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Biomedical subjects

E Callaway

Publications and source records attributed to E Callaway.

At least 55 records · Page 3Linked to original sources
PubMed1983

Visual evoked potential changes induced by methylphenidate in hyperactive children: dose/response effects.

Visual event related potentials (ERP) were recorded from 21 hyperactive children aged 7-13 years under two attention conditions at 4 levels of methylphenidate dose (placebo, low, medium and high). ERP measures were very sensitive to age (under or over 10 years) and attention condition, but less sensitive to drug dose. There appeared to be two classes of drug dose effect on ERP amplitude, those that changed monotonically with dose and those from which dose interacted with attention non-monotonically. Drug effect on ERP amplitude may also depend on age so that opposite effects may occur in young and old children. No latency measures showed a dose effect. It appears that methylphenidate can speed reaction times without shortening ERP latency. This suggests the drug acts more on response-related processes than on stimulus evaluation.

Attention Deficit Disorder with Hyperactivity↗
PubMed1982

An information processing model for schizophrenia.

A disorder of information processing must be present for a person to receive the diagnosis of schizophrenia, and is present when schizophrenic symptoms occur along with other diseases. We created a model for this disorder that resolves some paradoxic findings and suggests directions for future study. Basically, schizophrenics have a deficiency in information processing that can be characterized as conscious, serial, and limited in channel capacity. In contrast, those processes that seem automatic, unconscious, parallel, and almost unlimited in capacity seem to be normal or supernormal.

Arousal↗
PubMed1982

The effect of attentional effort on visual evoked potential N1 latency.

The latency of the visual evoked potential N1 component evoked by nontarget stimuli increases with an increased attention to nontarget stimuli. The latency increase seems related to a general effort at processing, rather than any early filtering. This phenomenon is illustrated in one study of hyperactive children and another of normal young adults. The literature of this phenomenon is reviewed, and various explanations are considered. It does not appear to be a result of a slow negative wave, but rather a genuine effect of one aspect of attention on N1.

Adolescent↗
PubMed1982

Clinical and biological effects of high doses of vitamin B6 and magnesium on autistic children.

In 1973 Rimland reported that some autistic children responded favorably to high doses of vitamin B6. Since this finding, different studies were performed to identify apparently B6 responsive subjects and to critically evaluate clinical and biological B6 responsiveness. Magnesium was included because large doses of B6 might increase irritability. 44 patients (mean age 9.3 years) were examined. All selected children had marked autistic symptoms. The children received a complete diagnostic work-up, including psychiatric, psychological, neurological and medical evaluation. Clinical data were scored using an estimate of global clinical state and numerical rating on a 18 item scale (Behavior Summarized Evaluation). In a first open trial 15 out of 44 children exhibited moderate clinical improvement with worsening on termination of the trial. Thirteen responders and 8 non responders were re-tested in a 2-week crossover, double-blind trial and the responses to the open trial were confirmed. Biochemical data analysis revealed that a significant decrease in urinary homovanillic acid (HVA) levels was observed during B6-Mg administration. During B6-Mg treatment, middle latency evoked potentials exhibited a significant increase of amplitude.

Adolescent↗
PubMed1981

Effects of pyridoxine and magnesium on autistic symptoms--initial observations.

In an open trial, a heterogeneous group of 44 children with autistic symptoms were treated with large doses of vitamin B6 and magnesium. Clinical improvement with worsening on termination of the trial was observed in 15 children. Thirteen responders and 8 nonresponders were retested in a 2-week, crossover, double-blind trial, and the responses to the open trial were confirmed.

Adolescent↗
PubMed1981

Effects of vitamin B6 on averaged evoked potentials in infantile autism.

In autistic children, averaged evoked potentials have been reported to have lower amplitudes and shorter latencies than those of normal children. Also, moderate clinical improvement has been observed in some autistic children after treatment with vitamin B6 and magnesium. We have studied biochemical and electrophysiological effects of vitamin B6 and magnesium in 12 autistic children and in 11 normal children. During treatment of the autistic children with B6, an increase of amplitude of middle-latency evoked potentials and a decrease of urinary homovanillic acid were found. The reverse was noted in the normal subjects.

Autistic Disorder↗
PubMed1980

Combined effects of alcohol and sleep deprivation in normal young adults.

The effect of combining sleep deprivation and moderate alcohol consumption in male college students differed from the effects of each treatment alone. Following either alcohol or sleep deprivation, there was mild performance impairment, decreased alertness and reduced amplitude and increased latency of cortical evoked potential (EP) components. Heart rate increased after alcohol and anxiety increased after sleep deprivation. When alcohol and sleep deprivation were combined, antagonistic effects were found for most measures (reaction time, heart rate, alertness, anxiety, latency of early EP components), but synergistic effects also occurred (performance accuracy, latency of late EP components). These effects were found in a double-blind experiment using 24 subjects. The experimental treatments were alcohol doses of 0, 0.45 and 0.90 ml/kg of 95% ethanol and 0 and 26 h of sleep deprivation.

