A psychophysiological investigation of cognitive-energetic relations in human information processing: a heart rate/additive factors approach

Anticipatory cardiac deceleration estimates cognitive performance in virtual reality beyond tonic heart period and heart period variability

Anticipatory cardiac deceleration is the lengthening of heart period before an expected event. It appears to reflect preparation that supports rapid action. The current study sought to bolster anticipatory deceleration as a practical and unique estimator of performance efficiency. To this end, we examined relationships between deceleration and virtual reality performance under low and high time pressure. Importantly, we investigated whether deceleration separately estimates performance beyond basal heart period and basal high-frequency heart rate variability (other vagally influenced metrics related to cognition). Thirty participants completed an immersive virtual reality (VR) cognitive performance task across six longitudinal sessions. Anticipatory deceleration and basal heart period/heart period variability were quantified from electrocardiography collected during pre-task anticipatory countdowns and baseline periods, respectively. At the between-person level, we found that greater anticipatory declaration was related to superior accuracy and faster response times (RT). The relation between deceleration and accuracy was stronger under high relative to low time pressure, when good performance requires greater efficiency. Findings for heart period and heart period variability largely converge with the prior literature, but importantly, were statistically separate from deceleration effects on performance. Lastly, deceleration effects were detected using anticipatory periods that are more practical (shorter and more intermittent) than those typically employed. Taken together, findings suggest that anticipatory deceleration is a unique and practical correlate of cognitive-motor efficiency apart from heart period and heart period variability in virtual reality.

Blood pressure reaction to negative stimuli: Insights from continuous recording and analysis

Individuals with a tendency toward abnormally enhanced cardiovascular responses to stress are at greater risk of developing essential hypertension later in life. Accurate profiling of continuous blood pressure (BP) reactions in healthy populations is crucial for understanding normal and abnormal emotional reaction patterns. To this end, we examined the continuous time course of BP reactions to aversive pictures among healthy participants. In two experiments, we showed participants negative and neutral pictures while simultaneously measuring their continuous BP and heart rate (HR) reactions. In this study, BP reactions were analyzed continuously, in contrast to previous studies, in which BP responses were averaged across blocks. To compare time points along a temporal continuum, we applied a multi-level B-spline model, which is innovative in the context of BP analysis. Additionally, HR was similarly analyzed in order to examine its correlation with BP. Both experiments revealed a similar pattern of BP reactivity and association with HR. In line with previous studies, a decline in BP and HR levels was found in response to negative pictures compared to neutral pictures. In addition, in both conditions, we found an unexpected elevation of BP toward the end of the stimuli exposure period. These findings may be explained by the recruitment of attention resources in the presence of negative stimuli, which is alleviated toward the end of the stimulation. This study highlights the importance of continuous measurement and analysis for characterizing the time course of BP reactivity to emotional stimuli.

Cardiac Response During Auditory Selective Attention to Tones and Affective Sounds

We conducted an experiment to determine if attention to affective sounds showed a lateral bias. Twenty-two participants were instructed to respond to one of two pure tones presented monaurally and to a set of pleasant and unpleasant sounds from the International Affective Digitized Sounds set. Participants were instructed to respond to pleasant or unpleasant sounds in the right or left ear, attending to pleasant/right, pleasant/left, unpleasant/right, and unpleasant/left sounds in separate blocks. Evoked cardiac response to the tones showed significant cardiac deceleration in response to attended sounds in the attended ear. In addition, pleasant sounds elicited significant cardiac deceleration when attended in the right ear, but not in the left. Unpleasant sounds elicited significant cardiac deceleration when attended in both ears. Consistent with the anterior valence hypothesis, our data suggests that pleasant sounds are mainly processed in the left hemisphere, but in contrast to this hypothesis, unpleasant sounds are processed bilaterally.

The heartbrake of social rejection: heart rate deceleration in response to unexpected peer rejection

Social relationships are vitally important in human life. Social rejection in particular has been conceptualized as a potent social cue resulting in feelings of hurt. Our study investigated the psychophysiological manifestation of hurt feelings by examining the beat-by-beat heart rate response associated with the processing of social rejection. Study participants were presented with a series of unfamiliar faces and were asked to predict whether they would be liked by the other person. Following each judgment, participants were provided with feedback indicating that the person they had viewed had either accepted or rejected them. Feedback was associated with transient heart rate slowing and a return to baseline that was considerably delayed in response to unexpected social rejection. Our results reveal that the processing of unexpected social rejection is associated with a sizable response of the parasympathetic nervous system. These findings are interpreted in terms of a cardiovagal manifestation of a neural mechanism implicated in the central control of autonomic function during cognitive processes and affective regulation.

