Sleep and Brain Connectivity
Massimini et al. (2005) attempted to study sleep and cortical connectivity by combining two different methods, TMS and EEG.
The abstract is below:
“When we fall asleep, consciousness fades yet the brain remains active. Why is this so? To investigate whether changes in cortical information transmission
play a role, we used transcranial magnetic stimulation together with highdensity electroencephalography and asked how the activation of one cortical area (the premotor area) is transmitted to the rest of the brain. During quiet
wakefulness, an initial response (È15 milliseconds) at the stimulation site was followed by a sequence of waves that moved to connected cortical areas several centimeters away. During non–rapid eye movement sleep, the initial
response was stronger but was rapidly extinguished and did not propagate beyond the stimulation site. Thus, the fading of consciousness during certain
stages of sleep may be related to a breakdown in cortical effective connectivity.”
Read the original study here (pdf).