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Biomedical subjects

F H Duffy

Publications and source records attributed to F H Duffy.

At least 55 records · Page 3Linked to original sources
PubMed1988

Differentiation of schizophrenics and normal controls is enhanced by the Goodin subtraction procedure.

The P300 event-related potential as calculated by the Goodin subtraction procedure (P300g) combines attentive and inattentive condition waveforms in order to isolate components specifically related to target stimulus processing. The waveform was compared with the more commonly employed unsubtracted P300 waveform associated with attended infrequent stimuli (P300ia). The P300g produced the largest overall schizophrenic and control group differences in mean integrated amplitude compared with the P300ia. A group by scalp region interaction in the P300g, indicative of group topographic alterations, was also noted which was not present in the unsubtracted P300ia. Furthermore, the P300g pinpointed the single best scalp region (left temporal) for maximal group separation. This temporal asymmetry was found to originate in the inattentive condition waveforms, indicating a possible abnormality in "nonvoluntary" processing. We conclude that combining attentive and inattentive condition waveforms to form the P300g enhanced clinically relevant group differences between schizophrenics and normals compared with the P300ia.

Acoustic Stimulation↗
PubMed1988

Neurophysiological studies in dyslexia.

Using sophisticated computer graphics technologies and sensitive methods, our original dyslexia study of dyslexic boys delineated specific areas of the brain which in combination could constitute a "physiological signature" of dyslexia. In addition to identifying aberrant brain function in the traditional language-associated left posterior region, we also observed medial frontal lobe differences from normals, a finding confirmed by others in recent research. Our subsequent study sought to refine further current definitional subgroupings within the broad entity known as dyslexia-pure. Indeed language-based subgroups appear to have identifiable and differing topographic signatures. Furthermore, based on correlations between neuropsychological test scores and neurophysiological measurements, we suggest that subgroup electrophysiological differences may reflect compensatory as well as pathological brain activity. We believe that the currently expanding understanding of the neurophysiology of dyslexia will lead eventually to improved diagnosis and remediation of this learning disability. The detailed mapping of brain electrical activity shows promise of providing the neuropsychologist and learning disability specialist with another "perspective" on reading disability. This technique may prove valuable in the diagnosis of dyslexia at an early age and in the tailoring of the learning experience to a child's specific deficits and capabilities.

Brain↗
PubMed1987

Lecithin: absence of neurophysiologic effect in Alzheimer's disease by EEG topography.

Ten patients with Alzheimer's disease participated in a 26-week double-blind trial of lecithin. EEG data were recorded at baseline, after administration of the placebo, and after administration of the drug. Topographic maps of EEG spectra were compared when patients were on and off drugs. A direct comparison of drug and nondrug data was not significant. A second approach, comparing differences between drug and nondrug with differences between the two nondrug conditions, also produced no evidence of a drug treatment effect. The data confirm other reports that lecithin has no effect upon spectrally analyzed EEG activity in Alzheimer's disease.

Aged↗
PubMed1986

Individualized behavioral and environmental care for the very low birth weight preterm infant at high risk for bronchopulmonary dysplasia: neonatal intensive care unit and developmental outcome.

