Brain stimuli plotted

Electrical responses in the brain, plotted on an oscilloscope could measure the effect of the stimuli. Two rhythms had been noted—a resting rhythm when 12 responses per second were recorded and an active rhythm, which was [unclear: characterised] by fast and sharp changes.

When a single stimulus reached the [unclear: resting] brain it showed up as a definite [unclear: response] at the specific receiving centre; [unclear: soon after] it also reached the brain dif[unclear: uscly] from the pool of neurones in the [unclear: train] stern. The effect was to replace the [unclear: csting] rhythm by an active rhythm; the [unclear: at] woke up or became active, yawned, [unclear: nd] so on. He was alerted. "But after a [unclear: hile] if you go on feeding in the same [unclear: timulus] you will go on picking up the [unclear: ingle] signal at the cortex, but the active [unclear: hythm] will fail to appear—and the animal will fail to be alerted," explained Dr. Scott.

This was what was known as the habituation of the activating mechanism There came a time when the cortex ceased to be alerted by a given stimuli. But if there was any change in the pitch or tone of the stimulus the reaction began all over again.

Maybe for the man concentrating on the radar screen, the stimulus or 'blip' ceased to activate; all the other unchanging stimuli about him likewise. An experiment was carried out to see what effect long exposure to a narrow range of unchanging sensation would have. Subjects were isolated from normal stimuli. Their eyes were covered with goggles which admitted light but did not permit vision; they could hear nothing save the hum of an amplifier and an air conditioner; their cubicle where they lay on a' comfortable couch was semi-sound proof; they could not feel because their hands were covered with cotton gloves and cardboard tubes; they did not shave or wash; they were allowed to go to the toilet and eat with guidance. "The aim was to make the subject's environment as bland, flat and perceptibly characterless as possible." The subject was well rested and eager for things to do, e.g. problems to solve. But his efficiency fell off dramatically; they did not succeed at tasks they set themselves. After 36 hours the students were utterly and desperately bored.

Besides test results demonstrating their inefficiency there were other examples too of their confusion. The musician who believed he had discovered a beautiful cadence for his symphonic work later found that it was one he had rejected a week earlier. In this environment the subjects became quite absent minded: those who attempted to think could not develop a clear, logical line.

Subjects also started reporting odd things. Most observed visual and auditory hallucinations which developed from the simple to the complex, and were similar to those experienced by people who take such drugs as mescal. Although on release the subjects assumed that their behaviour was quite normal they were still for a time quite inefficient. Most behaved as if they were mildly schizophrenic the symptoms of which persisted for several days.

Deterioration of a similar though milder sort, explained Dr. Scott, resulted in mental tasks requiring long concentration. Also, there was certain evidence that habituation to the activating aspects of the environment was accumulative; as the day wore on the brain ceased to be activated without a complete change of scene or activity. Recovery was effected through sleep—which was at the same time a period of perceptual isolation. Thus one had to recover from the ill effects of sleep before the beneficial effects could "come out.