Comments for Neuroconscience

Comment on Is the resting BOLD signal physiological noise? What about resting EEG? by Bryan Paton

Bryan Paton — Sat, 18 May 2013 23:04:46 +0000

I should add a caveat of “unless you are doing something like calibrated BOLD.”

Comment on Is the resting BOLD signal physiological noise? What about resting EEG? by Bryan Paton

Bryan Paton — Sat, 18 May 2013 23:00:58 +0000

I really do not know enough about whatever breath suspension might be but any changes relative to “normal” breathing in CO2 concentration (and the resulting pH change) and/or O2 saturation is going to affect the BOLD signal perhaps detrimentally.

Comment on Is the resting BOLD signal physiological noise? What about resting EEG? by Lawson ENglish

Lawson ENglish — Sat, 18 May 2013 15:35:07 +0000

RE: breath holding…

The respiratory suspension period isn’t breath-holding. It is actually a long, slow inhalation that starts with an exhale and ends with an exhale. My assumption is that the diaphragm is merely relaxing during this period. The current theory is that this is triggered by a slight change in CO2 sensitivity as a side-effect of how the thalamus is operating during this altered state.

If that is true, then whatever artifacts that arise from it should be different than those which arise from breath-holding.

Comment on Is the resting BOLD signal physiological noise? What about resting EEG? by Bryan Paton

Bryan Paton — Sat, 18 May 2013 14:28:03 +0000

It would indeed count for something and would as you indicate tend to eliminate one major source of noise. The pulsatile motion still remains but I could not say in what way it might effect such data. Holding your breath can though radically change the BOLD signal so the effects of breath holding may be beneficial on one hand but counter-productive on the other.

Comment on Is the resting BOLD signal physiological noise? What about resting EEG? by Lawson ENglish

Lawson ENglish — Sat, 18 May 2013 12:53:32 +0000

I understand that, but you’ve eliminated, or at least changed radically, one source of the noise, while at the same time, according to EEG research, boosted the Alpha EEG power good bit, and the alpha EEG coherence, at least in some people, to its theoretical maximum.

This gives you a radically different data set to work with than normal, and since the alpha EEG power and/or coherence of the person who shows this breath suspension state tends to fluctuate between normal levels, and these extreme levels in a singe meditation session, highly correlated with the change in breath8ing rate, you have a range of data available in a single session with a single subject.

Surely this counts for something in attempting to resolve the issue…

Comment on Is the resting BOLD signal physiological noise? What about resting EEG? by Bryan Paton

Bryan Paton — Fri, 17 May 2013 22:17:12 +0000

Pulsatile motion of the brain case and the blood vessels in the brain is the other major source of physiologically based movement noise.

Comment on Is the resting BOLD signal physiological noise? What about resting EEG? by Lawson ENglish

Lawson ENglish — Fri, 17 May 2013 12:02:17 +0000

Why?

Measuring fMRI during [apparent] breath suspension state would remove normal respiration artifacts from the equation, although research suggests that the person doesn’t actually stop breathing, but instead relaxes in a way that allows air to continue to circulate, primarily as a slow inhalation over the 60 second period, but possibly with secondary respiration due to the beating of the heart compressing the lungs slightly.

Even so, it would give you a different data point involving a radically lower frequency for diaphragmatic breathing — 0.008hz approximately — for that minute while the EEG power and coherence of alpha EEG might be dramatically raised during that same period: http://preview.tinyurl.com/9n5uowe (apologies for the facebook page -its the only permanent place I have to store images currently).

Comment on Is the resting BOLD signal physiological noise? What about resting EEG? by Matt Wall

Matt Wall — Fri, 17 May 2013 11:07:06 +0000

Outstanding summary Micah – definitely a big (but under-appreciated) issue in rsfMRI.

Comment on Is the resting BOLD signal physiological noise? What about resting EEG? by Bryan Paton

Bryan Paton — Fri, 17 May 2013 06:48:29 +0000

You will also need those practitioners who are able to slow their heart rate, in this case preferably to nil.

Comment on Is the resting BOLD signal physiological noise? What about resting EEG? by Bryan Paton

Bryan Paton — Fri, 17 May 2013 01:38:58 +0000

The TR of 2000 is not “untypical” for cardiac and respiration dynamics I agree it is terrible but this is the kind of data most people will collect/see. At such slow sample rates you can expect some interesting aliasing effects to occur. The RETROICOR toolbox takes this into account though in that it produces aliased versions of the input ECG, pulse or respiration signals.