Mnemonic search, but not arithmetic transformation, is associated with psychophysiological inhibition

The possibility that mnemonic search and arithmetic transformation induce transient heart rate (HR) slowing was studied. Transient HR slowing was assumed to result from the inhibition of premature responding during information processing. Twenty young men performed a 2-step reaction time task. Two precues were followed by a choice cue: 2 additional precues and 1 final choice cue. Choice cues were varied to compare spatial and perceptual-motor processing with mnemonic or arithmetic processing. Cardiac interbeat interval and impedance cardiograph measures were taken beat by beat. The preparation for the respond cue was associated with HR slowing followed by HR speeding associated with response initiation. Mnemonic search induced a transient HR slowing before the speeding initiated by the motor response. Arithmetic transformation did not, but processing of the arithmetic series decreased cue-induced transient HR slowing. Mnemonic search may be associated with a psychophysiological inhibition analagous to that observed in perceptual-motor tasks during response selection.

Growth spurts in brain maturation during middle childhood as indexed by EEG power spectra

Developmental changes in background EEG power spectra were examined in 5-12-year-old children. The results confirmed older and more recent studies that reported continuous maturation and more sudden growth spurts in power spectral amplitude. EEG power in the Delta and Theta frequency bands decreased gradually with age, while power in the Alpha and Beta bands changed very little. Changes in spectral power were relatively increased between 6 and 7 years and between 9, 10 and 11 years. Some methodological problems concerning the assessment of cross-sectional age changes in EEG power spectra were addressed. Peak frequency increased with age; between 5 and 12 years the peak in the power spectrum shifted from fast Theta via slow Alpha to fast Alpha. Transformation of absolute power into relative power produced a high degree of interdependency between the broad bands. This interdependency affected the change with age of relative Alpha. Absolute power Alpha only changed in the eldest children, but because of a substantial decrease in Delta and Theta with increasing age, the proportion of Alpha relative to the other three bands increased. Hence, relative Alpha provided a good indication of the general maturational trend.

Does the heart know what the ears hear? A heart rate analysis of auditory selective attention

Between- and within-channel auditory selective attention were examined by presenting subjects with tone pips randomly to opposite ears; some pips had a slightly different pitch. Subjects were instructed to count rare, deviant tone pips at one ear and ignore all input to the other ear. Heart rate was sampled twice: once for the attended tone pips and once for the nonattended stimulus series. Heart rate responded differently to attended tone pips. While subjects were waiting for the rare stimulus to occur, heart rate slowed until the deviant stimulus was detected, which was followed by heart rate acceleration. Anticipatory heart rate deceleration was largely absent for nonattended series, and rare tone pips presented at the nonattended ear were not followed by acceleratory recovery. All tone pips elicited cardiac cycle time effects, that is, stimuli presented at short delays after the R wave prolonged the concurrent interbeat interval more than stimuli presented later. The cardiac cycle time effect was not altered by stimulus relevance (attended vs. nonattended) or significance (standard vs. rare). These results suggest that all stimuli receive preliminary perceptual analysis, but only attended stimuli are processed for further evaluation.

Information processing in patients with early and continuously-treated phenylketonuria

A total of 33 patients with early and continuously-treated phenylketonuria (PKU) between 7 and 16 years of age and 33 matched controls participated in a study examining perceptual, central, and response-related mechanisms of information processing. The specific mechanisms studied were: perceptual filtering, memory search, response selection, response execution, and motor presetting. In addition, groups were compared on mean intelligence level and task oriented behaviour. The performance of the PKU patients practically matched that of the controls on all three tasks, suggesting that PKU patients who are continuously maintained on a well-controlled phenylalanine-restricted diet are not impaired in the elementary mechanisms of information processing. Furthermore, groups did not differ in mean IQ or task-oriented behaviour.

CONCLUSION

These results underline the importance of continued, well-controlled dietary treatment. Further studies are recommended to obtain a more complete evaluation of the potential of PKU patients under these stricter dietary treatment conditions.

