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PubMed1984

Performance and circadian rhythms.

Physiological studies frequently neglect effects due to individual differences, thus inflating the error variance term. Psychological determinants of endogenous arousal are examined in association with somatic functioning and circadian rhythms. Frontalis EMG and heart rate did not appear to display clear phasic circadian rhythms. The subjective perception of activation displayed a cubic trend, independent of sex, exhibiting two peaks, at 08.00-11.00 and 17.00-20.00. Peak performance on a choice reaction time task depended very much on whether it was executed in a free response or experimenter determined tempo condition, indicating the importance of stipulating the task demand characteristics. There was a certain stability in extraverts (cortically less aroused) across periods throughout the day with respect to physiological measures; the same was not true for introverts, who exhibited a complex interaction with time of day - stable introverts possessing higher cardiac rates than unstables in the earlier part of the day, the position reversing itself in the late evening. Personality variables can exercise moderating influences on physiological activity associated with performance.

Adolescent↗

PubMed1992

Behavioral microanalysis of spatial delayed alternation performance: rehearsal through overt behavior, and effects of scopolamine and chlordiazepoxide.

Rats were trained in an operant spatial delayed alternation task utilizing retention intervals from 2 to 32 s. In addition to response accuracy, operations of the levers during the retention intervals were recorded and analyzed. Animals were tested following the administration of the muscarinic antagonists scopolamine hydrobromide and methylbromide, and the benzodiazepine receptor agonist chlordiazepoxide. In vehicle-treated animals, the relative number of correct responses and correct rehearsal operations (operation of the forthcoming correct lever during retention intervals) varied with the length of the retention intervals, and these measures were correlated. The response rate for rehearsal operations increased with the length of the retention intervals. It is speculated that the delay-dependent increase in response rate reflects an effect of delayed reward that was also associated with a delay-dependent increase in the tendency to alternate between levers. The effects of delay on the accuracy of rehearsal operations may have contributed to the delay-dependent correct responding. Scopolamine hydrobromide (0.01, 0.03, 0.1, 0.3 mg/kg) and methylbromide (0.1, 0.3 mg/kg) impaired correct responding, but did not seem to interfere with the relative number of correct rehearsal operations. As only the presentation of the panel light indicated trial onset, it is speculated that the cholinergic receptor blockade resulted in an increase in the probability of a repositioning response that was triggered by light onset. Chlordiazepoxide (1, 3, 5, 10 mg/kg) did not affect behavioral performance. These results suggest that in tasks that allow the development of rehearsal operations, delay-dependent response accuracy does not represent a sufficient condition for conclusions on task demands on memory.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Expert control of the arterial blood pressure during surgery.

During and after many surgical procedures the patient's arterial blood pressure must be artificially decreased to a lower than normal level. Although there are alternatives, infusion of the drug sodium nitroprusside (SNP) is frequently the preferred technique to achieve this controlled hypotension. The fast action of the drug and the danger of a too low pressure make manual control of the SNP infusion flow rate, even if done by an expert, a difficult and demanding task. This is mainly due to an occasional large unpredictable variability over time of the patient's sensitivity to SNP, and to the fact that a multitude of other factors also influence the arterial pressure. Due to these and several other causes, current automatic controllers cannot handle all cases equally well. A new expert system based SNP controller was designed to perform well for all patients, regardless of their characteristics. It monitors and adjusts its own performance, employing a number of heuristics derived from a careful study of the properties of the arterial pressure signal, the effects of SNP and other clinical provocations on the arterial pressure, and the ways in which expert clinicians manually manage the SNP infusion. Expert systems technology allows the new controller to access and employ this type of expert medical knowledge, resulting in expert-level performance. The controller was tested on 30 patients undergoing cardiac surgery, both before, during and after bypass. It was safe, needed little attention, and performed well in all cases.

Animals↗

PubMed1986

Analysis of demand conditions associated with reluctant speech.

An analysis of five demand conditions affecting the reluctant speech of a preschool child was conducted in the classroom. Results indicated that demand conditions that did not permit escape from academic demand tasks, ignored mute responses, prompted answers and enthusiastically praised verbal responses resulted in higher rates of speech. Further, replication of these procedures across escape conditions resulted in increased speech rates that approximated those of a non-mute peer in the same classroom. Follow-up data at 8 months indicated that in the classroom the subject spoke more often to more people using a greater number of words, subsequent to analysis and intervention. The classroom teacher also reported a marked improvement in speech rate and quality and considered the time spent in analysis worthwhile. The study provides a model for further analysis of conditions associated with reluctant speech.

