Standard Deviation Rise Research Articles

Components of the evoked potential in the MES auditory cortex.

The electrical activity during the potential evoked by a p pulse was analyzed statistically by considering amplitude at each 3-msec. epoch a random variable. The rise in standard deviation during the evoked potential was abolished a) by local cocaine on the cortex, b) by a preceding evoked potential and c) by ischemia. The residual mean positive component, with zero standard deviation, was subtracted from the mean of the evoked potential. This yielded a positive-negative component, with which the spontaneous electrical activity is believed to interact. The evoked potential is thus described as the sum of the three random variables: a) spontaneous electrical activity, b) positive component, and c) positive-negative component, with a covariance term involving the spontaneous electrical activity and the positive-negative component.

A sensitive method for detecting the effect of radiation upon the human body.

The effect of ionizing radiation was investigated upon the electrical threshold of the eye as determined with electrical phosphenes as an index. The present experiment dates back to a chance observation that an enor-mous increase in electrical threshold of the eye and a conspicuous rise in standard deviation of threshold values occurred after a fluorography of the chest and continued for several days. 1. In 10 normal subjects, who were beginners in such measurements, definitely positive responses were obtained to X-ray irradiation with a dose of 50 mr. 2. It was found that the standard deviation in percentage of the mean of thresholds was a better indicator of the effect of radiation than the threshold value itself. This measure was designated the “phosphene index” and denoted by Pi. 3. The phosphene index was found decidedly higher in a group of 21 X-ray-technicians and physicians than in the control group of as many university students. 4. The time-course of the effect was investigated after momentary exposure to 50 mr, and two phases, acute and chronic, were distinguished. The acute effect lasted for a few days, declining rapidly. A residual effect of several per cent of the maximum remained for over 10 days (chronic phase). 5. There was an approximately linear relationship between the maximum acute effect and the logarithm of the applied dose within a range from 1 mr to 50 mr.