Stanford postdoctoral fellow Sashank Varma and Carnegie Mellon University neuroscientist Marcel Just's theory is called 4CAPS, an acronym for Capacity Constrained Concurrent Cortical Activation-based Production System.
The theory suggests that various brain areas volunteer themselves when their strengths are called for, and that they permit less efficient but capable areas to step forward when a specialised area gets injured or disabled, as may occur as a result of a stroke.
The researchers have made a number of computational models to demonstrate this process, such as a model that understands English sentences. They say when a stroke damages the part of the brain involved in language processing called Broca's area, located in the left prefrontal cortex, the corresponding site on the right side of the brain often becomes activated during language processing, even within hours after a stroke.
According to the theory, the same dynamic allocation mechanism that allows brain areas to volunteer themselves on a moment-by-moment basis would also come into play if Broca's area were damaged, and would allow any excess computational load to spill over to the right hemisphere mirror site on a more permanent basis.
The researchers also suggest that upon damage to some brain areas as a result of Alzheimer's disease, additional "helper" areas start performing such tasks as they normally do not perform in people without the disease. "Many brain-imaging studies have shown as the nature of the task changes, so does the set of activating brain areas. It is as though substitutions of team players are being made dynamically in response to changes in the game," said Just, the D.O. Hebb Professor of Psychology.
"We credit this dynamic mechanism with the fluidity or adaptability of human intelligence, and with much of the plasticity that occurs with learning or with recovery from brain damage," Just added.
The researchers say that the 4CAPS theory provides a framework for scientists and medical researchers to better understand nascent topics in neuroscience, such as how brain areas communicate and collaborate with one another during the thought process and how this can go awry. It also provides an account of what limits our ability to do multitasking.
"The thousands of facts that scientists have learned from brain imaging studies cry out for some sort of organization, some way to impose coherence, and ultimately to understand the brain system that is producing the results. The theory provides a new conceptual framework for understanding how the fluidity of thought arises from the dynamics of brain activity," Just said.
"As neurological issues arise in education, aging and development, and as a basis for a knowledge-based economy, it will become increasingly important that human brain function be understood by students, parents and educators, patients and doctors, trainees and managers, citizens and policy-makers," Just added.
The researchers have described their theory in a paper published in the journal Cognitive, Affective, and Behavioral Neuroscience.