Behavior Therapy↗

PubMed1991

Event-related potentials in drug-naive schizophrenic patients.

Decreased amplitudes of late components of event-related potentials (ERPs) in schizophrenia were ascribed to either psychotic features or to neuroleptic treatment of the patients. To rule out the drug effect, ERPs to stroboscopic stimuli were recorded in drug-naive schizophrenics and control subjects during no-task and simple-task sessions. Patients had significantly lower amplitudes of the late ERP components during both sessions, thus confirming similar results with treated schizophrenics. On the other hand, drug-naive patients did not differ from controls in the task-related relative facilitation of late ERP components. These results differ from findings of minimal ERP facilitation to task in treated schizophrenics. This discrepancy is discussed in the context of the effects of neuroleptic treatment and task demands on ERPs.

Adult↗

PubMed1991

U-shaped learning and frequency effects in a multi-layered perceptron: implications for child language acquisition.

A three-layer back-propagation network is used to implement a pattern association task in which four types of mapping are learned. These mappings, which are considered analogous to those which characterize the relationship between the stem and past tense forms of English verbs, include arbitrary mappings, identity mappings, vowel changes, and additions of a suffix. The degree of correspondence between parallel distributed processing (PDP) models which learn mappings of this sort (e.g., Rumelhart & McClelland, 1986, 1987) and children's acquisition of inflectional morphology has recently been at issue in discussions of the applicability of PDP models to the study of human cognition and language (Pinker & Mehler, 1989; Bever, in press). In this paper, we explore the capacity of a network to learn these types of mappings, focusing on three major issues. First, we compare the performance of a single-layered perceptron similar to the one used by Rumelhart and McClelland with a multi-layered perceptron. The results suggest that it is unlikely that a single-layered perceptron is capable of finding an adequate solution to the problem of mapping stems and past tense forms in input configurations that are sufficiently analogous to English. Second, we explore the input conditions which determine learning in these networks. Several factors that characterize linguistic input are investigated: (a) the nature of the mapping performed by the network (arbitrary, suffixation, identity, and vowel change); (b) the competition effects that arise when the task demands simultaneous learning of distinct mapping types; (c) the role of the type and token frequency of verb stems; and (d) the influence of phonological subregularities in the irregular verbs. Each of these factors is shown to have selective consequences on both successful and erroneous performance in the network. Third, we outline several types of systems which could result in U-shaped acquisition, and discuss the ways in which learning in multi-layered networks can be seen to capture several characteristics of U-shaped learning in children. In general, these models provide information about the role of input in determining the kinds of errors that a network will produce, including the conditions under which rule-like behavior and U-shaped learning will and will not emerge. The results from all simulations are discussed in light of behavioral data on children's acquisition of the past tense and the validity of drawing conclusions about the acquisition of language from models of this sort.

Child, Preschool↗

PubMed1983

Variations in early and late event-related components of the auditory evoked potential with task difficulty.

A variation in the difficulty of an auditory discrimination was used to investigate the relationship between the event-related P165, N2 and P3 components of the auditory evoked potential. Equivalent increases in the latencies of all 3 components were found with increased task difficulty. The P165 component, however, could be differentiated from the two later components since it increased in amplitude with increased task demands while the N2 and P3 amplitudes remained constant. It is suggested that the P165, N2 and P3 components comprise a functional sequence in the processing of rare events and possibly involved in a subject's preparations for the future.

Adult↗

PubMed1985

Sex differences in the lateralization of language discrimination vs language production.

Two tachistoscopic studies employing normal males and females were done to investigate the inconsistency of obtained sex differences on visual laterality tasks to the extent that this inconsistency is task specific. Type of linguistic task (discrimination vs production) and control of attention were manipulated. Results showed that on language discrimination, the sexes were fairly equally lateralized, while on production tasks, females showed greater laterality differences. The attempt to control for attention resulted in higher field differences, but especially so for females. It is suggested that more consideration of task demands in laterality experiments should help clarify the nature of sex differences in laterality.

Adolescent↗

PubMed1990

Effects of luminance and blur on hemispheric asymmetries in temporal integration.

