Synchronized thinking: brain activity linked to schizophrenia, skillful meditation.
The collective activity of huge assemblies of brain cells, as reflected in their rhythmic electrical discharges, contributes to the derailed perceptions and thoughts of schizophrenia as well as to the heightened mental states achieved by experienced meditators, two new studies find.
Results from both investigations, slated to appear in the Proceedings of the National Academy of Science, coincide with earlier reports that a certain form of synchronized electrical activity in groups of brain cells fosters perception, memory, and consciousness (SN: 3/11/00, p. 167).
All these studies rely on electroencephalogram electroencephalogram /elec·tro·en·ceph·a·lo·gram/ (EEG) (-en-sef´ah-lo-gram?) a recording of the potentials on the skull generated by currents emanating spontaneously from nerve cells in the brain, with fluctuations in potential seen as (EEG EEG: see electroencephalography. ) recordings of the rate and intensity at which cells on the brain's surface send messages. Of particular interest are the gamma waves produced when masses of neurons emit their electrical signals around 40 times a second.
Many neuroscientists suspect that gamma activity occurs when various chemical messengers foster efficient communication across large swaths of brain tissue.
"The absence of gamma activity is related to dysfunctional neural circuits that cause some of the core symptoms of schizophrenia," reports psychiatrist Robert W. McCarley of Harvard Medical School Harvard Medical School (HMS) is one of the graduate schools of Harvard University. It is a prestigious American medical school located in the Longwood Medical Area of the Mission Hill neighborhood of Boston, Massachusetts. in Boston, who directed one of the new studies.
McCarley's team studied 20 people with schizophrenia and 20 who had no mental disorder mental disorder
Any illness with a psychological origin, manifested either in symptoms of emotional distress or in abnormal behaviour. Most mental disorders can be broadly classified as either psychoses or neuroses (see neurosis; psychosis). Psychoses (e.g. . As EEG data were collected, participants looked at either of two computer-screen images containing four partial circles resembling open-mouthed Pacman figures. In one image, the shapes were placed and oriented to create the illusion of a square in the center of the figures. Each volunteer pressed a key to signal perception of the square.
Study volunteers with schizophrenia made substantially more errors and took longer to respond than the others did. During this task, only the mentally healthy volunteers exhibited gamma activity at the back of the brain, where much visual processing Visual processing is the sequence of steps that information takes as it flows from visual sensors to cognitive processing. The sensors may be zoological eyes or they may be cameras or sensor arrays that sense various portions of the electromagnetic spectrum. occurs. In the people with schizophrenia, neural synchronization also occurred but at a frequency below the gamma range, indicating weaker integration of critical neural networks. Those who had experienced intense hallucinations Hallucinations Definition
Hallucinations are false or distorted sensory experiences that appear to be real perceptions. These sensory impressions are generated by the mind rather than by any external stimuli, and may be seen, heard, felt, and even , delusions, and disorganized dis·or·gan·ize
tr.v. dis·or·gan·ized, dis·or·gan·iz·ing, dis·or·gan·iz·es
To destroy the organization, systematic arrangement, or unity of. thinking showed the lowest-frequency synchronization.
Although the volunteers with schizophrenia had for years taken various antipsychotic medications that diminished their symptoms, none of the drugs had pushed neural synchrony synchrony /syn·chro·ny/ (-krah-ne) the occurrence of two events simultaneously or with a fixed time interval between them.
atrioventricular (AV) synchrony into the gamma range.
John H. Krystal, a psychiatrist at Yale University Yale University, at New Haven, Conn.; coeducational. Chartered as a collegiate school for men in 1701 largely as a result of the efforts of James Pierpont, it opened at Killingworth (now Clinton) in 1702, moved (1707) to Saybrook (now Old Saybrook), and in 1716 was School of Medicine, says he's "cautiously optimistic" that a focus on gamma activity will yield insights into how the brain malfunctions in schizophrenia.
In the second new study, directed by neuroscientist Richard J. Davidson of the University of Wisconsin-Madison “University of Wisconsin” redirects here. For other uses, see University of Wisconsin (disambiguation).
A public, land-grant institution, UW-Madison offers a wide spectrum of liberal arts studies, professional programs, and student activities. , gamma activity gradually expanded across the brain during meditation by eight people skilled at the practice. These individuals had undergone Buddhism-based mental training for between 15 and 40 years. Meditators who had trained for the longest time displayed the most gamma activity.
Considerably smaller amounts of neural synchrony turned up during meditation in the brains of 10 college students who had just begun the practice. They had received a training session in meditation the week before testing and had then practiced the technique for 1 hour each day.
The experienced practitioners also exhibited substantially more gamma activity while at rest and not meditating than the students did. Further research needs to confirm that meditation training directly cultivates this brain response, rather than that people with high gamma activity are attracted to meditation, Davidson says.
These new findings are provocative but hard to interpret, remarks neuroscientist J. Anthony Movshon of New York University New York University, mainly in New York City; coeducational; chartered 1831, opened 1832 as the Univ. of the City of New York, renamed 1896. It comprises 13 schools and colleges, maintaining 4 main centers (including the Medical Center) in the city, as well as the . "No one has convincingly linked gamma activity to any underlying brain mechanism involved in thinking or perception," Movshon says.
Nonetheless, neural synchrony "could be a gateway to understanding all sorts of mental activity," McCarley holds.