Eight years of research reveals that we lose an important aspect of our consciousness while we sleep.
We experience something similar to being awake but also very different from being awake when we dream, and scientists are still trying to figure out exactly what's going on every now and then.
Since then, another clue has been found. A recent study revealed that an important aspect of consciousness – the capacity to recognize or be aware of sounds – actually shuts down while we sleep. This finding may shed light on how our brain dreams.
While few of us would like to have electrodes implanted in our skulls as we go about our daily lives, the team here used medical research on epileptic patients for their own work. It is difficult to understand how the brains of living people work while they are awake and asleep.
According to neurologist Yuval Nir of Tel Aviv University in Israel, “We were able to use a special medical method in which electrodes are placed in the brains of epileptic patients, monitoring the activity in different parts of their brains for diagnostic and therapeutic purposes.”
Patients volunteered for research in comparing the brain's response to auditory stimuli during wakefulness and sleep.
The electrodes allowed the researchers to observe changes in the response of the cerebral cortex during various stages of sleep compared to when patients were awake, down to individual neurons.
Volunteers had loudspeakers at their bedside, where the researchers made various sounds for the purposes of the study. Data was collected on more than 700 neurons (about 50 for each patient) over eight years.
Alpha-beta waves, which are associated with attention and anticipation, increased during sleep, but the brain's response to sound remained mainly active. It seems that incoming voices are evaluated but not conveyed to awareness.
Contrary to what was previously believed, brain signals related to sound do not last long when people are asleep. In reality, they continue to be stronger than we initially believed; there is only one major change in how they are processed while we sleep.
According to neuroscientist Hanna Hayat of Tel Aviv University, “the strength of the brain response during sleep was similar to that observed during wakefulness, except for one particular feature where a dramatic difference was noted: the activity of alpha-beta waves.”
High-level brain feedback, including whether the noises are new or not, controls alpha-beta waves (10-30 Hz), which helps our mind determine which sounds are important and which sounds need attention.
Alpha-beta wave patterns similarly shift upward under anesthesia, but not while people are asleep. It is an approach to understanding the "fascinating riddle" of how conscious and unconscious brains change.
Additionally, this allows researchers to tell researchers whether a patient is truly unconscious, during medical procedures, in patients in a coma, when looking for dementia symptoms, etc. provides a quantitative and accurate way to determine whether
Beyond this particular experiment, our findings have broad implications, Nir adds. “We aim to further examine the processes underlying this distinction in future studies.”
The study was published in the journal Nature Neuroscience.