A task involving temporal integration of form was employed to examine the effects of input characteristics on hemispheric asymmetries. In Experiment 1, decreases in luminance produced greater improvement of right hemisphere (RH) performance. In Experiment 2, dioptric blur produced greater impairment of left hemisphere (LH) performance. The results suggest that spatial frequencies below nine cycles per degree are processed more efficiently in the RH. In Experiment 3, effects of input characteristics on hemispheric asymmetry were found to be dependent on the spatial frequencies required for processing by task demands, as mediated by interflash interval (IFI) duration. Increased blur produced greater impairment of LH performance at short IFI duration; at a longer IFI duration, however, increased blur produced equal impairment of RH and LH performance.

Adult↗

PubMed1990

Behavioral performance effects of nicotine in smokers and nonsmokers.

Performance on finger-tapping and handsteadiness, tasks opposite in response requirements, was compared between male smokers and nonsmokers (n = 10 each) on two occasions, once following intake of nicotine (15 micrograms/kg) by measured-dose nasal spray and once following placebo. Compared with nonsmokers, smokers had significantly greater increase in finger-tapping speed due to nicotine. On the other hand, smokers tended to have improved performance on handsteadiness (i.e., less involuntary movement) due to nicotine, while nonsmokers had impaired performance, although this difference was not significant. Nicotine-induced changes in performance on each task were inversely related, suggesting specificity of the behavioral effects of nicotine depending on task demands, rather than a generalized effect. These effects of nicotine on behavioral performance may be important in understanding the reinforcing value of nicotine intake, and differences in effects as a function of smoking history may suggest chronic adaptation to nicotine.

Adult↗

PubMed1984

Phencyclidine (PCP): some human studies.

Studies on the effects of PCP have been conducted in volunteers in the Army Laboratories and elsewhere and in illicit users. The present review has summarized the observations of many investigators which showed that the acute effects of PCP following several routes of administration were shown to be dose-related. High doses of PCP produce disturbing manifestations including psychosis, numbness, light-headedness, vertigo, ataxia, and nystagmus due to acute intoxication. Furthermore, some subjects became irritable, argumentative or negative under the conditions of social stress and demanding tasks. In addition to a variety of central action, PCP has also been shown to affect cardiovascular function, heat storage, and exercise performance. PCP can also induce, although rarely, prolonged toxic psychosis in chronic abusers and precipitate psychotic episodes in psychotic and prepsychotic personalities. Tolerance, but not physical dependence, develops to the effects of PCP. Psychologic dependence as indicated by craving for the drug has however been reported.

Administration, Oral↗

PubMedDate not supplied

The relationship of patient difficulty to therapist performance in interpersonal psychotherapy of depression.

The efficacy of Interpersonal Psychotherapy (IPT) in the treatment of ambulatory major depression was demonstrated in the recently completed NIMH Treatment of Depression Collaborative Research Program (Elkin et al. 1986). Factors which enhance or impede the administration of the treatment delimit effective patient care and should therefore be understood. This report examines the relationship of pretreatment patient attitudes and in-treatment patient difficulty to the ability of therapists to competently conduct IPT, using data from a training program in IPT. The hypothesis was that the patient's ability and willingness to establish a relationship and undertake the task demands of therapy would influence the therapist's ability to administer treatment. Patient difficulty was found to be strongly related to both therapists' and supervisors' judgements of therapist performance during IPT sessions: when patients were more difficult, therapists were judged to have performed more poorly. Patients' preexisting negative expectations about the potential outcome of treatment were associated with patient difficulty and poorer therapist performance, while the level of presenting symptomatology was not. Thus, it appears that the patient's ability to engage in a productive therapeutic relationship rather than the severity of his presenting problems influenced the therapist's ability to competently perform IPT. The findings regarding the relationship of patient difficulty to ratings of therapist performance suggest that patient difficulty should be taken into account in assessing therapist competence, whether for studies of therapeutic efficacy or for clinical supervision and training in general.

Adult↗

PubMed1983

Personality style differences in visual search performance.

The present study continues the examination of the personality styles in normal populations that have been described in the clinical literature. Earlier work has focused on behavioral, attitudinal, and cognitive components of the personality styles. The present study extends our exploration of the cognitive domain by examining the performance of different personality groups on a visual scanning task. Hysterics searched a stimulus array for letter targets at a mean rate of 0.04 +/- SD 0.177 seconds per unit of information, which was slower than the control rate of 0.0225 +/- SD 0.0078 seconds. The results indicated that hysterics used a serial search strategy to compensate for an inability to process information efficiently and thus differed from compulsives who conformed to task demands and performed similarly to controls.

Achievement↗

PubMed1987

Effects of instructions on habituation of the orienting response: another perspective on the study by Gruzelier and Eves.

