Such bidirectional differences from normal suggest differing pathophysiology in the subgroups and support the multiple process view of depression.

Analysis of Variance↗

PubMed1990

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.

Antipsychotic Agents↗

PubMed1990

Early cognitive components of somatosensory event-related potentials.

Somatosensory event-related potentials (ERPs) were recorded during a selective attention task involving electrical stimuli delivered to index fingers or the left and right median nerves at the wrist. In 11 healthy, young subjects, ERPs were recorded from 6 scalp locations while they mentally counted the electrical stimuli designated as target. Sequential ERP events measured included N20 (negativity at 20 ms), P30, P45, N60, P100, N140, P180, and P400. Analysis of amplitude data indicated modifications of both early and late ERP events with selective attention. While electrical stimulation at the wrist yielded early ERP amplitudes that were larger overall and latencies that were generally shorter, the selection attention effects did not differ on the basis of site of stimulation. The early ERP selective attention effects had differing scalp topography, with the P30/P45 effect of maximal over postcentral gyrus and N60 effect maximal over prerolandic gyrus. The data further elucidate the temporal features and spatial distribution of somatosensory ERP processes involved in attentional activity.

Adult↗

PubMed1990

Are gender differences in schizophrenia reflected in brain event-related potentials?

Numerous studies have reported relationships between gender and cerebral event-related potentials (ERPs) recorded from the human scalp. Recent studies have suggested that the influences of gender on ERPs may differ in persons with schizophrenia compared to healthy controls. In a further evaluation of the influences of this critical subject variable on ERP characteristics in schizophrenia, ERPs of age- and gender-matched groups (n = 72 each) of unmedicated schizophrenic patients and healthy controls were compared. ERPs elicited by left and right median nerve stimulation, checkerboard pattern visual flash, and auditory clicks were recorded from 15 scalp leads. The results confirm previous findings showing that: (1) number of comparable gender effects present in the ERP records of these two large study groups and (2) specific Diagnosis x Gender interactions suggesting that schizophrenic illness may modify normal gender influences on ERP characteristics. These data illustrate the point that matching schizophrenic patients and healthy control populations for gender is essential but not sufficient. Even in carefully matched groups, gender confounding can persist as a source of error variance because the influence can vary for different diagnostic groups.

Adolescent↗

PubMed1990

Comparing principal components analyses of evoked potentials recorded from heterogeneous groups of subjects.

Principal components analysis of evoked potentials differing between groups presents an interpretive problem, particularly in psychiatric research. Two sets of principal components and associated factor scores may appear to differ. The issue is to determine the extent to which visually differing principal components and resultant factor scores span the same factor space. Sets of evoked potentials from controls and from schizophrenics were each subjected to principal components analysis, from which factor score coefficients were computed for all subjects. This allowed determination of the extent to which (1) the two sets of basis waves were similar and (2) the factor scores resulting from the set of basis waves derived from principal components analysis of the control subjects' evoked potential data adequately represented those of the schizophrenics and vice-versa. Canonical correlation analyses indicated substantial similarities between the principal component structures (sets of basis waves). Multiple correlational analyses confirmed that the basis waves from either group spanned the other group's factor space. Factor scores from either set of basis waves were highly correlated. These results suggest that principal component structures derived from evoked potentials of a control group may be used in computing evoked potential factor scores of psychiatrically diverse populations even though the average evoked potentials of the groups may differ in several ways.

Evoked Potentials↗

PubMed1990

An efficacy study of single- versus double-seizure induction with ECT in major depression.

Twenty-nine patients with major depression, with and without psychosis, were randomly assigned to bilateral conventional electroconvulsive therapy (ECT) or modified multiple monitored ECT (MMECT) limited to two seizure inductions in a session. From pretreatment to after the fourth treatment session, modified MMECT was associated with more rapid amelioration of depressive symptoms on the basis of blindly rated Hamilton Rating Scale for Depression scores. No medical complications occurred. Sixty-two percent of patients in the modified MMECT group had posttreatment confusion, whereas 15% of patients treated with conventional ECT were confused. Modified MMECT appears to confer some clinical advantage over conventional ECT in the treatment of major depression while carrying an increased risk of treatment-related reversible confusion.

Clinical Protocols↗

PubMed1988

Dealing with differential gender and age effects in evoked potential studies of psychopathology.

Data selected from comprehensive EP studies of a large sample of psychiatric patients and nonpatients illustrate the point that matching patient and control populations for age and gender is essential, but not sufficient, to control for these subject variables. It is necessary to test for the interactions resulting from different relationships between EP measures and gender and/or age in different diagnostic groups and to examine differences between subgroups defined by gender and age.

Adolescent↗

PubMed1988

Somatosensory evoked potential correlates of schizophrenic subtypes identified by the Millon Clinical Multiaxial Inventory.

Evoked potentials (EPs) of schizophrenic patients differ from those of normal controls and some other diagnostic groups, but EP measurements of the comparison groups often overlap considerably. This suggests that schizophrenics are heterogeneous with respect to EP measurements and that additional methods for clinical subtyping are needed to account for the heterogeneity. This study used criteria based on the Millon Clinical Multiaxial Inventory to partition 20 patients, who were all schizophrenic by three diagnostic systems, into two subgroups. Somatosensory EP measurements of these two subgroups differed, suggesting that neurophysiological heterogeneity within the total sample of schizophrenics was associated with corresponding heterogeneity of the clinical features in the Millon scales.

Adult↗

PubMed1988

A sensory evoked potential comparison of persons 'at risk' for Huntington's disease and hospitalized neurotic patients.

Scalp-recorded sensory evoked potentials (EPs) elicited by left and right median nerve stimulation (LSEP and RSEP), checkerboard pattern flash (VEP) and acoustic click (AEP) were obtained in 22 individuals 'at risk' (AR) for Huntington's disease and 22 hospitalized neurotic patients matched for age, gender and intelligence. EPs of AR subjects were generally similar to those of the neurotic comparison group, in terms of overall configuration; however, mean amplitudes were significantly lower for ARs. While the general amplitude reduction for ARs was seen in all three modalities, the somatosensory modality yielded the most abnormal findings.

Adult↗

PubMed1988

Evoked potential correlates of intelligence in nonpatient subjects.

To evaluate possible influences of intelligence on evoked potential (EP) characteristics in nonpatients. EPs of age and gender matched groups (N = 19 each) of 'high', 'medium', and 'low' IQ groups were compared. EPs elicited by left and right median nerve stimulation, checkerboard pattern visual flash, and acoustic clicks were recorded from 15 scalp leads. The results confirmed previous findings showing that higher IQs are associated with higher EP amplitudes. An unexpected finding was a trend towards higher IQ/EP correlations for left than right recording sites. It appears that intelligence is an important subject variable to be controlled in any EP investigation, and furthermore that EP topography should be considered in seeking IQ/EP correlations.

Adult↗

PubMed1988

Some quantitative EEG findings in unmedicated and medicated major depressives.

To confirm previous quantitative EEG findings in major depressive disorder and to assess effects of medication, EEGs were recorded under eyes closed and open conditions in 68 patients (34 unmedicated and 34 medicated) and nonpatients matched for age and sex. Time series analyses of amplitude, frequency and wave symmetry were performed; differences between eyes open and closed were adjusted for eyes closed values to obtain measures of reactivity. These reactivity measures yielded the main differences between unmedicated patients and nonpatients; depressives were more reactive. Reactivity differences were eliminated or reversed in medicated patients. The EEGs of unmedicated depressives appear to be overreactive, while medications decrease EEG reactivity.

Adolescent↗