It has been discovered that many of the activities usually attributed to the cerebral cortex are actually generated in other brain structures. The finding could help improve encephalogram reading and correct possible misinterpretations of previous studies.
This revealing study has been led by scientists from the Higher Council for Scientific Research (CSIC) in Spain and has been published in Cerebral Cortex.
The confusion between electrical signals that reach the cortex could be caused, the authors argue, because the curved shape of some brain structures, such as the cortex and the hippocampus, promotes a wide range of the electrical potentials of neurons, and causes intermingle with those of other structures.
The electroencephalogram reflects the variations in electrical potential that groups of neurons produce when they are activated together during the coding and processing of sensory, motor, and cognitive information. Its registration on the surface of the scalp makes it very accessible to control brain/machine devices, such as rehabilitation prostheses or communication units of diverse application.
“The records on the scalp demonstrate a basic fact in physics, and that is that the electrical potential extends well beyond the current generator, in this case, the neurons inside the brain. Due to its proximity to the skull, the electroencephalogram has been attributed to the neurons of the cortex, located in the outermost part of the brain. But there were no systematic studies confirming this assumption,” explains CSIC researcher Óscar Herreras of the Cajal Institute.
In this study, researchers from the Cajal Institute have made records, in the brains of mice, of the intracerebral electrical potential with high density probes in several cortical areas and other deep regions. The objective of these tests was to find the location of neuronal populations which activation generates electrical potentials and measure their range.
“The application of modern mathematical algorithms has allowed us to separate the electrical activity generated by different groups of neurons and describe what the electrical potential produced by each group is and how far it goes. Thus, we have verified that in the records of the cerebral cortex a very important part of the potential is produced by neurons located in distant structures, either from other cortical areas or from other deep structures, such as the hippocampus,” adds Herreras.
To verify the results obtained in rodents, the researchers designed computer models of brain activity produced by cortical and subcortical structures, with millions of neurons located in the same way as they are inside the brain.
“Our findings will serve to correct the interpretations of a large number of previous studies, as well as to optimize the interfaces between the brain and the machine, where one of the main difficulties is to recognize useful patterns in the electroencephalogram,” concludes the researcher.
Source: Agencia ID