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Biomedical subjects

R J Barry

Publications and source records attributed to R J Barry.

At least 73 records · Page 4Linked to original sources
PubMed1988

Significance and components of the orienting response: effects of signal value versus vigilance.

Bernstein et al. (1985) presented the results of an extensive study of the effects of stimulus significance upon electrodermal and heart rate responses. This report examines some of these data from the perspective of preliminary process theory (Barry, 1984b). The categorisation of significance manipulations into prestimulus vigilance and poststimulus signal value outcomes is supported by differential responding in the electrodermal and cardiac measures, as predicted by preliminary process theory.

Arousal↗
PubMed1988

An application of psychophysiology in sports psychology: heart rate responses to relevant and irrelevant stimuli as a function of anxiety and defensiveness in elite gymnasts.

One problem in the optimization of athletic performance is that consistency in practice situations is not always carried over to competitive situations. There is an increase in irrelevant stimuli in competition which cannot always be gated out satisfactorily by the anxious athlete. We investigated the physiological responses to relevant and irrelevant stimuli of 48 elite female gymnasts differing in levels of anxiety and defensiveness. Cardiac responses were recorded to tone presentations and analyzed as a function of instructions, anxiety manipulation and group. The results suggest that phasic responses of high-anxious gymnasts were larger than those of low-anxious gymnasts. High-anxious gymnasts experience more difficulty in completely gating out the occurrence of irrelevant stimuli than do low-anxious gymnasts. Finally, under anxiety-producing conditions, high levels of defensiveness and anxiety in combination appear to have a debilitating effect on the gymnast's ability to discontinue processing of irrelevant stimuli, while truly low-anxious subjects appear distracted from processing relevant stimuli. Further investigation of the interactions between levels of trait anxiety and anxiety-producing situations in a sport-specific domain appear warranted. The role of defensiveness in these interactions should also be investigated.

Adolescent↗
PubMed1988

Coding of stimulus parameters in autistic, retarded, and normal children: evidence for a two-factor theory of autism.

Phasic changes in respiratory period, electrodermal activity, and the vasoconstrictive peripheral pulse amplitude response, were examined in matched groups of autistic, retarded, and normal children using repeated presentation of simple visual and auditory stimuli of differing magnitudes. Analysis of response magnitudes as a function of group membership, trials, stimulus magnitude, and age, indicated both similarities and differences between the autistic and control groups. The autistic group differed from the control groups in its failure to show response habituation to repeatedly presented stimuli. However, data indicated that autistic children coded stimulus magnitude similarly to controls, suggesting that the failure to adequately process stimulus novelty does not reflect a general processing failure. Autistic children also exhibited relative hyperreactivity in all measures. Age effects showed this to be interpretable as reflecting developmental delay. These two differences support a recent two-factor theory of autism.

Adolescent↗
PubMed1987

The kinetic mechanism of yeast inorganic pyrophosphatase.

The kinetic mechanism of yeast inorganic pyrophosphatase (PPase) was examined by carrying out initial velocity studies. Ca2+ and Rh(H2O)4(methylenediphosphonate) (Rh(H2O)4PCP) were used as dead-end inhibitors to study the order of binding of Cr(H2O)4PP to the substrate site and Mg2+ to the "low affinity" activator site on the enzyme. Competitive inhibition was observed for Ca2+ vs Mg2+ (Kis = 0.93 +/- 0.03 mM), for Rh(H2O)4PCP vs Cr(H2O)4PP (Kis = 0.25 +/- 0.07 mM), and for RH(H2O)4PCP vs Mg2+ (Kis = 0.38 +/- 0.03 mM). Uncompetitive inhibition was observed for Ca2+ vs Cr(H2O)4PP (Kii = 0.49 +/- 0.01). On the basis of these results a rapid equilibrium ordered mechanism in which Cr(H2O)4PP binding precedes Mg2+ ion binding is proposed. The inert substrate analog, Mg(imidodiphosphate) (MgPNP) was shown to induce Mg2+ inhibition of the PPase-catalyzed hydrolysis of MgPP. The Mg2+ inhibition observed was competitive vs MgPP and partial. These results suggest that Mg2+/MgPNP release from the enzyme occurs in preferred rather than strict order and that the Mg2+/MgPP-binding steps are at steady state. Zn2+, Co2+, and Mn2+ (but not Mg2+) displayed activator inhibition of the PPase-catalyzed hydrolysis of PPi (this study) and of Cr(H2O)4PP (W.B. Knight, S. Fitts, and D. Dunaway-Mariano, (1981) Biochemistry 20, 4079). These findings suggest that cofactor release from the low affinity cofactor site on the enzyme must precede product release and that Zn2+, Mn2+, and Co2+ (but not Mg2+) have high affinities for the cofactor sites on both the PPase.M.MPP and PPase.M.M(P)2 complexes. The role of the metal cofactor in determining PPase substrate specificity was briefly explored by testing the ability of the Mg2+ complex of tripolyphosphate (PPPi) (a substrate for the Zn2+-activated enzyme but not the Mg2+-activated enzyme) to induce Mg2+ inhibition of PPase-catalyzed hydrolysis of MgPP. MgPPP was shown to be as effective as MgPNP in inducing competitive Mg2+ inhibition (vs MgPP). This result suggests that the low affinity Mg2+ cofactor-binding site present in the enzyme-MgPP complex is maintained in the enzyme-MgPPP complex. Thus, failure of Mg2+ to bind to the enzyme-MgPPP complex was ruled out as a possible explanation for the failure of the Mg2+-activated enzyme to catalyze the hydrolysis of MgPPP.

