Christof Koch in Scientific American Mind:
Millions of neurons in all corners of our gray matter send out an endless stream of signals. Many of the neurons appear to fire spontaneously, without any recognizable triggers. With the help of techniques such as electroencephalography (EEG) and microelectrode recordings, brain researchers are listening in on the polyphonic concert in our heads. Any mental activity is accompanied by a ceaseless crescendo and diminuendo of background processing. The underlying principle behind this seeming racket is not understood. Nevertheless, as everyone knows, the chaos creates our own unique, continuous stream of consciousness.
And yet it is very difficult to focus our attention on a single object for any extended period. Our awareness jumps constantly from one input to another. No sooner have I written this sentence than my eyes move from the computer screen to the trees outside my window. I can hear a dog barking in the distance. Then I remember the deadline for this article–which isn’t going to be extended again. Resolutely, I force myself to type the next line.
How does this stream of impressions come to be? Is our perception really as continuous as it seems, or is it divided into discrete time parcels, similar to frames in a movie? These questions are among the most interesting being investigated by psychologists and neuroscientists. The answers will satisfy more than our curiosity–they will tell us if our experience of reality is accurate or a fiction and if my fiction is different from yours.