When global information and local information collide: a brain potential analysis of the locus of interference effects

The objective of the current experiment was to perform a psychophysiological investigation of the interference effects of global information on the analysis of local information, and vice versa. Subjects' choice reactions to letters at one level of information in a compound letter stimulus were impaired when letters at the other (irrelevant) level signified the opposite response. In the absence of differences in processing speed, global and local information produced symmetrical interference effects. Interference effects did vary, however, as a function of temporal advantage for the processing of information from either level. The individually faster level (be it global or local) interfered with the slower level but was itself relatively immune to such interference by the slower level. Analysis of event-related brain potentials and of the electromyogram revealed that incongruent irrelevant letters induced perceptual conflict but not response competition, thus pointing to a perceptual locus of processing dominance for the faster processed level of information in the compound stimulus.

Information processing deficits in children with early and continuously treated phenylketonuria?

Thirty-three patients with early and continuously treated classical phenylketonuria (PKU) and 33 controls matched for age, gender, and educational level of both parents, participated in a chronometric study exploring elementary mechanisms of information processing. Subjects performed speeded performance tasks designed to systematically vary the load on perceptual, central, and output-related mechanisms of information processing. A preliminary analysis of the data indicated that the overall performance of patients with early and continuously treated PKU practically matched that of the controls on all three tasks. Although this finding must be interpreted with caution as it is based on only a preliminary analysis of the data, it suggests that PKU patients who are continuously maintained on a well-controlled phenylalanine-restricted diet are not deficient in the elementary mechanisms of processing. Given the more recent findings indicating that young children with early-treated classical PKU have specific cognitive deficits in the executive function skills, despite relatively strict dietary control, the authors suggest that future studies should focus on these higher-order cognitive processes.

On the discrimination between global and local trend hypotheses of life-span changes in processing speed

Meta-analyses of age effects on processing speed suggest a single, global mechanism underlying developmental speeding and slowing in the elderly. Myerson, Hale, Wagstaff, Poon and Smith (1990) proposed an information loss model assuming that a constant amount of information is lost at each processing step in all age groups whereas the rate of information loss differs between age groups. In this study, a series of simulations has been conducted comparing global versus local information loss. This has been outcomes of these deterministic and stochastic varieties of the information loss model. The outcomes of these comparisons were consistently negative; the information loss model fails to discriminate between global and local age effects on the reaction process. The simulations were followed by a discussion of Hohle's (1967) scheme for investigating selective age effects on processing speed. It was concluded that the combined approach of stage and distribution analysis of the reaction process augmented with psychophysiological time markers provides a powerful tool for the study of life-span changes in processing speed.

How are tonic and phasic cardiovascular changes related to central motor command?

We examined the influence of central motor command on heart rate, respiration, and peripheral vascular activity. Central command was enhanced or reduced using tendon vibration. Muscle tension was held constant permitting the examination of variation in central command. Experiment 1 demonstrated in 13 college-aged males an enhancement of heart rate and vascular responses to an isometric, extensor contraction when vibration of the flexor tendon was added. Experiment 2 asked whether changes in central command interacted with phasic cardiovascular changes such as stimulus-linked anticipatory cardiac deceleration. Twenty college-aged males performed either an isometric flexor or extensor contraction with or without flexor tendon vibration. As expected, vibration enhanced cardiovascular change with extensor contraction more than with flexor contraction. Relative to control contractions, however, the flexor change was not an absolute decrease in cardiovascular change. More importantly, tendon vibration failed to alter phasic cardiovascular changes. Force and central commands for force induce cardiovascular change, but this change seems independent of phasic changes induced by the anticipation and processing of environmental stimuli.

Scalp topography of event-related brain potentials and cognitive transition during childhood

This study examined the relation between cognitive development and the ontogenesis of event-related brain potentials (ERPs) during childhood. First, the level of cognitive development was assessed in girls between 5 and 7 years of age with a standard Piagetian conservation kit. Then these children performed 2 experimental tasks: a visual selective attention (oddball) task and an experimental analogue of the Piagetian conservation of liquid quantity task. The oddball task required the child to count silently the number of rare stimuli presented in a series of frequent stimuli. The ERPs elicited in this task showed a positive wave with a centroparietal scalp distribution and a maximum amplitude at around 600 ms poststimulus. In the experimental analogue of the conservation of liquid quantity task, the child was presented with a choice stimulus requiring a left- or right-hand button press. The proportion of correct responses discriminated successfully between conservers and nonconservers as established by traditional Piagetian assessment procedures. The ERPs obtained in the experimental analogue of the conservation task were characterized by a broad positivity with a centroparietal scalp distribution. The broad positivity discriminated significantly between nonconservers and conservers but not between age groups. These findings received additional support from topographic and symmetric dipole analyses of the ERPs. The results of the dipole analysis suggested more anterior ERP sources for the nonconservers during the early part of stimulus analysis and more lateralized ERP sources for conservers during the later part of information processing. It is concluded that ERPs may provide a window on the relation between brain maturation and stage-wise cognitive development.

