Memory capacity of a human brain is comparable to entire internet, study finds.
All previous researchers in the field of neuroscience are turned upside-down as recent research reveals something astonishing about the human brain's capacity.
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A team of researchers led by Salk University has found that memory capacity of a human brain is 10 times more than common estimates. It is in the petabyte range, which is almost as large as the entire internet.
“This is a real bombshell in the field of neuroscience,” said Terry Sejnowski, Salk professor and co-author of the study. “Our new measurements of the brain’s memory capacity increase conservative estimates by a factor of 10 to at least a petabyte, in the same ballpark as the World Wide Web.”
The human brain is often compared to a computer. In a computer, information is measured by the number of bits that can be stored. In the brain, information is stored in the form of synaptic strength, a complex structure in the hippocampus. A longstanding question about the brain was how much information can be stored at a synapse.
Synapses between neurons control the flow of information in the brain. An output wire ‘axon’ from one neuron connects to an input wire ‘dendrite’ of a second neuron and generates a pattern of electrical and chemical activity in brain which results in storing memory and thoughts. Understanding how and why synapses undergo changes holds the key to finding the answers about the brain’s capacity, which was more of a mystery until now.
For the study, researchers reconstructed a rat’s hippocampus tissue in 3D. They used advanced microscopy and computer algorithms to develop the image of rat’s brain, the connectivity, shapes, volume and surface area of brain tissue to very small, nanomolecular level and observed an unusual phenomenon for the very first time. Researchers expected synapses would be roughly similar in size but were surprised to discover they were nearly identical.
“When we first reconstructed every dendrite, axon, glial process, and synapse from a volume of hippocampus the size of a single red blood cell, we were somewhat bewildered by the complexity and diversity amongst the synapses," said co-author Kristen Harris, professor of neuroscience at the University of Texas. "While I had hoped to learn fundamental principles about how the brain is organized from these detailed reconstructions, I have been truly amazed at the precision obtained in the analyses of this report."
The difference in the sizes of the pairs of synapses was very small, only about eight percent. Because the memory capacity of neurons is dependent upon synapse size, the eight percent difference could hold the key here and can estimate the number of bits of information a single synaptic can store.
Researchers suggest that there could be about 26 categories of sizes of synapses, rather than just a few. This number translates into a storage capacity of roughly 4.7 bits of information per synapse, which is remarkably higher than previous suggestions. It was thought that brain was capable of just one to two bits for short and long memory storage in the hippocampus.
“Our data suggests that there are 10 times more discrete sizes of synapses than previously thought,” said Tom Bartol.
“This is roughly an order of magnitude of precision more than anyone else has ever imagined.”
The size and strengths of these synapses can also increase or decrease. Every 2 or 20 minutes, synapses go up or down to next size and adjust themselves according to the singles they receive.
“The implications of what we found are far-reaching,” said Sejnowski. “Hidden under the apparent chaos and messiness of the brain is an underlying precision to the size and shapes of synapse that was hidden from us."
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The study was published in journal eLife.