In order for us to be able to combine current sensory impressions with our knowledge and memories, information from different areas converges in our brain. But how do the neural circuits manage to coordinate the incoming information and keep making new connections? Researchers have now investigated this question in mice. According to this, special cells in the hippocampus apparently ensure that previously synchronized brain areas decouple once more, so that different types of information can be transmitted at different times.
When our brain processes information, different areas of the brain are networked. The nerve cells involved pass on their electrical signals at a certain frequency and thus create a common rhythm. Conscious perception is associated with high-frequency brain waves called gamma waves. Previous research has already shown that specific cell types are responsible for generating specific frequencies. So far, however, it has been unclear how the brain areas synchronized in this way decouple once more in order to create space for other signals.
Sync breaker
A team led by Ece Sakalar from the Medical University of Vienna in Austria has now dealt with this question. In order to observe the brain cells at work, the researchers fixed the heads of awake mice and measured the activity of their nerve cells in the so-called CA1 area of the hippocampus, a central switching point in the brain. They observed a certain type of inhibitory nerve cell that fires at certain phases of the gamma waves, disrupting the synchronized rhythm in this way.
“We identified these cells as neuroglial cells,” the researchers report. This is a cell type whose function has not yet been clarified. “In our preclinical experiments, we have now discovered that these cells, by briefly inhibiting other cell types, ensure that current perception and memories of past experiences can be processed both separately and in combination,” explains Sakalar’s colleague Balint Lasztoczi.
Perception and memory united and separated
In this way, the brain can switch between different input channels – similar to how we can select different stations on the radio. The researchers suspect that it is precisely this mechanism that enables us to link sensory perceptions to memories and at the same time to be able to distinguish between them. For example, if we look at a photo of our grandmother and are reminded of the smell of her cookies, we are aware of what is actually experienced and what is only remembered.
The smooth regulation of the various information flows is a basis for a functioning nervous system. In various neuropsychiatric diseases such as schizophrenia or autism, however, errors occur in the tuning of the brain waves. For example, in the case of schizophrenia patients, for example, the distinction between their own thoughts and the impressions from their environment becomes blurred. The realization that the neurogliaform cells represent a kind of traffic light in the flow of information might possibly open up new treatment approaches for these diseases. Future research should clarify to what extent these cells can be influenced by drugs in order to possibly alleviate the symptoms of neuropsychiatric diseases.
Source: Ece Sakalar (Medical University of Vienna, Austria) et al., Science, doi: 10.1126/science.abo3355