On the synchrony of stopping motor responses and delaying heartbeats

Recent evidence suggests that inhibition of a motor response may occur as late as the final stages of response execution. Response production involves central commands for autonomic support as well as motoric action. Autonomically controlled responses were used in conjunction with electromyographic and performance indices to examine the timing and flexibility of inhibition. Twenty young male Ss performed a choice reaction time task with stimuli timed according to when they occurred in relation to the R wave of the electrocardiogram. Stop signals, presented on 30% of the trials, induced inhibition. The performance and physiological results generally supported the horse-race model of inhibition. Inhibition was observed as late as during response execution. A short-latency, phasic lengthening of interbeat interval was suggested to reflect the midbrain coordination of the countermanding of response execution.

On the synchrony of stopping motor responses and delaying heartbeats

Recent evidence suggests that inhibition of a motor response may occur as late as the final stages of response execution. Response production involves central commands for autonomic support as well as motoric action. Autonomically controlled responses were used in conjunction with electromyographic and performance indices to examine the timing and flexibility of inhibition. Twenty young male Ss performed a choice reaction time task with stimuli timed according to when they occurred in relation to the R wave of the electrocardiogram. Stop signals, presented on 30% of the trials, induced inhibition. The performance and physiological results generally supported the horse-race model of inhibition. Inhibition was observed as late as during response execution. A short-latency, phasic lengthening of interbeat interval was suggested to reflect the midbrain coordination of the countermanding of response execution.

A nonstationarity test for the spectral analysis of physiological time series with an application to respiratory sinus arrhythmia

The spectral analysis of time series requires the signal to be at least weakly stationary; i.e., the mean, (co-) variance, and spectrum of the time series should not vary from segment to segment. It is commonly assumed that psychophysiological time series are not stationary. This study introduces a nonstationarity test to the psychophysiological literature, which is derived from evolutionary spectral analysis. Basically, the test consists of a double window technique in both the time and frequency domains, leading to a two-way analysis of variance for times and frequencies. In the current study, the nonstationarity test is applied to heart rate data obtained in a typical psychophysiological setting. Heart rate and respiration were measured in four age groups under four conditions--rest, paced breathing, vigilance, and reaction time. The results indicate that only few physiological time series were completely stationary. However, for every subject, and in every condition stationary stretches could be found that were long enough to apply spectral analysis. Spectral measures (power, coherence, and phase spectra) were then compared for stationary parts of the data and the total data. This comparison indicated that nonstationarity affects all spectral measures. Most importantly, Stationarity x Task Condition x Frequency Band interactions were observed for coherence and phase spectra, and there were significant interactions with age for each of the spectral indices. These findings suggest that nonstationarity may result in biased outcomes of significance tests of the effects of task manipulations on the spectral indices of cardiac time series. Thus, it was concluded that the stationarity test should be routinely applied in the spectral analysis of physiological time series. In addition, it was suggested that the nonstationarity test has an even wider range of application that might be of interest to the psychophysiologist.

Discovery of the P300: a tribute

The significant and enduring contributions made to cognitive psychophysiology by Samuel Sutton and his colleagues in the first two papers on the P300 component of the event-related brain potential are discussed. The remarkable quality of these contributions is revealed in the fact that the issues that motivated the series of experiments reported by these investigators continue to be of core importance to the field.

