Article

Breakdown of Cortical Effective Connectivity During Sleep

University of Milan, Milano, Lombardy, Italy
Science (Impact Factor: 33.61). 10/2005; 309(5744):2228-32. DOI: 10.1126/science.1117256
Source: PubMed

ABSTRACT

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 high-density 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 (approximately 15 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.

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    • "It is well known that slow waves oscillations are the electrophysiological correlate of millions of neurons switching between up and down states. The large slow waves may link to decreases in effective connectivity, which presence of widespread cortical disability between up and down states during early NREM sleep[44,45]. The high frequency oscillations like beta and gamma may play an important role in integrating the unity of conscious perception[46]. "
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