Ted Berger is a mind reader. The minds of rats, that is.  In his lab at the University of Southern California, the neurobiologist places a tiny array of electrodes onto a slice of a rat's brain in a petri dish. With the flip of a switch, graduate student Walid Soussou starts the flow of electrical signals into the tissue. The brain cells respond by generating their own electrical impulses. This swirling pattern of neural signals is picked up by the electrodes and appears on a nearby computer screen as a wash of colors ranging from brilliant red to dark blue.

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