Brain signal never switches off and also supports many cognitive functions. Researcher's look at one of the human brain's most fundamental "foundations" is an important step forward in understanding the functional architecture of the brain …
Courtsey: Kate Melville
Washington University School of Medicine researchers are taking the first direct look at one of the human brain's most fundamental "foundations": a brain signal that never switches off and may support many cognitive functions. Their findings, appearing in the Proceedings of the National Academy of Sciences, are an important step forward in understanding the functional architecture of the brain.
Washington University School of Medicine researchers are taking the first direct look at one of the human brain's most fundamental "foundations": a brain signal that never switches off and may support many cognitive functions. Their findings, appearing in the Proceedings of the National Academy of Sciences, are an important step forward in understanding the functional architecture of the brain.
In the past decade, however, scientists have realised that deeper structures underlie goal-oriented mental processes. These underlying brain processes continue to occur even when subjects aren't consciously using their brain to do anything, and the energies that the brain puts into them seem to be much greater than those used for goal-oriented tasks.
"The brain consumes a tremendous amount of the body's energy resources -- it's only two percent of body weight, but it uses about 20 percent of the energy we take in," says Raichle. "When we started to ask where all those resources were being spent, we found that the goal-oriented tasks we had studied previously only accounted for a tiny portion of that energy budget. The rest appears to go into activities and processes that maintain a state of readiness in the brain."
To explore this deeper level of the brain's functional architecture, Raichle and others have been using fMRI to conduct detailed analyses of brain activity in subjects asked to do nothing. However, a nagging question has dogged those and other fMRI studies: Scientists assumed that increased blood flow to a part of the brain indicates that part has contributed to a mental task, but they wanted more direct evidence linking increased blood flow to stepped-up activity in brain cells.
Courtsey: Kate Melville
Washington University School of Medicine researchers are taking the first direct look at one of the human brain's most fundamental "foundations": a brain signal that never switches off and may support many cognitive functions. Their findings, appearing in the Proceedings of the National Academy of Sciences, are an important step forward in understanding the functional architecture of the brain.
Washington University School of Medicine researchers are taking the first direct look at one of the human brain's most fundamental "foundations": a brain signal that never switches off and may support many cognitive functions. Their findings, appearing in the Proceedings of the National Academy of Sciences, are an important step forward in understanding the functional architecture of the brain.
In the past decade, however, scientists have realised that deeper structures underlie goal-oriented mental processes. These underlying brain processes continue to occur even when subjects aren't consciously using their brain to do anything, and the energies that the brain puts into them seem to be much greater than those used for goal-oriented tasks.
"The brain consumes a tremendous amount of the body's energy resources -- it's only two percent of body weight, but it uses about 20 percent of the energy we take in," says Raichle. "When we started to ask where all those resources were being spent, we found that the goal-oriented tasks we had studied previously only accounted for a tiny portion of that energy budget. The rest appears to go into activities and processes that maintain a state of readiness in the brain."
To explore this deeper level of the brain's functional architecture, Raichle and others have been using fMRI to conduct detailed analyses of brain activity in subjects asked to do nothing. However, a nagging question has dogged those and other fMRI studies: Scientists assumed that increased blood flow to a part of the brain indicates that part has contributed to a mental task, but they wanted more direct evidence linking increased blood flow to stepped-up activity in brain cells.
In the new study, the researchers took fMRI scans of five patients with intractable epilepsy. The scans, during which the subjects did nothing, were taken prior to the temporary installation of grids of electrodes on the surfaces of the patients' brains. The level of detail provided by the grids is essential clinically for pinpointing the source of the seizures for possible surgical removal, a last resort employed only when other treatments failed.
The results confirmed that the fMRI data she had gathered earlier reflected changes in brain cell activity exhibited in the gamma frequency signal. But she also noticed the persistent low-frequency signal, which also corresponded to the fMRI data. "When we looked back in the literature, we found that a similar signal had been the subject of a great deal of animal research using implanted electrodes in the 1960s through the 1980s," she says. "There were suggestions, for example, that when this low-frequency signal, which fluctuates persistently, is in a low trough, the brain may handle mental tasks more effectively."
"What we've shown provides a bridge between the fMRI work many scientists are doing now and the earlier work involving electrical recordings from the brain that emphasised slow activity," says he. "Bringing those two fields together may give us some very interesting insights into the brain's organisation and function."
The results confirmed that the fMRI data she had gathered earlier reflected changes in brain cell activity exhibited in the gamma frequency signal. But she also noticed the persistent low-frequency signal, which also corresponded to the fMRI data. "When we looked back in the literature, we found that a similar signal had been the subject of a great deal of animal research using implanted electrodes in the 1960s through the 1980s," she says. "There were suggestions, for example, that when this low-frequency signal, which fluctuates persistently, is in a low trough, the brain may handle mental tasks more effectively."
"What we've shown provides a bridge between the fMRI work many scientists are doing now and the earlier work involving electrical recordings from the brain that emphasised slow activity," says he. "Bringing those two fields together may give us some very interesting insights into the brain's organisation and function."
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