The Insula Mediates Access to Awareness of Visual Stimuli Presented Synchronously to the Heartbeat

In the paper

“Two independent brain imaging experiments using high-resolution fMRI revealed that the insular cortex was sensitive to both visible and invisible cardio-visual stimulation, showing reduced activation for visual stimuli presented synchronously to the heartbeat.”

• Also stated in: § Significance Statement · plain

  “Two fMRI experiments show that the insular region is sensitive to this cardio-visual synchrony even when the visual stimuli are rendered invisible through interocular masking.”

In the paper

“Importantly, this effect was robust and stable in 14 of the 15 present fMRI participants, showing lower BOLD activity in the synchronous condition in the right anterior insula.”

In the paper

“Furthermore, when decoupled (Experiment 5), no differences between visual stimuli that were”

In the paper

“The anterior cingulate cortex (ACC), right posterior superior temporal gyrus (rSTG), and occipital visual regions were consistently activated and were selected as ROIs for each subject (at p Ͻ 0.001 FDR).”

In the paper

“Estimating the mean BOLD signal response in the left and right anterior insulae (as defined above) for the synchronous and asynchronous cardio-visual conditions, we found that insula activation was weaker during synchronous than asynchronous cardio-visual stimulation (F (1,6) ϭ 17.7, p ϭ 0.005), compatible with suppression of visually induced activation in the insula depending on cardio-visual”

• Also stated in: § Neural suppression of seen synchronous cardio-visual stimuli: fMRI · plain

  “The difference between the BOLD activity in the anterior insulae between synchronous and asynchronous conditions was significant (F (1,6) ϭ 18.4, p ϭ 0.005), with no difference between the left and right insulae (F (1,6) ϭ 1.3, n.s.).”

In the paper

“Another line of work has linked self-awareness to the processing of interoceptive signals in the insular cortex (i.e., cardiac signals; Damasio, 2000;Craig, 2002;Critchley et al., 2004;Park et al., 2014)”

What the sources say

• Not checked yetcites Damasio, 2000
• Not checked yetcites Craig, 2002
• Not checked yetcites Critchley et al., 2004

In the paper

“To ensure that trial onset did not maintain a specific phase in relation to participants' heartbeat, an intertrial interval of 0.5, 0.8, or 1.3 s was presented between trials such that any spurious temporal relation between cardiac and visual stimuli would not be maintained.”

In the paper

“The target type, center-to-center distance between target and flanker, and cardio-visual synchronicity were fully randomized.”

In the paper

“These predictive models of interoception are held to mediate widespread sensory consequences of interoceptive signals such as cardiac activity (Barrett and Simmons, 2015), thus reducing their influence on perception (comparable to suppression of retinal changes due to ocular motion).”

What the sources say

• Not checked yetcites Barrett and Simmons, 2015

In the paper

“Pilot testing indicated that the BVP on the fingertip was delayed by ϳ250 ms compared with the ECG R-wave, but that the frequency detected by the BVP and ECG systems was identical (also see Lu et al., 2009).”

What the sources say

• Not checked yetcites Lu et al., 2009

In the paper

“However, the influence of interoception on visual awareness and the role of the insular cortex in this process remain unclear.”

• Also stated in: § Significance Statement · plain

  “their role in other forms of awareness such as visual awareness is yet unclear.”

In the paper

“Recently, theories have suggested that the insula may be involved in interoceptive inference in which predictions regarding interoceptive signals are compared with actual sensory and interoceptive afferent inputs (Critchley and Seth, 2012;Seth, 2013;Apps and Tsakiris, 2014).”

What the sources say

• Not checked yetcites Critchley and Seth, 2012
• Not checked yetcites Seth, 2013
• Not checked yetcites Apps and Tsakiris, 2014

In the paper

“The participants were explicitly asked not to monitor their heartbeat by means other than interoceptive attention (such as taking their pulse).”

In the paper

“A 1 s intertrial interval was used to avoid intertrial phase locking.”

In the paper

“The echo-planar images acquired during the functional runs were corrected for low frequencies (e.g., due to cardiac and breathing artifacts) and 3D motion and were then transformed to the native space of the anatomical run.”

In the paper

“The naivety of the subjects to this relationship was important to avoid recording any brain activity resulting from interoceptive attention to their heartbeat; therefore, this relationship was not mentioned before this task.”

In the paper

“Using the BVP signal, the six cardiac specific regressors created by the RETROICOR toolbox were used used as control covariates in our design matrix.”

In the paper

“Ten participants were excluded from the analysis (Experiment 1, n ϭ 1; Experiment 2, n ϭ 3; Experiment 4, n ϭ 3; Experiment 5, n ϭ 2; Experiment 7, n ϭ 1).”

In the paper

“This second task served as a functional localizer for the anterior insula regions, which have been shown previously to be activated by interoceptive attention to one's heartbeat (Critchley et al., 2004;Wiebking et al., 2014).”

