Besides receiving incoming signals from other brain cells, a neuron's branchlike dendrites somehow participate in computations that the cell makes to decide whether it should fire or not.
A new type of microscope may illuminate the murky details of that process and other neuronal functions by enabling researchers to peer into the brains of active laboratory rats, says Michale S. Fee of Lucent Technologies' Bell Laboratories in Murray Hill, N.J.
Currently, scientists must immobilize and anesthetize rats to inject dyes into single neurons and observe subcellular activity through a hole in the skull. Certain dye molecules fluoresce under laser light if they have bonded with calcium ions flowing into cell regions that are transmitting an electric pulse. Brain researchers already can observe those glowing molecules in subdued animals through large, stationary microscopes.