PubMed Health⌕ Search

Biomedical subjects

E Callaway

Publications and source records attributed to E Callaway.

At least 37 records · Page 2Linked to original sources
PubMed1986

The effects of stimulant drugs on information processing in elderly adults.

The effects of stimulant drug on information processing in elderly adults was studied. In Experiment 1, the effect of methylphenidate (MP) was examined in 8 young and 8 elderly women using a task (SERS) in which stimulus and response complexities were varied. MP speeded processing in the young but not in the elderly women. A second experiment was then conducted to isolate the age-stimulant effects. In Experiment 2, the effects of MP and 10 mg of d-amphetamine (DAMP) were studied in 12 young and 12 elderly men on different types of information processing. Stimulants changed performance on a continuous performance task in both groups. Both stimulants speeded processing on SERS in young, but not in elderly men. MP, however, speeded processing in both groups on a response processing task. The findings suggest that stimulants act on response processing and there appear to be several such processes. Some of these stages decline with age whereas others do not.

Adult↗
PubMed1985

Effects of oral scopolamine on human stimulus evaluation.

In a previous study of the effect of age on information processing, both age and stimulus complexity slowed reaction time (RT) and the latency of the P300 component of the brain event-related potential (ERP). The aim of the present study was to compare the effects of scopolamine (an anticholinergic) with the previously noted effects of age. The choice of scopolamine was prompted by current hypotheses concerning decline in cholinergic function with age. Twelve adult women were studied on a battery of tasks before and after scopolamine in oral doses of 0.0 (placebo), 0.6 and 1.2 mg. Reaction times (RT) and event-related potentials (ERP) were measured. The principal task was one that combined two levels of stimulus complexity and two levels of response difficulty to provide four subtasks. Scopolamine slowed RT and P300 as had age, but scopolamine slowed responses to simple stimuli more than responses to complex stimuli. Scopolamine effects on other tasks in the battery were small but consistent with an action of scopolamine on an early stimulus preprocessing stage that is independent of a stimulus evaluation stage that is also affected by age.

Adult↗
PubMed1985

The effect of methylphenidate on information processing.

Models of information processing currently popular in cognitive psychology divide the reaction process into a series of discrete separable stages. The distinction between one stage and another is verified by the additive factors method (AFM) as defined by Sternberg (1969). Task factors that do not interact with each other are inferred to affect different stages. The distinction between stimulus evaluation stages and response selection stages has been supported by brain event related potential (ERP) studies. The latency of the P300 component of the ERP is sensitive to changes in stimulus complexity but not to to changes in response complexity. The focus of this research is to determine the effects of stimulant drugs on stages of information processing using both reaction time (RT) and P300 latency within an AFM framework. Four doses of methylphenidate (MP) were used in a within-subjects design to examine the effects of MP on stimulus and response processing. We found that MP speeds RT, and that this effect does not interact with the effect of stimulus complexity on RT. MP dose interacts with response complexity, the dose for optimal speeding varying with the level of complexity. The latency of P300 is increased by stimulus complexity, and not by response complexity, nor is it affected by MP. These results show that the stimulant drug acts on processes involved in response selection, rather than in stimulus evaluation. Individual differences in drug response are dose dependent, but also point to an effect on response processing.

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↗
PubMed1975

Psychiatry today.

Explore the source record for details and available documents.

History, 20th Century↗
PubMed1974

Coupling between cortical potentials from different areas.

At any instant, the electroencephalogram can be classified as to (i) polarity and (ii) direction of change in polarity. This classification provides a way to measure coupling between cortical areas. The technique is simple, yet of wide potential utility for studying functional relationships between cortical areas. The results of applying this technique suggest how the potentials giving rise to the electroencephalogram may play a role in information processing in the central nervous system.

Cerebral Cortex↗