We hypothesize that the respiratory and functional states of the very low birth weight infant with bronchopulmonary dysplasia can be improved in the neonatal intensive care unit by prevention of inappropriate sensory input. To test this hypothesis, we developed for preterm newborns a behavior observation method that catalogues specific reaction patterns according to putative stress and relaxation behaviors. We then collected behavioral information and heart rate, respiratory rate, and transcutaneous PO2 readings before, during, and after routine care-giving interventions. Eight control and eight experimental infants were selected for study based on the following criteria: birth weight less than 1,250 g, gestational age less than 28 weeks, on the respirator greater than 24 hours in first 48 hours of life at greater than or equal to 0.60 FiO2 for more than two hours during first 48 hours of life. Additionally, the two groups were comparable on other medical and demographic variables, including severity of respiratory status for the first ten days and incidence of intraventricular hemorrhage, patent ductus arteriosus, and socioeconomic status. Systematic observations were conducted on days 10, 20, and 30 after birth and at 36 and 40 weeks postconception. For the intervention infants, our observations were discussed with the infants' primary nurses, and individualized modifications for each infant's care plan were implemented based on these observations. Experimental infants showed significantly briefer stays on the respirator (P less than .01) and in increased FiO2 (P less than .05). Their feeding behavior was normalized significantly earlier (P less than .01). Experimental infants also showed significantly better behavioral regulation scores at 1 month after their mothers' estimated dates of confinement (post-EDC), as measured with the Assessment of Preterm Infants' Behavior, significantly better Mental and Psychomotor Developmental Indices at 3, 6, and 9 months post-EDC, as measured with the Bayley Scales of Infant Development, and significantly better behavioral regulation scores at 9 months post-EDC, as measured in a videotaped play observation. Measurements of weight, height, and head circumference at 3, 6, and 9 months post-EDC showed no differences. All assessments were performed by one of two trained testers not familiar with the goals of the study or the group status of the infant. These results support the hypothesis that very low birth weight preterm babies profit significantly both medically and developmentally from individualized behavioral care in the neonatal intensive care unit.

Bronchopulmonary Dysplasia↗
PubMed1985

Comparative pharmacological effects on visual cortical neurons in monocularly deprived cats.

Monocularly deprived (MD) cats show a loss of responsiveness to visual stimulation of the deprived eye among visual cortical neurons. Several lines of evidence suggest that this effect involves, at least in part, a suppression of deprived eye input, possibly mediated by GABA inhibition. In order to better understand the nature of this suppression we have evaluated the effectiveness of different types of disinhibitory and excitatory agents to reverse the effects of MD. We investigated bicuculline (a GABA antagonist); picrotoxin (a GABA antagonist with a different mechanism of action from bicuculline); strychnine (a glycine antagonist); ammonium ion (a blocker of membrane chloride channels); physostigmine (a cholinesterase inhibitor); and naloxone (an opiate antagonist and also a GABA antagonist). All drugs were given intravenously. Bicuculline restored binocularity to 50% of the visual cortical neurons tested and naloxone to 36%. With both drugs, receptive fields of the normal eye tended to lose specificity. The emergent deprived eye receptive fields were usually similar to those of the normal eye after drug administration. Ammonium ion produced binocular responses in 27% of neurons tested, but receptive fields were grossly abnormal; moreover, ammonium infusion tended to depress neuronal responsiveness. All other drugs tested failed to restore binocularity. These experiments lend further credence to the hypothesis that GABA inhibition contributes to the cortical effects of MD, since only drugs with GABA antagonistic action were effective in restoring neuronal responsiveness to the deprived eye.

Acetates↗
PubMed1985

Dark rearing prolongs physiological but not anatomical plasticity of the cat visual cortex.

Recent studies (Cynader and Mitchell, '80; Mower et al., '81) have shown that total dark rearing prolongs susceptibility to the physiological effects of monocular deprivation (MD) in visual cortex beyond the normal age limits. The present study addressed whether this delayed physiological plasticity is accompanied by delayed anatomical plasticity in the geniculocortical pathway. Ocular dominance (OD) columns as defined by transsynaptic autoradiography following injection of 3H proline into one eye were studied both qualitatively and quantitatively in 17 cats. Compared to normal rearing (N-3), both binocular eyelid suture (N-2) and total dark rearing (N-3) resulted in incomplete segregation of OD columns in area 17. This apparent immaturity after binocular deprivation, however, did not reflect a delayed capacity for development and plasticity. Visual experience after dark rearing produced no marked changes. In cats who experienced MD after dark rearing, injection of either the nondeprived (N-2) or deprived eye (N-3) resulted in a nearly uniform distribution of label throughout layer IV of area 17. The same result occurred with binocular vision after dark rearing (N-1). MD from birth, however, produced expansion of columns from the nondeprived eye (N-1) and contraction of columns from the deprived eye (N-1). MD imposed after 4 months of normal vision resulted in normal OD columns (N-1). Electrophysiological studies revealed a high proportion of binocular cells within layer IV in cats who experienced monocular or binocular vision after dark rearing. Outside of layer IV there were clear environmental effects on OD of single cells in these cats. Measurements of cell sizes in the clateral geniculate nucleus showed shrinkage of cells innervated by the deprived eye when MD was initiated at birth (N-3). MD after dark rearing (N-4) produced no differences in cell sizes. It is concluded that visual input is necessary for the formation of normal OD columns, the critical period for formation and environmental modification of OD columns is limited to early life, and the physiological effects of visual experience after dark rearing reflect changes occurring beyond the geniculocortical pathway.

