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Biomedical subjects

G Fein

Publications and source records attributed to G Fein.

At least 91 records · Page 5Linked to original sources
PubMed1990

A double-blind study of symptom provocation to determine food sensitivity.

BACKGROUND: Some claim that food sensitivities can best be identified by intradermal injection of extracts of the suspected allergens to reproduce the associated symptoms. A different dose of an offending allergen is thought to "neutralize" the reaction. METHODS: To assess the validity of symptom provocation, we performed a double-blind study that was carried out in the offices of seven physicians who were proponents of this technique and experienced in its use. Eighteen patients were tested in 20 sessions (two patients were tested twice) by the same technician, using the same extracts (at the same dilutions with the same saline diluent) as those previously thought to provoke symptoms during unblinded testing. At each session three injections of extract and nine of diluent were given in random sequence. The symptoms evaluated included nasal stuffiness, dry mouth, nausea, fatigue, headache, and feelings of disorientation or depression. No patient had a history of asthma or anaphylaxis. RESULTS: The responses of the patients to the active and control injections were indistinguishable, as was the incidence of positive responses: 27 percent of the active injections (16 of 60) were judged by the patients to be the active substance, as were 24 percent of the control injections (44 of 180). Neutralizing doses given by some of the physicians to treat the symptoms after a response were equally efficacious whether the injection was of the suspected allergen or saline. The rate of judging injections as active remained relatively constant within the experimental sessions, with no major change in the response rate due to neutralization or habituation. CONCLUSIONS: When the provocation of symptoms to identify food sensitivities is evaluated under double-blind conditions, this type of testing, as well as the treatments based on "neutralizing" such reactions, appears to lack scientific validity. The frequency of positive responses to the injected extracts appears to be the result of suggestion and chance.

Double-Blind Method↗
PubMed1990

Preservation of normal cognitive functioning in elderly subjects with extensive white-matter lesions of long duration.

Although deep white-matter brain lesions are seen on magnetic resonance imaging in about one third of elderly subjects, their clinical significance is not known. In 1984, we studied three retired teachers who had extensive deep white-matter brain lesions on magnetic resonance imaging, yet functioned cognitively at an above-average level. Blinded review of 1981 computed tomographic scans revealed patchy white-matter lucencies for two of the subjects. Repeated magnetic resonance imaging in 1987 showed that the deep white-matter brain lesions were at least as extensive as in the initial study. One subject had developed renal failure, while the other two continued to function at a high level with no evidence of cognitive decline or psychiatric or neurologic impairment. The presence of extensive deep white-matter brain lesions for up to 7 years in two subjects whose cognitive, behavioral, and neurologic functioning is unimpaired suggests that deep white-matter brain lesions do not necessarily indicate a clinically significant central nervous system disease process.

Age Factors↗
PubMed1990

Representation of multi-channel evoked potential data using a dipole component model of intracranial generators: application to the auditory P300.

A number of procedures have been employed to decompose recorded scalp potential wave forms into their hypothesized constituent elements. The shortcomings of the various decomposition methods (principal components analysis, topographic components modeling, inverse dipole localization and spatio-temporal dipole modeling) are reviewed and a new dipole components model, which incorporates the strengths of the topographic components model and the spatio-temporal dipole model, is presented. This model decomposes ERPs into subcomponents reflecting the activity of dipole sources with location and orientation fixed across subjects and with the temporal activity of each dipole modeled as a decaying sinusoid. The requirement that the equivalent dipole generators be the same across subjects and experimental conditions permits analysis of inter-group differences and of the effects of experimental variables. An application of the model to data from a 3-tone auditory target detection task is presented, and equivalent dipole sources of the components of the auditory evoked potential are described. Assumptions inherent in the model, as well as practical obstacles to its widespread implementation, are discussed.

Acoustic Stimulation↗
PubMed1990

The cerebral laterality of mental image generation in normal subjects.

This research was an attempt to replicate and extend a published study that reported a left hemispheric locus for the generation of mental images. Several methodological problems were addressed, the stability of effects was assessed by repeating the experiment, and P300 latency was measured. A lateralized visual choice reaction time task was performed twice, once without the use of imagery and once with imagery. In each visual field, the use of imagery produced a speeding of reaction times when the target stimuli matched the image generated by the subject. A similar effect was present for P300 latency, and was still present in the reaction time data after partialling out the P300 latency effect. These results indicate that mental imagery can speed both stimulus evaluation and response processing. There was no difference in the amount of speeding for images in the two hemifields, providing no evidence for a preferential locus of mental image generation in either cerebral hemisphere.

