T
he discovery that new neurons can appear in the adult brain may be the most surprising of the last quarter century of neuroscience. The scale of the phenomenon and its significance remain to be established, but it appears that one of the oldest dogmas in the business is not true.

Antonio Damasio,

CHAIRMAN OF THE DEPARTMENT OF NEUROLOGY, UNIVERSITY OF IOWA COLLEGE OF MEDICINE; AUTHOR OF LOOKING FOR SPINOZA (HARCOURT, 2003) AND DESCARTES’ ERROR (HARPERCOLLINS/PENGUIN, 1995)

There have also been important paradigm shifts. For example: the notion that in the nervous system, as much as in the immune system, selection from among diverse elements is more important than instruction to shaping a functional structure; the notion that feeling and consciousness can be approached by neurobiology, no less so than memory or language; the notion that emotion and reason are not separate developments in evolution but related and interactive processes; and the notion that most neural events indispensable for mental states occur at the nonconscious level and that this goes well beyond the Freudian nonconscious (which is there too).

M
y favorite advance in the last 25 years is the development of brain-machine interfaces that provide direct connections and two-way communication between the brain and external devices. The so-called write-in systems have had substantial success. One example is the cochlear implant, which by electrically stimulating the auditory nerve allows deaf subjects to hear again. Another is deep brain stimulation for the treatment of Parkinson’s disease. Progress is also being made with retinal stimulators for the blind. An example of a so-called readout system under development is the cortical neural prosthetic, which can record the neural activity related to the movement intentions of paralyzed patients and use them as control signals to operate assistive devices, such as robots and computers. In the next 25 years less invasive brain-machine interfaces will be developed that are capable of recording from, and selectively stimulating, several orders of magnitude more neurons. In addition to helping patients, they will enable neuroscientists to discover the workings of the complex circuits that give rise to higher brain functions, including perception, decision making, attention, and awareness.
Richard Andersen, PROFESSOR OF NEUROSCIENCE, CALTECH


JUST A LITTLE
over 25 years ago, the study of the nervous system was revolutionized by the development of X-ray computerized tomography and, shortly thereafter, the advent of magnetic resonance imaging, or MRI.
The guesswork about brain structure soon disappeared. The impact on fundamental neuroscience is extraordinary. More recently, functional magnetic resonance imaging, or fMRI, has also allowed a preliminary look into brain function and has already overtaken earlier imaging techniques,
such as positron-emission tomography, that relied on radioisotopes. These developments are no less important than the development of the microscope. The impact of imaging in applied neuroscience—neurological and psychiatric diseases—is just as
remarkable. The practice of neurology is now unthinkable without the help of imaging, especially magnetic resonance. Moreover, the future of neuroimaging seems as bright as its recent past. Optical imaging will be thriving before Discover’s 50th anniversary.
Hanna Damasio, PROFESSOR OF NEUROLOGY, UNIVERSITY OF IOWA COLLEGE OF MEDICINE

To view last month's think tank article, click here.

To view all think tank article, click here.