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Biomedical subjects

E Callaway

Publications and source records attributed to E Callaway.

At least 19 recordsLinked to original sources
PubMed1992

Cholinergic activity and constraints on information processing.

In humans, close relationships are found between cholinergic activity and constraints placed on information processing operations. This is true for all operations where the effects of cholinergic activity have been studied. Studies of vigilance, memory, problem solving, stimulus processing and response processing are cited as illustrations. These studies suggest the hypothesis that cholinergic activity controls constraints in all information processing operations. Alternative hypotheses are proposed and experimental tests are suggested.

Acetylcholine↗
PubMed1992

Scopolamine effects on visual information processing, attention, and event-related potential map latencies.

We measured performance and event-related brain potential (ERP) map latencies in 12 subjects during four visual discrimination tasks to compare the timing of scopolamine effects on information processing and attention. "Topographic component recognition" found ERP map latencies at times of best fit with a component model map. This "common topography" criterion minimized topographic differences among conditions to facilitate latency interpretations. Scopolamine slowed N1 latency in all tasks, and P3 and reaction time in some tasks. The drug delayed responses to easy targets more than to hard targets. It also induced a disproportionate N1 delay for unilateral high spatial frequency gratings. Both effects reflect a scopolamine-induced impairment when processing targets that usually capture attention. Scopolamine also impaired accuracy for unilateral high spatial frequency gratings, and for gratings presented at probable locations, confirming and extending previous findings. Scopolamine-induced P1 and N1 delays showed that visual processing was affected. Several results were inconsistent with a serial stage model. We suggest that scopolamine both delays selected processes and impairs a processing mode based on automatic capture of attention, inducing more serial processing.

Adult↗
PubMed1992

Predictive value of objective esophageal insufflation testing for acquisition of tracheoesophageal speech.

This prospective study was undertaken to assess the predictive value of esophageal insufflation on the acquisition of tracheoesophageal (TE) speech. Fourteen total laryngectomy patients were evaluated prior to tracheoesophageal puncture (TEP) using objective esophageal pressure measurements. These patients then were followed prospectively for 6 to 13 months. Speech was assessed at the time of prosthesis fitting, at 1 month, at less than 6 months, and at greater than 6 months post-TEP. No patient underwent pharyngeal myotomy. Pre-TEP esophageal insufflation pressure was associated (P = .065) with successful TE speech at the time of prosthesis fitting, but was not associated with successful TE speech acquisition after 6 months. This study's results suggest that patients with poor pre-TEP esophageal insufflation test results will usually obtain successful TE speech given adequate time and training, even without pharyngeal myotomy.

Aged↗
PubMed1991

Clonidine and scopolamine: differences and similarities in how they change human information processing.

1. Humans have been tested on a choice reaction time task designed to disclose interactions between stimulus complexity and drug effect. 2. Tests were carried out using oral scopolamine (1.2 mg) and clonidine (0.2 mg). 3. Reaction times and event related potentials were measured. 4. Both drugs slowed reaction time and the N1 component of the ERP. 5. SCOP slows RTs to easy-to-discriminate stimuli more than RTs to harder stimuli. Its effect on P3 is the same for both types of stimuli. 6. CLON tends to slow P3 latencies to easy stimuli more than P3 latencies to harder stimuli, while the RT slowing is almost identical for both types of stimuli.

Adult↗
PubMed1991

The rear-view halo.

Explore the source record for details and available documents.

Cervical Vertebrae↗
PubMed1990

Beyond drug effects and dependent variables: the use of the Poisson-Erlang model to assess the effects of D-amphetamine on information processing.