Ready...go: Amplitude of the FMRI signal encodes expectation of cue arrival time

A neuroimaging study reveals novel insights into how the brain responds to an anticipated event, such as a starting gun or responding to a green light.

What happens when the brain awaits a signal of uncertain arrival time, as when a sprinter waits for the starting pistol? And what happens just after the starting pistol fires? Using functional magnetic resonance imaging (fMRI), we have discovered a novel correlate of temporal expectations in several brain regions, most prominently in the supplementary motor area (SMA). Contrary to expectations, we found little fMRI activity during the waiting period; however, a large signal appears after the “go” signal, the amplitude of which reflects learned expectations about the distribution of possible waiting times. Specifically, the amplitude of the fMRI signal appears to encode a cumulative conditional probability, also known as the cumulative hazard function. The fMRI signal loses its dependence on waiting time in a “countdown” condition in which the arrival time of the go cue is known in advance, suggesting that the signal encodes temporal probabilities rather than simply elapsed time. The dependence of the signal on temporal expectation is present in “no-go” conditions, demonstrating that the effect is not a consequence of motor output. Finally, the encoding is not dependent on modality, operating in the same manner with auditory or visual signals. This finding extends our understanding of the relationship between temporal expectancy and measurable neural signals.

Like the sprinter waiting for the starting pistol, all animals develop expectations about when events will occur in time. We explored the neural correlates of readiness and expectation using functional magnetic resonance imaging (fMRI), and found areas of the brain in which the fMRI signal remains at baseline during the waiting period and rises sharply after a cue to react (a “go” cue). Strikingly, the amplitude of the rise reflects a function of the probability of an event occurring at that time. The dependence on probability remains even in the absence of a motor act (that is, not pressing a button when the go cue appears). When the arrival time of the go cue is known in advance, the expectation-dependent signal disappears, indicating that this brain response reflects expectation, not simply elapsed time. These results match up with prior studies of expectation in the brain, with one important difference: previously, electrophysiology experiments showed that expectation is encoded by a build-up of spiking activity as the waiting period progresses, while our fMRI data reveal a signature of expectation that becomes apparent after the waiting concludes. We discuss the apparent mismatch between these different technologies for measuring expectation-related activity in the brain.

Neuroticism-Anxiety, Impulsive-Sensation Seeking and autonomic responses to somatosensory stimuli

This study focused on autonomic responding in participants who scored high vs. low on the Neuroticism-Anxiety (N-Anx) and Impulsive-Sensation Seeking (Imp-SS) dimensions of the Zuckerman-Kuhlman Personality Questionnaire--Form III. Participants were presented with series of tones (standards, deviants and novels) and they received a mild electric shock (one, two or three pulses) at each 15th tone. Resting pre-stimulus skin conductance level (SCL) and heart rate (HR) level was recorded, as well as the skin conductance response (SCR) and (anticipatory) HR response to the electric stimuli. The autonomic measures differentiated between high- vs. low Imp-SS participants but failed to discriminate between high- vs. low N-Anx participants, with the exception that high N-Anx participants showed smaller SCRs on some trials compared to the low N-Anx participants. High Imp-SS had a lower pre-stimulus SCL and smaller SCRs to deviant stimuli compared to low Imp-SS participants. Additionally, their HR acceleration was smaller in anticipation of the first and the deviant tones whereas their deceleratory response was larger relative to the HR changes observed for the low Imp-SS participants. This pattern of findings was taken to suggest that high Imp-SS participants are more arousable and less prone to defensive reactions to novel or aversive stimulation.

Trait anxiety and autonomic indicators of the processing of threatening information: A cued S1–S2 paradigm

The aim of this study was to use autonomic parameters in a cued S1-S2 task to examine associations between the processing of threatening information and trait anxiety in normal individuals. Forty-six student volunteers were designated high- or low-anxious due to pre-defined cutoff scores on the STAI. A cued S1-S2 task was presented in which the type of warning signal (S1) was consistently related to either threatening or non-threatening pictures (S2). Ten threat and 10 non-threat pictures were randomly presented. Heart rate and electrodermal activity were recorded in the time interval between S1 and S2. Results indicated deeper heart rate decelerations on threatening trials in high-anxious as compared to low-anxious individuals. For non-threatening trials, the opposite pattern was found. Moreover, high-anxious participants exhibited higher electrodermal responses to the S1, irrespective of the trial's valence as well as stronger responses to the threatening S2. Autonomic responses can, thus, be regarded as sensitive markers of information processing differences in trait anxiety.