Enzyme Activation↗
PubMed1987

Time-dependent bradycardia: a new effect?

Time-dependent bradycardia, a term introduced by the Laceys (Lacey and Lacey, 1980), refers to the fact that the duration of a cardiac cycle is related to when in that cycle, or the just preceding cycle, certain stimuli occur. Since stimulus effects on heart activity with very short latencies have been known for a long time, the question arises whether the effect is one in its own right, or whether it is simply a result of the new way of data reduction introduced by the Laceys. Theoretically, the effect can be explained without assuming anything beyond the well-known short latency bradycardia often observed upon stimulation. Derivation of the effect from an empirical curve of cardiac activity not related to cycle phase shows that we are not dealing with a new effect.

Adult↗
PubMed1987

A comparison of phasic cardiac responses derived from the electrocardiogram and the peripheral pulse.

In recent years, psychophysiologists have increasingly used the peripheral pulse as a more convenient source of cardiac information than the electrocardiogram. We explored some of the measurement problems associated with this choice by comparing estimates, produced by both data sources, of the cardiac response evoked by innocuous visual stimuli. The most important difference is that pulse transit time results in the immediately-prestimulus beat of a significant proportion of pulse-derived responses being mislabelled as the following beat, shifting the entire apparent response by one beat. This reduces correlations between the data streams, and has implications for the adequate measurement of evoked cardiac responses.

Adult↗
PubMed1987

Stimulus omission and the orienting response: latency differences suggest different mechanisms.

Following response habituation to a regularly-presented innocuous stimulus, omission of that stimulus may elicit a response. The missing-stimulus effect has been of some importance in the development of Orienting Response (OR) theory, particularly Sokolov's neuronal model/stimulus comparator mechanism. Western work on this effect has been somewhat equivocal, with only some subjects emitting small responses at stimulus omission. Barry (1984b) proposed that the fragility of the data might reflect the elicitation of a voluntary OR (Maltzman, 1979) rather than the more robust (reflexive) involuntary OR commonly emphasised in OR work. A prediction generated from this hypothesis, that the OR to stimulus omission has a longer latency than that associated with physical stimuli, was tested here. The first experiment found such an effect in the electrodermal responses to simple visual stimuli and their omission. This was replicated in a second experiment with both significant and indifferent visual stimuli. These latency delays (group mean differences ranged from 1.15 to 1.65 s) imply an intervening process in the elicitation of the electrodermal response to stimulus omission, compatible with it being viewed as a voluntary OR. An implication of these results for the conceptualization of other ORs to stimulus change is discussed.

Adult↗
PubMed1984

Cardiovascular and electrodermal responses to simple stimuli in autistic, retarded and normal children.