Animals↗
PubMed1984

Microiontophoretic bicuculline restores binocular responses to visual cortical neurons in strabismic cats.

Rearing cats with surgically induced strabismus resulted in an abnormally high percentage (80%) of monocularly driven neurons in visual cortex. Microiontophoretic application of the GABA antagonist bicuculline restored binocular responses to over 50% of these monocular cells. Elevation of spontaneous rate by glutamate failed to produce binocularity. These results indicate that intracortical inhibition plays a role in the abnormal ocular dominance distribution of strabismic cats.

Animals↗
PubMed1984

Extraction of clinical information from electroencephalographic background activity: the combined use of brain electrical activity mapping and intravenous sodium thiopental.

Traditional visual inspection of electroencephalographic (EEG) tracings and computer-assisted topographic mapping were compared in their abilities to detect and locate supratentorial lesions following intravenous sodium thiopental administration. Of the 13 subjects, 8 had atrophic and 5 had mass lesions, all defined by computed tomographic scan and 11 confirmed at operation. EEGs made before and after thiopental administration were evaluated separately from topographic maps of statistical difference between EEGs at multiple frequency ranges made before and after thiopental injection. Topographic mapping of statistical difference accurately detected all thirteen lesions, whereas EEG detected eight. In addition to demonstrating reduced beta production overlying structural abnormalities, topographic mapping revealed regionally augmented beta, especially over irritative lesions. Moreover, localization was possible with the topographic method after the first thiopental injection, whereas a second injection was required for EEG localization by visual inspection. Changes in slow (delta) activity were also useful in delineation of atrophic lesions, in which delta was usually augmented but occasionally regionally reduced. Multielectrode studies with topographic mapping appear essential in delineating cerebral abnormalities, because both slow and fast activities may be increased or reduced over such areas. The relative response of EEG background activity to thiopental at different frequencies may assist lesion characterization as well as localization.

Adolescent↗
PubMed1984

Age-related differences in brain electrical activity of healthy subjects.

A combined neurophysiological (electroencephalographic [EEG] and sensory evoked potential) and neuropsychological investigation was performed on 63 healthy men ranging in age from 30 to 80 years. Although alpha frequency diminished slightly with age, neither amplitude nor frequency demonstrated a high age correlation. Alpha blocking, in contrast, did correlate with age, in the direction of reduced alpha reactivity. EEG background activity underwent significant age-correlated change, consisting of reductions in slow activity and augmentation of fast activity, i.e., EEG desynchronization. Previously reported age-related EEG slowing may be related to the presence of disease in the populations studied. Topographic analysis revealed that the greatest change occurred in the temporal lobes. More change was noted either early or late in the age span, suggesting that aging is a nonlinear process. More features were derived from the right hemisphere than from the left, suggesting that the aging process is not completely symmetrical.

Adult↗
PubMed1984

Brain electrical activity in patients with presenile and senile dementia of the Alzheimer type.