Adult↗
PubMed1990

Cognitive impairments in abstinent alcoholics.

Impaired cognitive functioning in alcoholics is widespread during the first months of detoxification. Between half and two thirds of abstinent alcoholics exhibit cognitive impairments during this period, with residual deficits persisting for years after detoxification in some patients. The most severe deficits have been observed in visuospatial abilities, perceptual-motor integration, abstract reasoning, and new learning. The most significant predictors of cognitive dysfunction in persons recovering from alcoholism are the time elapsed since the last drink and the person's age. Surprisingly, the pattern and duration of a patient's alcohol abuse are relatively weak determinants of neuropsychological impairment during abstinence. Research investigating the hypothesis that cognitive impairments may be related to alcoholic persons resuming drinking has yielded mixed results, but a higher level of neuropsychological functioning is associated with increased rates of completing treatment programs and with greater success in the work environment after discharge from treatment. The possibility of cognitive limitations should be taken into account in planning treatment programs for alcoholism.

Adult↗
PubMed1989

EEG coherence in unmedicated schizophrenic patients.

We have recently shown that electroencephalogram (EEG) coherence data recorded with common reference methods, including those obtained from schizophrenics, are confounded by power and phase effects. Three published reports using bipolar recordings found that EEG coherence was higher in schizophrenics; however, only medicated patients were studied. To extend these findings, we measured EEG coherence from bipolar EEG recordings in unmedicated schizophrenics (n = 10), affective disorder patients (n = 8), and normal controls (n = 13) during resting and task conditions. Seven schizophrenics were restudied after a period of neuroleptic treatment. Schizophrenics had higher across-task interhemispheric (p less than 0.05) and intrahemispheric (p less than 0.04) coherence in the theta band and tended to have higher intrahemispheric alpha coherence (p less than 0.08). Medication treatment was associated with clinical improvement and increases in spectral power, but not with changes in coherence values. These results confirm those obtained by earlier investigations and suggest that increased coherence reflects the presence of anomalous cortical organization in schizophrenics rather than medication effects or transient states related to acute clinical disturbance.

Adult↗
PubMed1989

P300 latency variability in normal elderly: effects of paradigm and measurement technique.

The discrepancy in the literature concerning the sensitivity of delayed P300 latency in dementia revolves around the variability of P300 latency in normal elderly. Previous studies, which have produced conflicting results, have utilized different P300 paradigms and different methods for measuring P300 latency. We demonstrate that the reported differences in the variability of P300 latency in normal elderly are likely to have resulted from these differences in paradigm and measurement method. We gathered auditory P300 data from a sample of 50 normal elderly using both a 3-tone RT paradigm and a 2-tone oddball paradigm and measured P300 latency using both peak-picking on the average EP and a single-trial template-fitting procedure. P300 latency variability was increased for the 3-tone paradigm compared to the auditory oddball paradigm, and for the template-fitting method. compared to peak-picking. The increased P300 latency variability when the template-fitting method was employed resulted, in part, from the template-fitting procedure focussing on random noise when the signal-to-noise ratio was low. Increased variability of P300 latency in the 3-tone paradigm resulted from 13 subjects who had a very long-latency positive component (often in addition to an earlier, smaller component) in this paradigm that met the scoring criteria for P300, but that was not seen in the oddball paradigm. We speculate that for the 3-tone task, some subjects may adopt a strategy involving 2 stages of stimulus processing, which results in the generation of 2 positive components, obscuring group differences in P300 latency. These results raise questions concerning the use, in clinical studies designed to yield diagnostic measures, of complicated paradigms in which subjects might adopt varying processing strategies.

Aged↗
PubMed1989

Estimation of trial-to-trial variation in evoked potential signals by smoothing across trials.

Averaging single trial evoked potential data to produce an estimate of the underlying signal obscures trial-to-trial variation in the response. We describe a method for estimating slow changes in the evoked potential signal by smoothing the data over trials. We discuss the crucial issue of deciding how much to smooth and suggest that an appropriate smoothing parameter is one that minimizes the estimated mean average square error of the smoothed data. Equations to estimate the mean average square error for a one-dimensional local linear regression smoother are presented. Performance of the method is assessed using simulated evoked potential data with several different models of a changing signal and different values of the signal-to-noise ratio. We find that the method rarely imputes trial-to-trial variation to data sets that have an unchanging signal, while it almost always produces less error than averaging when estimating a varying signal. The ability of the method to reveal signal heterogeneity is hampered by very low signal-to-noise ratios. When applied to real auditory evoked potential data from a sample of elderly subjects, the method indicated a changing signal in 35% of all subjects and in 56% of subjects with signal-to-noise ratios above 0.6. Consistent patterns of variation in the auditory evoked potential were present in this sample.

