|MadSci Network: Neuroscience|
A machine that monitors electrical current produced by the brain was created by Hans Berger in 1924 (see http://www.uic.edu/depts/mcne/founders/page0008.html), and is called the electroencephalogram or EEG. More recently, methods of examining the electrical measures of brain connectivity during thought have been developed. One example of this is the article by Scott Makeig, Tzyy-Ping Jung, Anthony J. Bell, Dara Ghahremani, and Terrence J. Sejnowski "Blind Separation of Auditory Event-related Brain Responses into Independent Components", published in the Proceedings of the National Academy of Sciences, USA, volume 94: pages 10979-10984 (1997). There are a number of other researchers working on this problem. For instance, you might look at Nuwer, Marc MD, PhD. "Assessment of digital EEG, quantitative EEG, and EEG brain mapping: Report of the American Academy of Neurology and the American Clinical Neurophysiology Society" published in Neurology volume 49(number 1): pages 277-292, (July 1997), which you may be able to access through OVID.
This work looks at developing a machine sensitive to energy flow between various parts of the brain, but does not address the actual thoughts or dreams an individual is thinking or dreaming. Right now, the electrical activity of the brain can be associated with particular processes, such as sleep, dreaming, motor processes, sensory processes, and in some cases even particular thought (or cognitive) processes such as word processing (also called semantic processing). As an example of this work, see the web page of Dr. Helen Neville. But we cannot tell from the electrical signal of the brain WHAT is being thought or dreamt. We have to infer the content of the thought from the thinker's situation, and the content of the dream from the dreamer's statements after waking.
Different regions of the brain are involved in different mental processes, such as dreaming and different aspects of thought (or cognition). There is some difference (or variance) between individuals in what particular areas are involved in thought and dreaming. There is some difference between individuals in how different brain areas are connected. There is some difference between individuals in how the electrical currents that arise from the brain activity are conducted to the scalp, where they are recorded. There is a very large difference between individuals in the precise location of stored information. All of these facotrs, the locations involved, how the locations are connected, current conductions, and the precise location of stored information may determine the electrical activity of the brain during a particular thought. A discussion of some of these issues is in GERALD M. EDELMAN's "Building a Picture of the Brain", published in Annals of the New York Academy of Sciences, volume 882: pages 68-89, (June 30, 1999).
Will we ever be able to tell from the electrical activity of the brain the content of thought? My sense is that there are too many variables for us to ever be able to measure content of thoughts or dreams from electrical brain activity. This may be due to the involvment of chaotic events in brain function (see Paul Grobstein's "Variability in Brain Function and Behavior" published in The Encyclopedia of Human Behavior, Volume 4 pages 447-458, V.S. Ramachandran, editor, Academic Press, 1994), or a less supportable sense of the mystery of mind.
Try the links in the MadSci Library for more information on Neuroscience.