#resting-state

[jee-neuro-blog-blog]

Reference: van den Heuvel, M. P., Hulshoff Pol, H. E., 2010. Exploring the brain network: A review on resting-state fMRI functional connectivity. European Neuropsychopharmacology 20, 519-553.

[jee-neuro-blog-blog]

#1: Exploring the brain network: A review on resting-state fMRI functional connectivity

van den Heuvel, M. P., Hulshoff Pol, H. E., 2010. Exploring the brain network: A review on resting-state fMRI functional connectivity. European Neuropsychopharmacology 20, 519-553.

Summary

An emerging trend in neuroscience is to consider the brain as a huge network, and to figure out how this network operates. There appears to be not only structural or anatomical connectivity, but also functional connectivity in the brain; in other words, temporal dependence as opposed to spatial dependence of neuronal activities. This is supported by various imaging studies, especially fMRI studies. In this article, the resting-state fMRI signals are especially of interest. Resting-state fMRI can be processed using model-dependent methods such as the seed method, or model-free methods such as ICA methods. Model-free methods are used to find more general patterns as a whole, whereas the seed method uses a selected seed region and compared it to other regions. Currently there are about eight resting-state networks that have been reported consistently, and they also overlap with the other networks that have already been established, such as the primary motor network. Examining resting-state networks can provide insight in the organization of the human brain. It has also been newly hypothesized that diseases such as Alzheimer's disease and schizophrenia may be related with change (disruption) in the resting-state networks. There is even a suggestion that network efficiency may be correlated to cognitive abilities. This relatively new perspective of the brain as a network can be applied to many areas of neuroscience to provide a new framework.

Thoughts & Questions

I find the concept of the brain as a network very intriguing. I had never really considered resting-state networks prior to reading this article, although I had thought about how the brain never 'stops' while we are alive and breathing. The so-called default mode network hypothesized to be associated with integration of cognitive and emotional processing, mind wandering and monitoring the world around us, was especially interesting. It reminded me of how when I was young I would try to think of 'nothing' and it was practically impossible. Perhaps the resting-state networks give rise to consciousness or self-awareness in humans.

I am not sure that I completely understand the concept of 'functional connectivity' though. If they are not anatomically connected, how are they connected and how can they spontaneously fire together? In addition, how do researchers actually define the 'resting-state'? I think rest here means to physically rest and not be engaged in any activities. The article mentioned that participants in the study were required to relax and try not to think of anything without falling asleep. However there seems to be no objective way to concretely define the resting-state of the brain. If the brain is working so hard during the resting-state, it is probably not even appropriate to call it the 'resting-state'.