Attentive Perception Can Diminish Vagal Inhibition

A systematic decrease in heart rate when anticipating an important stimulus or when preparing to react is called anticipatory bradycardia. Numerous studies have shown that the initiation of motor activity prompts the termination of anticipatory bradycardia in reaction time tasks. However, in experiments with procedures based on more complex reactions, the termination of anticipatory bradycardia is delayed until later cardiac cycles. This unexpected effect may be attributed to perceptual processes that are engaged in the feedback mechanism essential for effectiveness in prolonged and complex motor reactions. The experiment presented in this article was carried out to verify the hypothesis that the initiation of a motor reaction, when processed simultaneously with sustained attentive perception, does not evoke acceleration of heart rate. The experimental task was a simulated shooting at a moving target. The procedure in the experimental group induced participants to attentively observe events before and after the required reaction, whereas in the control group, attentive perception of task events after the reaction was not possible. The expected pattern of heart-rate changes appeared in the experimental group. During the initial block of trials, the initiation of the motor reaction did not evoke immediate termination of anticipatory bradycardia. During later trials in the experimental group and during all trials in the control group, heart-rate changes were completely typical - heart rate increased after the motor reaction began. The results show that attentive perception engaged immediately after the initiation of motor activity can affect the pattern of phasic heart-rate changes observed during typical reaction time tasks. Additionally, the difference between the patterns characteristic of the initial and later trials suggests possible competition between the neuronal influences that modulate heart rate.

Cardiac concomitants of performance monitoring: context dependence and individual differences

Feedback processing is an important aspect of cognitive control and decision-making. Several studies have shown that heart rate slows following feedback that indicates incorrect performance or loss of money. The current study was the first to investigate (1) whether this slowing reflects an evaluation of the valence of the outcome or a system that indicates that the feedback contains informative value, (2) whether the slowing is determined by the value of the outcome relative to the range of possible outcomes, and (3) whether highly anxious individuals have a hypersensitive feedback monitoring system. The results showed that heart rate only slows when the feedback is performance based. The information provided by negative feedback is processed in a context-sensitive manner, suggesting that heart rate slowing following feedback reflects a signal associated with informative value for subsequent performance adjustment. Highly anxious individuals showed larger heart rate slowing in response to feedback indicating high stakes, but they failed to respond to feedback in a context-sensitive manner. These results were interpreted to suggest that anxious individuals are generally more sensitive to performance outcomes. Heart rate changes following informative feedback proved to be a sensitive index of component processes associated with performance monitoring.

The cardiac cycle time effect revisited: temporal dynamics of the central-vagal modulation of heart rate in human reaction time tasks

Lacey and Lacey (1974) suggested that during reaction time tasks higher brain centers dynamically adjust efferent vagal nerve pulses to the sino-atrial node of the heart, inducing phase-dependent heart rate changes. Since then, animal and human neuro-physiological results have provided evidence for this hypothesis. Higher subcortical and cortical brain centers may have reciprocal interactive pathways relating to autonomic control comparable to those at the level of peripheral autonomic changes and brain stem reflexes. In humans such central effects may be observed in the short latency vagal control of heart rate that has been studied mostly in reaction time (RT) tasks. RT task parameters modulate vagal pulses to the cardiac sino-atrial node (SAN), which in turn exerts a phase-dependent change in the ongoing cardiac interbeat interval. Simulations of human RT task effects in an animal model of heart rate change support this hypothesis. The current study examined evidence for vagal control of three human phasic heart rate responses in RT tasks. The evidence indicates that the initiation of an RT response triggers a reflexive shift from vagal activation to vagal inhibition. This shift is cardiac cycle phase dependent. Graded anticipatory cardiac deceleration during the warning interval of an RT task varies with task relevance and time uncertainty. This response may be part of a control process engaged in time keeping. Hence, temporal variables mediate the central-autonomic-vagal modulation of heart rate.

Electrophysiological evidence of intuition: part 1. The surprising role of the heart

OBJECTIVES

This study aims to contribute to a scientific understanding of intuition, a process by which information normally outside the range of conscious awareness is perceived by the psychophysiological systems. The first objective, presented in two empirical papers (Part 1 and Part 2), was to replicate and extend the results of previous experiments demonstrating that the body can respond to an emotionally arousing stimulus seconds before it is actually experienced. The second objective, to be presented in a third paper (Part 3), is to develop a theory that explains how the body receives and processes information involved in intuitive perception.

