8 - Brain Plasticity, Science, and Medicine

Summary

My motivation for pursuing studies in integrative neuroscience stemmed from a juvenile interest in the “great issues” of philosophy and psychology. As a student, it seemed obvious to me that the “rules” that underlie our psychology are discoverable brain rules, and that the disputes of historic philosophy would be trumped by neurological science. Alas, in the early period of my own studies, scientists had not gotten very far in addressing these great issues of philosophy and psychology in direct neurological terms. A dramatic change was to occur over the subsequent five decades of my scientific life.

Our own contributions to a progressive change in an understanding of our humanity initially stemmed from two principal sources. First, I led a team that created one of the first commercialized multiple-channel cochlear implants. These hearing recovery devices deliver patterned electrical stimuli to the auditory nerve in deaf individuals, thereby restoring aural speech understanding. Our ability to simulate the highly detailed representation of aural speech inputs normally delivered from the ear to the brain was, to say the least, crude. I've described it as akin to playing a Chopin sonata with your forearms. Not surprisingly, this new and radically degraded representational form of encoded speech was initially incomprehensible.

Several months later, our patients understood everything.

In the same era, research teams in Melbourne and Vienna created other multichannel cochlear implant models, applying very different speech encoding schemes. To our great surprise, several months later, even with their very different “front end” encoding, their patients also understood everything. The brain just didn't care. Moreover, both our patients and their patients said that their recovered speech sounded “just like it did before [they had lost their hearing].”

We realized that, especially given these three very different forms of artificial speech coding, a remarkable level of adaptive brain change – plasticity – must be contributing to the recovery of their speech understanding and the seamless cognitive extensions in the uses of aural language observed in cochlear implant patients. Contrary to the predominant neuroscientific view in this era, the adult human brain must be continuously plastic, on a grand scale.