Assessment, learning, and retention of heart beat discrimination

The heart rate discrimination task: a psychophysical method to estimate the accuracy and precision of interoceptive beliefs

Interoception - the physiological sense of our inner bodies - has risen to the forefront of psychological and psychiatric research. Much of this research utilizes tasks that attempt to measure the ability to accurately detect cardiac signals. Unfortunately, these approaches are confounded by well-known issues limiting their validity and interpretation. At the core of this controversy is the role of subjective beliefs about the heart rate in confounding measures of interoceptive accuracy. Here, we recast these beliefs as an important part of the causal machinery of interoception, and offer a novel psychophysical "heart rate discrimination" method to estimate their accuracy and precision. By applying this task in 223 healthy participants, we demonstrate that cardiac interoceptive beliefs are more biased, less precise, and are associated with poorer metacognitive insight relative to an exteroceptive control condition. Our task, provided as an open-source python package, offers a robust approach to quantifying cardiac beliefs.

A method of constant stimuli for examining heartbeat detection: comparison with the Brener-Kluvitse and Whitehead methods

A method of constant stimuli (MCS) for measuring heartbeat detection was examined by comparing performance on this method with the Brener and Kluvitse (BK) method and a variant of the Whitehead (WH') method. All methods required subjects to judge the simultaneity of heartbeat sensations and tones, and each yielded measures of judgment precision and of the temporal location of heartbeat sensations relative to the electrocardiogram R-wave. Both measures were found to be significantly correlated across tasks. A greater proportion of subjects met criteria for classification as heartbeat detectors on the MCS (54%) and BK (50%) tasks than on the WH' task (33%). In the MCS and BK tasks, subjects judged tones presented 100-300 ms after the R-wave to be most simultaneous with heartbeat sensations. Intratask correlations showed that only the MCS procedure yielded stable measurements of both judgment precision and temporal location. The MCS procedure possesses commendable psychometric properties and provides a simpler means than the BK procedure of examining heartbeat detection.

The temporal locations of heartbeat sensations

This experiment examined individual differences in the temporal location of heartbeat sensations and the reliability of their detection. Following practice on a familiarization task in judging light-tone simultaneity, 50 subjects were studied for two sessions on a heartbeat detection task, which required judging the simultaneity of heartbeat sensations and tones presented at six intervals following the onset of ventricular contraction. Subjects inspected the heartbeat-tone intervals as frequently and for as long as desired before choosing the one in which heartbeat sensations and tones were most simultaneous. The temporal locations of heartbeat sensations in subjects classified as "good heartbeat perceivers" (n = 16) ranged from 131 and 363 ms following ventricular contraction (mean = 228 ms). Correlations between the familiarization and heartbeat detection tasks in the accuracy of simultaneity judgments and in the frequency and duration of interval inspections suggest that general perceptual abilities and strategies may underlie success in detecting heartbeat sensations.

Heartbeat perception, instructions, and biofeedback in the control of heart rate

The present study was designed to examine the possibility that individual differences in heartbeat perception and instructions to control heart rate (HR) may influence the acquisition of voluntary control. Good (n = 20) and poor (n = 20) perceivers of cardiac activity were selected on the basis of their performance according to Whitehead et al. (1977) heartbeat discrimination procedure. Measures of state and trait anxiety (the State-Trait Anxiety Inventory Form X-1 and Form X-2) and Tellegen's Absorption Scale (TAS) were used to assess emotionality and absorptive ability. Good and poor heartbeat perceivers (a) were given non-motivating instructions to try to either increase or decrease their heart rate (HR) with, or (b) without the use of HR-feedback, and (c) were given motivating instructions to try to either increase or decrease their HR with, or (d) without HR-feedback. Heart rate, skin conductance (SC), and EMG activity were monitored. Subjects were also requested to indicate the cognitive strategies used during their HR control training. No relationship between heartbeat perception and state-trait anxiety measures was found. The results did not support the idea that individual differences in heartbeat perception are related to individual differences in HR-control. They did indicate, however, that motivating instructions improve the capacity to increase or decrease HR. Subjects were able to voluntarily increase or decrease their HRs with or without a feedback signal. However, more pronounced HR increases were obtained in the feedback as compared with the no-feedback condition. SC and EMG activity were in accordance with arousal levels demanded by HR decrease and increase tasks. Subjects used cognitive strategies concerning activation responses during HR-increase and relaxation responses during HR-decrease conditions.

Is an accurate verbal language necessary for heart rate discrimination?