What the sources say

• Not checked yetcites Critchley et al., 2004
• Not checked yetcites Wiebking et al., 2014

In the paper

“To test for possible effects of cardiac activity on the results, the cardiac signal was regressed out using the RETROICOR approach (Glover et al., 2000).”

What the sources say

• Not checked yetcites Glover et al., 2000

In the paper

“This indicates that cardio-visual effects on CFS (Experiments 1 and 2) depend on cardio-visual coupling and not on visual differences between synchronous and asynchronous visual stimulation.”

In the paper

“A prime candidate region responsible for suppressing such signals is the insular cortex because of the following: (1) it is involved in the processing of interoceptive information including cardiac signals (Craig, 2002;Critchley et al., 2004), (2) it is involved in the the comparison of auditory and cardiac signals (Critchley et al., 2004), and (3) it has recently been hypothesized as a site for”

What the sources say

• Not checked yetcites Craig, 2002
• Not checked yetcites Critchley et al., 2004
• Not checked yetcites Critchley and Seth, 2012

In the paper

“This suggests that the results in the anterior insulae are independent of vascular fluctuations and are more likely to reflect neuron-related BOLD changes.”

In the paper

“This task was always performed before the localizer task to ensure that participants were naive to the purpose of Experiment 8.”

In the paper

“We restricted our analysis to trials in which the participants were fully unaware of the visual stimuli (78.6% of trials).”

In the paper

“Because respiration signals were not available, they were not regressed from the functional data.”

In the paper

“For example, the heartbeat affects tactile afferent output (Macefield, 2003), muscle spindle discharge (Birznieks et al., 2012), and generates mechanical effects on the eyes modulating interocular pressure and eye movements (de Kinkelder et al., 2011).”

What the sources say

• Not checked yetcites Macefield, 2003
• Not checked yetcites Birznieks et al., 2012
• Not checked yetcites de Kinkelder et al., 2011

In the paper

“Previous investigations of cardiac influences on behavior and neural processing have focused on specific epochs of the cardiac cycle (e.g., systole vs diastole) and have been successful in showing cardiac effects on somatosensory (Edwards et al., 2009;Gray et al., 2009), nociceptive (Edwards et al., 2001;McIntyre et al., 2006;Edwards et al., 2008;Gray et al., 2010), and emotional (Gray et al., 200”

What the sources say

• Not checked yetcites Edwards et al., 2009
• Not checked yetcites Gray et al., 2009
• Not checked yetcites Garfinkel et al., 2014

In the paper

“These results converge in suggesting the possible role of the insula for multimodal predictive coding (Singer et al., 2009;Seth et al., 2011;Apps and Tsakiris, 2014) and salience processing (Seeley et al., 2007).”

What the sources say

• Not checked yetcites Singer et al., 2009
• Not checked yetcites Seth et al., 2011
• Not checked yetcites Seeley et al., 2007

In the paper

“The anterior insula has been implicated in temporal processing (Craig, 2009a;Wiener et al., 2010), which has been suggested to relate to its role in integrating internal interoceptive temporal cues with external signals (Wittmann, 2009;Wittmann et al., 2010).”

• Also stated in: § Discussion · plain

  “Indeed, the anterior insula has been activated in studies investigating temporal synchrony (Bushara et al., 2001) and the sense of agency and error monitoring that require matching exteroceptive sensory signals with self-generated actions (Menon et al., 2001;Klein et al., 2007;Karnath and Baier, 2010;Sperduti et al., 2011;Klein et al., 2013).”

What the sources say

• Not checked yetcites Craig, 2009a
• Not checked yetcites Bushara et al., 2001 source
• Not checked yetcites Menon et al., 2001

In the paper

“Interoceptive information regarding cardiac activity is conveyed by several afferent sources, including cardiac and somatosensory mechanoreceptors as well as blood vessel baroreceptors (Knapp and Brener, 1998), and is affected by several cardiac factors (Schandry et al., 1993).”

What the sources say

• Not checked yetcites Knapp and Brener, 1998
• Not checked yetcites Schandry et al., 1993

In the paper

“In the current study, however, the breaking CFS paradigms were supplemented with an additional psychophysical method of visual crowding (Experiment 7), which allowed us to replicate our finding in the accuracy domain, thus circumventing the possible limitations of time to emergence used with the CFS method.”

In the paper

“The insular cortex has been found to be activated by a wide range of perceptual and cognitive processes (Kurth et al., 2010).”

What the sources say

• Not checked yetcites Kurth et al., 2010

In the paper

“This region is thought to enable the convergence of interoceptive and exteroceptive signals (Craig, 2002;Critchley et al., 2004;Wiebking et al., 2014) and has recently also been proposed to underlie self-awareness (Damasio, 2000;Craig, 2009b;Craig, 2010;Apps and Tsakiris, 2014) and exteroceptive multisensory bodily perception and movement control in healthy and neurological patients (Karnath et al”

What the sources say

• Not checked yetcites Craig, 2002
• Not checked yetcites Critchley et al., 2004
• Not checked yetcites Karnath et al., 2005