Phasic changes in respiratory period, electrodermal activity (EDA), the evoked cardiac response (ECR), and the vasoconstrictive peripheral pulse amplitude response (PPAR), were examined in matched groups of autistic, retarded, and normal children, using repeated presentation of simple visual and auditory stimuli. Analysis as a function of group membership and age indicated that respiratory pause and EDA showed habituation in the retarded and normal groups, but not in the autistic group, with no age effects in any group. PPAR and ECR showed no habituation in any group, but within-group age differences, and a higher mean response level for the autistic subjects. The autistic children did not display the diminution of response level with increased age that was characteristic of both the control groups. These effects were obtained across both modalities. Results could not be attributed to between-group tonic cardiac arousal differences, and were interpreted as further indications of diminished sensitivity to reductions in stimulus novelty, as well as developmental delay, in early-onset psychosis.

Adolescent↗
PubMed1983

Developmental effects in the cerebral lateralization of autistic, retarded, and normal children.

This experiment was designed to determine whether increasing evidence of generalized developmental delay in early-onset psychosis was apparent at a cortical level in autistic children. Using magnitude of dominant ear advantage as an indicator of relative cerebral dominance, unwarned simple reaction time (RT) to monaural presentation of tones was investigated in matched groups of autistic, retarded, and normal children. Analysis of RTs and relative ear advantage as a function of group membership and chronological age indicated that the autistic children showed significant developmental delay in both RT and the establishment of cerebral dominance compared to the control groups. These results thus provide additional evidence of generalized maturational delay at a cortical level in early-onset psychosis, and suggest that the maturational delay of the autistic children is more extensive than the developmental deficits implied by their intellectual impairment.

Adolescent↗
PubMed1983

Flat feet in children.

In the assessment of the child with flat feet a sound knowledge of arch and subtalar biomechanics, epidemiology, and etiology is important. The occurrence and natural history of flat feet are presented, and treatment modalities that have withstood the test of time are discussed.

Arthrodesis↗
PubMed1983

A 50-cm fillet flap for preservation of maximal lower extremity residual limb length.

A 50-cm fillet flap permitted above-knee amputation in lieu of hip disarticulation in a 20-year-old woman who had sustained severe injuries in a motorcycle accident. Although the flap was unusually long, the principles followed were the same as those for posterior flaps used in below-knee amputations and fillet flaps of the digits. The flap allowed preservation of maximal length in the residual limb and fully sensible skin coverage, both of which facilitated prosthetic usage.

Adult↗
PubMed1981

General maturational lag as an essential correlate of early-onset psychosis.

Evidence for the increasing recognition of maturational lag in addition to intellectual impairment, associated with the syndrome of early-onset psychosis, is presented to indicate that developmental variables play a central role in the behavioral profile of autistic children. The failure of research to give methodological consideration to control of these variables is discussed, and implications for the interpretation of results from experimental studies are outlined. It is suggested that the distinction between controlling not only for mental age but also for chronological age to facilitate the delineation of specific deficits in this syndrome.

Adolescent↗
PubMed1980

Habituation of electrodermal and respiratory responses to visual stimuli as a function of personality differences in affect level.

The relationship between personality level of affect and habituation of electrodermal and respiratory measures was examined in two groups of normal subjects designated Low P (LP) and High P (HP) according to the P scale of the Eysenck Personality Questionnaire. Experiment 1 examined changes as a function of repeated presentation of simple visual stimuli. Group HP displayed reduced habituation rates for both respiratory pause and skin resistance response (SSR), although initial reactivity levels were similar for both groups. This effect was confirmed more strongly in Experiment 2, which utilized a simple counting task and groups separated more widely on P. The implications of these group differences were discussed in relation to the psychophysiological functioning of autistic children.

Adult↗
PubMed1980

A review of psychophysiology in early onset psychosis.

Research on psychophysiological functioning in early onset psychosis is reviewed within the context of etiological formulations stressing perceptual and selective attention abnormalities. Electroencephalographic (EEG) measures, including resting EEG level, alpha blocking, average evoked response, and contingent negative variation, have received most attention in the literature; cardiovascular and electrodermal indices have not been so extensively explored in this group of children. While the nature of differential reactivity in early onset psychosis has not been thoroughly investigated, limited evidence suggests that the central behavioral anomalies associated with the condition may result from abnormal neurophysiological reactivity to sensory stimulation. Further studies of the psychophysiological functioning of these children should yield data useful in the clarification of etiology.

Adolescent↗