The effects of vibrotactile masking on heartbeat detection: Evidence that somatosensory mechanoreceptors transduce heartbeat sensations.

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. 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 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. 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. A no-vibration control condition in which no masking stimuli were presented was also implemented. 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). 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.