According to recent research from MIT’s Picower Institute for Learning and Memory, the mammalian brain does not retain a single memory or even a few locations but rather in a dispersed, functionally integrated complex spanning several brain storage areas.
Co-lead and co-corresponding author Dheeraj Roy noted, “When talking about memory storage we all normally talk about the hippocampus or the cortex.” As a doctoral student at The Picower Institute, he worked with senior author and Picower Professor Susumu Tonegawa in the RIKEN-MIT Laboratory for Neural Circuit Genetics.
Memory encoding cells, or ‘engrams,’ are scatter throughout the brain, not just in the well-known memory areas, according to this study. Engram regions with high probability are list first in ranking order. It is our hope that this list will spur a slew of new investigations, both in our labs and outside.
1. Manipulation Of Memories On Brain Storage
The researchers conducted a series of experiments to test their hypotheses about how engram complex areas may interact and to see if their predictions were correct.
Optogenetics is a technology in which cells stimulated by flashes of light may controlled by genetically modified mice. A laser flash is administer to certain brain areas to determine if activating them will artificially duplicate the fear memory response of freezing in place, even when mice are place in a “neutral” cage where the zap not happen.
Optogenetic reactivations of engram complex neurons shown to follow the same patterns as those seen in normal memory recall. To see if reactivating several parts of the brain storage may improve memory recall, the researchers first proved that normal memory encoding and retrieval occurs over an extensive engram complex.
Moreover, previous studies have demonstrated that engaging only one engram region does not provide as vivid a memory as spontaneous recall does. ” As a result of this experiment, the researchers discovered that activating three engram complex areas at once resulted in more robust freezing behavior than stimulating only one or two of the regions involved.
2. Distributed Brain Storage Definition
A memory may be becoming more efficient and robust by storing a single memory across such a large part of the brain storage.
Using different memory engrams may allow us to remember a previous event more efficiently, as well as for the initial encoding, where different engrams may contribute information from the original experience. Second, if just a few parts of the brain are affect by illness, scattered memories might help us recall prior experiences and make us more resistant to harm in certain regions.
3. Creating A Memory Map
So, once the brains are maintain and optically cleaned using a process called SHIELD, the cells that engage by memory encoding or recall could easily seen under a microscope with ease. Computer-assisted counting of fluorescing cells in each sample allowed the scientists to build brain-wide maps of areas with apparent substantial activity in memory encoding or recall.
However, there were a number of locations that were not include on the maps. When comparing the brains of zap-encoding and zap-recalling mice to those of control mice, the researchers ruled out areas that may have affected by activity unrelated to the memory.
They were able to use this information to create an engram index that ranked the possibility of 117 different brain areas being engaged in the memory engram complex in order of importance. They expanded their study by creating new mice with neurons that could be tagged for both memory encoding and recall, allowing them to identify which cells had both functions.