This encompasses arterial mechanoreceptors in or near coronary arteries (Brown, 1965), and other interoceptors classified as cardiovascular receptors by Paintal ( 1972), including carotid, aortic, brachiocephalic and pulmonary baroreceptors, atrial mechanoreceptors, ventricular and epicardial mechanoreceptors and the Pacinian corpuscles, which Paintal classified as pseudo-baroreceptors. In other words, any mechanoreceptors within the sensory range of the pulse pressure wave could detect heartbeat stimuli.
In principle, this product of exteroception should provide sufficient heartbeat information to support good performance on valid tests of cardioceptive accuracy.
Explorations of this issue have led to a widespread agreement with Khalsa, Rudrauf, Feinstein, and Tranel ( 2009) characterization of interoception as “ afferent information that arises from anywhere and everywhere within the body, including through the skin via pathways that are usually considered to support exteroception.” 1 1 Pulsatile tinnitus (Hofmann et al., 2013) in which a discriminable auditory stimulus is generated on each heartbeat and transduced by the auditory channel is an example of how exteroceptive processes could be involved in heartbeat detection. This point has been elaborated by others (e.g., Cameron, 2001 Craig, 2003 Khalsa, Rudrauf, Hassanpour et al., 2009) who have provided details of the mechanoreceptors, afferent pathways, and central processes that are implicated in the detection of visceral activity, including the heartbeat. Individuals may detect the beating of their hearts through “ the afferent consequences of pulsatile changes on intra-cardiac mechanoreceptors, on baroreceptors in the aortic arch or carotid body, on mechanoreceptors in the muscles of the thorax, a limb, or a digit, on the auditory receptors via pulsatile actions on the Eustachian Tubes, or on the eyes by watching some part of the body move” (Brener, 1977, p. Despite this, measurements of the accuracy of heartbeat detection are the most common means of assessing individual differences in interoceptive sensitivity, creating confusion about what is meant by interoception. However, the types of mechanoreceptors and the afferent pathways (interoceptive, somatosensory, exteroceptive) responsible for transducing heartbeat sensations and conveying the information to the brain have yet to be identified. Heartbeat sensations are caused by pulsatile mechanical stimuli generated by ventricular contraction. The field of cardioception has received considerable attention from the scientific community for close to fifty years (Brener & Ring, 2016 Jones, 1994). Our findings reinforce the view that the somatosensory system is involved in cardioception and support the conclusion that both Pacinian and non-Pacinian somatosensory mechanoreceptors are implicated in heartbeat detection. Presentation of both the 250 Hz and the 6 Hz masking stimuli impaired the ability to judge the simultaneity of heartbeats and tones but did not influence the ability to judge the simultaneity of stimuli presented to different exteroceptive modalities (lights and tones).
A no-vibration control condition in which no masking stimuli were presented was also implemented. Twelve verified heartbeat detectors completed a multi-session experiment in which they judged heartbeat-tone and light-tone simultaneity under two vibrotactile masking conditions involving the stimulation of the sternum: (a) using 250 Hz vibrotactile stimuli to mask the Pacinian channel, and (b) using 6 Hz vibrotactile stimuli to mask the non-Pacinian channel. The current experiment sought evidence on this issue by exploring the effects of masking the functions of somatosensory Pacinian and non-Pacinian mechanoreceptors on the ability to detect heartbeat sensations. While the sensory sources of heartbeat sensations have yet to be identified, there is a growing consensus that visceral sensation, in general, is supported not only by the interoceptive system but also by the somatosensory system, and even by exteroception. The ability to detect heartbeat sensations is the most common basis for inferring individual differences in sensitivity to the interoceptive stimuli generated by the visceral activity.