A recent study by Gruzelier and Eves (1987, Int. J. Psychophysiol., 4: 289-291) purported to test the hypothesis of Iacono and Lykken (1979, Schizophrenia Bull., 5: 11-14), that instructions to subjects that clarify task demands facilitate habituation. However, the Gruzelier and Eves study did not provide an adequate test of this hypothesis. Moreover, contrary to the assertions of Gruzelier and Eves, the data presented in their paper are consistent with the predictions of Iacono and Lykken.

Acoustic Stimulation↗

PubMed1987

Rate of habituation of electrodermal orienting responses: a comparison of instructions to stop responding, count stimuli, or relax and remain indifferent.

Thirty-nine subjects listened to two series of repetitive tones, the second series of which was of higher or lower pitch and of higher intensity. Before the first series all subjects were given conventional instructions to relax and adopt a passive attitude to the tones. Before the second tone series one of three instructions was given: to maintain a relaxed and passive attitude, to inhibit responding, to count the stimuli silently. The three groups showed roughly equivalent rates of habituation to the first tones series but the group instructed to count the tones showed slower habituation than the groups instructed to remain indifferent or to inhibit responses. A recommendation to clarify task demands in habituation experiments, by informing subjects that the aim was to see how quickly subjects stopped responding, showed no advantages over conventional instructions.

Adult↗

PubMed1989

Eye movements and blinks: their relationship to higher cognitive processes.

Information about the timing of spontaneous eye blinks was abstracted while subjects performed a detection and identification task. We found blinks to be time-locked to saccadic eye movements involved in the identification of peripherally presented stimuli. The larger the required eye movement, the greater the likelihood of blink occurrence. Blink latencies were found to be significantly shorter for centrally, as compared to peripherally presented stimuli, and blinks were more likely to be associated with eye movement returning gaze to a central location than with movements associated with the identification of peripherally presented information. Thus, we conclude that the spontaneous or endogenous eye blink is triggered by aspects of information processing, and that blink latencies can be used as one tool for evaluating the level of complexity of such processing under a wide variety of task demands.

Blinking↗

PubMed1992

Active and passive P3 latency and psychometric performance: influence of age and individual differences.

The relationship of P3 latency of the event-related potential (ERP) to psychometric performance was investigated in 41 subjects who ranged in age from 20 to 88 years. P3 responses were recorded from subjects using an auditory oddball paradigm with and without task-demands. Subjects also received psychometric tests of verbal performance, visuospatial performance, concentration, and immediate, recent and remote memory. Factor analysis was used to reduce the set of psychometric measures to four factors (Verbal learning, general intelligence, narrative recall/fluency, and concentration). Both passive and active P3 latency showed a linear increase with age. Age was inversely correlated with verbal learning performance. After accounting for the influence of age, passive P3 latency correlated with the psychometric factor associated with narrative recall and verbal fluency. Active P3 latency was correlated with factors reflecting general intelligence and concentration. These findings suggest that cognitive processing speed contributes to psychometric performance in adults. The psychological or biological basis for this relationship remains to be identified.

Adult↗

PubMed1984

Clinical application of the P3 component of event-related potentials. II. Dementia, depression and schizophrenia.

Patients with dementia, schizophrenia and depression were tested with analogous auditory and visual event-related potential (ERP) paradigms designed to elicit a large P3. The patient groups were compared to age normative predictions derived from a large control sample for a number of ERP and behavioral variables. The results were similar for the auditory and visual paradigms. P3 latency was prolonged two or more S.D.s beyond that predicted by age for less than one-half of the demented patients. This latency prolongation was significant for the group as a whole but would result in too many false negatives if used diagnostically for individuals. Furthermore, increased P3 latency was not specific, as the schizophrenic patients also had later P3s. The amplitude of P3 was reduced in the demented patients, but it was also smaller in other patient groups. The only variable which distinguished the demented patients from both controls and from the other patients was the single trial P3 latency/RT correlation. The demented patients, as a group, had significantly lower P3 latency/RT correlations, but this effect also was not sensitive enough to be diagnostic for individuals. The data from these two paradigms suggest that the P3 amplitude and latency abnormalities observed reflect a common, rather than a diagnostically specific deficit. This study is in contrast to some others which report much more sensitivity and specificity in the use of P3 latency in the diagnosis of dementia. Differences in task demands, patient samples and ERP analysis techniques might explain some of the discrepancy.

Auditory Perception↗