Graphical and statistical techniques for cardiac cycle time (phase) dependent changes in interbeat interval

Cardiac cycle time effects refer to the relative lengthening or shortening of a single cardiac cycle as a function of when in the cycle brief sensorimotor events occur. These effects may provide short-latency measures of cardiac sensitivity to psychological events. Conventional representations have, however, failed to clearly separate changes in interbeat interval due to cycle time--i.e., phase dependent changes--from other types of change. This paper advocates a particular technique of plotting to solve these representation problems. Heartbeat timing is represented in real time and in the context of beats both preceding and following the event of interest. The plot, a phase-sensitive plot, conceptualizes phase-sensitive (cardiac cycle time) effects as a change in linear or higher order trend. Thus, an adaptation of trend analysis is proposed as an efficient statistical analysis that follows directly from the proposed representational technique.

Forearm, chest, and skin vascular changes during simple performance tasks

Momentary changes in vascular variables were examined in four experiments which all induced preparation for an expected stimulus. Response requirements were minimized to permit examination of changes during stimulus presentation unconfounded with overt movement. The hypothesis examined was that vascular changes serve to maximize tissue perfusion at the time of anticipated action. Impedance plethysmographic measures of the chest and forearm were scored both for transit times and amplitude/slope indices. Similar indices were derived from photo-plethysmographic signals from the nail-bed of the thumb. The results suggested that preparatory vascular changes could be divided into an initial expectancy phase started at least 2 or 3 seconds prior to the anticipated events and a specific preparatory phase occurring just prior to and during stimulus presentation. Transit time shortening and maintained vasoconstriction characterized the initial expectancy phase when a finger movement, but not an effortful grip, was the anticipated response. Transit time lengthening and vasodilation generally characterized the specific preparation phase, but are disrupted when a signal inhibiting the response is likely to occur. Decelerative heart rate changes were positively related to the slope of the systolic rise in the chest impedance measure, suggesting that both cardiac and vascular changes may act together. Overall, the results were moderately supportive of the view that the heart and vasculature act together to maximize tissue perfusion at the time of anticipated action.

Weak sensory stimuli induce a phase sensitive bradycardia

We attempted to demonstrate that significant perceptual stimuli would induce different degrees of heart rate deceleration depending on when (phase) in the cardiac cycle they occurred. Relative to previous work, we concurrently examined a number of factors that might alter the amplitude of such a cardiac cycle time effect. Stimulus intensity and presence or absence of a speeded response were manipulated. Liminal stimuli and a perceptual rather than motor set were expected to maximize any cardiac cycle time effect. Respiratory phase, length of average interbeat interval, and number of trials were also investigated. Twenty-four college aged, male volunteers were randomly separated into equal groups receiving instructions either to judge which of two weak visual stimuli occurred or to execute a speeded, discriminative response to the stimuli. Discriminative stimuli were presented at either 0, 150, 250, 350, or 500 ms after the R-wave of the electrocardiogram. Stimuli were presented with an intensity that had yielded either 63% or 90% correct detections in a prior psychophysical assessment. A phase dependent deceleration occurred after both intensities of stimuli. Poststimulus deceleration was greater for stimuli in early to mid cycle as suggested by earlier work. As expected, this result was clear when the stimuli were presented during the expiratory phase of respiration. Neither perceptual/motor set nor stimulus intensity altered the phase sensitive deceleration. Thus, phase sensitive deceleration was confirmed using demanding sensory stimuli and an improved representational technique.

Response inhibition initiates cardiac deceleration: evidence from a sensory-motor compatibility paradigm

Two experiments tested the hypothesis that response selection processes alter the timing of the shift between anticipatory cardiac deceleration and acceleratory recovery. Experiment 1 compared changes in cardiac interbeat interval induced by the manipulation of sensory-motor compatibility in a four choice reaction time task. A direct spatial mapping between a linear array of light-emitting diodes (LEDs) was compared to randomly assigned, indirect (non-compatible) mappings. Experiment 2 repeated these two tasks and added a two choice condition with direct spatial mapping, a task frequently employed to examine heart rate deceleration. Fifteen college aged males participated in Experiment 1; 18 college aged males participated in Experiment 2. In both experiments anticipatory cardiac deceleration either reached a plateau or shifted to acceleration by the interbeat interval in which the stimulus occurred. In contrast to previous reports, a secondary deceleration, rather than cardiac acceleration, often followed the stimulus. The secondary deceleration was greater with non-compatible mapping, slow response speeds, and short intertrial intervals. The findings suggested that the motoric inhibition required during response selection induces a phasic cardiac deceleration.