Neurophysiological and behavioral data obtained from 9 patients with presenile dementia and 10 with senile dementia of the Alzheimer type were compared with similar data from 25 age- and sex-equivalent controls. Compared with the healthy controls, both patients groups demonstrated increased background electroencephalographic slowing with a reduction in fast activity (synchronization). Topographic analyses of data from electroencephalographic and evoked potential studies indicate that areas of maximal group differences between the presenile patients and their controls include the right posterior temporal and, to a lesser extent, left midtemporal to anterior temporal areas, whereas the maximal differences between the senile patient group and their controls involve the midfrontal and anterior frontal lobes, bilaterally. Moreover, right-sided numerical features derived from topographic maps proved most useful in differentiating the presenile patients and their age-matched controls, whereas bilateral features were more useful in separating senile patients from their controls. These topographic dissimilarities between patient groups suggest that an age-disease interaction exists between patients with presenile and senile dementia of the Alzheimer type. Correlational analyses between neuropsychological test scores and neurophysiological features indicate that increased slowing and decreased fast activity were associated with poorer test performance.

Adult↗
PubMed1983

Human cerebral potentials associated with REM sleep rapid eye movements: links to PGO waves and waking potentials.

Eye movement triggered averaging and topographic display techniques indicate the presence of parieto-occipital potentials that precede the rapid eye movements of human REM sleep. Since these potentials have strong similarities with PGO waves in animals, including lateralization according to eye movement (EM) direction, and with waking EM-antecedent potentials in man, this suggests that PGO-like activity both exists in man, and may be functionally related to EM-antecedent potentials in waking. The ability to detect such central potentials opens the possibility of studying REM sleep central physiological structure in a variety of normal and pathological conditions in humans.

Adult↗
PubMed1983

Brain electrical activity mapping (BEAM) in schizophrenic patients.

A new topographic approach, brain electrical activity mapping, summarizes EEG and evoked potential data as color maps. Eleven drug-free and 14 medicated schizophrenic patients and 11 normal controls were studied with this technique. Compared with controls, both schizophrenic groups had more slow activity (delta, 0 to 3.5 Hz), greatest in frontal regions, and more fast activity (beta, 20 to 31.5 Hz) in postcentral regions. Both schizophrenic groups were different from controls late in the visual evoked potential and in the middle of the auditory evoked potential. Overall, using multivariate discriminant analysis, a very significant group separation effect was found, and retrospective classification was 95% successful in discriminating both schizophrenic groups from controls. To estimate the ability of our features to assign subjects prospectively to control or patient groups, we employed "jackknifing," which resulted in overall classification success rates of 84.0% for medicated schizophrenic patients v controls and 81.8% for drug-free schizophrenic patients v controls.

Adult↗
PubMed1983

Altered P300 topography in schizophrenia.

The spatiotemporal evolution of the P300 waveform was topographically mapped in a group of ten male chronic schizophrenics, using the technique of brain electrical activity mapping. Group-average P300 waveforms were constructed for the schizophrenic group and a group of matched controls. The control group's P300 showed a concentric development about a maximum in the centroparietal area, slightly displaced toward the left. In contrast, the schizophrenic group's P300 maximum was more anterior and to the right, with a deficiency in left temporal activity. Using the technique of significance probability mapping, it was demonstrated that the maximum between-group difference was localized to the left-middle and posterior temporal regions, where the schizophrenic group was deficient in activity.

Adult↗
PubMed1983

Altered topography of EEG spectral content in schizophrenia.

EEG data were recorded in resting and in specific test conditions designed to activate different regions of the brain in a group (n = 10) of chronic schizophrenics and matched controls. EEG spectral energy was computed using the Fast Fourier Transform and numerical matrices representing the topographic distribution of spectral energy in a specified band were constructed and displayed as color images. Significance Probability Mapping was employed to identify regions of maximal group difference; it was found that the schizophrenic group showed increased low frequency energy (0-7 c/sec) in the frontal regions and increased fast activity (12-32 c/sec) in post-central areas and the left anterior temporal area. The different psychological test conditions were associated with different patterns of energy distribution. The consistency of our findings with other investigations suggests that topographic mapping of brain EEG spectral activity may play a useful role in the functional understanding of schizophrenia.

Adult↗