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According to accepted dogma, the brain responds to sensory experiences somewhat like an electronic bucket brigade, with incoming signals passed from one region to the next in a somewhat linear fashion.
This passive role is being challenged by new studies led by neuroscientists and computational biologists at the Salk Institute. Instead of the bucket brigade metaphor, these scientists see the brain more as an improvisational jazz band adjusting its ongoing parts to the arrival of new voices or themes.
The result suggests a far more dynamic view of the brain's activity than is envisioned in standard analyses. It also opens new avenues to explore certain brain dysfunctions, including schizophrenia and autism.
The researchers understand that some important brain responses are too small or missing in autism, and a new framework of analysis may help them to understand why. Using the band metaphor, Salk scientists believe that there's a good possibility that in autism the coherence of the band is missing. There is no reorganization, and the instruments continue to play their own tunes.
Recent Discoveries
In a recent study, Salk investigators applied a recently developed mathematical technique called ICA (Independent Component Analysis) that allowed them to examine each of the more than 13,000 trials individually.
Seven independent sources of brain waves were discovered that adjust their signals following a flashed stimulus. Each source represents synchronous neuronal activity in a brain area, something like a heart's pacemaker. When the pacemaker stops functioning coherently and each heart cell chooses its own rhythm, fibrillation occurs.
The way doctors or paramedics get the heart beating again is to shock it, which resets the pacemakers to act in phase with one another. In the brain, a stimulus acts similarly, re-setting the phase of the oscillations and bringing them into synchrony, albeit briefly. Although most subjects showed evidence of several brain wave sources, they had individual differences with respect to strength, amplitude and frequency of the associated EEG waves.
Salk scientists are now focused on the next big question: Can they find differences that account for brain disorders such as schizophrenia or autism?