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Functional Connectivity and Neural Synchrony

Functional connectivity refers to the temporal correlation of different brain areas. For instance, if the activities of two distant areas increase or decrease at the same time, it means that the two areas have strong functional connectivity although they do not have direct synaptic connections. If the activity of one area is unrelated to the other, they have no functional connectivity. Here are the main research results.

  • General anesthetics reduce the connectivity between the frontal and parietal lobe (Figure 31h) (Lee et al., 2013; Bonhomme et al., 2019).
  • In a coma, the connectivity between medial prefrontal cortex (mPFC) and posterior cingulate cortex (PCC)/precuneus is destroyed (Silva et al., 2015).
  • The connectivity between the thalamus and the prefrontal cortex of vegetative people is abnormal. Recovery from persistent vegetative state is associated with restoration of thalamocortical connectivity (Laureys et al., 2000).
  • The connectivity of the default mode network (DMN) reflects the level of consciousness (Boly et al., 2009; Vanhaudenhuyse et al., 2010).
Images

Figure 31h. General anesthetics reduce the connectivity between the frontal lobe and the parietal lobe. [Image source: Lee et al., 2013]

DMN includes mPFC, PCC/precuneus, temporo-parietal junction (TPJ), hippocampus and thalamus. It has been found that the connectivity of DMN is correlated only to the alpha rhythm, not other frequency bands (Jann K et al., 2009; Knyazev et al., 2011). Since the connectivity of DMN reflects the level of consciousness, this underscores the important role of alpha rhythm in consciousness. Exactly how the alpha rhythm orchestrates the emergence of consciousness will be discussed in Chapter 35 and Chapter 36.

Basically, neuronal synchronization underlies functional connectivity. Brain waves originate from the simultaneous firing of tens of thousands of neurons. Therefore, to understand the origin of consciousness, we must know the mechanisms of neuronal firing as well as neural synchrony.

 

Author: Frank Lee
Posted on: 2020-08-25