Friday, 28 September 2007

Expanding the frontiers of human cognition

Chris Chatham: "The goal of developmental cognitive neuroscience is to uncover those mechanisms of change which allow the mature mind to emerge from the brain. The term encompasses a wide spectrum of research with one common fundamental assumption: the point of reference for this 'mature mind' is the healthy human adult, considered the apex of cognitive development.

Consideration of this assumption inspires a fascinating question. Are such mechanisms merely a kind of one-time developmental programme which self-terminates in the mature adult? Or, more likely, are they an emergent property of young neural networks? In other words, perhaps these developmental mechanisms are no more than a cascading reduction in entropy from the "blooming, buzzing confusion" of young, uncommitted networks to the specialized and entrenched patterns of connectivity in trained networks.

Current theories of lifespan trends in intelligence converge nicely with this idea. This work has shown that while measures of both fact knowledge and problem-solving trend together in early life, problem-solving and other forms of 'fluid' intelligence mysteriously plateau by early adulthood although fact knowledge continues its upward ascent. This apparent 'crystallization' of previously fluid intelligence may be a cognitive consequence of neuronal specialization. Perhaps, then, the adult mind is an artificial end point in the developmental process, enforced by limitations in neuronal real estate.

Imagine if these limitations were not present - what new vistas might the human mind reach? High-density intracranial electrode arrays, an invasive brain-computer interface technology, may someday progress to the point where they are not so quickly rejected by the body, but are rather greeted with the same axonal-dendritic kiss by which neurons embrace each other. And rather than interfacing the brain with simple computer programmes, as this technology is often used now, it might be used to interface the brain with massive biologically accurate computational models of the cortex.

Such a 'computational extension system' could conceivably be connected to nearly any cortical region, and become functional with exposure to adequately complex input. Extensions to sensory cortices might allow for more detailed perception of auditory or visual stimuli, improved spatial processing, or an exquisitely detailed kinaesthetic sense. The system might have its most extreme effects after bidirectional connection with prefrontal cortex and midbrain neuromodulatory systems, a network known to have undergone rapid expansion since homo sapiens diverged from other primates. Might a computational extension of prefrontal cortex affect cognition as profoundly as the evolutionary expansion of prefrontal cortex?

Though clearly plagued by ethical and practical issues, such an effort could have far-reaching consequences for our understanding of the mind. First, it would suggest that cognitive development is a process that unfolds naturally within uncommitted neuronal tissue. Second, it would allow unprecedented observation of the activity of such networks throughout their developmental cycle. Third, it may broaden our understanding of exactly how expansion of the brain - whether cultural, developmental, evolutionary, or computational - influences the emergence of mind."

Christopher H Chatham is pursuing a PhD in Cognitive Neuroscience at the University of Colorado, Boulder. He is also the author of the blog Developing Intelligence.

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