Over the past two weeks, I have specifically discussed the potential value of intensive brain plasticity-based brain fitness training for individuals with ALL of these (and other, related) personal histories. How in the heck can “one size fit all”? How on earth can the losses in mental faculties stemming from an explosion of little bubbles in the brain accompanying an IED blast be related to those derived from a slow, deliberate chemical poisoning of regenerative processes in the brain designed to limit the proliferation of cancerous tissues that are usually not even IN the brain, or to the normal deterioration of the fabric of the brain that accompanies getting older? Understanding the nature of the basic neurological processes that account for how the brain encodes and “represents” our experiences is a key to understanding what these assaults on our brains have in common.
The brain encodes our perceptions, thoughts and actions by generating coordinated, distributed neuronal responses that “represent” the ongoing details of each successive event. Three aspects of this encoding are crucial for generating crystal-clear representations of ongoing experiences.
FIRST, the brain has to accurately represent the DETAILS of these â€˜input’ or â€˜output’ streams. For example, in a normal young adult, the cerebral cortex areas representing incoming speech normally samples information in detail with narrow sound-frequency-selective â€˜channels’, detecting perturbations in those channels at rates of 25-30 “samples”/second (or higher). This very detailed analysis of the changes in inputs in fine grain in sound frequency and in fast time results in a very accurate and complete abstraction of ALL of the detailed features of aural speech inputs.
SECOND, the brain has to generate sharply coordinated responses to each important change in the incoming stimulus. We conducted studies a decade ago that showed that distributed COORDINATION of evoked neuronal responses to each little input perturbation was crucial for generating representations that were not easily degraded by external noise. A general rule of thumb: If an individual’s receptive abilities are easily disrupted by environmental noise, they are NOT representing information with an adequately high degree of distributed response coordination.
To understand why, imagine a football stadium full of fans. Now imagine a hundred fans in the stadium clapping in almost-perfect unison. Now imagine that the remaining 99,900 fans in the crowd begin to clap randomly. It takes a lot of other clapping by this great crowd to wipe out the “signal” generated by the mere 100 whose clapping is COORDINATED. Neurons in the cerebral cortex (and in other brain regions) are only effectively excited when their inputs are sharply COORDINATED. And just as in the stadium crowd, input coordination confers immunity from random, background activity (“noise”).
Many studies have shown that if an individual is noise sensitive, they shall also have a poorer memory. THE GENESIS OF STRONGLY CORRELATED MOMENTS OF DISTRIBUTED NEURONAL ACTIVITY IS CRUCIAL FOR MEMORY, because only highly temporally resolved and sharply coordinated activities effectively engage memory processes.
THIRD, the brain has to quickly evaluate ongoing actions, and use its analysis to bias activities representing the next EXPECTED action. This forward biasing is the engine that generates the current of our stream of consciousness. It is all about “the next best thing”! These ongoing biases (syntax) are absolutely crucial for our stable and reliable and fluent brain operations.
Back to brain bubbles, chemical brain poisoning, or slow brain deterioration in aging. In ALL of these cases, the ability of the brain to generate strongly coordinated representations of all of the details of “what’s happening” is degraded, because all of these conditions increase brain process noise. That noise results in progressively weaker neuronal discharge coordination. In this condition, the plastic processes of the brain necessarily slow down their operations, because that is the only way that the brain can make an accurate event-by-event analysis of what’s happening. In practice, whenever a brain is cognitively impaired, 1) its representation of the details of its perceptions or actions is inherently noisier and less coordinated, and 2) its input sampling rates decline, as the brain struggles to maintain control of its moment-by-moment recognition of “what’s happening”.
Such a brain now has sparser, less resolved, and more poorly coordinated information delivered to the “memory” processes of the brain. Such a brain takes longer and makes more errors in interpreting ongoing activities. All of these factors contribute to a slowing and weakening of the crucial forward-biasing that predicts “the next best thing”. What was a lively stream of consciousness can evolve into a sluggish, meandering slough â€“ and in the extreme, into a series of isolated, stagnant pools.
Whether the local damage to neurons and a degradation of their local inter-connections occurred via brain bubbles, chemical poisons, or age-related losses, the brains of individuals with all of these histories are still plastic. In each case, we can increase the fidelity of representation of successive details of inputs and actions. With that improved accuracy in the details of representation, higher sampling rates can be re-established. More powerful, predictive forward biasing will result from these improvements in signal resolution and speed.
It takes a helluva lot of hard work to achieve these improvements in an old or injured brain, but substantial improvement is almost always possible. The Posit Science and Scientific Learning Corporation training programs precisely target these crucial dimensions of functional loss â€“ and, blessedly, they can make a very big difference.