DESIGN

The study used a counterbalanced crossover design, in which 30 calm and 15 emotionally arousing pictures were presented to 26 participants under two experimental conditions: a baseline condition of normal psychophysiologic function and a condition of physiological coherence. Primary measures included: skin conductance; the electroencephalogram (EEG), from which cortical event-related potentials and heartbeat-evoked potentials were derived; and the electrocardiogram (ECG), from which cardiac decelerations/accelerations were derived. These measures were used to investigate where and when in the brain and body intuitive information is processed.

RESULTS

The study's results are presented in two parts. The main findings in relation to the heart's role in intuitive perception presented here are: (1) surprisingly, the heart appears to receive and respond to intuitive information; (2) a significantly greater heart rate deceleration occurred prior to future emotional stimuli compared to calm stimuli; (3) there were significant gender differences in the processing of prestimulus information. Part 2 will present results indicating where in the brain intuitive information is processed and data showing that prestimulus information from the heart is communicated to the brain. It also presents evidence that females are more attuned to intuitive information from the heart.

CONCLUSIONS

Overall, we have independently replicated and extended previous research documenting prestimulus responses. It appears that the heart is involved in the processing and decoding of intuitive information. Once the prestimulus information is received in the psychophysiologic systems, it appears to be processed in the same way as conventional sensory input. This study presents compelling evidence that the body's perceptual apparatus is continuously scanning the future. To account for the results presented in Parts 1 and 2, Part 3 will develop a theory based on holographic principles explaining how intuitive perception accesses a field of energy into which information about future events is spectrally enfolded.

The exhaustive additivity displayed by nitrous oxide has implications for cognitive-energetical theory

The cognitive-energetical approach, which relies on the discrete stage model of additive factors logic, asserts that basal energetical mechanisms such as arousal act via particular information processing stages. The anaesthetic gas nitrous oxide (N(2)O) produces additivity at four of the five perceptual and central stages, but its effect on the remaining stage, feature extraction, is unknown. We investigated this stage using 12 subjects who performed a visual oddball experiment in which two levels of stimulus quality, three levels of breathing mixture (air, 25% and N(2)O, 35%) and three levels of stimulus probability were combined factorially. Reaction time (RT) and P300 were collected simultaneously. The RT results showed additivity between N(2)O, stimulus quality and probability. P300 latency also showed additivity between N(2)O and stimulus quality. Since the discrete stage model cannot easily account for the exhaustive additivity displayed by N(2)O on perceptual and central stages, we performed a continuous cascade model simulation to determine whether it is better able to account for this phenomenon. We found that exhaustive additivity could be reproduced by adding a time delay to the activation rate of the first stage, which we interpreted as evidence that N(2)O causes slowing prior to stage processing. To account for these results, we propose a two-tiered energetical model in which a lower GABAergic reticular system (influenced by N(2)O) modulates the activity of upper 'arousal-like' multidimensional ascending thalamocortical systems. The applicability of this model to drugs such as the barbiturates, the benzodiazepines and ethanol, as well as the aging process, is discussed.

Motor control and state regulation in children with ADHD: a cardiac response study

The goal of the current study was to investigate whether poor motor control in children with Attention-Deficit Hyperactivity Disorder (ADHD) was associated with a state regulation deficit. For this purpose, 28 ADHD and 22 healthy children carried out two Go No-Go tests: one with a fast stimulus presentation rate, and the other with a slow stimulus presentation rate. Groups were compared on RT performance and on specific cardiac measures, reflecting arousal, motor activation/inhibition, and effort allocation. No group difference in the arousal measure (mean heart rate) was found. Further, groups did not differ with respect to response inhibition: in both the fast and slow condition, ADHD children made comparable numbers of errors of commission to the control group, and the groups did not differ with respect to the heart rate deceleration after the onset of the No-Go signal, reflecting motor inhibition. Group differences were found with respect to motor activation and effort allocation in the condition with a slow presentation rate. In this condition: (1) ADHD children reacted more slowly to Go signals than control children, suggesting poor motor activation; (2) the heart rate deceleration before the onset of Go signals, which is believed to reflect motor preparation, was less pronounced in the ADHD children; (3) after Go signals, where a response was given, the cardiac shift from deceleration to acceleration, indicating response initiation, was delayed in ADHD children; and (4) ADHD children had greater heart rate variability (0.10 Hz component) than the control group, indicating that less effort was allocated. No group differences in motor activation and effort allocation were found in the condition with a fast presentation rate of stimuli. We conclude, therefore, that a slow presentation rate of stimuli brings the ADHD child in a non-optimal activation state.