On the shift from anticipatory heart rate deceleration to acceleratory recovery: revisiting the role of response factors

The influence of inducing motor responses of low and high force at different times in the cardiac cycle was examined. A handgrip response was used which allowed the separation of response initiation from response completion. Based on earlier work, we expected initiation, rather than completion, to initiate poststimulus cardiac acceleration. We also thought that preparation for a high force response might alter preparatory changes of interbeat interval differently from preparation for a low force response. Fifteen college-aged male subjects performed a warned reaction time task in which a visual stimulus signalled a handgrip requiring either a high or a low force to close. NoGo trials in which an inhibit signal was presented occurred on 12% of the trials. Stimuli occurred either on the R-wave of the electrocardiogram or 300 ms later. Reaction speed was varied in different trial blocks by rewarding response times of 200 ms (+/- 50 ms), 300 ms, or 400 ms. Results based on the timing of response initiation were essentially identical to those based on the timing of response completion. High force relative to low force was associated with both earlier response initiation and earlier cardiac acceleration. Force did not alter preparatory cardiac deceleration. Force and response speed did, however, alter the level of heart rate after response occurrence. Thus, response initiation (or an earlier response process) appears to induce a cardiac acceleration whose level is influenced by the speed and force of the motor response.

An additive factors analysis of the effect(s) of location cues associated with auditory stimuli on stages of information processing

The additive factors method (AFM) was used as a tool for assessing the locus (or loci) of the detrimental effect of auditory location cues in the chain of (visual) information processing. In the first experiment the location variable was factorially combined with response specificity, which is assumed to affect the response adjustment stage. A second experiment was performed in which movement amplitude, assumed to affect the response programming stage, was manipulated in addition to the location variable and a different variety of response specificity. Finally, the location variable was combined with relative S-R frequency, which is also assumed to affect the response programming stage, in a third experiment. The results of these experiments showed additive effects of the location variable with motor variables. The remaining two experiments were designed to assess the effects of location cues on response selection. In these experiments the location variable was combined with the number of response alternatives. Response speed decreased with an increase in the number of response alternatives. However, the effects of the location variable and number of response alternatives were additive. According to the additive factor logic, then, the results of experiments 1, 2 and 3 seem to indicate that the locus of interference of the location cues is not in the later response stages of the reaction process. The results of the last two experiments were interpreted to suggest that the effects of location cues and the number of response alternatives affect either different processes within the response selection stage or affect different process stages. It was concluded that the latter alternative explains most of the data currently available and that the stimulus identification stage is the most likely candidate for the locus of the location effect.

Does the heart know what the eye sees? A cardiac/pupillometric analysis of motor preparation and response execution

Autonomic response measures are well suited for the study of preparation because they allow the analysis of covert aspects of performance. This is illustrated by an experiment in which task-evoked cardiac and pupillary responses were compared during a disjunctive (Go/No Go) reaction task. The motoric demands of the task were varied by manipulating foreperiod length (4 and 8 s) and probability of response (25%, 50%, and 75%). Reaction time increased with foreperiod length and decreased with probability of response. The depth of anticipatory heart rate deceleration was affected only by foreperiod length. Analysis of the beats during, and directly preceding and following the imperative stimulus revealed that interbeat intervals increased with probability of responding and foreperiod duration. The effect of stimulus timing relative to the R-wave of the ECG was also analyzed. Early occurring stimuli prolonged the cycle of their occurrence more than late occurring stimuli. The cycle time effect was somewhat more pronounced for No Go stimuli than for Go stimuli. The subsequent cycle was shorter for early occurring stimuli compared to late stimuli. This effect was stronger for Go compared to No Go trials. Both Go and No Go reactions elicited significant pupil dilations. The No Go dilation peaked earlier than the Go dilation and its amplitude was smaller. Probability of responding affected the latency of the No Go dilation but not that of the Go dilation. The current results justify an interpretation of preparation in terms of a timing mechanism (indexed by heart rate deceleration during the foreperiod) and a mechanism allocating processing resources to stimulus encoding (indexed by cardiac slowing just prior to stimulus occurrence) and response preparation (indexed by continued cardiac deceleration and pupillary dilation).