Don Tucker - Cognition and Neural Development

In this book, we begin with what we think is an insight. The mind is the brain. The mind is not just brainfunction, as if function could be separated from structure. Rather it is the very substance of the brain. As the mind operates, it reflects the ongoing neurodevelopmental process, continuing the self-organization of neural connections that began in the embryonic differentiation of the neural tube and that continues throughout life.

We think this insight is implicit in todays scientific research, but it is not yet fully apparent. Once it does become apparent, everyone will think Of course we knew this all along. We might say this insight is still preconscious in the minds of psychologists and neuroscientists, and even those who should bridge these disciplines, cognitive neuroscientists. The progress in science prepares us for this insight, yet it is still difficult to realize.

One problem is that mind naturally seems different from brain. The objectivity required for flexible scientific analysis is difficult when we have personal awareness of mental processes (more or less) but have no personal awareness of the neural mechanisms. From the naive view of the subjective mind, we then experience psychological processes as fundamentally separate from the bodily processes that generate them. It is natural, then, even for scientists to think that the brain function that creates our familiar psychological phenomena can arise from a brain whose basic structure, its anatomy, is fixed. Rather, the insight is that the phenomena of mind are due to the ongoing developmental changes in neuroanatomical differentiation. Every thought reorganizes the tissue.

Another problem is that the insight requires developmental reasoning. In modern training in both psychology and neuroscience, development is seen as a specialized topic, dealing with the minds of babies or the brains of embryos. If development is not your specialty, you never think about it. This is an important mistake. Development is the process of life. Just as biology cannot be understood except in the light of evolution, psychology cannot be understood except in the light of brain development. Psychology is, indeed, in each moment, brain development.

(p.vi) These impediments should be overcome soon enough. The theoretical progress that makes it possible to understand the neurodevelopmental nature of human cognition has been slow over the last couple centuries, but it is now well advanced. Perhaps most importantly, we have learned how neural connectivity implies cognitive function. This has come largely through connectionist computational modeling, showing how complex and naturalistic representation of concepts can be organized in the pattern of connections among simple neuronal elements. In addition, we have a lot of concrete evidence of the isomorphism (parallel forms) of psychological function and brain activity. This is being gathered by powerful methods of observing the brains activity in controlled cognitive experiments, first with hemodynamic (functional magnetic resonance imaging or fMRI) measures, and now with the temporal dynamics shown by dense array electroencephalography (dEEG). Both of these are being augmented by increasingly accurate measurement of network structure with nerve fiber tractography.

Now, the structure-function illusion still remains in this research. Cognitive neuroscientists still think the neuroanatomical structure is fixed, and the hemodynamic or electrophysiologic measures reflect the activity of the tissue that somehow gives rise to psychological function without changing its structure. But activity becomes structure. The advances in technology and measurement are preparing us for this insight. We will soon appreciate that the cognitive mechanisms of learning and memory are achieved through developmental neural plasticity. Neural structure is developing continuously, and this development is brain function. As a result, our familiar psychological experience throughout life is the direct reflection of ongoing neural ontogenesis.