Selective effects of physical exercise on choice reaction processes

The aim of the present study was to examine the effects of an exercise of moderate intensity (60% of maximal aerobic power) on specific information-processing mechanisms. 22 students completed 3 10-min. exercise bouts on a bicycle ergometer. Concomitantly, participants performed six manual-choice-reaction tasks manipulating task variables (Signal Intensity, Stimulus-Response Compatibility, and Time Uncertainty) on two levels. Reaction tests, randomly ordered, were administered at rest and during exercise. A significant underadditive interaction between Time Uncertainty and exercise was found for the highest quartiles of the distribution of reaction times. No other interaction effects were obtained for the other variables. These results reasonably support that moderate aerobic exercise showed selective rather than general influences on information processing.

Psychophysiological aspects of selective and divided attention during continuous manual tracking

Central, autonomic, and metabolic physiological measures were observed concurrently along with performance and subjective measures to compare the effects of tracking task difficulty during selective and divided attention. Eighteen dextral males performed visual compensatory manual tracking as a primary task while attending to or ignoring secondary-task auditory oddball stimuli. The difficulty of the tracking task was varied factorially by requiring participants to track with acceleration (second-order) or velocity (first-order) control and high or low bandwidth sum-of-sines disturbance. Tracking performance was affected by the difficulty manipulations but not by the attention manipulation. Event-related brain potential P300 amplitude to oddball target stimuli was sensitive to the division of attention and tracking order-of-control but not to tracking disturbance bandwidth when the oddball task was attended. Oxygen consumption, a measure of aerobic metabolism, was greater during acceleration than velocity tracking; however, cardiac measures were sensitive only to the division of attention. The results demonstrate that the attention and the task difficulty manipulations have physiologically dissociable effects that were interpreted as supporting a cognitive/energetic model of attention.

Anticipatory EMG responses of pericranial muscles in relation to heart rate during a warned simple reaction time task

Obrist's cardiac-somatic coupling hypothesis predicts a widespread inhibition of heart rate and task-irrelevant muscle activity during expectancy situations. This hypothesis was tested by measuring heart rate and pericranial electromyographic (EMG) activity during a warned simple reaction time task with visual or auditory reaction signals and hand or foot responses. In each of three groups of 24 participants, EMG activity of three different facial, masticatory, or neck muscles was recorded. During the warning interval preceding the presentation of the reaction signal, masticatory and lower facial muscles predominantly showed a gradual inhibition in activity concomitant with heart rate deceleration. In contrast, two upper facial muscles showed increasing activity. Pericranial EMG responses were little affected by reaction signal modality and were independent of responding limb. Greater heart rate deceleration was associated with greater inhibition and weaker facilitation of EMG responses. The results suggest a functional role of inhibitory EMG responses in increasing the perceptual sensitivity to expected signals.

Testing the global-slowing hypothesis: are alcohol's effects on human performance process-specific or task-general?

In an interesting recent meta-analysis, Maylor and Rabbitt (1993) suggested that alcohol's effects on human performance may not be process- or stage-specific, but reflect a general, undifferentiated, cognitive slowing. According to this view, performance is globally slowed by a constant multiplicative fraction (b), such that the longer a process takes without alcohol on board (a -), the more it will be slowed by alcohol (a +). In summary: RTa+ = b b (RTa-). In this sense, the effects of alcohol are determined simply by the duration of a process or stage--not by its function or content--and attempts to map the effects of alcohol to specific cognitive operations are essentially futile. This global-slowing hypothesis entails, then, (i) that the function relating RTa+ to RTa- will be linear and increasing; (ii) that the value of b will be significantly greater than 1.0; and (iii) that all experimental factors which increase the complexity (hence, duration) of a task or stage will interact with alcohol. In this study we tested the global-slowing hypothesis directly using fixed set, varied set and concurrent sets item-recognition paradigms. All three tasks showed convincing additivity between alcohol and other key experimental factors which affect response latency (e.g., setsize, response type); there was no hint of any of the spectrum of significant interactions predicted by the global-slowing hypothesis. A meta-analysis of varied set latencies, analogous to Maylor and Rabbitt's, yielded a reasonably linear alcohol/no-alcohol function, but with a slope constant (b) less than 1.0. In all, the data provided little support for the global-slowing hypothesis.