Adult↗
PubMed1979

Electroencephalogram correlates of higher cortical functions.

By means of two-stage, nonlinear multivariate pattern recognition, electroencephalograms (EEG's) were analyzed during performance of verbal and spatial tasks. Complex scalp distributions of theta-, beta-, and, to a lesser extent, alpha-band spectral intensities discriminated between the two members of a pair of tasks, such as writing sentences and Koh's block design. Small EEG asymmetries were probably attributable to limb movements and other uncontrolled noncognitive aspects of tasks. Significant EEG differences beteeen cognitive tasks were eliminated when controls for inter-task differences in efferent activity, stimulus characteristics, and performance-related factors were introduced. Each controlled task was associated with an approximately 10 percent reduction, as compared with visual fixation, in the magnitude of alpha- and beta-band spectral intensity. This effect occurred bilaterally and was approximately the same over occipital, parietal, and central regions, with some minor difference over the frontal region in the beta band. With these controls, no evidence for lateralization of different cognitive functions was found in the EEG.

Adult↗
PubMed1979

EEG patterns during 'cognitive' tasks. II. Analysis of controlled tasks.

This experiment was designed to distinguish possible EEG correlates of the cognitive components of tasks from EEG patterns associated with stimulus characteristics, limb and eye movements, and performance-related factors such as subjects' ability and effort. Thirty-two right-handed adults each performed 30 trials, lasting 6-15 sec each, of four simplified, controlled tasks: mental rotation of geometric forms, serial addition of a column of signed digits, substitution of letters with subsequent word recognition and visual fixation. The first three tasks could not be differentiated from each other. Each of these tasks could be differentiated from visual fixation by approximately 10% generalized reductions in alpha and beta band intensities, and slight increases in theta band intensities frontally and occipitally. We conclude that the EEG patterns which differentiated the complex tasks described in Part I were due to inter-task differences in stimulus characteristics, efferent activities and/or performance-related factors, rather than to cognitive differences. With these controls, no evidence for lateralization of different types of cognitive activity was found in the EEG.

Adult↗
PubMed1978

Time shift evoked potentials (TSEPs): method and basic results.

A simple technique for generating averaged evoked potentials to auditory signals that appear to move in space is described. Shifts in the apparent location of the signal were created by digitally delaying the output of a white noise generator with a minicomputer. The two channels were reconverted to two analog signals and presented binaurally through headphones. Shifts inthe apparent location of the signal produced a time shifted evoked potential (TSEP) that was not present during monaural control runs. TSEP amplitudes were largest near the vertex and varied as a function of the presentation format.

Acoustic Stimulation↗
PubMed1978

The effect of high doses of vitamin B6 on autistic children: a double-blind crossover study.

The authors used data from an earlier nonblind study to identify 16 autistic-type child outpatients who had apparently improved when given vitamin B6 (pyridoxine). In a double-blind study each child's B6 supplement was replaced during two separate experimental trial periods with either a B6 supplement or a matched placebo. Behavior was rated as deteriorating significantly during the B6 withdrawal.

Adolescent↗
PubMed1978

[Modifications in urinary homovanillic acid after ingestion of vitamin B6; functional study in autistic children (author's transl)].

Basing their study on the investigations which led to the dopaminergic theory of the psychoses, the authors studied homovanillic acid (principal derivative from dopamine) levels in the urines of 37 autistic children, and 11 normal children acting as controls. The favourable action of vitamin B6 on autism, reported by anglosaxon authors, was confirmed in 15 of the children. Furthermore, vitamin B6 reduces homovanillic acid levels in 33 autistic chilren and increases them in all the control group children.

Autistic Disorder↗
PubMed1977

Very short-term memory dysfunction in schizophrenia. Defective short time constant information processing in schizophrenia.

Disordered, very short-term memory (VSTM) has been hypothesized as the fundamental cognitive deficit in schizophrenia. We describe a method that measures VSTM using self-stimulated auditory average evoked potentials. This paradigm allows the VSTM hyothesis to be tested relatively free of superficial attentional and motivational artifacts. The experimental results are consistent with a VSTM dysfunction in schizophrenia. Very short-term memory dysfunction is discussed in light of recent blink reflex evidence that there is a short time constant information processing system with a time base similar to VSTM (ie, 1 to 1,000 msec). This leads to new testable hypotheses about information processing and VSTM in schizophrenia. It also lays the basis for interpreting this phenomenon as a pathologic exaggeration of an adaptive neurophysiologic mechanism.

Adaptation, Psychological↗