Several studies have shown that d-amphetamine (DAMP) speeds mean reaction time (RT). However, the use of mean RT may obscure important aspects of the drug response. Therefore we applied the Poisson-Erlang (PE) stochastic model of choice reaction time proposed by Pieters (1985) to the RT distribution. This model proposes that the RT distribution is generated by two states: Processing (P) and Distraction (D). RT represents the sum of the time spent in each of these states. P is the time taken to complete a set of cognitive operations which are required to give a correct response. D represents the time taken by all other activities. RTs were collected using a task (SERS) in which stimulus and response complexity each had two levels, easy and hard. Subjects were tested pre- and postdrug. Drug conditions were: placebo, 10 mg d-amphetamine (DAMP), 4 mg of the dopamine agonist, pimozide, and a combination of DAMP and pimozide (COMBO). Parameters of the model were derived using methods described by Pieters. Four measures were analyzed: Processing Time (PT); Mean Time per distraction (XTD); Distraction Rate (DR); and Total Distraction Time per trial (TDT). Mean RT is also presented. Analyses of the effects of task conditions on the parameters of the model were made using the predrug sessions. Mean RT was increased by both stimulus and response complexities as was PT. TDT was increased by the task conditions. The PE measures did not change over days. DAMP speeded mean RT. However, this effect did not interact with the task factors. DAMP speeded processing and reduced distraction. Processing was speeded only in the hard response condition, distraction time was reduced only in the easy response condition. The results indicate that the PE model can be successfully applied to fast RT tasks. More importantly, the parameters of the model revealed important pharmacological effects that were not apparent in mean RT. DAMP speeds cognitive operations related to motor preparation and reduces the effects of distraction. Consistent with past studies there are no indications that DAMP interacted with stimulus processing. The distraction effect appears to be mediated by an increase in the rate of distraction and a decrease in the average time of these distractions.

Adult↗
PubMed1990

Topographic segmentation of waking EEG in medication-free schizophrenic patients.

Lehmann has demonstrated that EEG topography can be used to segment EEG map series into a sequence of spatially stationary segments characterized by location of potential maxima and minima. We employed topographic segmentation techniques to study 9 channel EEGs recorded from 11 medication-free schizophrenic patients and 10 normal controls during resting and active task conditions, retesting 8 patients after neuroleptic treatment. To define EEG segments, average reference potential maps corresponding to global field power peaks in theta, alpha, and low beta activity were classified according to locations of extreme minimum and maximum values. Normals and schizophrenics did not differ in the number or types of switches between segments, or the frequency of hemisphere crossing of potential extrema. However, EEGs of normal subjects were characterized by significantly more (P less than 0.003) unused theta segment types (of a theoretically possible 36). Moreover, medication significantly (P less than 0.02) increased the number of unused theta segment types in EEGs of schizophrenics. We interpret these findings as evidence of increased spatial variability of brain electrical activity in schizophrenics and discuss their functional implications.

Adult↗
PubMed1990

Nonclosure of pharyngeal muscle after laryngectomy.

A prospective study was carried out to evaluate a new technique of pharyngeal repair following laryngectomy. The purpose of this study was to see whether satisfactory healing would occur if the pharyngeal constrictors were not sutured across the closure in the pharynx. If healing proved to be satisfactory the procedure might eliminate the need for primary or secondary myotomy or pharyngeal plexus neurectomy to facilitate tracheoesophageal speech. The results indicate that healing is as good in the group who did not have muscle closure as in those who did.

Evaluation Studies as Topic↗
PubMed1989

The effects of clonidine and yohimbine on human information processing.

The effects of clonidine and yohimbine on human information processing were tested in six normal volunteers ages 18-30 years. Subjects were tested in a pre-post design with sessions conducted at weekly intervals. Three drug conditions were: Placebo (lactose), 0.2 mg clonidine, and 30 mg yohimbine. Two choice reaction time (RT) tasks were used. One was a stimulus evaluation-response selection task (SERS) that has been shown to be sensitive to d-amphetamine, methylphenidate and scopolamine. The other task was to assess stimulus pre-processing and used spatial frequency as a discriminative stimulus. The principle finding was that clonidine slowed RT; this effect was significant for both tasks. In contrast, yohimbine tended to speed RT, but the effects were significant only for the spatial frequency task on some analyses while not for others. RTs to high spatial frequency stimuli were speeded more than for low spatial frequency. The effects of these two NE drugs were compared with findings with d-amphetamine and scopolamine and interpreted within the framework of a serial information processing model proposed by Callaway (1983). Specifically, it is suggested that yohimbine and clonidine affect an early pre-processing stage.

Adolescent↗
PubMed1989

The variety of relations between spatial frequency and reaction time.

While stimuli of lower spatial frequency often result in faster responses, this is not invariably the case. Some individuals respond faster to high frequency stimuli on tasks for which most others respond faster to low frequency stimuli. Past experience can also determine the degree to which a low frequency stimulus will mask a high frequency stimulus. These observations suggest that the effects of spatial frequency on visual information processing are under the control of higher level cognitive operations.

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↗