[Study of the organization of sensorimotor stages in man using delayed evoked potentials]

The main aim of this study was to test the relative organization of three of the stages of Sanders' 1990 information processing model: "features extraction", "response choice", and "motor adjustment". The variables influencing these stages: stimulus degradation, stimulus-response (SR) compatibility and preparatory period have been manipulated. Event related potentials (N100, N200, P300) and reaction time were recorded from ten healthy subjects, in a dichotic listening task. Reaction times are lengthened for degraded stimuli, in the absence of a preparatory period and for SR non compatible conditions. However, the interaction between preparatory period and stimulus degradation variables, suggests an overlapping of the corresponding stages contrary to Sanders' postulate. The non compatible condition increases the latency of N200 and P300 components. The results suggest that the response choice processing would be contemporary to the N200 component. They are discussed within the framework of models of early communication between sensory and motor systems.

Impending electrical shock can affect response force in a simple reaction task

For 20 subjects reaction times and force of response were measured on a simple reaction time task to visual stimuli while activation was manipulated by occasionally delivering a noninformative electrical shock. In blocks in which shocks were delivered, forces of response were larger than those in control blocks without shocks. The results are discussed in terms of Sanders' model of stress.

Heart rate and sustained attention during childhood: age changes in anticipatory heart rate, primary bradycardia, and respiratory sinus arrhythmia

This study examined age changes in three aspects of heart rate responsivity elicited in an auditory oddball task; anticipatory heart rate change, primary bradycardia, and respiratory sinus arrhythmia. Three age groups (5-, 7-, and 9-year-old boys) were presented with series of target (15%) and standard (85%) tones. The results were consistent with the findings reported previously in the adult literature. Heart rate decreased in anticipation of the target tone. The morphology of anticipatory deceleration was somewhat different for the 5-year-olds compared to the older children. Stimuli presented during the early part of the cardiac cycle induced added deceleration, but this primary bradycardia did not differ between age groups. Respiratory sinus arrhythmia did not discriminate between age groups but was suppressed during the performance of the oddball task relative to base level. It was concluded that these three aspects of heart rate responsivity show developmental constancy rather than change.

A motor presetting study in hyperactive, learning disabled and control children

Motor presetting was investigated in hyperactive children, learning disabled children and normal controls. The reaction time of the hyperactive group was more sensitive to increases in interstimulus interval (event rate) than was that of the learning disabled and the controls. This finding indicates that hyperactive children have difficulty with motor presetting.

Behavioral modulation patterns fit an animal model of vagus-cardiac pacemaker interactions

The present study used a computer model of the dynamic interaction between the vagus nerve and the sinoatrial pacemaker membrane potential in the heart of the rabbit to reconstruct heart rate changes under vagal excitation conditions. We asked whether a hypothetical pattern of vagal acetylcholine (ACh) release, which was based on human heart rate results in a reaction time task, could be fit to this model. The reconstructed heart rate results showed changes that were highly consistent with experimental human heart rate changes. The model reliably reproduced effects of parameters such as intrinsic heart rate level, ACh stimulus intensity, and ACh stimulus duration. In addition, the effects of anticipatory vagal ACh release, stimulus-induced ACh, and subsequent blocking of ACh, which usually interact in human cardiac cycle time functions, could be untangled in the reconstructed heart rate results. We concluded that the mathematical model may be useful for formulating hypotheses and constructing experimental task designs for studies of human heart rate.

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.

Effect of conflicting cues on information processing: the 'Stroop effect' vs. the 'Simon effect'

This study examined the relationship between two sources of interference in human information processing: the Stroop effect and the Simon effect. Forty subjects pressed a left- or right-hand key in response to a Stroop color word located on the left or right side of a screen. For one group, ink color was the relevant cue and, for another group, word meaning was the relevant cue. Independent variables were: congruence, i.e., agreement or lack thereof between the ink color and meaning of the Stroop word; spatial correspondence, i.e., agreement or lack thereof between the location of the Stroop word and the location of the key used to make the response; and stimulus duration, i.e., 400 or 100 ms. Each of these variables had a significant effect on RT, and there were no significant interactions. According to Sternberg's additive-factor logic, these findings suggest that the Stroop effect (congruence) and the Simon effect (spatial correspondence) involve separate stages of processing. If one assumes that manipulation of stimulus duration effects the encoding stage, then results also suggest that neither the Stroop effect nor the Simon effect involves the stimulus encoding stage.

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).