Aged↗
PubMed1989

Selecting the smoothing parameter for estimation of slowly changing evoked potential signals.

Brain evoked potential (EP) data consist of a true response ("signal") and random background activity ("noise"), which are observed over repeated stimulus presentations ("trials"). A signal that changes slowly from trial to trial can be estimated by smoothing across trials and over time within trials. We present a method for selecting the smoothing parameter by minimizing an estimate of the mean average squared error (MASE). We evaluate the performance of this method using simulated EP data, and apply the method to an example set of real flash evoked potentials.

Analysis of Variance↗
PubMed1988

Common reference coherence data are confounded by power and phase effects.

Coherence analysis of the EEG is used to study the coupling between cortical regions. High coherence between signals recorded at 2 electrodes is interpreted as evidence for neuroanatomic connections between the cortical areas underlying the electrodes. When common reference recordings are used, coherence measures the relationship between 2 time series, each of which is the difference between 2 signals measured at the scalp and is confounded by spectral power and phase at the recording and reference electrodes. Using multi-channel EEG data from 3 subjects, we illustrate the confounding of common reference data coherence computations and demonstrate the extreme effects of power and phase changes on coherence by simulating these changes in the EEG data. Common reference coherence data can be either inflated or deflated as a consequence of activity (i.e., spectral power) at the reference. Phase relationships among the reference and recording time series modulate the power effects on coherence. Both the power and phase effects can vary dramatically across frequencies, having profound and complicated effects on the shape of the coherence function. Based on these considerations, we conclude that common reference coherence data must be interpreted very cautiously and recommend that a new body of EEG coherence data must be gathered using reference-free recording methods before the utility of EEG coherence analysis for understanding brain function can be determined.

Cerebral Cortex↗
PubMed1988

EEG alpha asymmetry in dyslexics during speaking and block design tasks.

Lateral specialization for speech and spatial construction was investigated in a highly screened group of dyslexic and normal-reading boys, age 9-13, by examining the extent to which their EEG alpha asymmetry changed from one task to the other. EEG was recorded from central, midtemporal, and parietal leads during several minutes of spontaneous narrative speech, and while the child constructed block designs. The dyslexics showed the same strongly task-dependent asymmetry as the normal readers, comparable to that observed in our adult populations. The observations were confirmed with a second independently chosen cohort of subjects. This result is discussed in terms of the constraints it places on models of dyslexia which invoke disorders of lateral specialization and hemisphere integration.

Adolescent↗
PubMed1988

A fifteen-item modification of the Fuld Object-Memory Evaluation: preliminary data from healthy middle-aged adults.

A modification of the Fuld Object-Memory Evaluation (FOME) test was developed for use with middle-aged adults. To avoid the ceiling effect which occurs when the 10-item FOME is used with adults in this age group, we made the test more difficult by increasing the number of items to 15. We obtained preliminary data on the 15-item version of the test by administering it to 32 healthy, well-educated adults aged 35 to 55. This version of the test was difficult enough so that even high functioning adults needed multiple trials to memorize all items. No sex differences, and no significant correlations with education or age for any aspect of test performance were found. We present mean scores for recall on each trial, as well as averaged scores for storage, retrieval, consistent retrieval, and recall failure across five trials.

Journal Article↗
PubMed1987

Contralateral visual masking may be an artifact.

There are serious methodological problems in studies which report contralateral visual masking. Contralateral masking occurs when detection of a hemifield target stimulus is impaired by a pattern-masking stimulus presented to the opposite hemifield. We demonstrate that, in studies which used positive stimuli (i.e., black letters on a white field), contralateral masking may be an artifact. Although we observed contralateral masking when positive stimuli were presented, there was no evidence of masking with negative stimuli (i.e., white letters on a black field). A special masking stimulus with a positive mask contralateral to the target and a black hemifield ipsilateral to the target also failed to produce masking. Contralateral masking in this experiment was due to the flash of light in the field ipsilateral to the target; it was this ipsilateral stimulation, rather than contralateral interference, which impeded target recognition.

Adult↗