Interoception Conf Poster

Question 1

Can you walk me through your poster? - (8) (not rushed)

Answer 1

• We recorded single units from the posterior insula (PI), anterior insula (AI), and Heschl’s gyrus (HG) in patients with medically intractable epilepsy who were implanted with intracranial electrodes. While the patients passively listened to tones (did 300 trials of this), we simultaneously recorded the ECG.
• Our study aimed to answer two questions using human single-unit recordings: 1) Does cardiac-related information reach the insula and auditory cortex? 2) Does the cardiac phase modulate auditory responses in the auditory cortex?
• We found that in the PI and AI, some units (6% in PI and 5% in AI) responded to heartbeats, either increasing (point to PI and AI) or decreasing firing rate (point to decrease in PI) after R-peak onset.
• More interestingly, in HG, 8% of the units analysed showed an inhibitory response to heartbeats, with this unit in HG having firing rate dipping around 300ms after the R-peak (point to graph). This suggests that cardiac information also reaches the auditory cortex, but with an inhibitory effect.
• For the second question, we divided 300 sound trials into systole (early after R-peak) and diastole (later in the RR interval) (point to figure).
• For results, second question there is two example of units in HG, 0 is tone onset and shows firing rate and rastor plots during systole and diastole – see much more cluster of spikes in rastor plot and higher firing rate in HG during diastole and systole in 7% of untis I analysed but no units showing the opposite.
• Which what we expected in the baroreceptor hypothesis which states during systole (cardiac contraction) it induces cortical inhibition than diastole (cardiac relaxation)
• In conclusion, cardiac-related information reaches both the insula and the auditory cortex, and auditory responses in HG are modulated by the cardiac phase, particularly with inhibition during systole – which is consistent with baroreceptor hypothesis.