Three groups of subjects were required to discriminate levels of cardiac function over three sessions. Two groups were required to detect in which of two contiguous 4-sec periods their heart rate (HR) was slowest. One of these groups was given knowledge of results concerning the correctness of their decisions. Their performance improved significantly. The other group was not given knowledge of results and their performance hovered around chance level. The third group was told to detect the period in which their heart rate was fastest, but they were told 'correct', via knowledge of results, only if they had picked their slowest rate. Their performance was inferior to the knowledge of results group, but superior to the no-knowledge group. They showed, however, little evidence of improved performance over sessions. The results are discussed in terms of a verbal labelling control of required discriminations.

Heart rate discrimination and heart rate control: A test of Brener's theory

Three experiments were conducted to examine predictions from Brener's theory regarding the relationship between autonomic discrimination and autonomic control. Experiment 1 examined the possibility that training subjects to discriminate their heart rates would enhance their skill at controlling that response. Twenty subjects participated in two sessions during which one group of 10 subjects received training (knowledge of results) on the Ashton discrimination technique. The second group performed the discrimination task but received no training. All subjects then took part in a third session of heart rate (HR) control (both increase and decrease) where half of each of the aforementioned groups received feedback during the control task, while the other half performed the HR control task without feedback. Results indicated that for the control of both HR increases and decreases, there was no significant difference between those subjects trained to discriminate their HR, and those who had received no training to discriminate HR. The second experiment investigated the hypothesis that training subjects with feedback to control their HR would enhance their capacity to discriminate their heart activity. Ten subjects participated in two sessions of HR control during which half the subjects received feedback training to increase HR. During a third session, all subjects underwent a test of discrimination ability using the Ashton technique, and no knowledge of results regarding performance was provided. Results confirmed the hypothesis. The final experiment in the series investigated the discrimination/control relationship within a problem-solving framework and used 20 subjects. Results confirmed the hypothesis that subjects forewarned at the time of discrimination training that a heart rate control task was to follow would perform better than 10 subjects receiving no forewarning of the task objective. This effect took place independently of cardiac discrimination ability. A second finding from this experiment was that subjects trained to discriminate heart rate were better able to increase heart rate than untrained subjects. This result contradicts that of Experiment 1, and reasons for this anomaly are discussed in detail.

Visceral perception versus visceral detection: disentangling methods and assumptions

A within-subject experiment compared three paradigms commonly used in visceral perception: self-report, heartbeat tracking, and signal detection. Eighteen undergraduates estimated heart rate using each technique while engaging in a number of separate tasks conducted a week apart. Although all three techniques significantly tapped accuracy of heart rate perception, only the self-report and signal detection methods were reliable over time. Most important, there was no relationship involving any of the methods in measuring accuracy. The findings suggest some fundamental differences in the assumptions and perceptual properties of the various paradigms. A distinction is made between visceral perception and detection. Perception implies the subject's use of both internal physiological and external environmental information in the perception of visceral state. Detection connotes the subject's use of only physiological information--to the exclusion of all other factors. The relevance of these approaches for biofeedback and real-world symptom perception is discussed.

The effects of physical fitness and exercise on cardiac awareness

This experiment was run to further evaluate the role of individual difference factors in perception of heart beats (cardiac awareness). The present study examined 24 male subjects who showed high and moderate levels of physical fitness. Cardiac awareness was examined using Brener-Jones type discrimination trials. Subjects discriminated first while standing quietly on a treadmill (32 trials), then while walking briskly on a motorized treadmill (32 trials), and finally during recovery from exercise (elevated HR but behavioral quiescence) (16 trials). Results showed that only the moderate fitness group showed heightened awareness during exercise, while both groups showed greater than chance awareness during recovery from exercise. Neither group was highly aware while resting before exercise. These results fail to support notions that high fitness distance runners are highly aware of cardiac function during exercise. A number of reasons for this finding are discussed.

Concurrent assessment of heart rate discrimination and control

A procedure was devised to investigate discrimination and control of heart rate (HR) concurrently. Eighteen volunteers were divided into two equal groups instructed either to increase or to decrease HR during four experimental sessions. In addition, subjects were required to indicate whenever they thought they were successful during the HR control task by pressing a switch. Activation of the switch automatically enabled the presentation of a feedback tone provided that the HR level at that moment, met a preset criterion of change. The feedback was not available during pre- and post-training testing periods. Responses to bidirectional HR control instructions alone were also investigated. Respiration volume and general movement were recorded throughout. While the group given HR increase instructions improved both their discrimination and control performances, the group instructed to decrease HR did not improve. It is suggested that the optimal procedures for training HR increases and decreases may differ, but that the relationship between discrimination and control posited by the calibration model can accommodate these differences.